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  • Cell & Developmental Biology  (25.032)
  • Biochemistry and Biotechnology  (13.095)
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  • 101
    Digitale Medien
    Digitale Medien
    Characterization of sulfonylurea receptors in isolated human pancreatic islets (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 182-188 
    Details
    ISSN: 0730-2312
    Schlagwort(e): human islets ; insulin release ; sulfonylurea receptors ; oral antidiabetic compounds ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Current information on pancreatic islet sulfonylurea receptors has been obtained with laboratory animal pancreatic β cells or stable β-cell lines. In the present study, we evaluated the properties of sulfonylurea receptors of human islets of Langherans, prepared by collagenase digestion and density-gradient purification. The binding characterisitics of labeled glibenclamide to pancreatic islet membrane preparations were analyzed, displacement studies with several oral hypoglycemic agents were performed, and these latter compounds were tested as for their insulinotropic action on intact human islets. [3H]glibenclamide saturable binding was shown to be linear at ≤0.25 mg/ml protein; it was both temperature and time dependent. Scatchard analysis of the equilibrium binding data at 25°C indicated the presence of a single class of saturable, high-affinity binding sites with a Kd value of 1.0 ± 0.07 nM and a Bmax value of 657 ± 48 fmol/mg of proteins. The displacement experiments showed the following rank order of potency of the oral hypoglycemic agents we tested: glibenclamide = glimepiride 〉 tolbutamide 〉 chlorpropamide ≫ metformin. This binding potency order was parallel with the insulinotropic potency of the evaluated compounds. J. Cell. Biochem. 71:182-188, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 102
    Digitale Medien
    Digitale Medien
    A role for cadherins in cellular signaling and differentiation (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 168-176 
    Details
    ISSN: 0730-2312
    Schlagwort(e): cadherin ; catenin ; differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Cadherins form a family of cell-cell adhesion proteins that are critical to normal embryonic development. Expression of the various family members is regulated in a complex pattern during embryogenesis. Both reduced and inappropriate expression of cadherins have been associated with abnormal tissue formation in embryos and tumorigenesis in mature organisms. Evidence is accumulating that signals unique to individual members of the cadherin family, as well as signals common to multiple cadherins, contribute to the differentiated phenotype of various cell types. While a complete understanding of the regulation of cadherin expression of the molecular nature of intracellular signaling downstream of cadherin adhesion is essential to an understanding of embryogenesis and tumorigenesis, our knowledge in both areas is inadequate. Clearly, elucidating the factors and conditions that regulate cadherin expression and defining the signaling pathways activated by cadherins are frontiers for future research. J. Cell. Biochem. Suppls. 30/31:168-176, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 103
    Digitale Medien
    Digitale Medien
    Role of the pro-α2(I) COOH-terminal region in assembly of type I collagen: Disruption of two intramolecular disulfide bonds in pro-α2(I) blocks assembly of type I collagen (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 233-242 
    Details
    ISSN: 0730-2312
    Schlagwort(e): assembly of type I collagen ; COOH-terminal propeptide ; pesin-resistant heterotrimers ; disulfide bonds ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Collagen biosynthesis is a complex process that begins with the association of three procollagen chains. A series of conserved intra- and interchain disulfide bonds in the carboxyl-terminal region of the procollagen chains, or C-propeptide, has been hypothesized to play an important role in the nucleation and alignment of the chains. We tested this hypothesis by analyzing the ability of normal and cysteine-mutated pro-α2(I) chains to assemble into type I collagen heterotrimers when expressed in a cell line (D2) that produces only endogenous pro-α1(I). Pro-α2(I) chains containing single or double cysteine mutations that disrupted individual intra- or interchain disulfide bonds were able to form pepsin resistant type I collagen with pro-α1(I), indicating that individual disulfide bonds were not critical for assembly of the pro-α2(I) chain with pro-α1(I). Pro-α2(I) chains containing a triple cysteine mutation that disrupted both intrachain disulfide bonds were not able to form pepsin resistant type I collagen with pro-α1(I). Therefore, disruption of both pro-α2(I) intrachain disulfide bonds prevented the production and secretion of type I collagen heterotrimers. Although none of the individual disulfide bonds is essential for assembly of the procollagen chains, the presence of at least one intrachain disulfide bond may be necessary as a structural requirement for chain association or to stabilize the protein to prevent intracellular degradation. J.Cell. Biochem. 71:233-242, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 104
    Digitale Medien
    Digitale Medien
    Role of the pro-α2(I) COOH-terminal region in assembly of type I collagen: Truncation of the last 10 amino acid residues of pro-α2(I) chain prevents assembly of type I collagen heterotrimer (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 216-232 
    Details
    ISSN: 0730-2312
    Schlagwort(e): assembly of type I collagen ; COOH-terminal propeptide ; pepsin-resistant heterotrimers ; interspecies collagen molecule ; thermal stability ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Procollagen (Type I) contains a noncollagenous COOH-terminal propeptide (C-propeptide) hypothesized to be important in directing chain association and alignment during assembly. We previously expressed human pro-α2(I) cDNA in rat liver epithelial cells, W8, that produce only pro-α1(I) trimer collagen (Lim et al. [1994] MatrixBiol. 14: 21-30). In the resulting cell lines, α2(I) assembled with α1(I) forming heterotrimers. Using this cell system, we investigated the importance of the COOH-terminal propeptide sequence of the pro-α2(I) chain for normal assembly of type I collagen. Full-length human pro-α2(I) cDNA was cloned into expression vectors with a premature stop signal eliminating the final 10 amino acids. No triple-helical molecules containing α2(I) were detected in transfected W8 cells, although pro-α2(I) mRNA was detected. Additional protein analysis demonstrated that these cells synthesize small amounts of truncated pro-α2(I) chains detected by immunoprecipitation with a pro-α2(I) antibody. In addition, since the human-rat collagen was less thermostable than normal intraspecies collagen, wild-type and C-terminal truncated mouse cDNAs were expressed in mouse D2 cells, which produced only type I trimers. Results from both systems were consistent, suggesting that the last 10 amino acid residues of the pro-α2(I) chain are important for formation of stable type I collagen. J. Cell. Biochem. 71:216-232, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 105
    Digitale Medien
    Digitale Medien
    Hexose transporter expression and function in mammalian spermatozoa: Cellular localization and transport of hexoses and vitamin C (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 189-203 
    Details
    ISSN: 0730-2312
    Schlagwort(e): glucose transporters ; sperm ; dehydroascorbic acid ; fructose ; 2-deoxy-D-glucose ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: We analyzed the expression of hexose transporters in human testis and in human, rat, and bull spermatozoa and studied the uptake of hexoses and vitamin C in bull spermatozoa. Immunocytochemical and reverse transcription-polymerase chain reaction analyses demonstrated that adult human testis expressed the hexose transporters GLUT1, GLUT2, GLUT3, GLUT4, and GLUT5. Immunoblotting experiments demonstrated the presence of proteins of about 50-70 kD reactive with anti-GLUT1, GLUT2, GLUT3, and GLUT5 in membranes prepared from human spermatozoa, but no proteins reactive with GLUT4 antibodies were detected. Immunolocalization experiments confirmed the presence of GLUT1, GLUT2, GLUT3, GLUT5, and low levels of GLUT4 in human, rat, and bull spermatozoa. Each transporter isoform showed a typical subcellular localization in the head and the sperm tail. In the tail, GLUT3 and GLUT5 were present at the level of the middle piece in the three species examined, GLUT1 was present in the principal piece, and the localization of GLUT2 differed according of the species examined. Bull spermatozoa transported deoxyglucose, fructose, and the oxidized form of vitamin C, dehydroascorbic acid. Transport of deoxyglucose and dehydroascorbic acid was inhibited by cytochalasin B, indicating the direct participation of facilitative hexose transporters in the transport of both substrates by bull spermatozoa. Transport of fructose was not affected by cytochalasin B, which is consistent for an important role for GLUT5 in the transport of fructose in these cells. The data show that human, rat, and bull spermatozoa express several hexose transporter isoforms that allow for the efficient uptake of glucose, fructose, and dehydroascorbic acid by these cells. J. Cell. Biochem. 71:189-203, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 106
    Digitale Medien
    Digitale Medien
    Regulation of intracellular membrane interactions: Recent progress in the field of neurotransmitter release (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 103-110 
    Details
    ISSN: 0730-2312
    Schlagwort(e): secretion ; SNARE hypothesis ; priming, fusion competence ; phosphoinositides ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Maintenance of compartmental independence and diversity is part of the blueprint of the eukaryotic cell. The molecular composition of every organelle membrane is custom tailored to fulfill its unique tasks. It is retained by strict sorting and directional transport of newly synthesized cellular components by the use of specific transport vesicles. Temporally and spatially controlled membrane fission and fusion steps thus represent the basic process for delivery of both, membrane-bound and soluble components to their appropriate destination. This process is fundamental to cell growth, organelle inheritance during cell division, uptake and intracellular transport of membrane-bound and soluble molecules, and neuronal communication. The latter process has become one of the best studied examples in terms of regulatory mechanisms of membrane interactions. It has been dissected into the stages of transmitter vesicle docking, priming, and fusion: Specificity of membrane interactions depends on interactions between sets of organelle-specific membrane proteins. Priming of the secretory apparatus is an ATP-dependent process involving proteins and membrane phospholipids. Release of vesicle content is triggered by a rise in intracellular free Ca2+ levels that relieves a block previously established between the membranes poised to fuse. Neurotransmitter release is a paradigm of highly regulated intracellular membrane interaction and molecular mechanisms for this phenomenon begin to be delineated. J. Cell. Biochem. Suppls. 30/31:103-110, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 107
    Digitale Medien
    Digitale Medien
    Signal transduction by transforming growth factor-β: A cooperative paradigm with extensive negative regulation (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 111-122 
    Details
    ISSN: 0730-2312
    Schlagwort(e): TGF-β cooperative signaling ; SMADs ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Transforming growth factor-β (TGF-β) represents an evolutionarily conserved family of secreted factors that mobilize a complex signaling network to control cell fate by regulating proliferation, differentiation, motility, adhesion, and apoptosis. TGF-β promotes the assembly of a cell surface receptor complex composed of type I (TβRI) and type II (TβRII) receptor serine/threonine kinases. In response to TGF-β binding, TβRII recruits and activates TβRI through phosphorylation of the regulatory GS-domain. Activated TβRI then initiates cytoplasmic signaling pathways to produce cellular responses. SMAD proteins together constitute a unique signaling pathway with key roles in signal transduction by TGF-β and related factors. Pathway-restricted SMADs are phosphorylated and activated by type I receptors in response to stimulation by ligand. Once activated, pathway-restricted SMADs oligomerize with the common-mediator Smad4 and subsequently translocate to the nucleus. Genetic analysis in Drosophila melanogaster and Caenorhabditis elegans, as well as TβRII and SMAD mutations in human tumors, emphasizes their importance in TGF-β signaling. Mounting evidence indicates that SMADs cooperate with ubiquitous cytoplasmic signaling cascades and nuclear factors to produce the full spectrum of TGF-β responses. Operating independently, these ubiquitous elements may influence the nature of cellular responses to TGF-β. Additionally, a variety of regulatory schemes contribute temporal and/or spatial restriction to TGF-β responses. This report reviews our current understanding of TGF-β signal transduction and considers the importance of a cooperative signaling paradigm to TGF-β-mediated biological responses. J. Cell. Biochem. Suppls. 30/31:111-122, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 108
    Digitale Medien
    Digitale Medien
    G-protein regulatory pathways: Rocketing into the twenty-first century (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 137-146 
    Details
    ISSN: 0730-2312
    Schlagwort(e): G proteins ; signal transduction ; protein tyrosine kinases ; PMN ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Complex cellular responses involve the integration of heterotrimeric G protein systems with protein kinase signal transduction pathways. Key in this integration is the control of small GTP-binding proteins including Ras and Rho family members. In this paper, we discuss the control of signal transduction pathways by G proteins and their integration with specific tyrosine kinases. The integration of G proteins, kinases, and small GTP-binding proteins in controlling cellular responses is illustrated through the newly defined Gα12/13-regulated pathways. Furthermore, the polymorphonuclear leukocyte provides a primary cell system for analyzing the integration of G proteins, kinases, and small GTP-binding proteins in controlling cellular functions such as superoxide production, adherence, chemotaxis, and granule secretion. J. Cell. Biochem. Suppls. 30/31:137-146, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 109
    Digitale Medien
    Digitale Medien
    Peroxisomes in lipid metabolism (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 158-167 
    Details
    ISSN: 0730-2312
    Schlagwort(e): peroxisomes ; lipid metabolism ; H2O2 metabolism ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Gene targeting and the elucidation of mutations underlying inherited peroxisomal diseases have provided new insights in peroxisomal lipid metabolism in vivo. The work led to the identification of a novel peroxisomal β-oxidation pathway and established clearly that genes, which are required for efficient peroxisomal oxidation of fatty acids, at the same time are key regulators of PPARα function in vivo. The new mouse models may provide helpful tools in the search for unknown natural PPARα agonists and in screening for in vivo PPARα antagonists. J. Cell Biochem. Suppls. 30/31:158-167, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 110
    Digitale Medien
    Digitale Medien
    Nucleosome and chromatin structures and functions This article is a U.S. Government work and, as such, is in the public domain in the United States of America. (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 177-184 
    Details
    ISSN: 0730-2312
    Schlagwort(e): nucleosome ; chromosomes ; DNA ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: No abstract.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 111
    Digitale Medien
    Digitale Medien
    Regulation and regulatory parameters of histone modifications (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 203-213 
    Details
    ISSN: 0730-2312
    Schlagwort(e): histone acetylation and phosphorylation ; coactivators ; corepressors ; transcriptional activation and repression ; histone acetyltransferase ; histone deacetylase ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Histone acetylation and phosphorylation destablizes nucleosome and chromatin structure. Relaxation of the chromatin fiber facilitates transcription. Coactivator complexes with histone acetyltransferase activity are recruited by transcription factors bound to enhancers or promoters. The recruited histone acetyltransferases may acetylate histone or nonhistone chromosomal proteins, resulting in the relaxation of chromatin structure. Alternatively, repressors recruit corepressor complexes with histone deacetylase activity, leading to condensation of chromatin.This review highlights the recent advances made in our understanding of the roles of histone acetyltransferases, histone deacetylases, histone kinases, and protein phosphatases in transcriptional activation and repression. Exciting reports revealing mechanistic connections between histone modifying activities and the RNA polymerase II machinery, the coupling of histone deacetylation and DNA methylation, the possible involvement of histone deacetylases in the organization of nuclear DNA, and the role of chromatin modulators in oncogenesis are discussed. J. Cell. Biochem. Suppls. 30/31:203-213, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 112
    Digitale Medien
    Digitale Medien
    Linkages of nuclear architecture to biological and pathological control of gene expression (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 220-231 
    Details
    ISSN: 0730-2312
    Schlagwort(e): nuclear architecture ; gene expression ; tumor cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Functional interrelationships between components of nuclear architecture and control of gene expression are becoming increasingly evident. There is growing appreciation that multiple levels of nuclear organization integrate the regulatory cues that support activation and suppression of genes as well as the processing of gene transcripts. The linear organization of genes and promoter elements provide the potential for responsiveness to physiological regulatory signals. Parameters of chromatin structure and nucleosome organization support synergism between activities at independent regulatory sequences and render promoter elements accessible or refractory to transcription factors. Association of genes, transcription factors, and the machinery for transcript processing with the nuclear matrix facilitates fidelity of gene expression within the three-dimensional context of nuclear architecture. Mechanisms must be defined that couple nuclear morphology with enzymatic parameters of gene expression. The recent characterization of factors that mediate chromatin remodeling and intranuclear targeting signals that direct transcription factors to subnuclear domains where gene expression occurs, reflect linkage of genetic and structural components of transcriptional control. Nuclear reorganization and aberrant intranuclear trafficking of transcription factors for developmental and tissue-specific control that occurs in tumor cells and in neurological disorders provides a basis for high resolution diagnostics and targeted therapy. J. Cell. Biochem. Suppls. 30/31:220-231, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 113
    Digitale Medien
    Digitale Medien
    Intranuclear targeting of DNA replication factors (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 243-249 
    Details
    ISSN: 0730-2312
    Schlagwort(e): functional organization ; nucleus ; targeting sequence ; DNA replication ; nuclear matrix ; cell cycle ; DNA methyltransferase ; DNA ligase I ; PCNA ; DNA replication factors ; GFP ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Mammalian nuclei are highly organized into functional compartments. Major nuclear processes like DNA replication and RNA processing take place in distinct foci. These microscopically visible foci are formed by the assembly of, for example, DNA replication factors and associated proteins into megadalton complexes often referred to as protein machines or factories. Thus far, two proteins, DNA ligase I and DNA methyltransferase (DNA MTase), have been analyzed in greater detail. In both cases, the assembly process appears to be controlled by distinct targeting sequences that were attached to the catalytic protein core in the course of evolution and mediate the association with replication factories in mammalian cells. The dynamics of these nuclear structures throughout the cell cycle are analyzed using green fluorescent protein (GFP). Further studies are needed to elucidate the architecture, regulation, and role of these subnuclear structures. J. Cell. Biochem. Suppls. 30/31:243-249, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 114
    Digitale Medien
    Digitale Medien
    Marrow stromal cells as stem cells for continual renewal of nonhematopoietic tissues and as potential vectors for gene therapy (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 284-285 
    Details
    ISSN: 0730-2312
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: No abstract.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 115
    Digitale Medien
    Digitale Medien
    Rat urinary chemiluminescence: effect of ethanol and/or hexachlorobenzene uptake (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 63-68 
    Details
    ISSN: 0884-3996
    Schlagwort(e): ethanol ; hexachlorobenzene ; porphyria ; oxidative stress ; spontaneous urinary chemiluminescence ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Hexachlorobenzene (HCB) administration to rats induces porphyria cutanea tarda, characterized by high levels of urinary porphyrins (〉40 μg/day) and accumulation of highly carboxylated porphyrins in liver (〉15 μg/g of tissue). Ethanol administration, under the conditions employed, was not porphyrinogenic and was able to diminish some of the responses elicited by HCB. Furthermore, ethanol and/or HCB administration leads to organ disturbances that involve oxidative stress. We have measured the changes in urinary chemiluminescence (CL) levels, as part of a systematic evaluation of the metabolic alterations in rats chronically treated with ethanol and/or HCB. The results, that constitute the first set of urinary CL data obtained from an animal model system, indicate that the measurement of the spontaneous urinary CL can constitute a fast, simple and sensitive method to evaluate disturbances associated with oxidative stress. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 116
    Digitale Medien
    Digitale Medien
    Stopped-flow analysis of Ru(bpy)33+chemiluminescent reactions (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 85-90 
    Details
    ISSN: 0884-3996
    Schlagwort(e): stopped-flow ; chemiluminescence ; multicomponent analysis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The stopped-flow technique was employed to measure chemiluminescent emission from the reaction of a mixture of oxalate and proline with a chemiluminescence reagent, tris(2,2′-bipyridine)ruthenium(III), or Ru(bpy)33+. Ru(bpy)33+ is a versatile reagent and is often used in bioanalytical applications, including the detection of certain drugs and their metabolites, for example. Unfortunately, Ru(bpy)33+ has not yet been fully examined as a possible chemiluminescence reagent for simultaneous kinetic determinations. In this work, a differential reaction rate method, based on simple least squares regressions of the pseudo-first order decay data, was used to resolve two compounds, oxalate and proline, reacting simultaneously with Ru(bpy)33+. Our results indicate that stopped-flow analyses with Ru(bpy)33+ could provide a viable method for simultaneous determinations of unresolvable analytes of environmental and pharmaceutical importance. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 117
    Digitale Medien
    Digitale Medien
    Ultraweak light emission is a common response of bacterial cells to chemico-physical stressThis paper has not been peer reviewed. (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 287-293 
    Details
    ISSN: 0884-3996
    Schlagwort(e): electroporation ; UV light ; oxidative stress ; catalase ; superoxide dismutase ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Escherichia coli JM101 cells were subjected to pore-forming electric fields, irradiation with ultraviolet light or oxidative stress by either the lipoxygenase products 9- and 13-hydroperoxyoctadecadienoic acids (9- and 13-HPOD) or hydrogen peroxide. It was found that all chemico-physical stresses enhanced ultraweak light emission from the bacterial cells, the most effective treatment being electroporation (up to 20-fold increase in luminescence compared to the control value), followed by oxidative stress with 9- or 13-HPOD (up to 4-fold increase) and irradiation with UV light (up to 2.8-fold increase). Bacterial luminescence was always in the red edge of the spectrum and was paralleled by changes in membrane oxidative index and specific activity of catalase and superoxide dismutase. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 118
    Digitale Medien
    Digitale Medien
    Clinical and analytical performance of automated immunochemiluminometric assays for determination of cardiac markers in serumThis paper has not been peer reviewed (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 307-309 
    Details
    ISSN: 0884-3996
    Schlagwort(e): immunoassay ; biological markers ; myocardial infarction ; diagnostic sensitivity ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Three new immunochemiluminometric assays for quantitation of cardiac markers, i.e. creatine kinase isoenzyme MB (CK-MB), myoglobin and cardiac troponin I (cTnI), were evaluated with the Sanofi Access analyser. The complete profile requires 20 min to perform, the method being suitable in true stat situations. In patients with early myocardial infarction (median time of sample collection: 210 min from onset, range 30-450; n = 44), the diagnostic sensitivity of Access cTnI was 66%, compared with 80% for myoglobin, and 43% for CK-MB. For comparison, cTnI, with an automated immunofluorimetric assay was also measured (sensitivity, 45%; p 〈 0.05 vs. Access cTnI). Our data confirmed myoglobin as the first biochemical marker to appear elevated after infarction. However, cTnI may be a more sensitive marker for early detection of cardiac damage than initially thought, when determined by an ultrasensitive method such as an immunochemiluminometric assay. © 1998 John Wiley & Sons, Ltd.
