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  • Artikel  (73)
  • Saccharomyces cerevisiae  (45)
  • insect cells  (28)
  • 1995-1999  (73)
  • Werkstoffwissenschaften, Fertigungsverfahren, Fertigung  (73)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 403-411 
    ISSN: 1476-5535
    Schlagwort(e): Saccharomyces cerevisiae ; Process control ; State estimation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary In order to study and control fermentation processes, indirect on-line measurements and mathematical models can be used. Here an on-line model for fermentation processes is presented. The model is based on atom and partial mass balances as well as on stability equations for the protolytes. The model is given an adaptive form by including transport equations for mass transfer and expressions for the fermentation kinetics. The state of the process can be estimated on-line using the balance component of the model completed with measurement equations for the input and the output flows of the process. Adaptivity is realized by means of on-line estimation of the parameters in the transport and kinetic expressions using recursive regression analysis. On-line estimation of the kinetic and mass transfer parameters makes model-based predictions possible and enables intelligent process control while facilitating testing of the validity of the measurement variables. A practical MS-Windows 3.1 model implementation called FMMS—Fermentation Monitoring and Modeling System is shown. The system makes it easy to configure the operating conditions for a run. It uses Windows dialogs for all set-ups, model configuration parameters, elemental compositions, on-line measurement devices and signal conditioning. Advanced on-line data analysis makes it possible to plot variables against each other for easy comparison. FMMS keeps track of over 100 variables per run. These variables are either measured or estimated by the model. Assay results can also be entered and plotted during fermentation. Thus the model can be verified almost instantly. Historical fermentation runs can be re-analyzed in simulation mode. This makes it possible to examine different signal conditining filters as well as the sensitivity of the model. Combined, the data analysis and the simulation mode make it easy to test and develop model theories and new ideas.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 440-450 
    ISSN: 1476-5535
    Schlagwort(e): Yeasts ; Autolysis ; Saccharomyces cerevisiae ; Kloeckera apiculata ; Candida stellata
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Cell suspensions ofSacharomyces cerevisiae, Kloeckera apiculata andCandida stellata were autolyzed in phosphate buffer, pH 4.5, for up to 10 days. Cell dry weights decreased by 25–35% after 10 days. Based on initial cell dry weight, the soluble autolysate consisted of: carbohydrate (principally polysaccharide) 3–7%; organic acids 3–6%; protein 12–13%; free amino acids 8–12%; nucleic acid products 3–5%; and lipids 1–12%. The main organic acids in autolysates were propionic, succinic and acetic and the main amino acids were phenylalanine, glutamic acid, leucine, alanine and arginine. Approximately 85–90% of cellular RNA and 25–40% of cellular DNA were degraded during autolysis. Both neutral lipid and phospholipid components were degraded, with neutral lipids but not phospholipids being found in autolysates. Scanning and transmission electron micrographs showed retention of cell wall structure and shape during autolysis, but there was extensive intracellular disorganization withinS. cerevisiae andC. stellata. There were differences in the autolytic behavior ofK. apiculata compared withS. cerevisiae andC. stellata.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 461-466 
    ISSN: 1476-5535
    Schlagwort(e): Flocculation ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A comparative study has been made of different laboratory and industrial wild-type strains ofSaccharomyces cerevisiae in relation to their flocculation behavior. All strains were inhibited by mannose and only one by maltose. In regard to the stability of these characters in the presence of proteases and high salt concentrations, a relevant degree of variation was found among the strains. This was to such an extent that it did not allow their inclusion in the Flol or NewFlo phenotypes. Genetic characterization of one wild-type strain revealed that the flocculation-governing gene was allelic toFLO1 found in genetic strains.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 396-402 
    ISSN: 1476-5535
    Schlagwort(e): Acid phosphatase ; Phytase ; Aspergillus ; Saccharomyces cerevisiae ; Phosphorus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Four acid phosphatase (phosphomonoesterase E.C.3.1.3.2) genes, werecloned by polymerase chain reaction (PCR). These were pho3, pho5 and pho11 fromSaccharomyces cerevisiae and the gene for a phosphate-respressible acid phosphatase fromAspergillus niger. The individual genes were subcloned into anA. oryzae expression vector downstream from a starch-inducible α-amylase promoter and the resulting expression constructs were transformed into a mutant strain ofA. oryzae, AO7. Southern hybridization analysis confirmed that the acid phosphatase genes had been integrated into the host genome with estimates of integrated copy numbers ranging from 2 to 20 for individual transformants. Northern hybridization analysis of total RNA from individual transformants revealed the presence of a single transcript of the expected size of 1.8 kb. Production of recombinant protein was induced by the addition of 30 g L−1 of soluble starch in the fermentationmedia. Active acid phosphatases, not present in control cultures, were detected in the supernatant fractions of transformant cultures by acid phosphatase activity staining of non-denaturing polyacrylamide gels. The ability of the recombinant acid phosphatases to hydrolyze phytate was assessed by referenced phytase (myoinositol hexakisphosphate phosphohydrolase E.C. 3.1.3.8) activity assay procedures. A two- to six-fold increase in phytase activity was measured in transformants compared to control, untransformedA. oryzae. Sufficient quantities ofA. niger and pho5 recombinant acid phosphatases were generated from large-scale fermentations to assess the efficacy of these enzymes as phytate-degrading enzymes when included in poultry diets. Data indicated an increase in available phosphorus of 1 g kg−1 obtained with yeast acid phosphatase andA. niger acid phosphatase representing 40% utilization of unavailable dietary P compared to 48% utilization for commercial phytase.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 15 (1995), S. 94-102 
    ISSN: 1476-5535
    Schlagwort(e): protoplast fusion ; killer character ; flocculence ; Saccharomyces cerevisiae ; industrial yeast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Conditions were optimized for rapid release and improved regeneration of protoplasts ofSaccharomyces cerevisiae NCIM 3458. Rapid protoplast release was also obtained with representatives of several other yeast genera under the modified conditions of treatment. The application of the procedure in construction of a highly flocculentSaccharomyces cerevisiae with a killer character is described. Fusion was effected between UV-killed protoplasts ofS. cerevisiae NCIM 3578 with a killer character and live protoplasts of the highly flocculentS. cerevisiae NCIM 3528 in the presence of polyethylene glycol (PEG) 6000. Fusants were selected using benomyl resistance as marker, the killer toxin producer rather than the highly flocculent yeast being resistant to the fungicide at a concentration of 100 μg ml−1. Fusants were also characterized by their DNA contents, capacity for ethanolic fermentation of molasses sugar and levels of invertase, alcohol dehydrogenase and pyruvate decarboxylase activities.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 17 (1996), S. 124-127 
    ISSN: 1476-5535
    Schlagwort(e): yeasts ; killer toxin ; fingerprinting ; Saccharomyces cerevisiae ; selected starters ; wine-making
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The extreme variability of the killer phenomenon in nature, expressed differently in different strains of the same yeast species, embodies an exceptional potential for the discrimination of yeasts at the strain level. Killer-sensitive relationships between a killer reference panel of 24 yeasts belonging to 13 species of six genera, and different industrial wine-starters ofSaccharomyces cerevisiae can be used profitably for a rapid and simple fingerprinting procedure.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 16 (1996), S. 102-109 
    ISSN: 1476-5535
    Schlagwort(e): Millet ; Pennisetum typhoides ; liquefaction ; saccharification ; baker's yeast ; Saccharomyces cerevisiae ; fermentation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract A fermentation medium based on millet (Pennisetum typhoides) flour hydrolysate and a four-phase feeding strategy for fed-batch production of baker's yeast,Saccharomyces cerevisiae, are presented. Millet flour was prepared by dry-milling and sieving of whole grain. A 25% (w/v) flour mash was liquefied with a thermostable 1,4-α-d-glucanohydrolase (EC 3.2.1.1) in the presence of 100 ppm Ca2+, at 80°C, pH 6.1–6.3, for 1 h. The liquefied mash was saccharified with 1,4-α-d-glucan glucohydrolase (EC 3.2.1.3) at 55°C, pH 5.5, for 2 h. An average of 75% of the flour was hydrolysed and about 82% of the hydrolysate was glucose. The feeding profile, which was based on a model with desired specific growth rate range of 0.18–0.23 h−1, biomass yield coefficient of 0.5 g g−1 and feed substrate concentration of 200 g L−1, was implemented manually using the millet flour hydrolysate in test experiments and glucose feed in control experiments. The fermentation off-gas was analyzed on-line by mass spectrometry for the calculation of carbon dioxide production rate, oxygen up-take rate and the respiratory quotient. Off-line determination of biomass, ethanol and glucose were done, respectively, by dry weight, gas chromatography and spectrophotometry. Cell mass concentrations of 49.9–51.9 g L−1 were achieved in all experiments within 27 h of which the last 15 h were in the fedbatch mode. The average biomass yields for the millet flour and glucose media were 0.48 and 0.49 g g−1, respectively. No significant differences were observed between the dough-leavening activities of the products of the test and the control media and a commercial preparation of instant active dry yeast. Millet flour hydrolysate was established to be a satisfactory low cost replacement for glucose in the production of baking quality yeast.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 16 (1996), S. 117-123 