    Materialart: Digitale Medien
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  • 119
    Digitale Medien
    Digitale Medien
    Determination by HPLC of adrenalin (E) and of noradrenalin (NE) in certain species of mesopelagic fish in the Strait of MessinaThis paper has not bee peer reviewed (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 311-314 
    Details
    ISSN: 0884-3996
    Schlagwort(e): bioluminescence ; adrenalin ; noradrenalin ; photophores ; HPLC ; mesopelagic fish ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The presence of adrenalin (E) and noradrenalin (NE) was found by HPLC both in the photophores and at other tissue levels of numerous species of mesopelagic fish in The Strait of Messina, with the aim of determining the incidence of these catecholamines in photophores, in light transmission and the eventual presence at other tissue levels. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
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  • 120
    Digitale Medien
    Digitale Medien
    Impaired reactive oxygen metabolism of phagocytic leukocytes in NIDDM patients. A role for non-enzymatic glycosylation of collagen (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 273-278 
    Details
    ISSN: 0884-3996
    Schlagwort(e): diabetes ; leukocytes ; monocytes ; extracellular matrix ; non-enzymatic glycosylation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Non-enzymatic glycosylation (NEG) of collagen has been previously shown to significantly influence the reactive oxygen metabolism (ROM) of phagocytic cells in healthy subjects. Considering the role of NEG in the pathophysiology of diabetes, we have further analysed the oxidative metabolism of polymorphonuclear cells (PMNs) and monocytes in 23 patients with non-insulin dependent diabetes mellitus in order to better elucidate a possible pathogenic role of NEG of the extracellular matrix in long-term complications of diabetes. Experiments were performed in triplicate on native-collagen and glycated-collagen coated vials, using a chemiluminescence (CL) assay. Results show that PMNs from diabetic patients display a significant increased basal and zymosan-induced CL activity with respect to controls that are not related to the glycation state of the substrate. Conversely, the CL activity of monocytes induced by zymosan shows a decrease in diabetic patients with respect to healthy volunteers (p 〈 0.05). Moreover, monocyte CL was reduced by the glycated matrix, both in healthy volunteers and in diabetic subjects (p 〈 0.05 and p 〈 0.01, respectively). These data highlight a complex role of phagocytic leukocytes in the pathophysiology of extracellular matrix alterations secondary to NEG that are typically present in clinical conditions such as diabetes or ageing. © 1998 John Wiley & Sons, Ltd.
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  • 121
    Digitale Medien
    Digitale Medien
    Chemiluminescent assay of β-D-galactosidase based on indole luminescence (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 349-354 
    Details
    ISSN: 0884-3996
    Schlagwort(e): β-D-galactosidase ; enzyme immunoassay ; chemiluminescence ; 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-gal) ; thyroxine ; indole derivative ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: We developed a novel chemiluminescent assay of β-D-galactosidase (β-gal) based on the chemiluminescence of indole. 5-Bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-gal) was used as a substrate for β-gal and also as a light emitter. X-gal was hydrolysed by β-gal to liberate free indoxyl, followed by oxidation to indigo dye, and simultaneously produces hydrogen peroxide (H2O2). H2O2 reacts with the residual X-gal in the presence of horseradish peroxidase (HRP) to emit light. The measurable range of β-gal obtained by this method was 6 × 10-14 mol/L to 6 × 10-11 mol/L; the detection limit was 3 amol/assay. This chemiluminescent assay could be applied to an enzyme immunoassay of thyroxine using β-gal as the enzyme label. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 122
    Digitale Medien
    Digitale Medien
    Chemiluminescence of cereal products. III. Two-dimensional photocount imaging of chemiluminescence (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 21-24 
    Details
    ISSN: 0884-3996
    Schlagwort(e): 2-D imaging ; chemiluminescence ; auto-oxidation ; hydration ; cereal products ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Two-dimensional (2-D) spatial distributions of ultra-weak chemiluminescence (photon imaging) from auto-oxidizing and water-hydrated cereal food products were measured by means of a high-sensitivity 2-D photon counting system - an intensified charge coupled device (CCD) camera. The 2-D images obtained reveal the dynamics and emission patterns of very slow auto-oxidation reactions and much faster processes of water penetration into cereal products. The enhancement of chemiluminescence by the addition of water appears to involve complex processes with an inhomogenous spatial and energy distribution within cereal products. The effect of antioxidants, free radical promoters and scavengers suggests that oxidative radical reactions contribute significantly to the observed chemiluminescence. The possible involvement of hydrophilic interactions, H2O-biopolymers and recombination of trapped radicals is also discussed. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
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  • 123
    Digitale Medien
    Digitale Medien
    Total antioxidant capacity (TAC): is it an effective method to evaluate the oxidative stress in uraemia?This paper has not been peer reviewed (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 315-319 
    Details
    ISSN: 0884-3996
    Schlagwort(e): CRF ; TAC ; lipids ; apolipoproteins ; oxLDLAb ; diet ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Lipoprotein abnormalities are common in uraemia and are considered important factors for development of atherosclerosis and progression of renal disease. Reduction of total antioxidant capacity (TAC) and lipid peroxidation (LP) probably play a major role in both processes. The aim of this study was to assess the effect of renal function, dietary manipulation and lipids on TAC of uraemic patients with different chronic renal failure (CRF). Sixty patients (36M, 24F), aged 60 ± 12 years were divided into five groups according to serum creatinine levels (sCr, mg/dl) -  CRFI, 1.5-3; CRFII, 〉 3-5.5; CRFIII, 〉 5.5; CRFIV, 〉 3 on vegetarian supplemented diet (SD); CRFV haemodialysis patients (HD)-and investigated for TAC by enhanced chemiluminescent assay, autoantibodies against oxidized LDL (oxLDLAb), lipids, apolipoprotein AI, B, Lp(a) and uric acid (UA). The results were compared to a control group of 19 people (8M, 11F), aged 52 ± 11 years with sCr 〈 1.5. TAC increased significantly with the progression of CRF and was strongly related to both sCr and UA. Lipids and SD did not show any influence on TAC. Unexpectedly, lipid peroxidation did not correlate to TAC, neither to sCr or UA. HD accounted for a mild reduction of both TAC and LP. Patients on SD showed a marked reduction of LP as compared to patients with a similar degree of renal failure (CRF-III) but on conventional diet. Our results suggest that elevated TAC in uraemia is likely to be dependent on increased UA levels and does not seem to induce an effective protection in vivo from oxidative stress. In conclusion, TAC does not appear to be a reliable method for assessing the oxidative susceptibility of CRF patients. © 1998 John Wiley & Sons, Ltd.
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  • 124
    Digitale Medien
    Digitale Medien
    Highly sensitive chemiluminescent method for the detection of cell contaminationThis paper has not been peer reviewed. (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 303-305 
    Details
    ISSN: 0884-3996
    Schlagwort(e): chemiluminescence ; PCR ; contamination ; polymorphism ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Minisatellite analysis is commonly used in forensic disputes but can also be applied to the investigation of cell contamination. Such a problem arises, for example, when transplantation is performed. The presence of contamination has been investigated by other authors using radioactive methods. In the present study we describe a method that allows the detection of contamination with high sensitivity without using radioactive substances. Our technique is based on the use of polymerase chain reaction (PCR) amplification of minisatellite sequences (VNTR), followed by chemiluminescent detection. In particular, biotin-labelled dCTP is included in the PCR mixture and detection of PCR products is obtained following the CSPD chemiluminescent protocol (Southern-Light Nucleic Acid Detection Systems). We applied this method to artificial mixes of DNA of two individuals with alleles of different sizes. We performed progressive dilutions of an individual DNA into the other's DNA and revealed a contamination of 1 in 2500 cells. We also tested our technique searching for maternal contamination in cord blood samples in 60 cases and revealed a 18.3% contamination. The technique that we set up proves to be a very sensitive one which could be applied not only to the detection of maternal cells in cord blood but also in studying any other kind of contamination. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 1 Ill.
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  • 125
    Digitale Medien
    Digitale Medien
    Using non-radioactive probes on plants: a few examplesThis paper has not been peer reviewed. (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 295-301 
    Details
    ISSN: 0884-3996
    Schlagwort(e): plant virus ; diagnosis ; transgenic plants ; non-radioactive probes ; digoxigenin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Due to costs in using and disposing of radiochemicals and to health considerations, we have been developing applications which include non-isotopic detection of DNA and proteins using chemiluminescence. Our major interests are in the detection of viral nucleic acids and in the analysis of transgenic plants. Generally, probes were labelled with digoxigenin, either by the random priming method or by PCR, and then detected with CSPD or CDP-Star. We routinely use a tissue blotting protocol for diagnosing TYLCV, a plant virus becoming a pest in the Mediterranean region. Test results were comparable with those using the same radiolabelled probe. When total nucleic acids are extracted from the plant samples and used in dot-blot or Southern blot assays, viral DNAs are promptly detected by chemiluminescence. In transgenic plants, chemiluminescence was used to detect the transgene on genomic Southern blots, the transgenic mRNAs on Northern blots, and the transgenic protein on Western blots. In Southern and Northern blots, the quality of the results obtained was usually satisfactory, but not as good as with a radiolabelled probe, the main problem being the signal-to-background ratio. Our goal is now to improve the quality of results in demanding applications such as genomic Southern blots, by reducing the background on membranes. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 126
    Digitale Medien
    Digitale Medien
    Chemiluminometric β-galactosidase detection as a basis for a tetracycline screening test in milkThis paper was presented in part as a lecture at the Luminescence Assays for Industry Symposium, University of Cambridge, UK, 22-23 September 1997. Full abstracts for the symposium appear in Vol. 12, pp. 93-112, 1997. (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 279-283 
    Details
    ISSN: 0884-3996
    Schlagwort(e): chemiluminescence ; β-galactosidase ; tetracyclines ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The observation that tetracyclines inhibit the biosynthesis of β-galactosidase in Escherichia coli to a greater extent than other antibacterials was exploited for the development of a chemiluminometric method to detect residues of this class of antibiotics in milk. The procedure involves the incubation of a milk sample with 107 CFU/ml of an E. coli strain in the presence of IPTG, an inducer of β-galactosidase, and of EGTA, a chelator of calcium ions, followed by a 1000-fold dilution and measurement of the residual enzymatic activity using the chemiluminogenic substrate Galacton. Chemiluminometry proved an essential tool in this procedure because the extensive dilution of the sample, necessary to avoid light quenching by turbidity, results in an insufficient level of β-galactosidase activity to be measurable by colorimetry. This tetracycline galactosidase (TG) test has been validated and compared in the field to existing commercial screening assays for antibiotics. Its detection limit for tetracyclines ranges between 40 and 65 μg/kg, which is below the European maximum residue limit (MRL = 100 μg/kg) in milk. No other antibacterials, at concentrations commonly expected in milk, were found to interfere with the TG test. Strategies to avoid false positive reactions possibly arising from very high somatic cell counts will be reported elsewhere. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 127
    Digitale Medien
    Digitale Medien
    What do we measure with luminol-, lucigenin- and penicillin-amplified chemiluminescence? 1. Investigations with hydrogen peroxide and sodium hypochlorite (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 355-363 
    Details
    ISSN: 0884-3996
    Schlagwort(e): hydrogen peroxide ; sodium hypochlorite ; reactive oxygen species ; chemiluminescence ; luminol ; lucigenin ; penicillin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Evidence is provided that the amplifiers luminol and lucigenin react with different reactive oxygen species (ROS), depending on the ROS-generating system used. H2O2 is used to produce calibration curves for luminol- and lucigenin-amplified chemiluminescence. With this chemiluminescence generator we characterized the specificity and sensitivity of luminol- and lucigenin-amplified chemiluminescence and also studied penicillin G, a known enhancer of luminol-amplified chemiluminescence. The combination of luminol and lucigenin in reciprocally changing concentrations is effective in an additive manner, but the weak amplifier penicillin increases luminol-amplified chemiluminescence distinctly more than in an additive manner in different combinations. Lucigenin-amplified chemiluminescence is increased by penicillin at about 1% of the optimum concentration of penicillin; increasing concentrations of penicillin are less and less effective. On the other hand, low lucigenin concentrations enhance penicillin-amplified chemiluminescence at optimum penicillin concentrations more than in an additive manner. Fe2+ does not alter luminol-, lucigenin- or penicillin-amplified chemiluminescence. Co2+ increases luminol-amplified chemiluminescence by a factor of 100. Lucigenin- and penicillin-amplified chemiluminescence are minimally enhanced by Co2+. Cu2+ enhances luminol-amplified chemiluminescence with increasing concentrations by a factor of 1000. Lucigenin-amplified chemiluminescence increases also by the factor of 1000, but the concentration-reaction curve is not as steep. NaOCl enhances H2O2/Fe2+-driven luminol-amplified chemiluminescence in a concentration-dependent manner by a factor of 104 (in the highest concentration of 10 mmol/L) and lucigenin amplified chemiluminescence only by a factor of about 25. Catalase (CAT) abolishes luminol-, lucigenin- and penicillin-amplified chemiluminescence completely, whereas superoxide dismutase (SOD) has no effect on luminol- or penicillin-amplified chemiluminescence, but enhances lucigenin-amplified chemiluminescence five-fold increasingly with increasing SOD activity. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 7 Ill.
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  • 128
    Digitale Medien
    Digitale Medien
    Immobilization of luciferase from a firefly lantern extract on glass strips as an alternative strategy for luminescent detection of ATP (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 371-378 
    Details
    ISSN: 0884-3996
    Schlagwort(e): bioluminescence ; luciferase ; ATP ; immobilization ; glass ; poly-L-lysine ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The bioluminescent reaction catalysed by firefly luciferase has become widely established as an outstanding analytical system for assay of ATP. When used in solution, luciferase is unstable and cannot be re-used, a problem that can be partially circumvented by immobilizing the enzyme on solid substrates. Transparent glass is especially advantageous over alternative immobilizing matrices, since it allows most of the emitted photons to be detected. We report a new method for luciferase immobilization on glass which does not require prior silanization and glutaraldehyde activation, thus saving preparation time and minimizing enzyme inactivation. Our method is based on the co-immobilization by adsorption of luciferase (from a firefly lantern extract) and poly-L-lysine (PL) on non-porous glass strips. Luciferase immobilized in this way exhibits minimal variations in intersample activity, high sensitivity for ATP detection (linear luminescence responses down to 50 nmol/L) and good stability (full activity for at least 60 days when stored at -80°C). PL-mediated immobilization of luciferase on glass strips provides an attractive strategy for the design of specific ATP biosensors, with potential in industry, environmental screening, medicine and biological research. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
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  • 129
    Digitale Medien
    Digitale Medien
    Antioxidant properties of bile salt micelles evaluated with different chemiluminescent assays: a possible physiological role (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 327-337 
    Details
    ISSN: 0884-3996
    Schlagwort(e): bile acids ; chemiluminescence ; superoxide ; antioxidants ; micelles ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The antioxidant activity of a representative series of free, glycine- and taurine-conjugated bile acids was evaluated by two different chemiluminescent assays: (a) the enhanced chemiluminescence system based on horseradish peroxidase and luminol/oxidant/enhancer reagent, and (b) the hypoxanthine/xanthine oxidase/Fe2+-EDTA/luminol system. Bile acids were studied at final concentrations ranging from 1 to 28 mmol/L. All of the bile acids studied inhibited the steady-state chemiluminescent reaction and the extent of inhibition depended upon the structure of the bile acids, whereas the duration was related to bile acid concentration. The mechanism of the light inhibition is probably due to trapping of oxygen free radicals generated in the chemiluminescent reactions, within bile acid micelles. The free radicals trapped into micelles reduced the formation of luminol radicals and consequently the light output; when the micelles were saturated, the oxygen free radicals in solution again produced luminol radicals. The micelle interaction with reactive oxygen species could be a physiological mechanism of defence against the toxicity of those species in the intestinal content. On the other hand, alterations in bile acid organ distribution, concentration and composition leads to a membrane damage caused by their detergent-like properties, which could be associated to oxygen free radical production. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
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  • 130
    Digitale Medien
    Digitale Medien
    LuxR controls the expression of Vibrio fischeri luxCDABE clone in Escherichia coli in the absence of luxI gene (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 365-369 
    Details
    ISSN: 0884-3996
    Schlagwort(e): Vibrio fischeri ; LuxR ; lux ; bioluminescence ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: We have recently suggested that the expression of V. fischeri right lux operon is initiated from two sites, the first located upstream of the luxI gene, while the second seems to be located upstream of the luxC gene. The transcription from both sites is negatively controlled by H-NS protein. E. coli MC4100 rpoS hns mutant harbouring the V. fischeri luxCDABE genes showed constitutive mode and 70,000-fold higher luminescence than the wild-type cells. The present study shows that the expression of luxCDABE genes in E. coli MC4100 wild-type cells is also controlled by LuxR protein in the absence of the autoinducer. The co-presence of a ptac-controlled luxR gene in a trans position to a plasmid carrying the luxCDABE genes resulted in 100,000 times higher luminescence. In the absence of the autoinducer, the presence of the luxR gene under its own regulated control resulted in about 100-200-fold increase of luminescence from the luxC upstream site. Taken together, it seems that the LuxR protein initiates the formation of the V. fischeri lux system cloned in E. coli from two sites located upstream and downstream of the luxI gene. Only the activation of the first site requires the presence of the autoinducer, whereas the second site is fully activated by LuxR protein in the absence of the autoinducer. © 1998 John Wiley & Sons, Ltd.
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  • 131
    Digitale Medien
    Digitale Medien
    Book Review: A Practical Guide to Industrial Uses of ATP  -  Luminescence in Rapid Microbiology. Edited by P. E. Stanley, R. Smither and W. J. Simpson. Cara Technology Ltd., Lingfield (1997), £58, ISBN 0 952 93450 7. (Available from CRTT Ltd., Cambridge. Fax: +44 1223 461777.) (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 113-113 
    Details
    ISSN: 0884-3996
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
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  • 132
    Digitale Medien
    Digitale Medien
    Preliminary studies of the enhanced electrochemiluminescence of 2,3-diaminonaphthalene in the presence of specific metal ions (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 139-145 
    Details
    ISSN: 0884-3996
    Schlagwort(e): electrochemiluminescence ; metal ions ; 2,3-diaminonaphthalene ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Electrochemiluminescence (ECL) of 200 ppm 2,3-diaminonaphthalene (2,3-DAN) was studied alone and in conjunction with 100 ppm of 34 different metal and non-metal ions and revealed three relatively intense ECL responses from interactions of 2,3-DAN with Au+, Fe+3 and V+5. ECL responses from Cr+6 or Ru+3 with 2,3-DAN were less intense, but noteworthy, as was the coloured fluorescent product of the non-metal ion Se+4 interaction with 2,3-DAN. Several intense 2,3-DAN-metal ion ECL reactions were studied in greater detail and revealed various titration curves with ionic detection limits in the low ppm range, using a fixed level (200 ppm) of 2,3-DAN. © 1998 John Wiley & Sons, Ltd.
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  • 133
    Digitale Medien
    Digitale Medien
    H-NS controls the transcription of three promoters of Vibrio fischeri lux cloned in Escherichia coli (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 185-188 
    Details
    ISSN: 0884-3996
    Schlagwort(e): Vibrio fischeri ; H-NS ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: We have recently proposed that the expression of V. fischeri right lux operon is controlled by two promoters; the first one located upstream of the luxI gene, while the second one seems to be located upstream of the luxC gene. The transcription from both promoters is negatively controlled by H-NS protein. Escherichia coli MC4100 rpoS hns mutant that carried the V. fischeri lux system with a deletion in either the luxI or luxR gene showed a constitutive mode and more than 10,000-fold higher luminescence than the control cells. The present study shows that neither luxR nor luxI are required for the transcription of the luxCDABE genes in an H-NS deficient strain of E. coli. The MC4100 rpoS hns mutant harbouring the luxCDABE-carrying plasmid showed constitutive mode and 70,000-fold higher luminescence than the wild-type cells. The question whether both the left and the right operons of V. fischeri lux system are controlled by H-NS was addressed with the aid of plasmids harbouring the lacZ gene fused with luxR or luxI. In MC4100 hns rpoS background, luxR and luxI genes were very early and actively transcribed, as judged by the strong β-galactosidase activity that was developed at early stage of growth. The β-galactosidase activity in the wild-type cells was 20-40 times lower and occurred mainly during the second half of the growth cycle. It thus appears that H-NS inhibits the transcription of three promoters of the lux system of V. fischeri; the left operon that codes for LuxR protein and two promoters located upstream and downstream to luxI gene. © 1998 John Wiley & Sons, Ltd.
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  • 134
    Digitale Medien
    Digitale Medien
    Preface (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 285-285 
    Details
    ISSN: 0884-3996
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: No abstract.
    Materialart: Digitale Medien
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  • 135
    Digitale Medien
    Digitale Medien
    Serum antioxidant capacity in healthy and diabetic subjects as determined by enhanced chemiluminescenceThis paper has not been peer reviewed (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 321-325 
    Details
    ISSN: 0884-3996
    Schlagwort(e): free radicals ; antioxidant ; total antioxidant capacity ; Trolox ; Insulin-dependent diabetes mellitus (IDDM) ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Free radicals are considered to be important factors involved in many physiopathological processes. Several methods have been proposed for studying the mechanisms of antioxidant protection against free radical-induced injury, including the measurement of the total antioxidant capacity (TAC) in body fluids, based on enhanced chemiluminescence. This technique is calibrated against Trolox™ and assay results are expressed as μmol/L of Trolox equivalents. Since many of the complications induced by diabetes appear to be mediated by oxygen free radical generation, we have investigated serum antioxidant capacity in a group of healthy subjects and in insulin-dependent diabetic (IDDM) subjects. A statistically significant difference was noticed in TAC values between the IDDM group and the young control group. Even if the biological meaning of this significant reduction in TAC remains to be explained, an overproduction of precursors of reactive oxygen free radicals and/or a decreased scavenger systems efficiency can be associated with the increased risk of atherosclerotic cardiovascular disease in diabetic patients. © 1998 John Wiley & Sons, Ltd.
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  • 136
    Digitale Medien
    Digitale Medien
    A new screening method to detect water-soluble antioxidants: acetaminophen (tylenol®) and other phenols react as antioxidants and destroy peroxynitrite-based luminol-dependent chemiluminescence (1998)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 13 (1998), S. 339-348 
    Details
    ISSN: 0884-3996
    Schlagwort(e): peroxynitrite ; antioxidants ; luminol ; acetaminophen ; phenols ; catecholamines ; norepinephrine ; isoproterenol ; epinephrine ; SIN-1 ; sydnonimines ; polyphenols ; catechins ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: This study is based on a simple chemical interaction of peroxynitrite (O=N—O—O-) and luminol, which produces blue light upon oxidation. Since peroxynitrite has a half-life of about 1 s, a drug known as linsidomine (SIN-1) is used as a peroxynitrite generator. Peroxynitrite can oxidize lipids, proteins and nucleic acids. Upon the stimulation of inflammation and/or infection, macrophages and neutrophils can be induced to produce large amounts of peroxynitrite, which can oxidize phenols and sulphhydryl-containing compounds. Therefore, phenols and sulphhydryls eliminate peroxynitrite. This is an example of the Yin-Yang hypothesis e.g. oxidation-reduction. Acetaminophen (Tylenol®) can inhibit fever and some types of pain without being a particularly effective anti-inflammatory. Since it is a phenol, it could act as a nitration target for peroxynitrite. Then peroxynitrite, the possible cause of pain and elevated temperature, might be destroyed in the reaction. Acetaminophen is a phenolic compound which produces a clear inhibitory dose-response curve with peroxynitrite in its range of clinical effectiveness. Whether acetaminophen actually works as we suggest is to be proven. Three different types of reaction could decrease the amount of peroxynitrite: (a) interference with base-catalysed opening of the SIN-1 molecule; (b) destruction of one or both substances needed to form it -  superoxide and/or nitric oxide; when the SIN-1 degrades to superoxide and nitric oxide, the former may be destroyed by superoxide dismutase (SOD); (c) peroxynitrite may react directly with phenols (mono-, di-, tri- and tetraphenols), possibly by nitration. Nordihydroguaiaretic acid and 2-hydroxyestradiol (catechol estrogen) are potent inhibitors of luminol light emission. Epineprine, isoproterenol, pyrogallol, catechol and ascorbic acid (a classic antioxidant) are all inhibitors of luminol chemiluminescence. Isoproterenol, norepinephrine/and epinephrine first inhibit light but overall stimulate the light production. Initially, SIN-1 degrades to produce peroxynitrite, which reacts with luminol to produce blue light. If any of three catecholamines are present with the reaction that produces light, there is an initial inhibition of light production, and then a marked stimulation. A possible reason for this is that these catechols are oxidized and the metabolized phenol stimulates the production of light from luminol. Also, during oxidation of catecholamines superoxide is sometimes formed, which could stimulate production of peroxynitrite. This simple screening system is introduced to find useful antioxidants against peroxynitrite. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 137
    Digitale Medien
    Digitale Medien
    Optimizing seeding and culture methods to engineer smooth muscle tissue on biodegradable polymer matrices (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 46-54 
    Details
    ISSN: 0006-3592
    Schlagwort(e): smooth muscle ; polyglycolic acid ; biodegradable ; tissue engineering ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The engineering of functional smooth muscle (SM) tissue is critical if one hopes to successfully replace the large number of tissues containing an SM component with engineered equivalents. This study reports on the effects of SM cell (SMC) seeding and culture conditions on the cellularity and composition of SM tissues engineered using biodegradable matrices (5 × 5 mm, 2-mm thick) of polyglycolic acid (PGA) fibers. Cells were seeded by injecting a cell suspension into polymer matrices in tissue culture dishes (static seeding), by stirring polymer matrices and a cell suspension in spinner flasks (stirred seeding), or by agitating polymer matrices and a cell suspension in tubes with an orbital shaker (agitated seeding). The density of SMCs adherent to these matrices was a function of cell concentration in the seeding solution, but under all conditions a larger number (approximately 1 order of magnitude) and more uniform distribution of SMCs adherent to the matrices were obtained with dynamic versus static seeding methods. The dynamic seeding methods, as compared to the static method, also ultimately resulted in new tissues that had a higher cellularity, more uniform cell distribution, and greater elastin deposition. The effects of culture conditions were next studied by culturing cell-polymer constructs in a stirred bioreactor versus static culture conditions. The stirred culture of SMC-seeded polymer matrices resulted in tissues with a cell density of 6.4 ± 0.8 × 108 cells/cm3 after 5 weeks, compared to 2.0 ± 1.1 × 108 cells/cm3 with static culture. The elastin and collagen synthesis rates and deposition within the engineered tissues were also increased by culture in the bioreactors. The elastin content after 5-week culture in the stirred bioreactor was 24 ± 3%, and both the elastin content and the cellularity of these tissues are comparable to those of native SM tissue. New tissues were also created in vivo when dynamically seeded polymer matrices were implanted in rats for various times. In summary, the system defined by these studies shows promise for engineering a tissue comparable in many respects to native SM. This engineered tissue may find clinical applications and provide a tool to study molecular mechanisms in vascular development. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 46-54, 1998.
    Zusätzliches Material: 8 Ill.
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  • 138
    Digitale Medien
    Digitale Medien
    Intracellular compounds quantification by means of flow cytometry in bacteria: Application to xanthan production by Xanthomonas campestris (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 87-94 
    Details
    ISSN: 0006-3592
    Schlagwort(e): flow cytometry ; spectrofluorymetry ; intracellular protein and nucleic acids quantification ; cell viability ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The use of flow cytometry (FCM) to quantitatively analyze intracellular compounds is studied. FCM is a very useful technique for individual cell studies in microbial systems, and gives access to information which cannot be obtained in any other way. Nevertheless, it provides data in arbitrary units, that is, relative data. This analytical technique could be employed for kinetic modeling of microbial systems and even for internal phenomena analysis, but for this purpose, absolute data - that is concentration of intracellular compounds - must be used.In this work, relative flow cytometry data are transformed into absolute data by means of calibrations employing the same fluorochromes with another technique: spectrofluorymetry. Calibrations of DNA, RNA, and protein intracellular concentrations are presented for the bacteria, Xanthomonas campestris. Other analytical methods, based on biochemical determinations, were also employed to quantify intracellular compounds, but the results obtained are very poor compared with those achieved by means of spectrofluorymetry (SFM). Calibration equations and data obtained by both techniques are given. Evolutions of protein and nucleic acids during Xanthomonas campestris growth and xanthan gum production are shown. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 87-94, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 139
    Digitale Medien
    Digitale Medien
    Ionic interactions in nanofiltration of β casein peptides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 109-117 
    Details
    ISSN: 0006-3592
    Schlagwort(e): nanofiltration ; selectivity ; inorganic membrane ; peptide ; pH ; ionic strength ; polyelectrolyte ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Nanofiltration (NF) membrane technology shows interesting potentials for separating organic components on the basis of solute charge and size in the range of 300-1000 g mol-1. Separation properties of two inorganic NF membranes were studied with a set of 10 small peptides (molecular mass range: 300-900 g mol-1; 3 〈 pI 〈 10) contained in a well-characterized tryptic β casein hydrolysate. Peptides transmission strongly depended on ionic interactions in the system. Physicochemical conditions such as ionic strength and especially pH were crucial to the separation, because the membrane and peptides showed amphoteric properties. Thus, the three categories of peptides (acid, basic, neutral) were separated according to their pI because of presumed concentration gradients of charged peptides at the membrane: positive for basic peptides and negative for acid peptides. At optimum pH 8 this led to high transmissions of basic peptides (even over 100%), intermediate transmissions for neutral peptides, and low transmissions for acid peptides. The addition of multicharged cationic and anionic species in the hydrolysate induced a markedly enhanced selectivity when the polyelectrolyte was a membrane coion and a complete reversion of selectivity when it was a membrane counterion. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 109-117, 1988.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 140
    Digitale Medien
    Digitale Medien
    Dynamic determination of anaerobic acetate kinetics using membrane mass spectrometry (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 127-135 
    Details
    ISSN: 0006-3592
    Schlagwort(e): membrane mass spectrometer ; kinetic measurements ; anaerobic biofilm ; acetate ; inhibition ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A small, stirred, 14.4-mL tank reactor was designed to serve as a measurement cell for short-term investigation of microbial kinetics. A mass spectrometer membrane probe allowed the measurement of the dissolved gases of hydrogen, methane, oxygen, and carbon dioxide. pH was measured by an electrode and controlled by addition of acid or alkali. The highly sensitive measurement of gases with low solubility allowed rapid measurements at very low conversion. In kinetic experiments, a stepwise increase of substrate concentration (method A) and continuous feed of substrate (method B) were used, allowing quick estimation of substrate kinetics. Acetate conversion in mixed culture biofilms from a fluidized bed reactor was investigated. Substrate inhibition was found to be negligible in the concentration range studied. Experiments at various pH values showed that the undissociated acid form was the kinetic determinant. Kinetic parameters for Haldane kinetics of protons were KSH = 1.3 × 10-5 mol m-3 and KIH = 8.1 × 10-3 mol m-3. With free acid (HAc) as the rate determining species, the kinetic parameters for method A were KSHAc = 0.005 mol m-3 and KIHAc = 100 mol m-3 and for method B were KSHAc = 0.2 mol m-3 and KIHAc = 50 mol m-3. The maximum biomass activity occurred at around pH 6.5. Acetate was exclusively converted to methane and CO2 at pH 〉 6. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 127-135, 1998.