    ISSN: 1476-5535
    Schlagwort(e): baker's yeast ; Saccharomyces cerevisiae ; fed-batch cultivation ; ethanol sensor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Growth kinetics ofSaccharomyces cerevisiae in glucose syrup from cassava starch and sugarcane molasses were studied using batch and fed-batch cultivation. The optimum temperature and pH required for growth were 30°C and pH 5.5, respectively. In batch culture the productivity and overall cell yield were 0.31 g L−1 h−1 and 0.23 g cells g−1 sugar, respectively, on glucose syrup and 0.22 g L−1 h−1 and 0.18 g cells g−1 sugar, respectively, on molasses. In fed-batch cultivation, a productivity of 3.12 g L−1 h−1 and an overall cell yield of 0.52 g cells g−1 sugar in glucose syrup cultivation and a productivity of 2.33 g L−1 h−1 and an overall cell yield of 0.46 g cells g−1 sugar were achieved in molasses cultivation by controlling the reducing sugar concentration at its optimum level obtained from the fermentation model. By using an on-line ethanol sensor combined with a porous Teflon® tubing method in automating the feeding of substrate in the fed-batch culture, a productivity of 2.15 g L−1 h−1 with a yield of 0.47 g cells g−1 sugar was achieved using glucose syrup as substrate when ethanol concentration was kept at a constant level by automatic control.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 495-501 
    ISSN: 1476-5535
    Schlagwort(e): Saccharomyces cerevisiae ; Non-alcohol beer ; Wort ; Immobilization ; DEAE-cellulose carrier ; Low temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A system for production of non-alcohol beer is described. A limited fermentation is carried out with immobilized cells ofSaccharomyces cerevisiae in a packed bed reactor. In the reactor, combined stress factors such as low temperature (2–4°C) and anaerobic conditions limit cell metabolism. Of the available sugars only a small amount of glucose is metabolized, resulting in low concentrations of ethanol (〈0.08%). The absence of oxygen affects the redox balance of the yeast cell, and thus stimulates formation of esters and higher alcohols. Products are formed by reduction of wort aldehydes, as well as reduction of intracellular metabolites. Despite the stress conditions, biomass increases during prolonged production periods. In batch experiments,S. cerevisiae strain W34 grows at low temperatures and a mininum growth temperature of −2 °C was found, indicating that a further reduction of temperature during production will not inhibit growth. The characteristics of the system allow its use in very different applications. Potential applications of the immobilized system are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 514-522 
    ISSN: 1476-5535
    Schlagwort(e): Saccharomyces cerevisiae ; Molecular taxonomy ; Classification ; Alcoholic fermentation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Archaic speculations and firmly established legends regarding the origin of the yeastSaccharomyces cerevisiae and related species are revisited in light of past and recent ecological evidence pointing to a strict association with artificial, man-made environments such as wineries and fermentation plants. The nomenclature within this industrially important group is also discussed in view of the modifications imposed from application of molecular techniques to classification.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 17 (1996), S. 303-313 
    ISSN: 1476-5535
    Schlagwort(e): grape(s) ; wine yeast(s) ; Saccharomyces cerevisiae ; genetic analysis ; electrophoretic karyotyping ; segregation of chromosomal length polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Numerous studies have described the yeast biota of grapes, and grape must in order to understand better the succession of yeasts during fermentation of wine. The origin of the wine yeasts has been rather controversial. By using more elaborate isolation methods, classical genetic analysis and electrophoretic karyotyping of monosporic clones, with this study, credible proof now exists that the vineyard is the primary source for the wine yeasts and that strains found on the grapes can be followed through the fermentation process.
    Materialart: Digitale Medien
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  • 12
    ISSN: 1573-0972
    Schlagwort(e): Ergosterol ; fatty acids ; phospholipids ; Saccharomyces cerevisiae ; Torulaspora delbrueckii ; wine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Saccharomyces cerevisiae and Torulaspora delbrueckii were grown under different O2 availabilities on grape must. Oxygen requirements for the two yeasts were different: under anaerobic conditions, S. cerevisiae produced a higher percentage of unsaturated fatty acids, and had a greater cell yield and fermentation activity than T. delbrueckii. Addition of ergosterol (25mg/l) and oleic acid (31mg/l) caused total recovery of cellular growth and the fermentation activity of S. cerevisiae in anaerobiosis, but not of T. delbrueckii. However a short period of aeration to a 48 h culture in anaerobiosis, led to total recovery of the cellular growth and fermentation activity in both yeasts. Likewise, the effect of a short aeration period on unsaturated fatty acid biosynthesis was similar for both species.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 13 (1997), S. 711-712 
    ISSN: 1573-0972
    Schlagwort(e): Endopolygalacturonase ; pectic enzymes ; Saccharomyces cerevisiae ; yeast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The laboratory strain of S. cerevisiae, IM1-8b, showed pectolytic activity in the presence of either glucose, fructose, or sucrose as the carbon source, but not with galactose. The enzyme activity was rapidly lost with shaking. The optimum pH and temperature for activity were 4.5 and 45°C, respectively. The enzyme was an endopolygalacturonase, since it preferentially hydrolysed pectate over pectin and decreased the viscosity of a 5% polygalacturonic solution by about 30% in 30min producing oligogalacturonic acid and digalacturonic acid as end-products.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 15 (1999), S. 561-564 
    ISSN: 1573-0972
    Schlagwort(e): α-Amylase ; fusion protein ; glucoamylase ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract A fusion gene containing the Bacillus subtilis α-amylase gene and Aspergillus awamori glucoamylase cDNA was expressed in Saccharomyces cerevisiae. The resulting bifunctional fusion protein having both α-amylase and glucoamylase activities secreted into the culture medium was purified to apparent homogeneity by affinity chromatography and gel filtration on Sephadex G-100. The enzyme had an apparent molecular mass of 150 kDa and showed an optimum pH and temperature of 6.0 and 60 °C, respectively. The main hydrolysis products from soluble starch were glucose and maltose.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 15 (1999), S. 629-630 
    ISSN: 1573-0972
    Schlagwort(e): Ethanol ; multi-drug resistance ; Saccharomyces cerevisiae ; trichothecin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Trichothecin-resistant mutants were isolated from saké yeast. These mutants were subjected to saké brewing, and showed a higher ethanol productivity than did the parents. They showed multidrug resistance, and resistance to organic compounds. We considered that the higher ethanol productivity of the mutants was related to their resistance to organic compounds and to their ethanol tolerance.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 14 (1997), S. 107-111 
    ISSN: 1573-0972
    Schlagwort(e): Glutaraldehyde ; immobilization ; monochloroacetic acid ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 14 (1997), S. 243-246 
    ISSN: 1573-0972
    Schlagwort(e): Amino acid analogue ; Saccharomyces cerevisiae ; secondary products ; wine yeast ; winemaking
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Mutants resistant to the amino acid analogues dl-thiaisoleucine, dl-4-azaleucine, 5,5,5-trifluoro-dl-leucine and l-O-methylthreonine, were isolated from Saccharomyces cerevisiae wine yeast strains. The fermentative production of secondary metabolites by the mutants was tested in grape must. Higher alcohols, acetaldehyde and acetic acid concentration varied depending on strain and analogue. Most of the mutants produced increased amounts of amyl alcohol. A remarkable variability in the level of n-propanol, isobutanol, acetaldehyde and acetic acid was observed. In practical application, the use of mutants resistant to amino acid analogues can improve the quality of wines by reducing or increasing the presence of some secondary compounds.
    Materialart: Digitale Medien
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  • 18
    ISSN: 1573-0972
    Schlagwort(e): Adenosine phosphates ; fermentation ; flor-veil-forming yeast ; nicotinamide adenine dinucleotides ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Significant changes in the intracellular concentrations of adenosine phosphates and nicotinamide adenine dinucleotides were observed during fermentation of grape must by three different strains ofSaccharomyces cerevisiae: S. cerevisiae var.cerevisiae, a typical fermentative yeast strain and two flor-veil-forming strains,S. cerevisiae var.bayanus andS. cerevisiae var.capensis. The intracellular concentration of ATP was always higher inS. cerevisiae var.cerevisiae than in the flor-veil-forming strains. NAD+ and NADP+ concentrations decreased at faster rates in the flor-veil-forming yeasts than in the other yeast but NADH concentration was the same in all yeasts for the first 10 days of fermentation. NADPH concentration was always lower inS. cerevisiae var.cerevisiae than in the other yeasts and this yeast also showed higher rates of growth and fermentation during the early stages of the fermentation and the presence of non-viable cells at the end of fermentation. In contrast, the flor-veil-forming strains maintained growth and fermentation capabilities for a relatively long time and viable cells were present throughout the entire fermentation process (31 days).