    Zusätzliches Material: 6 Ill.
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  • 141
    Digitale Medien
    Digitale Medien
    Influence of hydrodynamic conditions on naphthalene dissolution and subsequent biodegradation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 145-154 
    Details
    ISSN: 0006-3592
    Schlagwort(e): bioavailability ; PAH ; biodegradation ; dissolution ; hydrodynamic ; mixing ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The influence of hydrodynamic conditions on the dissolution rate of crystalline naphthalene as a model polycyclic aromatic hydrocarbon (PAH) was studied in stirred batch reactors with varying impeller speeds. Mass transfer from naphthalene melts of different surface areas to the aqueous phase was measured and results were modeled according to the film theory. Results were generalized using dimensionless numbers (Reynolds, Schmidt, and Sherwood). In combined mass transfer and biodegradation experiments, the effect of hydrodynamic conditions on the degradation rate of naphthalene by Pseudomonas 8909N was studied. Experimental results were mathematically described using mass-transfer and microbiological models. The experiments allowed determination of mass-transfer and microbiological parameters separately in a single run. The biomass formation rate under mass transfer limited conditions, which is related to the naphthalene biodegradation rate, was correlated to the dimensionless Reynolds number, indicating increased bioavailability at increased mixing in the reactor liquid. The methodology presented in which mass transfer processes are quantified under sterile conditions followed by a biodegradation experiment can also be adapted to more complex and realistic systems, such as particulate, suspended PAH solids or soils with intrapartically sorbed contaminants when the appropriate mass-transfer equations are incorporated. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 145-154, 1998.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 142
    Digitale Medien
    Digitale Medien
    Agitator speed and dissolved oxygen effects in Xanthan fermentations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 198-210 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Xanthan fermentation ; agitator speed ; caverns ; dissolved oxygen ; specific oxygen uptake rate ; specific Xanthan production rate ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Agitation speed affects both the extent of motion in Xanthan fermentation broths because of their rheological complexity and the rate of oxygen transfer. The combination of these two effects causes the dissolved oxygen concentration and its spatial uniformity also to change with agitator speed. Separating these complex interactions has been achieved in this study in the following way. First, the influence of agitation speeds of 500 and 1000 rpm has been investigated at a constant nonlimiting dissolved oxygen concentration of 20% of air saturation using gas blending. Under these controlled dissolved oxygen conditions, the results demonstrate that the biological performance of the culture was independent of agitation speed as long as broth homogeneity could be ensured. With the development of increasing rheological complexity lending to stagnant regions at Xanthan concentrations 〉20 g/L, it is shown that the superior bulk mixing achieved at 1000 rpm, compared with 500 rpm, leading to an increased proportion of the cells in the fermentor to be metabolically active and hence higher microbial oxygen uptake rates, was responsible for the enhanced performance. Second, the effects of varying dissolved oxygen are compared with a control in each case with an agitator speed of 1000 rpm to ensure full motion, but with a fixed, nonlimiting dissolved oxygen of 20% air saturation. The specific oxygen uptake rate of the culture in the exponential phase, determined using steady-state gas analysis data, was found to be independent of dissolved oxygen above 6% air saturation, whereas the specific growth rate of the culture was not influenced by dissolved oxygen, even at levels as low as 3%, although a decrease in Xanthan production rate could be measured. In the production phase, the critical oxygen level was determined to be 6% to 10%, so that, below this value, both specific Xanthan production rate as well as specific oxygen uptake rate decreased significantly. In addition, it is shown that the dynamic method of oxygen uptake determination is unsuitable even for moderately viscous Xanthan broths. © 1998 John Wiley & Sons, Inc. Biotechnol. Bioeng. 57: 198-210, 1998.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 143
    Digitale Medien
    Digitale Medien
    Bilayer permeability-based substrate selectivity of an enzyme in liposomes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 216-219 
    Details
    ISSN: 0006-3592
    Schlagwort(e): liposomes ; vesicles ; microreactor ; permeability ; chymotrypsin ; enzyme ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Liposomes were prepared from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), which contained the water soluble proteinase α-chymotrypsin. This liposome entrapped enzyme showed selectivity for externally added substrates in that only small substrates (benzoyl-l-Tyr-p-nitroanilide or acetyl-l-Phe-p-nitro-anilide) - for which the liposome bilayer was permeable - were transformed into products. Large substrates (succinyl-l-Ala-l-Ala-l-Pro-l-Phe-p-nitroanilide or casein) could not penetrate from the external aqueous phase into the liposomes, and were not hydrolyzed. This substrate selectivity is entirely based on the compartimentation and permeability properties of the liposome microreactor. © 1998 John Wiley & Sons, Inc.Biotechnol. Bioeng. 57: 216-219, 1998.
    Zusätzliches Material: 5 Ill.
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  • 144
    Digitale Medien
    Digitale Medien
    The primary production of an infectious recombinant Herpes Simplex Virus vaccine (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 262-271 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Herpes Simplex Virus type 2 ; DISC HSV-2 ; heparin ; dextran sulphate ; cell rupture ; virus release ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The production and extracellular release of a recombinant Herpes Simplex Virus (type 2) from monolayers of infected complementing Vero cells (CR2) are addressed. Growth and virus production conditions are identified that provide adequate virus titers with cell seeding densities and viral multiplicities of infection that could be reasonably handled in manufacturing. Harvesting by sonication of cell monolayers is shown to give the highest recovery of infectious virus (to 2.5 × 106 pfu/mL) but leads to process stream contamination by cellular proteins through the rupturing of cells (to 28 pg protein/pfu). By comparison, freeze-thaw cycles and osmotic rupture by hypotonic saline or glycerol shock procedures yield only low virus recovery (typically 〈10% of that by sonication), and are accompanied by yet higher levels of protein contamination (up to 30-fold higher pg protein/pfu). Addition of the polyanionic polymers, heparin or dextran sulphate to a harvest using either hypotonic saline, glycerol shock or isotonic phosphate buffered saline increased the yield of infectious virus in the supernatant. By contrast, addition of polycationic poly-l-lysine resulted in negligible increase in the supernatant virus titer. The highest virus titers (4.7 × 107 pfu/mL) were achieved following treatment of roller bottle cultured cells displaying a high cytopathic effect with heparin at 50 μg/mL for at least 3 h post harvest. This procedure also gave the lowest levels of protein contamination (〈2 pg protein/pfu). The fivefold lower yield of infectious virus from cultures displaying a low cytopathic effect (〈70% CPE) indicates the importance of cell physiological state at harvest. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 262-271, 1998.
    Zusätzliches Material: 8 Ill.
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  • 145
    Digitale Medien
    Digitale Medien
    Retention and regeneration of native NAD(H) in noncharged ultrafiltration membrane reactors: Application to l-lactate and gluconate production (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 510-517 
    Details
    ISSN: 0006-3592
    Schlagwort(e): NAD(H) retention ; coenzyme regeneration ; coupled reactions ; glucose dehydrogenase ; lactate dehydrogenase ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: NAD(H) was retained in a noncharged ultrafiltration membrane reactor for the simultaneous and continuous production of l-lactate and gluconate with coenzyme regeneration. Polyethyleneimine (PEI), a 50-kDa cationic polymer, achieved coenzyme retentions above 0.8 for PEI/NAD(H) molar ratios higher than 5. The ionic strength of the inlet medium caused a decrease of NAD(H) retention that can be counterbalanced by an initial addition of 1% bovine serum albumin (BSA). Continuous reactor performance in the presence of PEI and BSA showed that NAD(H), glucose dehydrogenase, and lactate dehydrogenase were retained by 10-kDa ultrafiltration membranes; l-lactate and gluconate were produced at conversions higher than 95%. PEI enhanced the thermal stability of the enzymes used and increased the catalytic efficiency of glucose dehydrogenase, while no effect was found on the kinetic parameters of lactate dehydrogenase. A model that implements the kinetic equations of the two enzymes describes the reactor behavior satisfactorily. In brief, the use of PEI to retain NAD(H) is a new interesting approach to be widely applied in continuous synthesis with the large number of known dehydrogenases. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 510-517, 1998.
    Zusätzliches Material: 9 Ill.
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  • 146
    Digitale Medien
    Digitale Medien
    Oscillation characteristics of biofilm streamers in turbulent flowing water as related to drag and pressure drop (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 536-544 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biofilm ; streamers ; biofouling ; drag ; fast Fourier transform analysis ; hydrodynamics ; oscillations ; pressure drop ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Mixed population biofilms consisting of Pseudomonas aeruginosa, P. fluorescens, and Klebsiella pneumoniae were grown in a flow cell under turbulent conditions with a water flow velocity of 18 cm/s (Reynolds number, Re, =1192). After 7 days the biofilms were patchy and consisted of cell clusters and streamers (filamentous structures attached to the downstream edge of the clusters) separated by interstitial channels. The cell clusters ranged in size from 25 to 750 μm in diameter. The largest clusters were approximately 85 μm thick. The streamers, which were up to 3 mm long, oscillated laterally in the flow. The motion of the streamers was recorded at various flow velocities up to 50.5 cm/s (Re 3351) using confocal scanning laser microscopy. The resulting time traces were evaluated by image analysis and fast Fourier transform analysis (FFT). The amplitude of the motion increased with flow velocity in a sigmoidal shaped curve, reaching a plateau at an average fluid flow velocity of approximately 25 cm/s (Re 1656). The motion of the streamers was possibly limited by the flexibility of the biofilm material. FFT indicated that the frequency of oscillation was directly proportional to the average flow velocity (u(ave)) below 9.5 cm/s (Re 629). At u(ave) greater than 9.5 cm/s, oscillation frequencies were above our measurable frequency range (0.12-6.7 Hz). The oscillation frequency was related to the flow velocity by the Strouhal relationship, suggesting that the oscillations were possibly caused by vortex shedding from the upstream biofilm clusters. A loss coefficient (k) was used to assess the influence of biofilm accumulation on pressure drop. The k across the flow cell colonized with biofilm was 2.2 times greater than the k across a clean flow cell. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 536-544, 1998.
    Zusätzliches Material: 7 Ill.
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  • 147
    Digitale Medien
    Digitale Medien
    Rational engineering of the TOL meta-cleavage pathway (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 240-249 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biochemical systems theory ; BST ; metabolic control analysis ; MCA ; TOL ; catechol-2,3-dioxygenase ; C23O ; toluate-1,2-dioxygenase ; TO ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The meta-cleavage pathway of Pseudomonas putida mt-2 was simulated using a biochemical systems simulation developed by Regan (1996). A non-competitive inhibition term for catechol-2,3-dioxygenase (C23O) by 2-OH-pent-2,4-dienoate (Ki = 150 μM) was incorporated into the model. The simulation predicted steady state accumulation levels in the μM range for metabolites pre-meta-cleavage, and in the mM range for metabolites post-meta-cleavage. The logarithmic gains L[V-i, Xj] and L[X-i, Xj] clearly indicated that the pathway was most sensitive to the concentration of the starting substrate, benzoate, and the first enzyme of the pathway, toluate-1,2-dioxygenase (TO). The simulation was validated experimentally; it was found that the amplification of TO increased the steady state flux from 0.024 to 0.091 (mmol/g cell dwt)/h. This resulted in an increased accumulation of a number of the pathway metabolites (intra- and extracellularly), especially cis-diol, 4-OH-2-oxovalerate, and 4-oxalocrotonate. Metabolic control analysis indicated that C23O was, in fact, the major controling enzymic step of the pathway with a scaled control coefficient of 0.83. The amplification of TO resulted in a shift of some of the control away from C23O. Catechol-2,3-dioxygenase, however, remained as the major controling element of the pathway. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:240-249, 1998.
    Zusätzliches Material: 11 Ill.
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  • 148
    Digitale Medien
    Digitale Medien
    In vivo 13C-NMR studies of polymer synthesis in Rhizobium meliloti M5N1 strain (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 250-253 
    Details
    ISSN: 0006-3592
    Schlagwort(e): in vivo 13C-NMR ; Rhizobium meliloti ; polymer biosynthesis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The use of in vivo 13C-NMR approach for the monitoring of the synthesis of various polymers within cells of Rhizobium meliloti (M5N1 strain) is reported. Significant differences in polymer biosynthesis have been shown as a function of the metabolic state of the cells and the labeled carbon source used. Consumption of carbon source and produced glycogen was complete with mid-exponential phase harvested cells. This was not the case with stationary phase harvested cells, for which polyhydroxybutyrate synthesis was higher and gluconate synthesis was lower than the former. [1-13C]fructose-grown cells produced more exopolysaccharide and polyhydroxybutyrate, but less β-(1,2) glucan and gluconate than [1-13C]glucose-grown cells. This approach offers a suitable tool to examine the kinetics of polymer biosynthesis by Rhizobia. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:250-253, 1998.
    Zusätzliches Material: 3 Ill.
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  • 149
    Digitale Medien
    Digitale Medien
    Metabolite-balancing techniques vs. 13C tracer experiments to determine metabolic fluxes in hybridoma cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 258-262 
    Details
    ISSN: 0006-3592
    Schlagwort(e): mass balance ; metabolic flux ; 13C tracer ; NMR spectroscopy ; mass spectroscopy ; hybridoma ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The estimation of intracellular fluxes of mammalian cells using only mass balances of the relevant metabolites is not possible because the set of linear equations defined by these mass balances is underdetermined. In order to quantify fluxes in cyclic pathways the mass balance equations can be complemented with several constraints: (1) the mass balances of co-metabolites, such as ATP or NAD(P)H, (2) linear objective functions, (3) flux data obtained by isotopic-tracer experiments. Here, these three methods are compared for the analysis of fluxes in the primary metabolism of continuously cultured hybridoma cells. The significance of different theoretical constraints and different objective functions is discussed after comparing their resulting flux distributions to the fluxes determined using 13CO2 and 13C-lactate measurements of 1 - 13C-glucose-fed hybridoma cells. Metabolic fluxes estimated using the objective functions “maximize ATP” and “maximize NADH” are relatively similar to the experimentally determined fluxes. This is consistent with the observation that cancer cells, such as hybridomas, are metabolically hyperactive, and produce ATP and NADH regardless of the need for these cofactors. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:258-262, 1998.
    Zusätzliches Material: 4 Ill.