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 25-27 
    ISSN: 1573-0972
    Schlagwort(e): Batch fermentation ; immobilization ; Saccharomyces cerevisiae ; secondary products ; wine yeast ; wine making
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Five, highly flocculeng strains of Saccharomyces cerevisiae, isolated from wine, were immobilized in calcium alginate beads to optimize primary must fermentation. Three cell-recycle batch fermentations (CRBF) of grape musts were performed with the biocatalyst and the results compared with those obtained with free cells. During the CRBF process, the entrapped strains showed some variability in the formation of secondary products of fermentation, particularly acetic acid and acetaldehyde. Recycling beads of immobilized flocculent cells is a good approach in the development and application of the CRBF system in the wine industry.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 14 (1998), S. 595-597 
    ISSN: 1573-0972
    Schlagwort(e): Lipase ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Seven strains of Saccharomyces cerevisiae all produced lipase when grown in shake flask culture. The best strain, DSM 1848, produced 4.0U of lipase in the medium containing olive oil and yeast extract. Production of the lipase was growth-associated.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 14 (1998), S. 649-653 
    ISSN: 1573-0972
    Schlagwort(e): 2,3-Butanediol ; Kloeckera apiculata ; Saccharomyces cerevisiae ; Saccharomycodes ludwigii ; wine making ; Zygosaccharomyces bailii
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The capacity to produce 2,3-butanediol by 90 strains of four different species of wine yeasts (Kloeckera apiculata, Saccharomyces cerevisiae, Saccharomycodes ludwigii, Zygosaccharomyces bailii) was tested in grape must by automated multiple development HPTLC. The total amount of 2,3-butanediol produced varied between 23mg l−1 and 857.7mg l−1 according to the yeast species. S. cerevisiae and Z. bailii behaved similarly, producing elevated amounts of 2,3-butanediol. K. apiculata and Sc. ludwigii, in contrast, were low producers. When considerable amounts of 2,3-butanediol were found, little acetoin was present; the amounts of butanediol and acetoin were characteristic of the individual species.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    World journal of microbiology and biotechnology 14 (1998), S. 719-725 
    ISSN: 1573-0972
    Schlagwort(e): Coulter counter ; mechanical properties ; micromanipulation ; osmotic pressure ; Saccharomyces cerevisiae ; yeast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract A new micromanipulation technique which has previously been used to measure the mechanical properties of single animal cells has now been applied to yeast cells. In this study this technique was used to measure yeast cell strength and cell size across a 2l batch fermentation. Alternatively the cell size could also be determined using a Coulter counter while cell measurement was diluted with a conducting fluid (Isoton II). For the cell strength, it was found that the osmotic pressure of diluents did affect cell strength. However, it was also found that there was no significant effect of osmotic pressure of diluents on cell size whether a Coulter counter or micromanipulation was used for measurement. Micromanipulation has been shown to be a powerful technique for measuring the mechanical properties of yeast cells and it will be very useful for studying their behaviour in cell disruption equipment, e.g. high-pressure homogenizers.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 380-390 
    ISSN: 0006-3592
    Schlagwort(e): insect cells ; baculovirus ; bcl-2 ; recombinant proteins ; cell viability ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The effect of bcl-2 expression on cell viability and recombinant protein synthesis was investigated in the Spodoptera frugiperda Sf-9 and Trichoplusia ni BTI-Tn-5B1-4 (High Five™) insect cell lines. It was found that coinfection with a baculovirus expressing bcl-2 [Autographa californica nuclear polyhedrosis virus (AcNPV)-bcl2] extended the life span of High Five™ cells but not Sf-9 cells when compared to infection with recombinant baculoviruses expressing either human tissue plasminogen activator (AcNPV-tPA) or Escherichia coli β-galactosidase (AcNPV-βgal). Similar results were obtained in coinfection experiments; i.e., AcNPV-bcl2 coinfection increased the life span of High Five™ cells over that of cells infected with either AcNPV-tPA or AcNPV-βgal alone, but they did not affect the life span of coinfected Sf-9 cells. Coinfection of Sf-9 cells with AcNPV-bcl2 and AcNPV-βgal resulted in a decrease in the maximum β-gal expression levels of over 90% when compared to infection with AcNPV-βgal alone. A similar trend was found in the β-gal mRNA levels. Coinfection also resulted in a reduced β-gal expression level in High Five™ cells, but the reduction was consistent with what would be expected when two recombinant viruses compete for use of the cellular machinery. In contrast to the inhibitory effect of AcNPV-bcl2 coinfection on βgal expression, t-PA expression levels were either not affected (Sf-9 cells) or were increased 50% (High Five™ cells) over those obtained by infection with AcNPV-tPA alone. These results support the hypotheses that bcl-2 can inhibit transcription of genes under polyhedrin promoter control and that β-gal expression levels, but not t-PA expression levels, are controlled at the transcriptional level. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 380-390, 1997.
    Zusätzliches Material: 7 Ill.
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  • 24
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 592-608 
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; metabolic modeling ; sensitivity analysis ; glycolysis ; compartmentation ; transient response ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A mathematical model of glycolysis in Saccharomyces cerevisiae is presented. The model is based on rate equations for the individual reactions and aims to predict changes in the levels of intra- and extracellular metabolites after a glucose pulse, as described in part I of this study. Kinetic analysis focuses on a time scale of seconds, thereby neglecting biosynthesis of new enzymes. The model structure and experimental observations are related to the aerobic growth of the yeast. The model is based on material balance equations of the key metabolites in the extracellular environment, the cytoplasm and the mitochondria, and includes mechanistically based, experimentally matched rate equations for the individual enzymes. The model includes removal of metabolites from glycolysis and TCC for biosynthesis, and also compartmentation and translocation of adenine nucleotides. The model was verified by in vivo diagnosis of intracellular enzymes, which includes the decomposition of the network of reactions to reduce the number of parameters to be estimated simultaneously. Additionally, sensitivity analysis guarantees that only those parameters are estimated that contribute to systems trajectory with reasonable sensitivity. The model predictions and experimental observations agree reasonably well for most of the metabolites, except for pyruvate and adenine nucleotides. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 592-608, 1997.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 229-236 
    ISSN: 0006-3592
    Schlagwort(e): bioreactor ; fluidized bed ; murine granulocyte-macrophage colony stimulating factor ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Continuous production of a recombinant murine granulocyte-macrophage colony-stimulating factor (MuGM-CSF) by immobilized yeast cells, Saccharomyces cerevisiae strain XV2181 (a/a, Trp1) containing plasmid pαADH2, in a fluidized bed bioreactor was studied at a 0.03 h-1 dilution rate and various particle loading rates ranging from 5% to 33% (v/v). Cells were immobilized on porous glass beads fluidized in an air-lift draft tube bioreactor. A selective medium containing glucose was used to start up the reactor. After reaching a stable cell concentration, the reactor feed was switched to a rich, nonselective medium containing ethanol as the carbon source for GM-CSF production. GM-CSF production increased initially and then dropped gradually to a stable level. During the same period, the fraction of plasmid-carrying cells declined continuously to a lower level, depending on the particle loading. The relatively stable GM-CSF production, despite the large decline in the fraction of plasmid-carrying cells, was attributed to cell immobilization. As the particle loading rate increased, the plasmid stability also increased. Also, as the particle loading increased from 5% to 33%, total cell density in the bioreactor increased from 16 to 36 g/L, and reactor volumetric productivity increased from 0.36 to 1.31 mg/L·h. However, the specific productivity of plasmid-carrying cells decreased from 0.55 to 0.07 mg/L·g cell. The decreased specific productivity at higher particle loading rates was attributed to reduced growth efficiency caused by nutrient limitations at higher cell densities. Both the reactor productivity and specific cell productivity increased by two- to threefold or higher when the dilution rate was increased from 0.03 to 0.07 h-1. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 703-712 
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; Ty3 retrotransposon ; cloned gene integration ; stability ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The Ty3 retrotransposon of Saccharomyces cerevisiae was employed for the site-specific integration of heterologous genes into the yeast genome. A GAL-regulated promoter allowed induction of the retrotransposition process, and a bacterial neor gene inserted in the Ty3 element was used as a selectable model heterologous gene. The frequency of transposition of this neor-marked element was found to be comparable to that of an unmarked element. Three amplification systems were constructed; the systems varied with respect to the location and number of the GAL-regulated helper and neor-marked Ty3 elements. For all three systems, neor integrations were readily selected with a maximum of two insertions obtained per round of amplification. A sequential amplification strategy was effective for further increasing the number of integrated cloned genes, and families of strains varying by only one neor insertion were easily obtained. Resistance to the antibiotic G418 correlated well with the number of integrated neor genes, and Northern blots verified the relationship between cloned gene number (up to four) and neor expression. Structural stability of the integrated genes was also demonstrated. By controlling the number of rounds of amplification and the level of G418 selection, precise numbers of integrated heterologous genes could be obtained. Because the amplification process can be repeated using different cloned genes inserted in the Ty3 element, these results demonstrate the potential of retrotransposition for the regulated integration of a series of different genes at nondeleterious chromosomal locations.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 27
    ISSN: 0006-3592
    Schlagwort(e): malate dehydrogenase ; protein chromatography ; Saccharomyces cerevisiae ; direct extraction ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A novel technique for protein chromatography has been developed, which can be used to extract proteins from particulate-containing solutions (such as fermentation broths or preparations of disrupted cells) on a continuous basis, and delivers clarified streams of purified product. Adsorbents deployed in this type of contactor are based on PVA-coated perfluorocarbons derivitized with affinity ligands such as triazine dyes. In this article, we describe the application of this equipment for the continuous purification of malate dehydrogenase from an unclarified homogenate of Saccharomyces cerevisiae, using a Procion Red HE-7B-derivitized adsorbent. Although operating conditions were not optimized to produce a product of maximized purification factor, concentration, and yield, we have shown that MDH can be purified continuously in 78% yield at a rate of 70 U/min, with a purification factor of approximately 10. This corresponds to specific productivity of approximately 0.35 U/min per milliliter of settled adsorbent, a higher specific productivity than was feasible with the same adsorbent using expanded bed adsorption (EBA). © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 427-441, 1997.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 142-152 