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  • 150
    Digitale Medien
    Digitale Medien
    Quantitative enzymatic production of 6-O -acylglucose esters (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 505-509 
    Details
    ISSN: 0006-3592
    Schlagwort(e): lipases ; Candida antarctica lipase ; emulsifiers ; food additives ; glucose ; surfactants ; synthesis in organic solvents ; glucose fatty acid esters ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Selective production of emulsifiers from glucose and fatty acids has been achieved using an immobilized Candida antarctica lipase. Optimization of process selectivity considers the solubilities of the sugar and its monoesters in acetone at different temperatures, the percentage of this organic solvent in the reaction mixture, and the reaction temperature. The solvent (acetone) is both easily eliminated and accepted by the European Community for use in the manufacture of foods and/or food additives. Different fatty acids with a longer length chain than that of caprylic acid may be employed. For saturated fatty acids longer than lauric acid, continuous precipitation of the monoester as it is formed at 40°C permits nearly complete conversion (98%) of glucose to the monoester within 2-3 days. The procedure does not require total dissolution of the sugar, and precipitation of the monoester permits selective conversion of charges of glucose higher than 100 mg/mL solvent. A scaleup of the process under the optimum conditions gives high yields of 6-O-lauroyl glucose, which may be readily prepared on a gram scale. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 505-509, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 151
    Digitale Medien
    Digitale Medien
    Resistance of biofilms to the catalase inhibitor 3-amino-1,2,4-triazole (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 156-162 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Pseudomonas aeruginosa ; Pseudomonas fluorescens ; Klebsiella pneumoniae ; 3-amino-1,2,4-triazole ; catalase ; hydrogen peroxide ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Consortia of catalase positive bacteria consisting of Pseudomonas aeruginosa, Pseudomonas fluorescens, and Klebsiella pneumoniae, in both the planktonic form and as biofilms, disproportionate hydrogen peroxide into oxygen and water. The biofilm, however, continued to disproportionate the hydrogen peroxide in the presence of the catalase inhibitor, 3-amino-1,2,4-triazole, while the planktonic organisms did not. While the bacterial catalase-peroxidase-dismutase system was probably responsible for the disproportionation of hydrogen peroxide in both cases, biofilms resisted inhibition of this enzyme system. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 156-162, 1998.
    Zusätzliches Material: 6 Ill.
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  • 152
    Digitale Medien
    Digitale Medien
    Probing residue-level unfolding during lysozyme precipitation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 144-155 
    Details
    ISSN: 0006-3592
    Schlagwort(e): lysozyme ; protein precipitation ; thiocyanate ; hydrogen exchange ; nuclear magnetic resonance ; protein unfolding ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We have employed nuclear magnetic resonance (NMR) measurements of hydrogen exchange to identify residue-level conformational changes in hen egg white lysozyme (HEWL) as induced by salt precipitation. Deuterated HEWL was dissolved into a phosphate (H2O) buffer and precipitated at pH 2.1 upon addition of solid KSCN or (ND4)2SO4, allowing isotope labeling of unfolded regions. After 1 h, each precipitate was then dissolved at pH 3.8 to initiate refolding and preserve labeling and subsequently purified for NMR analysis. HEWL precipitated by 1.0 M KSCN exhibited increased hydrogen exchange at 14 residues out of 42 normally well-protected in the native state. Of the affected residues, 9 were situated in the β-sheet/loop domain. A similar, though less extensive, effect was observed at 0.2 M KSCN. Precipitation by 1.2 M (ND4)2SO4 resulted in none of the changes detected with KSCN. The popularity of ammonium sulfate as a precipitant is thus supported by this observed preservation of structural integrity. KSCN, in comparison, produced partial unfolding of specific regions in HEWL due most likely to known preferential interactions between -SCN and proteins. The severity of unfolding increased with KSCN concentration such that, at 1.0 M KSCN, almost the entire β-sheet/loop domain of HEWL was disrupted. Even so, a portion of the HEWL core encompassed by three α-helices remained intact, possibly facilitating precipitate dissolution. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 144-155, 1998.
    Zusätzliches Material: 6 Ill.
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  • 153
    Digitale Medien
    Digitale Medien
    Alcohol inhibition and specificity studies of lipase B from Candida antarctica in organic solvents (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 163-170 
    Details
    ISSN: 0006-3592
    Schlagwort(e): enzymes ; organic solvents ; alcohol inhibition ; activity coefficients ; substrate specificity ; rate-limiting step ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Alcohol inhibition of the lipase B from Candida antarctica has been studied through two different approaches: using the same inhibitor (1-butanol) in different organic solvents and using different inhibitors (differing in chain length) in the same solvent. The competitive inhibition constant values obtained in each case correlate with the calculated activity coefficients of the substrate, suggesting that desolvation of the alcohol is the major force changed. Data dispersion observed using the second approach has been interpreted to come from contributions of enzyme-inhibitor interactions to the binding energy. On the other hand, deacylation has been found to be much less influenced by the solvent variation than the acylation step, despite of the fact that solvation of the substrate involved in this step (the alcohol) is expected to change more than for the ester. Concerning the specificity behavior of the enzyme, a bimodal pattern was observed for the deacylation rate dependence on the alcohol chain length, with the highest values for hexanol (C6) and decanol (C10). With regard to the ester specificity, ethyl caproate (C6) is the preferred one. These results have been confronted with those reported for the lipase from Candida rugosa. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 163-170, 1998.
    Zusätzliches Material: 5 Ill.
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  • 154
    Digitale Medien
    Digitale Medien
    Enantioselective hydroxylation of 4-alkylphenols by vanillyl alcohol oxidase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 171-177 
    Details
    ISSN: 0006-3592
    Schlagwort(e): 4-alkylphenols ; vanillyl alcohol oxidase ; covalent flavoprotein ; enantioselectivity ; 4-vinylphenol ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Vanillyl alcohol oxidase (VAO) from Penicillium simplicissimum catalyzes the enantioselective hydroxylation of 4-ethylphenol, 4-propylphenol, and 2-methoxy-4-propylphenol into 1-(4′-hydroxyphenyl)ethanol, 1-(4′-hydroxyphenyl)propanol, and 1-(4′-hydroxy-3′-methoxyphenyl)propanol, respectively, with an ee of 94% for the R enantiomer. The stereochemical outcome of the reactions was established by comparing the chiral GC retention times of the products to those of chiral alcohols obtained by the action of the lipases from Candida antarctica and Pseudomonas cepacia. Isotope labeling experiments revealed that the oxygen atom incorporated into the alcoholic products is derived from water. During the VAO-mediated conversion of 4-ethylphenol/4-propylphenol, 4-vinylphenol/4-propenylphenol are formed as side products. With 2-methoxy-4-propylphenol as a substrate, this competing side reaction is nearly abolished, resulting in less than 1% of the vinylic product, isoeugenol. The VAO-mediated conversion of 4-alkylphenols also results in small amounts of phenolic ketones indicative for a consecutive oxidation step. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:171-177, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 155
    Digitale Medien
    Digitale Medien
    Analysis and simulation of complex interactions during dynamic microfiltration of Escherichia coli suspensions (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 189-202 
    Details
    ISSN: 0006-3592
    Schlagwort(e): artificial neural network (ANN) ; microfiltration ; cell harvesting ; membrane fouling ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Microfiltration is an important unit operation in downstream processing. However, due to the influence of membrane fouling, prediction of the filtration performance for biological suspensions is difficult. This paper describes a modeling approach that allows a comprehensive description of filtration performance. On the basis of experimental data and linguistic information, a specific artificial neural network was developed that predicts the process behavior within a certain range of parameters. This approach allows us to analyze influences of fermentation on filtration. By using extensive simulations, the interactions of 17 parameters were examined and the fouling causes determined. The model was developed for cell harvesting of Escherichia coli through a shear-enhanced module. The method can be applied to any cross-flow filtration process. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:189-202, 1998.
    Zusätzliches Material: 15 Ill.
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  • 156
    Digitale Medien
    Digitale Medien
    Optimising fed-batch production of recombinant proteins using the baculovirus expression vector system (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 178-188 
    Details
    ISSN: 0006-3592
    Schlagwort(e): fed-batch culture ; response surface model ; optimisation ; β-galactosidase ; Sf9 cells ; baculovirus expression vector system ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Fed-batch culture can offer significant improvement in recombinant protein production compared to batch culture in the baculovirus expression vector system (BEVS), as shown by Nguyen et al. (1993) and Bedard et al. (1994) among others. However, a thorough analysis of fed-batch culture to determine its limits in improving recombinant protein production over batch culture has yet to be performed. In this work, this issue is addressed by the optimisation of single-addition fed-batch culture. This type of fed-batch culture involves the manual addition of a multi-component nutrient feed to batch culture before infection with the baculovirus. The nutrient feed consists of yeastolate ultrafiltrate, lipids, amino acids, vitamins, trace elements, and glucose, which were added to batch cultures of Spodoptera frugiperda (Sf9) cells before infection with a recombinant Autographa californica nuclear polyhedrosis virus (AcNPV) expressing β-galactosidase (β-Gal). The fed-batch production of β-Gal was optimised using response surface methods (RSM). The optimisation was performed in two stages, starting with a screening procedure to determine the most important variables and ending with a central-composite experiment to obtain a response surface model of volumetric β-Gal production. The predicted optimum volumetric yield of β-Gal in fed-batch culture was 2.4-fold that of the best yields in batch culture. This result was confirmed by a statistical analysis of the best fed-batch and batch data (with average β-Gal yields of 1.2 and 0.5 g/L, respectively) obtained from this laboratory. The response surface model generated can be used to design a more economical fed-batch operation, in which nutrient feed volumes are minimised while maintaining acceptable improvements in β-Gal yield. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 178-188, 1998.
    Zusätzliches Material: 2 Ill.
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  • 157
    Digitale Medien
    Digitale Medien
    Quantitating secretion rates of individual cells: Design of secretion assays (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 214-226 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; diffusion ; encapsulation ; secretion ; screening ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: To observe events occurring in the microenvironment surrounding individual cells, a mathematical framework has been developed describing the behavior of a compound following its secretion by a single cell. This description is based on the diffusional and binding processes taking place in the vicinity of the cell surface. It allows prediction of the rate of capture and accumulation of a secreted compound around a single cell. This concept provides the basis for the design of two experimental assays for measuring single-cell secretion rates: (1) Cells are immobilized in hydrogel microbeads which contain capture sites for the secreted compound; and (2) artificial receptors are bound directly to the cell surface which are capable of binding molecules secreted by individual cells. This general methodology is developed in the specific case of the model organism Saccharomyces cerevisiae secreting a heterologous protein, but can be applied to any cell/secreted protein combination. Binding studies have shown that approximately 2 × 105 of these artificial receptors can be attached to the surface of a single yeast cell. At this surface density of a putative artificial receptor, it is predicted that single-cell secretion rates of 47 molecules/cell/sec of a 150 kDa protein can be detected. Simulations indicate that a microbead loaded with 5 × 106 capture antibodies will result in detection of secretion of this protein at rates as low as 4 molecules/cell/sec. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 214-226, 1998.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 158
    Digitale Medien
    Digitale Medien
    Metabolic design: How to engineer a living cell to desired metabolite concentrations and fluxes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 239-247 
    Details
    ISSN: 0006-3592
    Schlagwort(e): metabolic design analysis ; gene engineering ; biochemical reaction networks ; modular/top-down approach ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A biotechnological aim of genetic engineering is to increase the intracellular concentration or secretion of valuable compounds, while making the other concentrations and fluxes optimal for viability and productivity. Efforts to accomplish this based on over-expression of the enzyme, catalyzing the so-called “rate-limiting step,” have not been successful. Here we develop a method to determine the enzyme concentrations that are required to achieve such an aim. This method is called Metabolic Design Analysis and is based on the perturbation method and the modular (“top-down”) approach - formalisms that were first developed for the analysis of biochemical regulation such as, Metabolic Control Analysis. Contrary to earlier methods, the desired alterations of cellular metabolism need not be small or confined to a single metabolite or flux. The limits to the alterations of fluxes and metabolite concentrations are identified. To employ Metabolic Design Analysis, only limited kinetic information concerning the pathway enzymes is needed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 239-247, 1998.
    Zusätzliches Material: 1 Ill.
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  • 159
    Digitale Medien
    Digitale Medien
    Metabolic capacity of Bacillus subtilis for the production of purine nucleosides, riboflavin, and folic acid (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 227-238 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Bacillus subtilis ; folic acid ; metabolic engineering ; metabolic fluxes ; purine nucleosides ; riboflavin ; stoichiometric model ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We developed a stoichiometric model of Bacillus subtilis metabolism for quantitative analysis of theoretical growth and biochemicals production capacity. This work concentrated on biochemicals that are derived from the purine biosynthesis pathway; inosine, guanosine, riboflavin, and folic acid. These are examples of commercially relevant biochemicals for which Bacillus species are commonly used production hosts. Two previously unrecognized, but highly desirable properties of good producers of purine pathway-related biochemicals have been identified for optimally engineered product biosynthesis; high capacity for reoxidation of NADPH and high bioenergetic efficiency. Reoxidation of NADPH, through the transhydrogenase or otherwise, appears to be particularly important for growth on glucose, as deduced from the corresponding optimal carbon flux distribution. The importance of cellular energetics on optimal performance was quantitatively assessed by including a bioenergetic efficiency parameter as an unrestricted, ATP dissipating flux in the simulations. An estimate for the bioenergetic efficiency was generated by fitting the model to experimentally determined growth yields. The results show that the maximum theoretical yields of all products studied are limited by pathway stoichiometry at high bioenergetic efficiencies. Simulations with the estimated bioenergetic efficiency of B. subtilis, growing under glucose-limiting conditions, indicate that the yield of these biochemicals is primarily limited by energy and thus is very sensitive to the process conditions. The maximum yields that can reasonably be expected with B. subtilis on glucose were estimated to be 0.343, 0.160, and 0.161 (mol product/mol glucose) for purine nucleosides, riboflavin, and folic acid, respectively. Potential strategies for improving these maximum yields are discussed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 227-238, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 160
    Digitale Medien
    Digitale Medien
    Catabolite repression mutants of Saccharomyces cerevisiae show altered fermentative metabolism as well as cell cycle behavior in glucose-limited chemostat cultures (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 203-213 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; cell cycle behavior ; catabolite repression mutants ; CDC28 expression ; G1 length ; chemostat and batch cultures ; Metabolic Control Analysis ; glycolysis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In glucose-limited continuous cultures, a Crabtree positive yeast such as Saccharomyces cerevisiae displays respiratory metabolism at low dilution rates (D) and respiro-fermentative metabolism at high D. We have studied the onset of ethanol production and cell cycle behavior in glucose-limited chemostat cultures of the wild type S. cerevisiae strain CEN.PK122 (WT) and isogenic mutants, snf1 (cat1) and snf4 (cat3) defective in proteins involved in catabolite derepression and the mutant in glucose repression mig1 (cat4).The triggering of fermentative metabolism was dependent upon catabolite repression properties of yeast and was coincident with a significant decrease of G1 length. WT cells of the strain CEN.PK122 displayed respiratory metabolism up to a D of 0.2 h-1 and exhibited longer G1 lengths than the snf1 and snf4 mutants that started fermenting after a D of 0.1 and 0.15 h-1, respectively. The catabolite derepression mutant snf4 showed a significant decrease in the duration of G1 with respect to the WT. An increase of 300% to 400% in the expression of CDC28 (CDC28-lacZ) with a noticeable shortening in G1 to values lower than ∼150 min, was detected in the transformed wild type CEN.SC13-9B in glucose-limited chemostat cultures. The expression of CDC28-lacZ was analyzed in the wild type and isogenic mutant strains growing at maximal rate on glucose or in the presence of ethanol or glycerol. Two- to three-fold lower expression of the CDC28-lacZ fusion gene was detected in the snf1 or snf4 disruptants with respect to the WT and mig1 strains in the presence of all carbon sources. This effect was further shown to be growth rate-dependent exhibiting apparently, a threshold effect in the expression of the fusion gene with respect to the length of G1, similar to that shown in chemostat cultures.At the onset of fermentation, the control of the glycolytic flux was highly distributed between the uptake, hexokinase, and phosphofructokinase steps. Particularly interesting was the fact that the snf1 mutant exhibited the lowest fluxes of ethanol production, the highest of respiration and correspondingly, the branch to the tricarboxylic acid cycle was significantly rate-controling of glycolysis. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 203-213, 1998.
    Zusätzliches Material: 6 Ill.
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  • 161
    Digitale Medien
    Digitale Medien
    I. Study of protein aggregation due to heat denaturation: A structural approach using circular dichroism spectroscopy, nuclear magnetic resonance, and static light scattering (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 273-280 
    Details
    ISSN: 0006-3592
    Schlagwort(e): heat denaturation ; protein aggregation ; RNase A ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The objective of this study was to investigate the relationship between oxidized RNase A protein structure and the occurrence of protein aggregation using several spectroscopic techniques. Circular dichroism spectroscopy (CD) measurements taken at small temperature intervals were used to determine the protein's melting temperature, Tm, of approximately 65°C in deionized water. A more detailed examination of the protein structure was undertaken at several temperatures around Tm using near- and far-UV CD and one-dimensional nuclear magnetic resonance (NMR) measurements. These measurements revealed the presence of folded structures at 55°C and below, while denatured structures appeared at 65°C and above. Concurrent static light scattering (SLS) measurements, employed to detect the presence of RNase A aggregates, showed that RNase A aggregation was observed at 65°C and above, when much of the protein was denatured. Subsequent NMR time-course data demonstrated that aggregates forming at 75°C and pH 7.8 were indeed derived from heat-denatured protein. However, aggregation was also detected at 55°C when the spectroscopic data suggested the protein was present predominantly in the folded configuration. In contrast, heat denaturation did not lead to RNase A aggregation in a very acidic environment. We attribute this phenomenon to the effect of charge-charge repulsion between the highly protonated RNase A molecules in very acidic pH. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:273-280, 1998.
    Zusätzliches Material: 8 Ill.