    ISSN: 0006-3592
    Schlagwort(e): insect cells ; baculovirus ; protein expression ; high cell density ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Per cell protein expression in virally-infected insect cells declines significantly at high cell density resulting in a decrease in volumetric productivity. Specific protein expression levels in Spodoptera frugiperda (Sf-21) cells could be increased at high cell densities by increasing the oxygen supply and by supplementing the medium with glutamine post-infection. β-Galactosidase yield was increased from 411 to 855 IU/ml by increasing the glutamine concentration in the medium by 46% and increasing the gas phase oxygen concentration from 21 to 80%. Similarly, the yield of a secreted alkaline phosphatase was increased from 14.2 to 26.2 IU/mL using the same conditions. Part of the increase in production with Sf-21 culture was due to increased release to the extra-cellular compartment at the higher oxygen concentrations. Increasing the gas phase oxygen concentration to 95% in conjunction with a 100% increase in glutamine and glucose concentrations did not improve the yield any further. Peak production under elevated oxygen and nutrient conditions occurred at 72 h about 24-48 h earlier than under normal conditions. In a Trichoplusia ni cell line (BTI-TN-5B1-4), the maximum secreted alkaline phosphatase activity was increased from 10 to 27.2 IU/mL by similarly manipulating the oxygen supply. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 142-152, 1997.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 371-374 
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; cell mass sensor ; optical density probe ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the highly competitive market of commercial bakers' yeast, fermentations are operated for maximum efficiency and minimum production cost. In order to maintain competitiveness, the fermentations must be highly consistent with minimum variation in yeast performance, maximum yield on raw materials, and minimum production of undesirable side products. The use of advanced instrumentation is of critical importance to achieving these goals by the production engineer. An in situ optical density probe was used to determine the yeast cell density in full-scale commercial bakers' yeast fermentations. The optical density probe results were compared with oxygen uptake rate analyses, packed cell volume, and off-line measured cell dry weights. The most accurate measurement of cell density was found to be the optical density probe. This instrument allowed the on-line determination of cell density with highly consistent results from fermentation batch to batch and with out the need for intermittent recalibration. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
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  • 30
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; hepatitis B surface antigen (HBsAg) ; continuous culture ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We have studied the growth rate dependence of hepatitis B surface antigen (HBsAg) p24s monomer and lipoprotein particle synthesis produced in Saccharomyces cerevisiae using galactose-limited continuous culture. The hepatitis B virus S gene, which encodes the p24s monomer, is transcribed under the control of the GAL 10p on a chimeric 2-μm plasmid harbored in a haploid yeast strain. Monomers autonomously form lipoprotein aggregates (particles) in vivo using only host-cell-derived components. Steady states were evaluated in a range from 0.015 h-1 to washout (0.143 h-1). Both p24s monomer and HBsAg particle levels, at steady state, varied in an inverse linear manner with growth rate. A consistent excess of total p24s monomer to HBsAg particle, estimated at five- to tenfold by mass, was found at all dilution rates. The average copy number of the 2-μm plasmid (carrying LEU2 selection) remained constant at 200 copies per cell from washout to 0.035 h-1. Surprisingly, the average copy number was undetectable at the lowest dilution rate tested (0.015 h-1), even though HBsAg expression was maximal. Total p24s monomer and HBsAg particle values ranged twofold over this dilution rate range. No differences in the trends for HBsAg expression and average copy number could be detected past the critical dilution rate where aerobic fermentation of galactose and ethanol overflow were observed. HBsAg expression in continuous culture was stable for at least 40 generations at 0.100 h-1. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 31
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 659-666 
    ISSN: 0006-3592
    Schlagwort(e): suspension culture ; insect cells ; baculovirus ; multiplicity of infection ; time of infection ; model ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In vitro infection of insect cells with baculoviruses is increasingly considered a viable means for the production of biopesticides, recombinant veterinary vaccines, and other recombinant products. Batch fermentation processes traditionally employ intermediate to high multiplicities of infection necessitating two parallel scale-up processes - one for cells and one for virus. In this study, we consider the use of multiplicities of infection as low as 0.0001 plaque-forming units per cell, a virus level low enough to enable infection of even large reactors (e.g., 10 m3) directly from a frozen stock. Using low multiplicities in the Sf9/β-gal-AcNPV system, recombinant protein titers comparable with the maximum titer observed in high multiplicity infections were achieved. Cultures yielding the maximum titer were characterized by reaching a maximum cell density between 3 and 4 × 109 cell L-1. This optimal cell yield did not depend on the multiplicity of infection, supporting the existing view that batch cultures are limited by availability of substrate. Up to a certain cell density, product titer will increase almost linearly with availability of biocatalyst, that is, cells. Beyond this point any further cell formation comes at the expense of final product titer. Low multiplicity infections were found not to cause any significant dispersion of the protein production process. Hence, product stability is not a major issue of concern using low multiplicities of infection. The sensitivity to initial conditions and disturbances, however, remains an issue of concern for the commercial use of low multiplicity infections. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 681-698 
    ISSN: 0006-3592
    Schlagwort(e): stoichiometry ; biomass yield ; product yield ; metabolic fluxes ; Saccharomyces cerevisiae ; Candida utilis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Using available biochemical information, metabolic networks have been constructed to describe the biochemistry of growth of Saccharomyces cerevisiae and Candida utilis on a wide variety of carbon substrates. All networks contained only two fitted parameters, the P/O ratio and a maintenance coefficient. It is shown that with a growth-associated maintenance coefficient, K, of 1.37 mol ATP/ C-mol protein for both yeasts and P/O ratios of 1.20 and 1.53 for S. cerevisiae and C. utilis, respectively, measured biomass yields could be described accurately. A metabolic flux analysis of aerobic growth of S. cerevisiae on glucose/ethanol mixtures predicted five different metabolic flux regimes upon transition from 100% glucose to 100% ethanol. The metabolic network constructed for growth of S. cerevisiae on glucose was applied to perform a theoretical exercise on the overproduction of amino acids. It is shown that theoretical operational product yield values can be substantially lower than calculated maximum product yields. A practical case of lysine production was analyzed with respect to theoretical bottlenecks limiting product formation. Predictions of network-derived irreversibility limits for Ysp (μ) functions were compared with literature data. The comparisons show that in real systems such irreversibility constraints may be of relevance. It is concluded that analysis of metabolic network stoichiometry is a useful tool to detect metabolic limits and to guide process intensification studies. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 33
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 494-499 
    ISSN: 0006-3592
    Schlagwort(e): cell metabolism ; baculovirus ; insect cells ; recombinant protein OSF-2 ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The properties of Sf9 and Tn5 insect cells were analyzed comparatively under serum-free culture conditions. Sf9 cells in SF900II medium apparently utilized sucrose as a primary nutrient both before and after virus infection, yielding small amounts of lactate and ammonia. Tn5 cells in Excell 401 medium consumed all the nutrients examined, including sucrose. The productivity of a recombinant glycoprotein, OSF-2, by Tn5 cells, was moderate in both monolayer and spinner cultures, but the ability to secrete it was compromised in the former case. Relative to the Tn5 cultures, Sf9 produced 30-fold more OSF-2 in either culture mode. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 34
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 909-920 
    ISSN: 0006-3592
    Schlagwort(e): baculovirus ; insect cells ; metabolism ; Sf-9; high five™ ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Nutrient utilization and byproduct accumulation were monitored in Spodoptera frugiperda Sf-9 and Trichoplusia ni BTI-Tn-5B1-4 (High Five™) cell lines during growth and following viral infection in suspension cultures in order to develop a better understanding of cell metabolism and to acquire information relevant to large scale fed-batch bioreactors. The utilization of glucose, dissolved oxygen, and amino acids were monitored in Sf-9 cell cultures grown in Sf-900 II serum-free medium (SFM) and in High Five™ cell cultures grown in both Sf-900 II and Express Five SFM. Using the optimal medium for each cell line, i.e., Sf-900 II SFM for Sf-9 cells and Express Five SFM for High Five™ cells, the cell growth rate, maximum cell density, specific glucose and glutamine utilization rates, and specific alanine production rate were comparable during cell growth. In addition, the expression level of recombinant human tissue plasminogen activator was comparable in the two cell lines on a per cell basis. It was found, however, that lactate and ammonia accumulated in High Five™ cell cultures, but not in Sf-9 cell cultures. In addition, High Five™ cells utilized asparagine more rapidly than glutamine, whereas Sf-9 cells consumed only minimal asparagine, and the oxygen utilization rate was significantly higher in High Five™ cell cultures. It was also found that the medium had a significant effect on High Five™ cell metabolism, e.g., the specific glucose utilization rate and the specific lactate and alanine production rates were significantly higher in Sf-900 II SFM than in Express Five SFM. In addition, the maximum cell density and specific asparagine utilization rate were significantly higher in Express Five SFM. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55:909-920, 1997.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 203-213 
    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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  • 36
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 135-143 
    ISSN: 0006-3592
    Schlagwort(e): baker's yeast; ; knowledge-based system ; fuzzy logic ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A real-time fuzzy-knowledge-based system for fault diagnosis and control of bioprocesses was constructed using the object-oriented programming environment Small-talk/V Mac. The basic system was implemented in a Macintosh Quadra 900 computer and built to function connected on line to the process computer. Fuzzy logic was employed in handling uncertainties both in the knowledge and in measurements. The fuzzy sets defined for the process variables could be changed on-line according to process dynamics. Process knowledge was implemented in a graphical two-level hierachical knowledge base. In on-line process control the system first recognizes the current process phase on the basis of top-level rules in the knowledge-base. Then, according to the results of process diagnosis based on measurement data, the appropriate control strategy is subsequently inferred making use of the lower level rules describing the process during the phase in question. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 193-208 
    ISSN: 0006-3592
    Schlagwort(e): yeast intermediary metabolism ; carbon and phosphorylation fluxes ; amphibolic pathways ; NADH oxidation ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the present work we develop a method for estimating anabolic fluxes when yeast are growing on various carbon substrates (glucose, glycerol, lactate, pyruvate, acetate, or ethanol) in minimal medium. Fluxes through the central amphibolic pathways were calculated from the product of the total required amount of a specified carbon intermediate times the growth rate. The required amount of each carbon intermediate was estimated from the experimentally determined macromolecular composition of cells grown in each carbon source and the monomer composition of macromolecules.Substrates sharing most metabolic pathways such as ethanol and acetate, despite changes in the macromolecular composition, namely carbohydrate content (34% ± 1 and 21% ± 3, respectively), did not show large variations in the overall fluxes through the main amphibolic pathways. For instance, in order to supply anabolic precursors to sustain growth rates in the range of 0.16/h to 0.205/h, similar large fluxes through Acetyl CoA synthase were required by acetate (4.2 mmol/hr g dw) or ethanol (5.2 mmol/h g dw).The Vmax activities of key enzymes of the main amphibolic pathways measured in permeabilized yeast cells allowed to confirm, qualitatively, the operation of those pathways for all substrates and were consistent on most substrates with the estimated fluxes required to sustain growth.When ATP produced from oxidation of the NADH synthesized along with the key intermediary metabolites was taken into account, higher YATPmax values (36 with respect to 24 g dw/mol ATP) were obtained for glucose. The same result was obtained for glycerol, ethanol, and acetate. A yield index (YI) was defined as the ratio of the theoretically estimated substrate flux required to sustain a given growth rate over the experimentally measured flux of substrate consumption. Comparison of Yl between growth on various carbon sources led us to conclude that ethanol (Yl = 0.84), acetate (Yl = 0.77), and lactate (Yl = 0.77) displayed the most efficient use of substrate for biomass production. For the other substrates, the Yl decayed in the following order: pyruvate 〉 glycerol 〉 glucose.An improvement of the quantitative understanding of yeast metabolism, energetics, and physiology is provided by the present analysis. The methodology proposed can be applied to other eukaryotic organisms of known chemical composition. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
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  • 38
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 97-106 
    ISSN: 0006-3592
    Schlagwort(e): antibody integrity ; human monoclonal antibodies ; insect cells ; mammalian cell culture ; proteolytic activity ; protein microheterogeneity ; serum-free media ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: To investigate the effects of factors secreted by different cell lines on human monoclonal antibody (MAb) integrity, 600 mg of a human MAb, which specifically binds to human erythrocytes, were produced in a perfusion process. After purification by protein A affinity chromatography, the MAb was used for integrity testing in supernatants of several cell lines to investigate their potential to degrade the antibody in the extracellular environment. One insect cell line (IPLB-SF-21 AE) and four mammalian cell lines [CHO K1, BHK-21 (C13), C1271, P3-X63-Ag8.653], all of them commonly used for the production of recombinant proteins, and the human-human-mouse heterohybridoma cell line itself (H-CB-hahE), were adapted to serum-free culture media. For integrity testing all cell lines were cultivated in spinner flasks using serum-free media supplemented with 30 μg mL-1 of purified MAb. MAb integrity was assayed by SDS polyacrylamide gel electrophoresis (SDS-PAGE), isoelectric focusing, both followed by Western blotting, and an antigen binding assay. None of the mammalian cells showed any detectable effects on antibody stability and integrity during exponential growth, whereas isoelectric focusing of monoclonal antibody taken from IPLB-SF-21 AE culture supernatants revealed a new band indicating a partial modification of the MAb by secreted factors of these cells. This observation did not correlate with the total proteolytic activity, which was measured in all supernatants and found to be lowest in the insest cell cultures. For mammalian cell cultures, it could be concluded from these findings that shifts of the antibody microheterogeneity pattern, which can be found normally as a result of variations in different production parameters, are not caused by extracellular factors once the product has been secreted into the supernatant. In addition to their well-known advantages in posttranslational modifications (e.g., formation of complex type N-glycans), mammalian cells appear to be more suitable as expression systems for human monoclonal antibodies to be used in vivo when compared with baculovirus-infected insect cells. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
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  • 39
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 386-400 
    ISSN: 0006-3592
    Schlagwort(e): microfiltration ; yeast ; filtration ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: To develop a highly efficient cell harvest step under time constraint, a novel rotating disk dynamic filtration system was studied on the laboratory scale (0.147-ft.2 nylon membrane) for concentrating recombinant yeast cells containing an intracellular product. The existing cross-flow microfiltration method yielded pseudo-steady state flux values below 25 LMH (L/m2. h) even at low membrane loadings (10 L/ft.2). By creating high shear rates (up to 120,000-1) on the membrane surface using a rotating solid disk, this dynamic filter has demonstrated dramatically improved performance, presumably due to minimal cake buildup and reduced membrane fouling. Among the many factors investigated, disk rotating speed, which determines shear rates and flow patterns, was found to be the most important adjustable parameter. Our experimental results have shown that the flux increases with disk rotating speed, increases with transmembrane pressure at higher cell concentrations, and can be sustained at high levels under constant flux mode. At a certain membrane loading level, there was a critical speed below which it behaved similarly to a flat sheet system with equivalent shear. Average flux greater than 200 LMH has been demonstrated at 37-L/ft.2 loading at maximum speed to complete sixfold concentration and 15-volume diafiltration for less than 100 min. An order of magnitude improvement over the crossflow microfiltration control was projected for large scale production. This superior performance, however, would be achieved at the expense of additional power input and heat dissipation, especially when cell concentration reaches above 80 g dry cell weight (DCW)/L. Although a positive linear relationship between power input and dynamic flux at a certain concentration factor has been established, high cell density associated with high viscosity impacted adversely on effective average shear rates and, eventually, severe membrane fouling, rather than cake formation, would limit the performance of this novel system. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 3-11 
    ISSN: 1573-0778
    Schlagwort(e): cell line establishment ; cryopreservation ; insect cells ; development of ; insect cells ; characterization of ; isoenzymes ; lepidopteran cell cultures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Conclusions With the wide availability of insect cell culture media, it can generally be considered a routine process to develop new cell lines. Exceptions to this statement do exist, of course. Difficulties may arise when attempting to culture a specific cell type. For example, while there are a few cell lines from insect fat body and at least one from the midgut, it may not be possible to obtain cell lines from these tissues from all insect species due to terminal differentiation and other factors. Also, researchers have desired cell lines from certain species, such as the honey bee, for which no success has been obtained. As in the early days of tissue culture, it is difficult to discern why negative results occur. However, as more is learned about the physiology and nutrition of various insects and tissues, we may get clues which will help solve these questions. The remaining chapters in this book will provide the reader with exciting uses for insect cell culture. As I mentioned earlier, the baculovirus expression vector system has provided a stimulus to the field of insect cell culture not seen previously.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 33-41 
    ISSN: 1573-0778
    Schlagwort(e): insect cells ; metabolism ; energetics ; amino acids ; fluxes ; oxygen uptake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 139-144 
    ISSN: 1573-0778
    Schlagwort(e): insect cells ; proteins ; post-translational modification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 299-304 
    ISSN: 1573-0778
    Schlagwort(e): biosafety ; insect cells ; containment ; risk ; virus ; mycoplasma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Conclusions The hazards posed to the environment by the accidental release of baculovirus expression vectors can be put into perspective by the results obtained from experiments in which AcNPV was released deliberately into the field (Bishop et al., 1992). Polyhedrin positive viruses will persist in soil and on leaf surfaces for periods comprising weeks and months. However, polyhedrin negative viruses (similar to those used as expression vectors) do not survive in similar situations. In consequence, accidental release of baculovirus expression vectors poses negligible hazard. The risk of such a release will largely depend on the skill of the operators. This does not take into account the hazard posed by the recombinant product which is being made by the virus-infected insect cell. Synthesis of a mammalian-specific toxin, of course, would require particularly careful manipulation of the virus-infected cell culture. The fact that insect cell lines represent an undefined risk, in terms of carriage of adventitious agents means that their containment should be maintained at a minimum of the European containment level 2. Where the tissue of origin has a high risk of infection with human pathogens or where cells may have been used in a virus culture laboratory then appropriate testing is advisable. Careful risk assessment respecting the scale of work and whole procedures (in addition to individual assessment of agents and reagents) will ensure safe working conditions for laboratory staff. If applied properly safety procedures will also succeed in encouraging clean, efficient and well documented work procedures which are synonymous with the economical use of time and resources and good science.