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  • 162
    Digitale Medien
    Digitale Medien
    On the performance of a hollow-fiber bioreactor for acidolysis catalyzed by immobilized lipase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 114-123 
    Details
    ISSN: 0006-3592
    Schlagwort(e): batch-stirred tank reactor ; interesterification ; immobilized enzyme ; butterfat ; membrane bioreactor ; Mucor javanicus ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The present communication describes the chemical modification of anhydrous butterfat by interesterification with oleic acid catalyzed by a lipase of Mucor javanicus. Two reactor configurations were tested, a batch-stirred tank reactor containing suspended lipase and a batch-stirred tank reactor in combination with a hollow-fiber membrane module containing adsorbed lipase. The goal of this research was to assess the advantage of using a (hydrophobic) porous support to immobilize the lipase in attempts to engineer butterfat with increased levels of unsaturated fatty acid residues (oleic acid) at the expense of medium-to-long chain saturated fatty acids (myristic and palmitic acids). Reactions were carried out at 40°C in the absence of solvent under controlled water activity, and were monitored by chromatographic assays for free fatty acids. The results obtained indicate that the rate of interesterification using the proposed reactor configuration is enhanced by a factor above 100 relative to that using suspended lipase, for the same protein mass basis. Although hydrolysis of butterfat occurred to some degree, the enzymatic process that uses the hollow-fiber reactor was technically superior to the stirred tank system. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 114-123, 1998.
    Zusätzliches Material: 5 Ill.
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  • 163
    Digitale Medien
    Digitale Medien
    Analysis of cell cycle activity and population dynamics in heterogeneous plant cell suspensions using flow cytometry (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 515-528 
    Details
    ISSN: 0006-3592
    Schlagwort(e): flow cytometry ; plant cell culture ; bromodeoxyuridine ; cell cycle ; hydrodynamic shear ; temperature effects ; Solanum aviculare ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Flow cytometry was used to measure cell cycle parameters in Solanum aviculare plant cell suspensions. Methods for bromodeoxyuridine (BrdU) labeling of plant nuclei were developed so that cell cycle times and the proportion of cells participating in growth could be determined as a function of culture time and conditions. The percentage of cells active in the cell cycle at 25°C decreased from 52% to 19% within 7.6 d of culture; presence of a relatively large proportion of non-active cells was reflected in the results for culture growth. While the maximum specific growth rate of the suspensions at 25°C was 0.34 d-1 (doubling time: 2.0 d), the specific growth rate of active cells was significantly greater at 0.67 d-1, corresponding to a cell cycle time of 1.0 d. A simple model of culture growth based on exponential and linear growth kinetics and the assumption of constant cell cycle time was found to predict with reasonable accuracy the proportion of active cells in the population as a function of time. Reducing the temperature to 17°C lowered the culture growth rate but prolonged the exponential growth phase compared with 25°C; the percentage of cells participating in the cell cycle was also higher. Exposure of plant cells to different agitation intensities in shake flasks had a pronounced effect on the distribution of cells within the cell cycle. The proportion of cells in S phase was 1.8 times higher at a shaker speed of 160 rpm than at 100 rpm, while the frequency of G0 + G1 cells decreased by up to 27%. Because of the significant levels of intraculture heterogeneity in suspended plant cell systems, flow cytometry is of particular value in characterizing culture properties and behavior. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 515-528, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 164
    Digitale Medien
    Digitale Medien
    Directed evolution of an esterase for the stereoselective resolution of a key intermediate in the synthesis of epothilones (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 554-559 
    Details
    ISSN: 0006-3592
    Schlagwort(e): directed evolution ; esterase ; epothilon ; Pseudomonas fluorescens ; stereoselectivity ; mutator strain ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The directed evolution of an esterase from Pseudomonas fluorescens using the mutator strain Epicurian coli XL1-Red was investigated. Mutants were assayed for their ability to hydrolyze a sterically hindered 3-hydroxy ester, which can serve as a building block in the synthesis of epothilones. Screening was performed by plating esterase producing colonies derived from mutation cycles onto minimal media agar plates containing indicator substances (neutral red and crystal violet). Esterase-catalyzed hydrolysis of the 3-hydroxy ester (ethyl or glycerol ester) was detected by the formation of a red color due to a pH decrease caused by the released acid. Esterases isolated from positive clones were used in preparative biotransformations of the ethyl ester. One variant containing two mutations (A209D and L181V) stereoselectively hydrolyzed the ethyl ester resulting in 25% ee for the remaining ester. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 554-559, 1998.
    Zusätzliches Material: 2 Ill.
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  • 165
    Digitale Medien
    Digitale Medien
    Solubilization of subtilisin in CO2 using fluoroether-functional amphiphiles (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 572-580 
    Details
    ISSN: 0006-3592
    Schlagwort(e): fluoroether surfactants ; liquid CO2 ; high pressure ; emulsion ; solubilization ; subtilisin Carlsberg ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Carbon dioxide is a naturally abundant, environmentally benign solvent whose use, like water, in a process is not regulated by either EPA or FDA. Unfortunately, polar compounds such as amino acids and proteins are essentially insoluble in carbon dioxide. Further, alkyl-functional surfactants, which have been shown to allow extraction of proteins into conventional organic solvents, exhibit very poor or negligible solubility in CO2 at pressures below 50 MPa. Consequently, highly CO2-soluble fluoroether-functional surfactants have been generated and used to solubilize subtilisin Carlsberg from aqueous buffer and cell culture medium into CO2, with recovery accomplished by depressurization. Both the amount of protein solubilized in the emulsion and the extent of activity retention by the protein following recovery are functions of the initial protein concentration in the buffer. This, plus the observation that the presence of protein affects the stability of the emulsion, suggests that some of the protein is sacrificed to act as a stabilizer in these systems. In addition to solubilization via an inverse emulsion, it has also been shown that one can strip protein-surfactant aggregates from a middle phase emulsion using pure CO2, suggesting an ion-pairing type mechanism. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 572-580, 1998.
    Zusätzliches Material: 7 Ill.
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  • 166
    Digitale Medien
    Digitale Medien
    Microporous microparticles designed as stable immunoadsorbents (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 581-586 
    Details
    ISSN: 0006-3592
    Schlagwort(e): apolipoprotein B ; immunoadsorbent ; microencapsulation ; affinity chromatography ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We have developed a solid-phase immunoadsorbent based on encapsulated goat anti-apolipoprotein B polyclonal antibodies previously crosslinked with a 0.25% glutaraldehyde solution, and designed to remove by immunoaffinity the excess of apolipoproteins B from the plasma of patients affected by familial hypercholesterolemia. Compared to a classical immunoadsorbent prepared by activation of Sepharose CL-4B with cyanogen bromide, the resulting immunoadsorbent exhibits both optimal adsorption capacity and stability over the entire range of chemical and biochemical conditions during its practical handling. This approach will serve as a model system to demonstrate the applicability of microparticles as immunoadsorbents, which can be achieved for other encapsulated crosslinked proteins. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 581-586, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 167
    Digitale Medien
    Digitale Medien
    A membrane bioreactor for biotransformations of hydrophobic molecules (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 587-594 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biotransformation ; membrane bioreactor ; silicone rubber ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The Membrane Bioreactor for Biotransformations (MBB) is based on the aqueous/organic two-phase system, and uses a tubular silicone rubber membrane to separate the two liquid phases. This avoids the key problem associated with direct contact two-phase processes, specifically, product emulsification. The baker's yeast mediated reduction of geraniol to citronellol was used as a model biotransformation to demonstrate MBB operation. Values for the overall mass transfer coefficient were determined for geraniol, (2.0 × 10-5 ms-1), and for citronellol, (2.1 × 10-5 ms-1) diffusion across the silicone rubber membrane. Using these values, and the specific activity of the biocatalyst (5 nmols-1g biomass-1), a suitable membrane surface area: biomass ratio was determined as 2.4 × 10-3 m2g biomass-1. The bioreactor was operated at this surface area: biomass ratio and achieved a product accumulation rate 90-95% that of a conventional direct contact two-phase system. The slight reduction in product accumulation rate was shown not to be due to mass transfer limitations with respect to reactant delivery or product extraction. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 587-594, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 168
    Digitale Medien
    Digitale Medien
    The effects of turbulent jet flows on plant cell suspension cultures (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 595-604 
    Details
    ISSN: 0006-3592
    Schlagwort(e): turbulent jet ; plant cells ; Morinda citrifolia ; shear damage ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Cell suspensions of Morinda citrifolia were subjected to turbulent flow conditions in a submerged jet apparatus, to investigate their hydrodynamic shear susceptibility. The suspensions were exposed to repeated, pressure-driven passages through a submerged jet. Two nozzles, of 1 mm and 2 mm diameter, were employed. Average energy dissipation rates were in the range 103-105 W/kg and cumulative energy dissipation in the range 105-107 J/m3. System response to the imposed conditions was evaluated in terms of suspension viability (determined using a dye exclusion technique) and variations in both chain length distribution and maximum chain length. Viability loss was well-described by a first-order model, and a linear relationship was identified between the specific death rate constant and the average energy dissipation rate. This relationship was consistent with results obtained using the same suspension cultures in a turbulent capillary flow device. Morphological measurements indicated that exposure to the hydrodynamic environment generated in the jet resulted in a significant reduction in both the average and maximum chain lengths, and the reduction in the maximum chain length was identified as an appropriate measure of sustained damage. Analysis of both viability and chain length in terms of cumulative energy dissipated revealed good agreement with results reported by other authors for morphologically different plant cell systems. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 595-604, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 169
    Digitale Medien
    Digitale Medien
    Modeling of biomass productivity in tubular photobioreactors for microalgal cultures: Effects of dilution rate, tube diameter, and solar irradiance (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 605-616 
    Details
    ISSN: 0006-3592
    Schlagwort(e): solar irradiance ; tubular photobioreactor ; microalgal culture ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A macromodel is developed for estimating the year-long biomass productivity of outdoor cultures of microalga in tubular photobioreactors. The model evaluates the solar irradiance on the culture surface as a function of day of the year and the geographic location. In a second step, the geometry of the system is taken into account in estimating the average irradiance to which the cells are exposed. Finally, the growth rate is estimated as a function of irradiance, taking into account photoinhibition and photolimitation. The model interconnects solar irradiance (an environmental variable), tube diameter (a design variable), and dilution rate (an operating variable). Continuous cultures in two different tubular photobioreactors were analyzed using the macromodel. The biomass productivity ranged from 0.50 to 2.04 g L-1 d-1, and from 1.08 to 2.76 g L-1 d-1, for the larger and the smaller tube diameter photobioreactors, respectively. The quantum yield ranged from 1.1 to 2.2 g E-1; the higher the incident solar radiation, the lower the quantum yield. Simultaneous photolimitation and photoinhibition of outdoor cultures was observed. The model reproduced the experimental results with less than 20% error. If photoinhibition was neglected, and a growth model that considered only photolimitation was used to fit the data, the error increased to 45%, thus reflecting the inadequacy of previous outdoor growth models that disregard photoinhibition. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 605-616, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 170
    Digitale Medien
    Digitale Medien
    Biooxidation capacity of the extremely thermoacidophilic archaeon Metallosphaera sedula under bioenergetic challenge (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 617-624 
    Details
    ISSN: 0006-3592
    Schlagwort(e): thermoacidophile ; chemolithotroph ; heat shock ; chemical stress ; continuous culture ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The biooxidation capacity of an extremely thermoacidophilic archaeon Metallosphaera sedula (DSMZ 5348) was examined under bioenergetic challenges imparted by thermal or chemical stress in regard to its potential use in microbial bioleaching processes. Within the normal growth temperature range of M. sedula (70-79°C) at pH 2.0, upward temperature shifts resulted in bioleaching rates that followed an Arrhenius-like dependence. When the cells were subjected to supraoptimal temperatures through gradual thermal acclimation at 81°C (Han et al., 1997), cell densities were reduced but 3 to 5 times faster specific leaching rates (Fe3+ released from iron pyrite/cell/h) could be achieved by the stressed cells compared to cells at 79°C and 73°C, respectively. The respiration capacity of M. sedula growing at 74°C was challenged by poisoning the cells with uncouplers to generate chemical stress. When the protonophore 2,4-dinitrophenol (5-10 μM) was added to a growing culture of M. sedula on iron pyrite, there was little effect on specific leaching rates compared to a culture with no protonophore at 74°C; 25 μM levels proved to be toxic to M. sedula. However, a significant stimulation in specific rate was observed when the cells were subjected to 1 μM nigericin (+135%) and 2 μM (+63%); 5 μM levels of the ionophore completely arrested cell growth. The ionophore effect was further investigated in continuous culture growing on ferrous sulfate at 74°C. When 1 μM nigericin was added as a pulse to a continuous culture, a 30% increase in specific iron oxidation rate was observed for short intervals, indicating a potential positive impact on leaching when periodic chemical stress is applied. This study suggests that biooxidation rates can be increased by strategic exposure of extreme thermoacidophiles to chemical or thermal stress, and this approach should be considered for improving process performance. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 617-624, 1998.
    Zusätzliches Material: 6 Ill.
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  • 171
    Digitale Medien
    Digitale Medien
    Direct fermentation of 2-keto-l-gulonic acid in recombinant Gluconobacter oxydans (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 309-315 
    Details
    ISSN: 0006-3592
    Schlagwort(e): l-ascorbic acid ; vitamin C ; 2-keto-l-gulonic acid ; l-sorbose dehydrogenase ; l-sorbosone dehydrogenase ; Gluconobacter ; chemical mutation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We isolated Gluconobacter oxydans T-100 that had an activity to produce 2-KLGA from d-sorbitol; however, the yield of 2-KLGA was quite insufficient. Therefore, enzymes involved in the biosynthesis of l-sorbosone and 2-KLGA, l-sorbose dehydrogenase (SDH) and l-sorbosone dehydrogenase (SNDH), respectively, were purified from G. oxydans T-100. A genomic library of G. oxydans T-100 was screened to clone both genes for SDH and SNDH based on their amino acid sequences. SNDH and SDH were encoded in sequential open reading frames with 1497 and 1596 nucleotides, respectively, which were verified by the expression in Escherichia coli. The amino acid sequence of SDH and SNDH showed close similarity with E. coli choline dehydrogenase (CDH) and betaine-aldehyde dehydrogenase (BADH), respectively, which cooperatively play a key role for conferring osmotic tolerance. Because the yield of 2-KLGA by G. oxydans introduced with the genes for SDH and SNDH were insufficient, replacement of the promoter with that of Escherichia coli tufB1 in combination with chemical mutagenesis by N-methyl-N′-nitro-N-nitrosoguanidine resulted in improvement of the production level. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:309-315, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 172
    Digitale Medien
    Digitale Medien
    Allocation of ATP to synthesis of cells and hydrolytic enzymes in cellulolytic fermentative microorganisms: Bioenergetics, kinetics, and bioprocessing (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 316-320 
    Details
    ISSN: 0006-3592
    Schlagwort(e): ATP allocation ; celluloytic microorganisms ; consolidated bioprocessing ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Under anaerobic, carbon limited conditions, celluloytic fermentative microorganisms face a metabolic choice with respect to the allocation of relatively scarce ATP: to invest it in cells or in hydrolytic enzymes. A model is proposed that defines an allocation parameter reflecting the fractional expenditure of ATP on cell synthesis relative to the total ATP available (gross ATP synthesized less maintenance). This parameter is then incorporated into an ATP-centered model of anaerobic cellulose fermentation based on the ethanol fermentation of yeast and the cellulase system of Trichoderma reesei. Results indicate that high processing rates are possible via a consolidated bioprocessing strategy, especially at high cellulase specific activities, and that cell/cellulase allocation represents an interesting system in which to study, and perhaps exploit, microbial evolution and metabolic control. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:316-320, 1998.
    Zusätzliches Material: 6 Ill.
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  • 173
    Digitale Medien
    Digitale Medien
    Yeast cell permeabilizing β-1,3-Glucanases: A tool for the integration of downstream processes and metabolic engineering applications to yeast (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 321-324 
    Details
    ISSN: 0006-3592
    Schlagwort(e): yeast cell wall porosity and permeability ; β-1,3-glucanase ; selective protein release ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In this article, we consider the impact on downstream process design resulting from the use of metabolically engineered yeast strains. We address the issue of how manipulation of cell wall permeability can improve the release and subsequent recovery of heterologous products produced in yeast. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:321-324, 1998.
    Materialart: Digitale Medien
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  • 174
    Digitale Medien
    Digitale Medien
    High cell density culture of metabolically engineered Escherichia coli for the production of poly(3-hydroxybutyrate) in a defined medium (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 325-328 
    Details
    ISSN: 0006-3592
    Schlagwort(e): poly(3-hydroxybutyrate) ; Escherichia coli ; filamentation suppression ; defined medium ; high cell density culture ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A recombinant Escherichia coli strain XL1-Blue harboring a stable high-copy-number plasmid pSYL107 containing the Alcaligenes eutrophus polyhydroxyalkanoate biosynthesis genes and the Escherichia coli ftsZ gene was employed for the production of poly(3-hydroxybutyrate) (PHB) by fed-batch culture in a defined medium. Suppression of filamentation by overexpressing the cell division protein FtsZ allowed production of PHB to a high concentration (77 g/L) with high productivity (2 g/L/h) in a defined medium, which was not possible with the recombinant E. coli that underwent filamentation. Further optimization of fed-batch culture condition resulted in PHB concentration of 104 g/L in a defined medium, which was the highest value reported to date by employing recombinant E. coli. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:325-328, 1998.