    Materialart: Digitale Medien
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  • 44
    ISSN: 1573-0778
    Schlagwort(e): Autographa california nuclear polyhedrosis viruses ; insect cells ; recombinant alkaline phosphatase ; separation efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Recombinant alkaline phosphatase expressed in insect cells was concentrated by a factor of one and half times at a separation efficiency of 54.2% using hydrogel ultrafiltration. Enzyme concentration was confirmed by SDS-PAGE as well as by spectrophotometric measurement. Wild and recombinant Autographa californica nuclear polyhedrosis viruses (AcNPV) were concentrated 1.4 and 1.6 times of the feed solution at 48.5 and 60.0% separation efficiency, respectively. Hydrogel ultrafiltration appears to be an attractive alternative for the concentration of AcNPV and recombinant proteins from insect cells.
    Materialart: Digitale Medien
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  • 45
    ISSN: 1573-0778
    Schlagwort(e): anoxia ; hyperthermia ; insect cells ; stress proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract In this study, we compare stress protein induction in anoxic and hyperthermicSpodoptera frugiperda cells. Anoxia transiently induces a cluster of heat shock proteins at 71 and 72 kDa. This is a subset of a larger group of stress proteins induced by heat shock. Several heat shock proteins reported in this study were previously undetected inS. frugiperda. With these additional proteins, the stress response of hyperthermicS. frugiperda closely resembles that ofDrosophila melanogaster. Prior investigations of stress protein induction during oxygen deprivation focused on mammalian cells. In sharp contrast to these cells, anoxicS. frugiperda cells neither induce glucose-regulated proteins nor suppress the heat shock family of 71/72 kDa proteins. These findings provide insight into the virtually unexplored area of stress protein induction in anoxic insect cells. In addition, they help to explain the effects of oxygen deprivation on heterologous protein yield from virally infected insect cells and to develop an oxygenregulated promoter for stably transformed insect cells.
    Materialart: Digitale Medien
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 24 (1997), S. 1-9 
    ISSN: 1573-0778
    Schlagwort(e): insect cells ; metabolism ; energetics ; amino acids ; fluxes ; oxygen uptake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 221-229 
    ISSN: 1573-0778
    Schlagwort(e): insect cells ; bioreactors ; shear ; stirred vessel ; buble column ; airlift ; scale-up
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Conclusion In this chapter we have attempted to evaluate the most important parameters which can be useful for the pur-pose of design and scale up. Insect cells and animal cells in general can be grown well in large vessels. However, none of the theories and parameters discussed in this chapter have been validated on a larger scale than laboratory and small pilot reactors. Selection of the most suitable design and scale-up method there-fore needs in particular studies in larger vessels. The Kolmogorov theory and the killing-volume model are in this respect the most promising approaches for the optimal design of large-scale animal-cell bioreactors.
    Materialart: Digitale Medien
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  • 48
    ISSN: 1573-0778
    Schlagwort(e): baculovirus ; β-galactosidase ; insect cells ; lipids ; serum-free medium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The lipid emulsion components of a serum-free insect cell medium were varied and evaluated for effects on cell growth and recombinant protein expression. The growth of High-FiveTM cells was significantly affected by polyol Pluronic F-68 and Tween-80, but not by lipids. Pluronic was essential for cell growth, while Tween-80 was required to achieve maximum cell densities. A dose response effect was observed for Tween-80 with optimal cell growth at a concentration of 25 mg/l. Cholesterol had a minor effect on cell growth, but was essential for the expression of recombinant proteins. The expression of β-galactosidase (β-gal) was directly affected by cholesterol with optimal expression at a concentration of 5.4 mg/l. Vitamin E, important as an antioxidant to stabilize lipids, did not directly affect recombinant protein expression. Although lipids were not required for cell growth, the presence of lipids were required during the cell growth phase in order to achieve efficient infection with baculovirus. These studies help to define the important components, and range of concentrations, for lipid emulsions which can effectively replace serum in insect cell culture.
    Materialart: Digitale Medien
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 173-189 
    ISSN: 1573-0778
    Schlagwort(e): insect cells ; bioreactors ; parameters ; production
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 163-171 
    ISSN: 1573-0778
    Schlagwort(e): insect cells ; shear sensitivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Conclusions While insect cells can be easily damaged in bioreactors as a result of hydrodynamic forces, it is also relatively easy to prevent this damage. Of several possible damage mechanisms, the best understood and preventable is the attachment of cells to gas-liquid interfaces and the subjection of these attached cells to the hydro-dynamic forces and/or physical forces associated with these interfaces. For example, cells attached to gas bubbles in a bioreactor can be transported into the foam layer where they are physically removed from the cell suspension, or they can be killed when the gas bubble they are attached to ruptures at the medium-air interface at the top of the bioreactor. The easiest method to prevent this damage is through the use of specific surface active compounds, such as Pluronic F-68 or Methocel E-50 which prevent the cells from attaching to the gas-medium interface.
    Materialart: Digitale Medien
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 261-270 
    ISSN: 1573-0778
    Schlagwort(e): insect cells ; parvoviruses ; virion ; immune response ; capsid proteins ; VLPs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 52
    ISSN: 1573-0778
    Schlagwort(e): factor VIII ; light chain ; heavy chain ; baculovirus expression system ; insect cells ; enhanced secretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The light and truncated heavy chains of human factor VIII, expressed separately in baculovirus-infected insect cells, exhibited different secretory behaviour when compared with each other and with a biologically active fusion molecule of the truncated heavy and light chains. The light chain was very efficiently secreted into culture medium, as judged by high extracellular protein levels and the absence of evidence for light chain retention within cells. Alternatively, proteins containing the heavy chain sequence were poorly secreted and appeared to be sequestered within cells, suggesting that regions within the heavy chain are responsible for the low levels of secreted protein which have generally been observed for recombinant factor VIII.
    Materialart: Digitale Medien
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  • 53
    ISSN: 1573-0778
    Schlagwort(e): baculovirus ; multiplicity of infection ; time of infection ; time of harvest ; apolipoprotein E ; insect cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The baculovirus expression vector system was employed to produce human apolipoprotein E and β-galactosidase in order to study the effect of multiplicity of infection on secreted and non-secreted recombinant protein production. Prior knowledge of the influence of other cell culture and infection parameters, such as the cell density at time of infection and the time of harvest, allowed determination of the direct and indirect influences of multiplicity of infection on recombinant protein synthesis and degradation in insect cells. Under non-limited, controlled conditions, the direct effect of multiplicity of infection (10−1−10 pfu/cell) on specific recombinant product yields of non-secreted β-galactosidase was found to be insignificant. Instead, the observed increased in accumulated product was directly correlated to the total number of infected cells during the production period and therefore ultimately dependent on an adequate supply of nutrients. Only the timing of recombinant virus and protein production was influenced by, and dependent on the multiplicity of infection. Evidence is presented in this study that indicates the extremely limited predictability of post-infection cell growth at very low multiplicities of infection of less than 0.1 pfu/cell. Due to the inaccuracy of the current virus quantification techniques, combined with the sensitivity of post-infection cell growth at low MOI, the possibility of excessive post-infection cell growth and subsequent nutrient limitation was found to be significantly increased. Finally, as an example, the degree of product stability and cellular and viral protein contamination at low multiplicity of infection is investigated for a secreted recombinant form of human apolipoprotein E. Comparison of human apolipoprotein E production and secretion at multiplicities of infection of 10−4−10 pfu/cell revealed increased product degradation and contamination with intracellular proteins at low multiplicities of infection.
    Materialart: Digitale Medien
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  • 54
    ISSN: 1573-0778
    Schlagwort(e): insect cells ; membrane-targeting ; nicotinic acetylcholine receptor α-subunit ; Spodoptera frugiperda ; stable expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract We have synthesised the α-subunit of the chick nicotinic acetylcholine receptor (nAChR) in stable, continuous insect (Spodoptera frugiperda) cell lines. A cDNA was integrated randomly into the insect cell genome under control of a baculovius immediate early gene promoter. Transformed cells were obtained by co-transfection of the insect cells with pIEK1.nAChRα, encoding the α-subunit cDNA, and pIEK1.neo, encoding the neomycin resistance gene. G-418-resistant clones were selected and expanded into continuous cell lines synthesising the chick nAChR α-subunit. Using fluorescence microscopy and ligand binding studies we were able to demonstrate efficient membrane targeting of the receptor subunit in the insect cell plasma membrane. Stable insect cell lines may thus have significant advantages over transient baculovirus vectors for the synthesis and characterisation of heterologous receptor proteins.
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Cytotechnology 20 (1996), S. 209-219 
    ISSN: 1573-0778
    Schlagwort(e): baculovirus ; insect cells ; mathematical model ; population balance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Conclusions Infection of insect cells with baculovirus is a potentially attractive means for producing both viral insecticides and recombinant proteins. The continuation of mathematical modelling studies such as those reviewed in this paper are essential in order to realise the full potential of the system. Through mathematical models it is possible to predict complex behaviours such as those observed when infecting cells at low MOI or when propagating virus in a continuous culture system. A purely empirical analysis of the same phenomena is very difficult if not impossible. The present three models are — despite their complexity and the effort that has gone into developing them — all first generation models. They summarise, to a large extent, our present quantitative understanding of the interaction between baculovirus and insect cells, when looked upon as a black box system. The binding and initial infection processes are still quantitatively poorly understood and further work in this area is much needed. On the longer term, a second generation of models is likely to consider interior processes such as viral DNA and RNA accumulation in much more detail using a structured model of the infection cycle.
    Materialart: Digitale Medien
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  • 56
    ISSN: 0006-3592
    Schlagwort(e): Optimization ; metabolic systems ; linear programming ; S-system representation ; ethanol ; glycerol ; carbohydrates ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Three metabolic models for the production of ethanol, glycerol, and carbohydrates in yeast are optimized with respect to different production rates. While originally nonlinear, all three optimization problems are reduced in such a way that methods of linear programming can be used. The optimizations lead to profiles of enzyme activities that are compatible with the physiology of the cells, which guarantees their viability and fitness, and yield higher rates of the desired final end products than the original systems. In order to increase ethanol rate production at least three times, six enzymes must be modulated. By contrast, when the production of glycerol or carbohydrates is optimized, modulation of just one enzyme (in the case of glycerol) or two enzymes (in the case of carbohydrates) is necessary to yield significant increases in product flux rate. Comparisons of our results with those obtained from other methods show great similarities and demonstrate that both are valid methods. The choice of one or the other method depends on the question of interest. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 758-772, 1997.
    Zusätzliches Material: 2 Ill.
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  • 57
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 180-189 
    ISSN: 0006-3592
    Schlagwort(e): dynamic model ; transient experiment ; catabolic decoupling ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The dynamic behavior of a continuous culture of Saccharomyces cerevisiae subjected to a sudden increase in the dilution rate has been successfully modelled for anaerobic growth on glucose, and for aerobic growth on acetate, on ethanol, and on glucose. The catabolism responded by an immediate jump whereas biosynthesis did not. Thus catabolism was in excess to anabolism. The model considers the decoupling between biosynthesis and catabolism, both types of reactions being modelled by first-order kinetic expressions evolving towards maximal values. Yield parameters and maximal reaction rates were identified in steady state continuous cultures or during batch experiments. Only the time constant of biosynthesis regeneration, τX, and the time constant of catabolic capacity regeneration, τcat, had to be identified during transient experiments. In most experiments τX was around 3 h, and τcat varied between 2 and 2.5 h for the different metabolisms investigated. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 180-189, 1998.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 474-482 
    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.
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  • 59
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 351-359 
    ISSN: 0006-3592
    Schlagwort(e): bioreactor ; high density ; insect cells ; perfusion ; Sf9 ; ultrasonic filter ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The baculovirus/insect cell expression system has provided a vital tool to produce a high level of active proteins for many applications. We have developed a very high-density insect cell perfusion process with an ultrasonic filter as a cell retention device. The separation efficiency of the filter was studied under various operating conditions. A cell density of over 30 million cells/mL was achieved in a controlled perfusion bioreactor and cell viability remained greater than 90%. Sf9 cells from a high-density culture and a spinner culture were infected with two recombinant baculoviruses expressing genes for the production of human chitinase and monocyte-colony inhibition factor. The protein yield on a cell basis from infecting high-density Sf9 cells was the same as or higher than that from the spinner Sf9 culture. Virus production from the high-density culture was similar to that from the spinner culture. The results show that the ultrasonic filter did not affect insect cells' ability to support protein expression and virus production following infection with baculovirus. The potential applications of the high-density perfusion culture for large-scale protein expression from Sf9 cells are also highlighted. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:351-359, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 305-316 
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; intracellular metabolites ; glycolysis ; adenine nucleotide pool ; glucose effect ; metabolic dynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The goal of this work was to obtain rapid sampling technique to measure transient metabolites in vivo. First, a pulse of glucose was added to a culture of the yeast Saccharomyces cerevisiae growing aerobically under glucose limitation. Next, samples were removed at 2 to 5 s intervals and quenched using methods that depend on the metabolite measured. Extracellular glucose, excreted products, as well as glycolytic intermediates (G6P, F6P, FBP, GAP, 3-PG, PEP, Pyr) and cometabolites (ATP, ADP, AMP, NAD+, NADH) were measured using enzymatic or HPLC methods. Significant differences between the adenine nucleotide concentrations in the cytoplasm and mitochondria indicated the importance of compartmentation for the regulation of the glycolysis. Changes in the intra- and extracellular levels of metabolites confirmed that glycolysis is regulated on a time scale of seconds. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 305-316, 1997.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 61
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 447-454 
    ISSN: 0006-3592
    Schlagwort(e): plasmid stability ; protein production ; proteinase A ; Saccharomyces cerevisiae ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Overexpression of the homologous protein proteinase A (PrA) in Saccharomyces cerevisiae has been achieved by inserting the PrA gene (PEP4) with its own promoter on a 2μ multicopy plasmid. With this system the specific PrA production rate was found to be described well by a linear function of the oxidative glucose metabolism, the reductive glucose metabolism, and the oxidative ethanol metabolism, with a significant lower yield resulting from the reductive glucose metabolism compared with the oxidative glucose metabolism. To describe the experimental data, a simple mathematical model has been set up. The model is based on an assumption of a limited respiratory capacity as suggested by Sonnleitner and Käppeli but extended to describe production of an extracellular protein. The model predicts correctly the critical dilution rate to be between 0.15 and 0.16 h-1, the decrease in the biomass yield above the critical dilution rate, and the production of proteinase A at different dilution rates. Both the experimental data and model simulations suggest that the optimum operating conditions for protein production is just at the critical dilution rate. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 447-454, 1997.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 62
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 610-619 
    ISSN: 0006-3592
    Schlagwort(e): dynamic model ; Saccharomyces cerevisiae ; oxidative capacity ; feedback control ; calorimetry ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The objective of this study was to characterize the dynamic adaptation of the oxidative capacity of Saccharomyces cerevisiae to an increase in the glucose supply rate and its implications for the control of a continuous culture designed to produce biomass without allowing glucose to be diverted into the reductive metabolism. Continuous cultures subjected to a sudden shift-up in the dilution rate showed that the glucose uptake rate increased immediately to the new feeding rate but that the oxygen consumption could not follow fast enough to ensure a completely oxidative metabolism. Thus, part of the glucose assimilated was degraded by the reductive metabolism, resulting in a temporary decrease of biomass concentration, even if the final dilution rate was below Dcrit. The dynamic increase of the specific oxygen consumption rate, qO2, was characterized by an initial immediate jump followed by a first-order increase to the maximum value. It could be modeled using three parameters denoted qjumpO2, qmaxO2, and a time constant τ. The values for the first two of the parameters varied considerably from one shift to another, even when they were performed under identical conditions. On the basis of this model, a time-dependent feed flow rate function was derived that should permit an increase in the dilution rate from one value to another without provoking the appearance of reductive metabolism. The idea was to increase the glucose supply in parallel with the dynamic increase of the oxidative capacity of the culture, so that all of the assimilated glucose could always be oxidized. Nevertheless, corresponding feed-profile experiments showed that deviations in the reductive metabolism could not be completely suppressed due to variability in the model parameters. Therefore, a proportional feedback controller using heat evolution rate measurements was implemented. Calorimetry provides an excellent and rapid estimate of the metabolic activity. Satisfactory control was achieved and led to constant biomass yields. Ethanol accumulated only up to 0.49 g L-1 as compared to an accumulation of 1.82 g L-1 without on-line control in the shift-up experiment to the same final dilution rate. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 610-619, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 63
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 214-226 
    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
    Standort Signatur Erwartet Verfügbarkeit
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  • 64
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 656-663 
    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
    Standort Signatur Erwartet Verfügbarkeit
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  • 65
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 408-418 
    ISSN: 0006-3592
    Schlagwort(e): insect cells ; shear stress ; agitation rate ; aeration rate ; Pr55gag ; virus-like particles ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In this work the maximal operational hydrodynamic conditions (agitation and aeration rate) that cause no adverse effect in Sf-9 cells growth in SF900II serum-free medium were determined. Shear stresses higher than 1 N m-2 and aeration rates higher than 0.04 vvm affect cell growth and when these conditions increase to 1.5 N m-2 and 0.11 vvm, cell growth is completely inhibited with significant cell morphology changes and a strong decrease in viability.Although the pO2 did not show a significant effect upon cell growth in the range from 10 to 50%, cell infection and specific productivity were dramatically affected. The production was optimal at a pO2 of 25% with decreases higher than 50% being observed when the pO2 decreased to 10 or increased to 50%.The maximum product quality, i.e., the percentage of product in the form of high molecular weight particles, is not coincident with maximum product titer. Although the highest Pr55gag particle titer was obtained at 96 hours post infection (hpi) and at pO2 of 25%, the best product quality (defined by gel filtration chromatography and Western immunoblot) was obtained at 48 hpi, independently of the pO2 used.The effect of overcritical conditions upon productivity was also studied. As obtained for cell growth, cell infection is affected by shear stresses above 1 N m-2 and by aeration rates higher than 0.04 vvm, with decreases in Pr55gag particle titer higher than 70%, even when the overcritical values are still far from the limit at which cell death occurs.The results obtained and the optimization strategy used allowed the maximization of the oxygen supply without damaging the cells, with important consequences on the scale-up of a production process involving this insect cell/baculovirus expression system. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 408-418, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 66
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 125-132 
    ISSN: 0006-3592