    Zusätzliches Material: 3 Ill.
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  • 175
    Digitale Medien
    Digitale Medien
    A new addition to the combinatorial library (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 1-1 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: No abstract.
    Materialart: Digitale Medien
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  • 176
    Digitale Medien
    Digitale Medien
    Metabolic engineering of cultured tobacco cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 329-332 
    Details
    ISSN: 0006-3592
    Schlagwort(e): tobacco cultured cells ; heat-shock promoter of Arabidopsis thaliana ; strong promoter from tobacco cell ; β-glucuronidase ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Construction of a gene expression system in tobacco cultured cells (BY2) was studied. A 925 bp promoter fragment of a heat-shock protein gene (HSP18.2) of Arabidopsis thaliana showed clear heat-shock response of expression of the β-glucuronidase (GUS) reporter gene in BY2 cells. Similar results were observed in a 500 mL flask and 3-L jar fermentor.Isolation of strong promoters in BY2 cells was tried. cDNA clones, in which the mRNA level is high in log-phase cells and the copy number in the genome is low, were isolated. These clones showed high homology with F1-ATPase (mitochondria type), elongation factor 1-α, and a gene with an unknown function of A. thaliana (clone 27), respectively. A 5′-flanking region of clone 27 showed 6.2 times the promoter activity of the CaMV35S promoter in BY2 cells.Three cDNA clones, which are expressed in the stationary growth phase of BY2 cells, were isolated by a differential screening. These clones showed high sequence homologies to alcohol dehydrogenase, pectin esterase, and extensin. Promoters of these genes will be useful in gene expression in high cell-density culture. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:329-332, 1998.
    Zusätzliches Material: 4 Ill.
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  • 177
    Digitale Medien
    Digitale Medien
    Quantification of metabolites in the indole alkaloid pathways of Catharanthus roseus: Implications for metabolic engineering (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 333-338 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Catharanthus roseus ; hairy roots ; indole alkaloids ; tabersonine ; elicitation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In this article, we present a review of the current state of metabolic engineering in Catharanthus roseus. A significant amount of research has contributed to characterization of several individual steps in the biosynthetic pathway of medicinally valuable alkaloids. However, knowledge of the regulation of these pathways is still sparse. Using hairy root cultures, we studied the responses of alkaloid metabolism to environmental stimulation such as light and elicitation. Through precursor feeding studies, the putative rate-limiting steps of the terpenoid pathway in hairy root cultures also have been examined. Relating this knowledge to specific events at the molecular level, and the cloning of corresponding genes are the next key steps in metabolic engineering of the C. roseus alkaloids. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:333-338, 1998.
    Zusätzliches Material: 4 Ill.
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  • 178
    Digitale Medien
    Digitale Medien
    Serum increases the CD13 receptor expression, reduces the transduction of fluid-mechanical forces, and alters the metabolism of HL60 cells cultured in agitated bioreactors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 259-268 
    Details
    ISSN: 0006-3592
    Schlagwort(e): HL60 cells ; CD13 ; serum ; hydrodynamic effects ; mRNA ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The effects of serum medium concentration on the CD13 receptor surface content and mRNA levels of HL60 (human promyelocytic leukemia) cells were examined using flow cytometry and Northern blotting. Increasing the serum concentration from 2.5% to 10% and from 5% to 10% increased the CD13 receptor surface content of HL60 cells by 100% and 25%, respectively, in spinner flasks agitated at 60 rpm. In bioreactors at 80 rpm, increasing the serum concentration from 2.5% to 10% and from 5% to 10% increased the CD13 receptor surface content by 60% and 35%, respectively. This increase in CD13 receptor surface content was correlated with a 30% and a 20% increase in CD13 mRNA levels. Increasing serum concentrations also increased the average HL60 cell size under non-damaging conditions (60 rpm in spinner flasks, 80 rpm in bioreactors). Under conditions of agitation at 300 rpm in 2 L bioreactors, increasing serum concentrations (2.5% vs. 10%, 5% vs. 10%) allowed for higher HL60 apparent growth rates, but decreased the CD13 receptor surface content and mRNA levels. In view of our earlier findings on the effects of agitation on the CD13 antigen, these data suggest that serum reduces the transduction of mechanical forces that affect CD13 expression. At 300 rpm, HL60 cells cultured in 10% serum exhibited glucose consumption and lactate production rates that were approximately 50% and 60% lower than the values of cells cultured in 5% and 2.5% serum, respectively. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 259-268, 1998.
    Zusätzliches Material: 9 Ill.
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  • 179
    Digitale Medien
    Digitale Medien
    Double inhibition model for degradation of phenol by Pseudomonas putida Q5 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 560-567 
    Details
    ISSN: 0006-3592
    Schlagwort(e): phenol degradation ; Pseudomonas putida ; inhibition model ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A semiempirical model, based on the presence of an inhibitory intermediate metabolite excreted to the broth, was developed to better predict the dynamic responses to shock loadings of Pseudomonas putida Q5 degrading phenol. Compared to the Haldane equation, the new model exhibited better prediction capabilities for a broad range of inlet concentration and dilution rate step changes. The experiments were performed at 10° and 25°C and ranged from stable responses to washouts. The time delays observed experimentally were successfully predicted with the dual-inhibition model and a very good agreement with the observed phenol profile also was found in a pulse experiment. A possible intermediate metabolite was detected by HPLC analyses based on the high correlation shown with the predicted inhibitory intermediate metabolite in the model. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 560-567, 1998.
    Zusätzliches Material: 10 Ill.
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  • 180
    Digitale Medien
    Digitale Medien
    Preparation of a new thermo-responsive adsorbent with maltose as a ligand and its application to affinity precipitation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 568-579 
    Details
    ISSN: 0006-3592
    Schlagwort(e): thermo-responsive polymer ; immobilized maltose ; affinity precipitation ; thermolabile enzyme ; concanavalin A ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A thermo-responsive polymer on which maltose was covalently immobilized as an affinity ligand was newly synthesized for purification of thermolabile proteins from the crude solution by affinity precipitation. Among the thermo-responsive polymers synthesized as carriers for adsorbent, poly(N-acryloylpiperidine)-cysteamine (pAP) has a lower critical solution temperature (LCST) of around 4°C, at which its solubility exhibits a sharp change. Adsorbent for affinity precipitation was prepared by combining pAP with maltose using trimethylamine-borane as a reducing reagent. This adsorbent (pAPM) obtained showed a good solubility response: pAPM in the basal buffer (pH 7.0) became soluble below 4°C and was completely insoluble above 8°C. The affinity precipitation method using pAPM consisted of the following four steps: adsorption at 4°C, precipitation of the complex at 10°C, desorption by adding the desorption reagent at 4°C, and recovery of a target protein at 10°C. In the affinity precipitation of Con A from the crude extract of jack bean meal, 82% of Con A added was recovered with 80% purity by addition of 0.2 M methyl-α-D-mannopyranoside as a desorption reagent. In the repeated purification of Con A from the crude extract, pAPM could be satisfactorily reused without decrease in the affinity performance. Moreover, when pAPM was used for the purification of thermolabile α-glucosidase from the cell-free extract of Saccharomyces cerevisiae, 68% of total activity added was recovered and the specific activity per amount of protein of the purified solution was enhanced 206-fold higher than that of the cell-free extract without thermal deactivation of the enzyme. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 568-579, 1998.
    Zusätzliches Material: 7 Ill.
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  • 181
    Digitale Medien
    Digitale Medien
    Use of soybean oil and ammonium sulfate additions to optimize secondary metabolite production (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 580-588 
    Details
    ISSN: 0006-3592
    Schlagwort(e): soybean oil ; ammonium sulfate ; secondary metabolite production ; streptomyces ; lipase ; homologs ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A valine-overproducing mutant (MA7040, Streptomyces hygroscopicus) was found to produce 1.5 to 2.0 g/L of the immunoregulant, L-683,590, at the 0.6 m3 fermentation scale in a simple batch process using soybean oil and ammonium sulfate-based GYG5 medium. Levels of both lower (L-683,795) and higher (HH1 and HH2) undesirable homolog levels were controlled adequately. This batch process was utilized to produce broth economically at the 19 m3 fermentation scale. Material of acceptable purity was obtained without the multiple pure crystallizations previously required for an earlier culture, MA6678, requiring valine supplementation for impurity control.Investigations at the 0.6 m3 fermentation scale were conducted, varying agitation, pH, initial soybean oil/ammonium sulfate charges, and initial aeration rate to further improve growth and productivity. Mid-cycle ammonia levels and lipase activity appeared to have an important role. Using mid-cycle soybean oil additions, a titer of 2.3 g/L of L-683,590 was obtained, while titers reached 2.7 g/L using mid-cycle soybean oil and ammonium sulfate additions. Both higher and lower homolog levels remained acceptable during this fed-batch process. Optimal timing of mid-cycle oil and ammonium sulfate additions was considered a critical factor to further titer improvements. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 580-588, 1998.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 182
    Digitale Medien
    Digitale Medien
    Chinese hamster ovary cells with constitutively expressed sialidase antisense RNA produce recombinant dnase in batch culture with increased sialic acid (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 589-595 
    Details
    ISSN: 0006-3592
    Schlagwort(e): CH0 cells ; sialidase activity ; recombinant DNase ; sialic acid ; antisense DNA ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Under some cell culture conditions, recombinant glycoprotein therapeutics expressed in Chinese hamster ovary (CHO) cells lose sialic acid during the course of the culture (Sliwkowski et al., 1992; Munzert et al., 1996). A soluble sialidase of CHO cell origin degrades the expressed recombinant protein and has been shown to be released into the culture fluid as the viability of the cells decreases. To reduce the levels of the sialidase and to prevent desialylation of recombinant protein, a CHO cell line has been developed that constitutively expresses sialidase antisense RNA. Several antisense expression vectors were prepared using different regions of the sialidase gene. Co-transfection of the antisense constructs with a vector conferring puromycin resistance gave rise to over 40 puromycin resistant clones that were screened for sialidase activity. A 5′ 474 bp coding segment of the sialidase cDNA, in the inverted orientation in an SV 40-based expression vector, gave maximal reduction of the sialidase activity to about 40% wild-type values. To test if this level of sialidase would lead to increased sialic acid content of an expressed recombinant protein, the 474 antisense clone was employed as a host for expression of human DNase as a model glycoprotein. The sialic acid content of the DNase produced in the antisense cultures was compared with material made in the wild-type parental cell line. About 20-37% increase in sialic acid content, or 0.6-1.1 mole of additional sialic acid out of a total of 3.0 mole on the product, was found on the DNase made in the antisense cell lines. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 589-595, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 183
    Digitale Medien
    Digitale Medien
    Site-directed and random immobilization of subtilisin on functionalized membranes: Activity determination in aqueous and organic media (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 608-616 
    Details
    ISSN: 0006-3592
    Schlagwort(e): site-directed mutagenesis ; oriented immobilization ; subtilisin ; membrane ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Kinetic comparisons have been made between a randomly immobilized and a site-specifically immobilized subtilisin BPN′ on microfiltration membranes of varying hydrophilicities in both aqueous and organic media. Site-directed mutagenesis was employed to introduce a single cysteine into the amino acid sequence of subtilisin at a location away from the active site. Immobilization of this mutant enzyme was then carried out using the single cysteine residue to orient the active site of the enzyme away from the membrane surface. Kinetic comparison of the immobilized mutant enzyme with the randomly immobilized wild-type enzyme in aqueous media showed an activity enhancement on both hydrophilic silica-containing and hydrophobic poly(ether)sulfone membranes. Higher loading efficiencies were observed for the site-directed enzyme on immobilization. Optimal enzyme loading values were calculated for the randomly immobilized enzyme. An enhancement of activity was also observed for the site-directed immobilized systems using nearly anhydrous hexane as the solvent. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 608-616, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 184
    Digitale Medien
    Digitale Medien
    Monitoring recombinant human interferon-gamma N-glycosylation during perfused fluidized-bed and stirred-tank batch culture of CHO cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 596-607 
    Details
    ISSN: 0006-3592
    Schlagwort(e): micellar electrokinetic capillary chromatography ; capillary isoelectric focusing ; Chinese hamster ovary ; interferon-gamma ; perfusion culture ; glycosylation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Chinese hamster ovary cells producing recombinant human interferon-γ were cultivated for 500 h attached to macroporous microcarriers in a perfused, fluidized-bed bioreactor, reaching a maximum cell density in excess of 3 × 107 cells (mL microcarrier)-1 at a specific growth rate (μ) of 0.010 h-1. During establishment of the culture, the N-glycosylation of secreted recombinant IFN-γ was monitored by capillary electrophoresis of intact IFN-γ proteins and by HPLC analysis of released N-glycans. Rapid analysis of IFN-γ by micellar electrokinetic capillary chromatography resolved the three glycosylation site occupancy variants of recombinant IFN-γ (two Asn sites occupied, one Asn site occupied and nonglycosylated) in under 10 min per sample; the relative proportions of these variants remained constant during culture. Analysis of IFN-γ by capillary isoelectric focusing resolved at least 11 differently sialylated glycoforms over a pI range of 3.4 to 6.4, enabling rapid quantitation of this important source of microheterogeneity. During perfusion culture the relative proportion of acidic IFN-γ proteins increased after 210 h of culture, indicative of an increase in N-glycan sialylation. This was confirmed by cation-exchange HPLC analysis of released, fluorophore-labeled N-glycans, which showed an increase in the proportion of tri- and tetrasialylated N-glycans associated with IFN-γ during culture, with a concomitant decrease in the proportion of monosialylated and neutral N-glycans. Comparative analyses of IFN-γ produced by CHO cells in stirred-tank culture showed that N-glycan sialylation was stable until late in culture, when a decline in sialylation coincided with the onset of cell death and lysis. This study demonstrates that different modes of capillary electrophoresis can be employed to rapidly and quantitatively monitor the main sources of glycoprotein variation, and that the culture system and operation may influence the glycosylation of a recombinant glycoprotein. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 596-607, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 185
    Digitale Medien
    Digitale Medien
    Kinetic, dynamic, and pathway studies of glycerol metabolism by Klebsiella pneumoniae in anaerobic continuous culture: IV. Enzymes and fluxes of pyruvate metabolism (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 617-626 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Klebsiella pneumoniae ; glycerol ; pyruvate kinase ; pyruvate:formate-lyase ; pyruvate dehydrogenase ; in vitro and in vivo activities ; dynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The activities of pyruvate kinase (PK), pyruvate: formate-lyase (PFL), pyruvate dehydrogenase (PDH), and citrate synthase (CS) involved in the anaerobic glycerol conversion by Klebsiella pneumoniae were studied in continuous culture under conditions of steady states and sustained oscillations. Both the in vitro and in vivo activities of PK, PFL, and PDH are strongly affected by the substrate concentration and its uptake rate, as is the in vitro activity of CS. The flux from phosphoenolpyruvate to pyruvate is found to be mainly regulated on a genetic level by the synthesis rate of PK, particularly at low substrate concentration and low growth rate. In contrast, the conversion of pyruvate to acetyl-CoA is mainly regulated on a metabolic level by the in vivo activities of PFL and PDH. The ratio of in vitro to in vivo activities is in the range of 1 to 1.5 for PK, 5 to 17 for PFL and 5 to 80 for PDH under the experimental conditions. The regulation of in vivo activity and synthesis of these enzymes is sensitive to fluctuations of culture conditions, leading to oscillations of both the in vitro and in vivo activities. In particular, PFL is strongly affected during oscillations; its average in vitro activity is only about half of its corresponding steady-state value under similar environmental conditions. The average in vitro activities of PDH and PK under oscillations are close to their corresponding steady-state values. In contrast to all other enzymes measured for the glycerol metabolism by K. pneumoniae PFL and PDH are more effectively in vivo utilized under oscillations than under steady state, underlining the peculiar role of pyruvate metabolism in the dynamic responses of the culture. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 617-626, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 186
    Digitale Medien
    Digitale Medien
    Hydrodynamic characteristics and gas-liquid mass transfer in a biofilm airlift suspension reactor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 627-635 
    Details
    ISSN: 0006-3592
    Schlagwort(e): airlift reactor ; biofilm ; hydrodynamics ; mass transfer ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The hydrodynamics and mass transfer, specifically the effects of gas velocity and the presence and type of solids on the gas hold-up and volumetric mass transfer coefficient, were studied on a lab-scale airlift reactor with internal draft tube. Basalt particles and biofilm-coated particles were used as solid phase. Three distinct flow regimes were observed with increasing gas flow rate. The influence of the solid phase on the hydrodynamics was a peculiar characteristic of the regimes. The volumetric mass transfer coefficient was found to decrease with increasing solid loading and particle size. This could be predominantly related to the influence that the solid has on gas hold-up. The ratio between gas hold-up and volumetric mass transfer coefficient was found to be independent of solid loading, size, or density, and it was proven that the presence of solids in airlift reactors lowers the number of gas bubbles without changing their size. To evaluate scale effects, experimental results were compared with theoretical and empirical models proposed for similar systems. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 627-635, 1998.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 187
    Digitale Medien
    Digitale Medien
    Flotation characteristics of cyanobacterium Anabaena flos-aquae for gas vesicle production (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 636-641 
    Details
    ISSN: 0006-3592
    Schlagwort(e): flotation ; cyanobacterium (blue-green algae) ; gas vesicle ; buoyancy ; filament density ; photobioreactor ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Cyanobacterium Anabaena flos-aquae was cultivated in photobioreactors for production of intracellular gas vesicles (GVs), as potential oxygen microcarriers. Natural flotation of the buoyant culture was investigated as a potential means of cell harvesting, because filtration and centrifugation tended to destroy the vesicles. Best flotation was found with actively growing culture and when conducted in the dark. The flotation-related cell properties, including the specific GV content, vesicle-collapsed filament density, and intracellular carbohydrate content, were measured to understand the phenomena. During the batch culture, the specific GV content remained relatively constant at 370 μL/(g dry cells) but the filament density (ranging 1.02 to 1.08 g/cm3) showed a decrease-then-increase profile. The increase began when the growth slowed down because of the reduced light availability at high cell concentrations. The dark flotation was studied with both actively growing (μ ≈ 0.2 day-1) and stationary-phase cultures. The specific GV content of the stationary-phase culture remained relatively constant while that of the growing culture increased slightly. The intracellular carbohydrate content of the growing culture decreased much faster and more significantly, from 57 to 10 mg/(g dry cells) in ≤ 8 h. The filament density also decreased, apparently parallel to the profiles of carbohydrate content. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 636-641, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 188
    Digitale Medien
    Digitale Medien
    Experimental and modeling study of diauxic lag of Pseudomonas denitrificans switching from oxic to anoxic conditions (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 649-655 
    Details
    ISSN: 0006-3592
    Schlagwort(e): diauxie ; biphasic growth ; Pseudomonas denitrificans ; nitrate ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We have shown that Pseudomonas denitrificans undergo a diauxie when switching from dissolved oxygen to nitrate as terminal electron acceptor. The length of time under aeration significantly affected the length of the diauxic lag, whereas the presence or absence of nitrate in the culture under aeration had a marginal effect. Nitrate consumption was very low during the lag period and then increased rapidly, coinciding with exponentially increasing biomass concentrations. Biochemical rate expressions that account for enzyme synthesis and activity in response to culture conditions and enzyme specific levels were developed. The new model successfully predicts the different lengths of diauxic lags observed in the experiments as well as the growth pattern and nitrate uptake. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 649-655, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 189
    Digitale Medien
    Digitale Medien
    High-level expression of secreted glycoproteins in transformed lepidopteran insect cells using a novel expression vector (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 656-663 
    Details
    ISSN: 0006-3592
    Schlagwort(e): protein expression ; secreted glycoproteins ; insect cells ; cell transformation ; silkmoth actin gene promoter ; lepidoptera ; baculovirus enhancer ; baculovirus transcriptional activator ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: An expression cassette for continuous high-level expression of secreted glycoproteins by transformed lepidopteran insect cells has been developed as an alternative to baculovirus and mammalian cell expression systems. The expression cassette utilizes the promoter of the silkmoth cytoplasmic actin gene to drive expression from foreign gene sequences, and also contains the ie-1 transactivator gene and the HR3 enhancer region of BmNPV to stimulate gene expression. Using an antibiotic-resistance selection scheme, we have cloned a Bm5 (silkmoth) cell line overexpressing the secreted glycoprotein juvenile hormone esterase (JHE-KK) at levels of 190 mg/L in batch suspension cultures. A baculovirus (AcNPV) expressing the same gene under the control of the p10 promoter of AcNPV produced only 4 mg/L active JHE in static cultures of infected Sf21 cells. A cloned Bm5 cell line overexpressing a soluble isoform of the α-subunit of the granulocyte-macrophage colony stimulating factor receptor (solGMRα) was also generated and produced five times more solGMRα in static cultures than a cloned BHK cell line obtained by transformation with a recombinant expression cassette utilizing the human cytomegalovirus (CMV) enhancer-promoter system. Finally, we show that recombinant protein expression levels in transformed Bm5 cells remain high in serum-free media, that expression is stable even in the absence of antibiotic selection, and that lepidopteran cells other than Bm5 may be used equally efficiently with this new expression cassette for producing recombinant proteins. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 656-663, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 190
    Digitale Medien
    Digitale Medien
    Influence of morphology and rheology on the production characteristics of the basidiomycete Cyathus striatus (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 525-533 
    Details
    ISSN: 0006-3592
    Schlagwort(e): fermentation ; basidiomycete ; rheology ; morphology ; pellet size ; scale-up ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The influence of the pellet morphology of the basidiomycete Cyathus striatus on the production of the antibiotics striatals A, B, and C was investigated. The main operating parameters in fermenters of different sizes were the tip speed and the volumetric power input. Different methods were developed for quantification of morphological characteristics. The apparent viscosity of the suspension was measured with a cylinder rheometer. Sediment density was measured with a sedimentation apparatus. Particle size distributions were recorded with an image analysis system. By means of the presented measuring methods, morphological characteristics could be determined and enabled an early assessment of the fermentation course and the antibiotics production. During the exponential growth phase of the fungus the relative sediment height correlated with the biomass concentration. The pellet morphology at this stage influenced the later production of striatals. The yield of the striatals was markedly influenced by pellet size and sediment density. Since these morphological characteristics determine the rheological properties of the culture the measurement of the apparent viscosity of the culture in the production phase allowed predictions of the production yield. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 525-533, 1998.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 191
    Digitale Medien
    Digitale Medien
    Adsorptive control of water in esterification with immobilized enzymes: II. Fixed-bed reactor behavior (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 445-453 
    Details
    ISSN: 0006-3592
    Schlagwort(e): immobilized enzymes ; organic solvents ; esterification ; water ; continuous flow reactor ; adsorption modeling ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Experimental and theoretical studies are conducted to understand the dynamic behavior of a continuous-flow fixed-bed reactor in which an esterification is catalyzed by an immobilized enzyme in an organic solvent medium. The experimental system consists of a commercial immobilized lipase preparation known as Lipozyme as the biocatalyst, with propionic acid and isoamyl alcohol (dissolved in hexane) as the reaction substrates. A complex dynamic behavior is observed experimentally as a result of the simultaneous occurrence of reaction and adsorption phenomena. Both propionic acid and water are adsorbed by the biocatalyst resulting in lower reaction rates. In addition, an excessive accumulation of water in the reactor leads to a rapid irreversible inactivation of the enzyme. A model based on previously-obtained adsorption isotherms and kinetic expressions, as well as on adsorption rate measurements obtained in this work, is used to predict the concentration and thermodynamic activity of water along the reactor length. The model successfully predicts the dynamic behavior of the reactor and shows that a maximum thermodynamic activity of water occurs at a point at some distance from the reactor entrance. A cation exchange resin in sodium form, packed in the reactor as a selective water adsorbent together with the catalyst particles, is shown to be an effective means for preventing an excessive accumulation of water formed in the reaction. Its use results in longer cycle times and greater productivity. As predicted by the model, the experimental results show that the water adsorbed on the catalyst and on the ion exchange resin can be removed with isoamyl alcohol with no apparent loss in enzyme activity. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 445-453, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 192
    Digitale Medien
    Digitale Medien
    Adsorptive control of water in esterification with immobilized enzymes: I. Batch reactor behavior (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 434-444 
    Details
    ISSN: 0006-3592
    Schlagwort(e): immobilized enzymes ; organic solvents ; esterification ; water ; adsorption ; adsorption modeling ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Reducing the influence of an undesired product in an enzymatic reaction could have a significant impact on the productivity of such systems. Here, we focus on the removal of water formed during an enzymatic esterification in a batch reactor. A commercial immobilized lipase preparation, known as Lipozyme, is used as the biocatalyst and propionic acid and isoamyl alcohol dissolved in hexane are the substrates. In this system, the water formed will partition between the catalyst and the medium. As the more polar reactants are converted into the less polar ester product, the water is partitioned more towards the biocatalyst and the accumulation of water eventually causes lower reaction rates. Addition of a strong-acid cation exchange resin in sodium form is found to control the water accumulation on the biocatalyst without stripping the essential water needed for the enzyme to function and substantial improvements in conversion are achieved. A mathematical model is developed to describe the batch reaction behavior with and without added absorbent, which successfully predicts the behavior of water and its effects. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 434-444, 1998.
    Zusätzliches Material: 10 Ill.
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  • 193
    Digitale Medien
    Digitale Medien
    Production of D-phenylglycine from racemic (D,L)-phenylglycine via isoelectrically-trapped penicillin G acylase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 454-461 
    Details
    ISSN: 0006-3592
    Schlagwort(e): isoelectric membranes ; immobilized reactors ; penicillin G acylase ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Penicillin G acylase (PGA) is exploited for producing pure D-phenylglycine from a racemate mixture, via an acylation reaction onto a cosubstrate, the ester methyl-4-hydroxyphenyl acetate. The reaction, when carried in a batch, is severely hampered by the reverse process, by which the product, 4-hydroxyphenylacetyl-(L)phenyl glycine, upon consumption of L-phenylglycine, is converted by the enzyme back into free substrate and 4-hydroxyphenyl acetic acid via lysis of the amido bond. To prevent this noxious reaction, a multicompartment electrolyzer with isoelectric membranes (MIER) is used as enzyme reactor, operating in an electric field. PGA is trapped between pI 5.5 and pI 10.5 membranes, together with an amphoteric, isoelectric buffer (lysine). As the 4-hydroxyphenylacetyl-(L)phenyl glycine product is formed, it vacates the reaction chamber by electrophoretic transport and is collected close to the anode, in a chamber delimited by pI 2.5 and 4.0 membranes. The same fate occurs to the free acid 4-hydroxyphenyl acetic acid, formed upon spontaneous (and enzyme-driven) hydrolysis of the methyl ester in the reaction chamber. These combined processes leave behind, in the enzyme reaction chamber, the desired product, pure D-phenylglycine. The advantages of the MIER reactor over batch operations: the consumption of the L-form in the racemate is driven to completion and the enzyme is kept in a highly stable form, maintaining 100% activity after one day of operation, during which time the PGA enzyme, in the batch reactor, has already lost 〉75% catalytic activity. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 454-461, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 194
    Digitale Medien
    Digitale Medien
    Local macromolecule diffusion coefficients in structurally non-uniform bacterial biofilms using fluorescence recovery after photobleaching (FRAP) (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 462-473 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biofilm ; macromolecule transport mechanism ; local diffusion coefficients ; fluorescence recovery ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Pure culture Pseudomonas putida biofilms were cultivated under controlled conditions to a desired overall biofilm thickness, then employed within classical half-cell diffusion chambers to estimate, from transient solute concentrations, the effective diffusion coefficient for several macromolecules of increasing molecular weight and molecular complexity. Results of traditional half-cell studies were found to be erroneous due to the existence of microscopic water channels or crevasses that perforate the polysaccharidic gel matrix of the biofilm, sometimes completely to the supporting substratum. Thus, half-cell devices measure a composite transfer coefficient that may overestimate the true, local flux of solutes in the biofilm polysaccharide gel matrix.An alternative analytical technique was refined to determine the local diffusion coefficients on a micro-scale to avoid the errors created by the biofilm architectural irregularities. This technique is based upon the Fluorescence Return After Photobleaching (FRAP), which allows image analysis observation of the transport of fluorescently labeled macromolecules as they migrate into a micro-scale photobleached zone. The technique can be computerized and allows one to map the local diffusion coefficients of various solute molecules at different horizontal planes and depths in a biofilm. These mappings also indirectly indicate the distribution of water channels in the biofilm, which was corroborated independently by direct microscopic observation of the settling of fluorescently-labeled latex spheres within the biofilm. Fluorescence return after photobleaching results indicate a significant reduction in the solute transport coefficients in biofilm polymer gel vs. the same value in water, with the reduction being dependent on solute molecule size and shape. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 462-473, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 195
    Digitale Medien
    Digitale Medien
    Growth and energy metabolism in aerobic fed-batch cultures of Saccharomyces cerevisiae: Simulation and model verification (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 474-482 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; fed-batch cultivation ; overflow metabolism ; respiration ; ethanol inhibition ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A kinetic model of overflow metabolism in Saccharomyces cerevisiae was used for simulation of aerobic fed-batch cultivations. An inhibitory effect of ethanol on the maximum respiration of the yeast was observed in the experiments and included in the model. The model predicts respiration, biomass, and ethanol formation and the subsequent ethanol consumption, and was experimentally validated in fed-batch cultivations. Oscillating sugar feed with resulting oscillating carbon dioxide production did not influence the maximum respiration rate, which indicates that the pyruvate dehydrogenase complex is not involved as a bottleneck causing aerobic ethanol formation. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 474-482, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 196
    Digitale Medien
    Digitale Medien
    Start-up and the effect of gaseous ammonia additions on a biofilter for the elimination of toluene vapors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 483-491 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biofiltration ; toluene ; start-up ; nitrogen limitation ; heat and carbon balances ; water evaporation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Biotechnological techniques, including biofilters and biotrickling filters are increasingly used to treat air polluted with VOCs (Volatile Organic Compounds). In this work, the start-up, the effect of the gaseous ammonia addition on the toluene removal rate, and the problems of the heat accumulation on the performance of a laboratory scale biofilter were studied. The packing material was sterilized peat enriched with a mineral medium and inoculated with an adapted consortium (two yeast and five bacteria). Start-up showed a short adaptation period and an increased toluene elimination capacity (EC) up to a maximum of 190 g/m3/h. This was related to increased CO2 outlet concentration and temperature gradients between the packed bed and the inlet (Tm-Tin). These events were associated with the growth of the microbial population. The biofilter EC decreased thereafter, to attain a steady state of 8 g/m3/h. At this point, gaseous ammonia was added. EC increased up to 80 g/m3/h, with simultaneous increases on the CO2 concentration and (Tm-Tin). Two weeks after the ammonia addition, the new steady state was 30 g/m3/h. In a second ammonia addition, the maximum EC attained was 40 g/m3/h, and the biofilter was in steady state at 25 g/m3/h. Carbon, heat, and water balances were made through 88 d of biofilter operation. Emitted CO2 was about 44.5% of the theoretical value relative to the total toluene oxidation, but accumulated carbon was found as biomass, easily biodegradable material, and carbonates. Heat and water balances showed strong variations depending on EC. For 88 d the total metabolic heat was -181.2 × 103 Kcal/m3, and water evaporation was found to be 56.5 kg/m3. Evidence of nitrogen limitation, drying, and heterogeneities were found in this study. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 483-491, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 197
    Digitale Medien
    Digitale Medien
    Inulase-secreting strain of Saccharomyces cerevisiae produces fructose (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 492-497 
    Details
    ISSN: 0006-3592
    Schlagwort(e): yeast ; inulin ; inulase ; fructose ; secretion ; hexokinases ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The gene encoding inulase of the yeast Kluyveromyces marxianus (INU1Km) was cloned and expressed in the inulin-negative yeast Saccharomyces cerevisiae. Cells of S. cerevisiae transformed with the INU1Km gene have acquired extracellular inulase activity and were able to grow in the medium with inulin as a sole carbon source. The S. cerevisiae strain was constructed that is capable of heterologous expression of secreted K. marxianus inulase and is defective in fructose uptake due to null-mutations of the hexokinase structural genes HXK1 and HXK2. When grown in inulin-containing media, this strain is capable of accumulating at least 10% glucose-free fructose in the culture liquid. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 492-497, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
  • 198
    Digitale Medien
    Digitale Medien
    Malcolm Lilly (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 525-526 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: No abstract.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
  • 199
    Digitale Medien
    Digitale Medien
    UCL biochemical engineering (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 527-533 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: No abstract.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
  • 200
    Digitale Medien
    Digitale Medien
    Use of dextrans as long and hydrophilic spacer arms to improve the performance of immobilized proteins acting on macromolecules (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 518-523 
    Details
    ISSN: 0006-3592
    Schlagwort(e): protein-protein affinity chromatography ; dextrans as spacer arms ; adsorption of immunoglobulins on protein A ; hydrolysis of casein by rennin ; immobilized protein A ; immobilized rennin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: New dextran-agarose supports, suitable for covalent immobilization of enzymes and proteins acting on macromolecular substrates, were prepared. The thick internal fibers of agarose gels were covered by a low-density layer of long, flexible, hydrophilic, and inert dextran molecules. Rennin and protein A were immobilized on these novel supports and the resulting derivatives exhibited a very high capacity for biological recognition of soluble macromolecular substrates. Caseinolytic activity of this immobilized enzyme was 15-fold higher than activity of directly immobilized rennin, through short spacer arms, on agarose gels. Similarly, the new derivatives of immobilized protein A were able to adsorb up to 2 molecules of immunoglobulin per each molecule of immobilized protein A. When the immobilized proteins were secluded away from the support surface by using these new long and hydrophilic spacer arms, they exhibit minimal steric hindrances that could be promoted by the proximity of the support surface. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 518-523, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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