    Schlagwort(e): metabolic engineering ; metabolic flux analysis ; metabolic control analysis ; thermokinetics ; Saccharomyces cerevisiae ; Penicillium chrysogenum ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Metabolic engineering has been defined as the purposeful modification of intermediary metabolism using recombinant DNA techniques. With this definition metabolic engineering includes: (1) inserting new pathways in microorganisms with the aim of producing novel metabolites, e.g., production of polyketides by Streptomyces; (2) production of heterologous peptides, e.g., production of human insulin, erythropoitin, and tPA; and (3) improvement of both new and existing processes, e.g., production of antibiotics and industrial enzymes. Metabolic engineering is a multidisciplinary approach, which involves input from chemical engineers, molecular biologists, biochemists, physiologists, and analytical chemists. Obviously, molecular biology is central in the production of novel products, as well as in the improvement of existing processes. However, in the latter case, input from other disciplines is pivotal in order to target the genetic modifications; with the rapid developments in molecular biology, progress in the field is likely to be limited by procedures to identify the optimal genetic changes. Identification of the optimal genetic changes often requires a meticulous mapping of the cellular metabolism at different operating conditions, and the application of metabolic engineering to process optimization is, therefore, expected mainly to have an impact on the improvement of processes where yield, productivity, and titer are important design factors, i.e., in the production of metabolites and industrial enzymes. Despite the prospect of obtaining major improvement through metabolic engineering, this approach is, however, not expected to completely replace the classical approach to strain improvement - random mutagenesis followed by screening. Identification of the optimal genetic changes for improvement of a given process requires analysis of the underlying mechanisms, at best, at the molecular level. To reveal these mechanisms a number of different techniques may be applied: (1) detailed physiological studies, (2) metabolic flux analysis (MFA), (3) metabolic control analysis (MCA), (4) thermodynamic analysis of pathways, and (5) kinetic modeling. In this article, these different techniques are discussed and their applications to the analysis of different processes are illustrated. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:125-132, 1998.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 67
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 139-148 
    ISSN: 0006-3592
    Schlagwort(e): metabolic engineering ; pathway analysis ; metabolic and energetic model ; physiological state ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In this work, an integrated modeling approach based on a metabolic signal flow diagram and cellular energetics was used to model the metabolic pathway analysis for the cultivation of yeast on glucose. This approach enables us to make a clear analysis of the flow direction of the carbon fluxes in the metabolic pathways as well as of the degree of activation of a particular pathway for the synthesis of biomaterials for cell growth. The analyses demonstrate that the main metabolic pathways of Saccharomyces cerevisiae change significantly during batch culture. Carbon flow direction is toward glycolysis to satisfy the increase of requirement for precursors and energy. The enzymatic activation of TCA cycle seems to always be at normal level, which may result in the overflow of ethanol due to its limited capacity. The advantage of this approach is that it adopts both virtues of the metabolic signal flow diagram and the simple network analysis method, focusing on the investigation of the flow directions of carbon fluxes and the degree of activation of a particular pathway or reaction loop. All of the variables used in the model equations were determined on-line; the information obtained from the calculated metabolic coefficients may result in a better understanding of cell physiology and help to evaluate the state of the cell culture process. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:139-148, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 68
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 631-638 
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; fermentation ; on-line simulation ; state estimation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In order to study and control fermentation processes, indirect on-tine measurements and mathematical models can be used. In this article we present a mathematical on-line model for fermentation processes. The model is based on atom and partial mass balances as well as on equations describing the acid-base system. The model is brought into an adaptive form by including transport equations for mass transfer and unstructured expressions for the fermentation kinetics. The state of the process, i.e., the concentrations of biomass, substrate, and products, can be estimated on-line using the balance part of the model completed with measurement equations for the input and output flows of the process. Adaptivity is realized by means of on-line estimation of parameters in the transport and kinetic expressions using recursive regression analysis. These expressions can thus be used in the model as valid equations enabling prediction of the process. This makes model-based automation of the process and testing of the validity of the measurement variables possible. The model and the on-line principles are applied to a 3.5-L laboratory tormentor in which Saccharomyces cerevisiae is cultivated. The experimental results show that the model-based estimation of the state and the predictions of the process correlate closely with high-performance liquid chromatography (HPLC) analyses. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 69
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 468-490 
    ISSN: 0006-3592
    Schlagwort(e): baculovirus ; insect cells ; infection ; internalization ; enveloped viruses ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A quantitative understanding of virus trafficking would be useful in treating viral-mediated diseases, developing protocols for viral gene therapy, designing infection regimens for viral expression systems, and optimizing vaccine and recombinant protein production. Here, we present a mathematical model of the attachment, internalization, endosomal fusion, lysosomal routing, and nuclear accumulation of baculovirus in SF21 insect cells. The model accounts for multivalent bond formation of the virus with cell surface receptors. The model mimics accurately the experimental trafficking dynamics of the virus at both low and high virion to cell ratios, and estimates a receptor number of 11,000 per cell. A significant amount of virus was degraded intracellularly. Independent of the virion to cell ratio, half of the internalized virus was degraded with the rest accumulating in the nucleus. The formalism used in the model may be generally useful for other acid-dependent enveloped viruses. A subset of the model has been used previously to describe the trafficking of Semliki Forest virus, an acid-dependent enveloped RNA virus.Two pathways have previously been implicated for the in vitro entry of the budded form of the baculovirus: adsorptive endocytosis and plasma membrane fusion. Experimental evidence is presented which strongly suggests that the physical number of viruses entering by plasma membrane fusion is not significant relative to receptor-mediated endocytosis. © 1997 John Wiley & Sons, Inc., Biotechnol Bioeng 54: 468-490, 1997.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 70
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 45-51 
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; δ sequences cloned genes ; integration ; stability ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The chromosomal δ sequences of the yeast Saccharomyces cerevisiae were employed as recombination sites to integrate the bacterial neor gene and the yeast SUC2 gene into the yeast genome. A dominate selection method employing the aminoglycoside antibiotic G418 was used. Transformation efficiencies and growth behaviors of the transformants were studied. Transformants were obtained with more than 40 integrations; the majority of insertions were tandem with a maximum of three different insertion sites utilized at one time. After 70-100 generations of growth in nonselective medium, the high copy number SUC2-neor integrants were found to be unstable; only minor instability was observed for the neor and low copy number SUC2-neor integrants. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 71
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 316-327 
    ISSN: 0006-3592
    Schlagwort(e): Saccharomyces cerevisiae ; glucose transport ; glucose-6-phosphate inhibition ; kinetic modeling ; in vivo kinetics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the present study, the glucose transport into the yeast Saccharomyces cerevisiae has been investigated. The approach suggested is based on a rapid sampling technique for studying the dynamic response of the yeast to rapid changes in extracellular glucose concentrations. For this purpose a concentrated glucose solution has been injected into a continuous culture at steady state growth conditions resulting in a shift of the extracellular glucose level. Samples have been taken every 5 s for determination of extracellular glucose and intracellular glucose-6-phosphate concentrations. Attempts to fit the experimental observations with simulations from existing models failed. The mechanism then proposed is based on a facilitated diffusion of glucose superimposed by an inhibition of glucose-6-phosphate. The use of the so-called in vivo approach suggested in this article appears to be proper, because the investigations can be performed at defined physiological states of the microbial cultures. Furthermore, the experimental observations are not being corrupted by the preparation of the samples for the transport studies as it happens during radioactive measurements. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 72
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 401-405 
    ISSN: 0006-3592
    Schlagwort(e): insect cells ; microfiltration ; hollow fiber ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: An efficient method was developed for media separation and cell collection for eukaryotic cells growing in suspension. The method is based on tangential flow microfiltration using an open channel arrangement in a hollow fiber configuration. Best results (highest processing flux rate) for polysulfone hollow fibers were obtained using fibers with internal diameter of 0.75 mm, 0.45 μm pore size, and a cell suspension flow at a shear rate of 14000 s-1 (0.032 L/min per fiber). A flux rate of 500 L/m2 h can be obtained by maintaining the surface area/cell ratio at 0.05 m2/10 L of cells at a concentration of 2.5 × 106 cells/mL. Forty liters of infected insect cells can be concentrated 10 times in 20 min without affecting cell viability. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 73
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 32-44 
    ISSN: 0006-3592
    Schlagwort(e): insect cells ; baculovirus expression vector system ; multiplicity of infection ; time of infection ; substrate limitation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The inability to infect insect cell cultures at the highest achievable cell densities has imposed major limitations to both the fundamental understanding of the Baculovirus Expression Vector System (BEVS) as well as full exploitation of its potential productive capacity for recombinant (β-galAcNPV) products. The current literature does not characterize and identify the exact nature of the observed limitations, which therefore has become the major objective and contribution of the following study. Critical densities for infection of Spodoptera frugiperda (Sf9) cells with nuclear polyhedrosis virus expressing β-galactosidase (Autographa californica) grown in media both containing fetal calf serum (FCS) and free of serum were found to be at 2 × 106 and 5 × 106 cells/ml respectively. Medium exchange was found to completely reverse the effect if renewed up to 24 hours post-infection (HPI). The inevitable arrest of uninfected cell growth and decreased production of recombinant products at high cell densities of infection were both correlated to nutrient depletion. Cystine was found to be depleted in uninfected insect cell cultures at the onset of the stationary phase and in serum-free insect cell cultures infected with baculovirus above a cell density of 5 × 106 cells/ml. Neither glucose depletion nor accumulation of possible inhibitory metabolites such as alanine, ammonia, or lactate could be correlated to growth arrest or decreased recombinant product yields. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 32-44, 1997.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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