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  • Biochemistry and Biotechnology  (854)
  • Animals  (521)
  • AERODYNAMICS
  • 1995-1999  (1,471)
  • 1980-1984
  • 1925-1929  (1)
  • 1995  (1,471)
  • 1926  (1)
Collection
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  • 1995-1999  (1,471)
  • 1980-1984
  • 1925-1929  (1)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Phylogenetic position of Dictyostelium inferred from multiple protein data sets (1995)
    Springer
    Journal of molecular evolution 41 (1995), S. 238-246 
    Details
    ISSN: 1432-1432
    Keywords: Cellular slime molds ; Animals ; Fungi ; Plantae ; Maximum-likelihood method ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phylogenetic position of Dictyostelium inferred from 18S rRNA data contradicts that from protein data. Protein trees always show the close affinity of Dictyostelium with animals, fungi, and plants, whereas in 18S rRNA trees the branching of Dictyostelium is placed at a position before the massive radiation of protist groups including the divergence of the three kingdoms. To settle this controversial issue and to determine the correct position of Dictyostelium, we inferred the phylogenetic relationship among Dictyostelium and the three kingdoms Animalia, Fungi, and Plantae by a maximum-likelihood method using 19 different protein data sets. It was shown at the significance level of 1 SE that the branching of Dictyostelium antedates the divergence of Animalia and Fungi, and Plantae is an outgroup of the Animalia-Fungi-Dictyostelium clade.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170678
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  • 2
    Electronic Resource
    Electronic Resource
    Segmentation and tracking of piglets in images (1995)
    Springer
    Machine vision and applications 8 (1995), S. 187-193 
    Details
    ISSN: 1432-1769
    Keywords: Tracking ; Segmentation ; Pigs ; Animals ; Computer vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract An algorithm was developed for the segmentation and tracking of piglets and tested on a 200-image sequence of 10 piglets moving on a straw background. The image-capture rate was 1 image/140 ms. The segmentation method was a combination of image differencing with respect to a median background and a Laplacian operator. The features tracked were blob edges in the segmented image. During tracking, the piglets were modelled as ellipses initialised on the blobs. Each piglet was tracked by searching for blob edges in an elliptical window about the piglet's position, which was predicted from its previous two positions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01215814
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  • 3
    Electronic Resource
    Electronic Resource
    Adaptive on-line model for aerobic Saccharomyces cerevisiae fermentation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 631-638 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; fermentation ; on-line simulation ; state estimation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480611
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetics of chlorinated ethylene dehalogenation under methanogenic conditions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 659-666 
    Details
    ISSN: 0006-3592
    Keywords: methanogenic activity ; ethylene ; dechlorination ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetics were determined for methanogenic activity and chlorinated ethylene dehalogenation by a methanol-enriched, anaerobic sediment consortium. The culture reductively dechlorinated perchloroethylene (PCE) to trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), vinylchloride (VC), and ethylene and ethane. The absence : of methanol or the addition of 2-bromoethanesulfonic. acid in the presence of methanol suppressed both methanogenic activity and dechlorination. In contrast, acetate production continued in the presence of 2-bromoethanesulfonic acid. These results suggest that dechlorination was strongly linked to methane formation and not to acetate production. A kinetic model, developed to describe both methanogenesis and dechlorination, successfully predicted experimentally measured concentrations of biomass, methane, substrate, and chlorinated ethylenes. The average maximum specific dehalogenation rates for PCE, TCE, 1,1-DCE, and VC were 0.9 ± 0.6, 0.4 ± 0.1, 12 ± 0.1, and 2.5 ± 1.7 μmol contaminant/ g. DW/day, respectively. This pattern for dechlorination rates is distinctly different than that reported for transition metal cofactors, where rates drop by approximately one order of magnitude as each successive chlorine is removed. The experimental results and kinetic analysis suggest that it will be impractical to targeting methanol consuming methanogenic organisms for in situ ground-water restoration. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480614
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  • 5
    Electronic Resource
    Electronic Resource
    Enhancement of antibody production by growth factor addition in perfusion and hollow-fiber culture systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 673-680 
    Details
    ISSN: 0006-3592
    Keywords: bovine serum albumin ; growth factor ; hollow-fiber culture ; perfusion culture ; antibody production rate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of the high-molecular-weight growth factors, transferrin and bovine serum albumin (BSA), on antibody production were analyzed quantitatively in continuous hollow-fiber cultivation over a period of 60 days. Transferrin enhanced cell growth but had no significant effect on the specific antibody production rate, whereas BSA significantly enhanced antibody production. The antibody production rate was increased 4- and 14-fold respectively by feeding BSA at 2 and 5 g L-1 into the EC side of the system (the side connected to the cell-containing outer part of the hollow-fiber unit) compared with the production achieved without BSA. Addition of 5 g L1 BSA into the IC side of the system (the side connected to the inner part of the hollow-fiber unit) resulted in a 2.5-fold increase in the antibody production rate. The effect of BSA was also analyzed using the perfusion culture system with a separation unit. When fresh medium containing either 2 or 5 g L-1 BSA was fed into the reactor, both the specific growth rate and specific death rate increased, while the specific antibody production rate was increased 2- and 25-fold, respectively, by feeding BSA at these two concentrations compared with no addition. Comparing the two systems, the increase in the antibody production rate achieved with the hollow-fiber system was threefold greater than that in the perfusion culture system with the same concentration of BSA feeding. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480616
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  • 6
    Electronic Resource
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    Membrane bioreactor with a porous hydrophobic membrane as a gas-liquid contactor for waste gas treatment (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 107-115 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; waste gas treatment ; hydrophobic microporous membrane ; mass transfer ; propene ; Xanthobacter ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel type of bioreactor for waste gas treatment has been designed. The reactor contains a microporous hydrophobic membrane to create a large interface between the waste gas and the aqueous phase. To test the new reactor, propene was chosen because of its high air/water partition coefficient, which causes a low water concentration and hampers its removal from air. Propene transfer from air to a suspension of propene-utilizing Xanthobacter Py2 cells in the membrane bioreactor proved to be controlled by mass transfer in the liquid phase. The resistance of the membrane was negligible. Simulated propene transfer rates agreed well with the experimental data. A stable biofilm of Xanthobacter Py2 developed on the membrane during prolonged operation. The propene flux into the biofilm was 1 × 10-6 mol m-2 s-1 at a propene concentration of 9.3 × 10-2 mol m-3 in the gas phase. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450203
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  • 7
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    Influence of cell- and media-derived factors on the integrity of a human monoclonal antibody after secretion into serum-free cell culture supernatants (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 97-106 
    Details
    ISSN: 0006-3592
    Keywords: antibody integrity ; human monoclonal antibodies ; insect cells ; mammalian cell culture ; proteolytic activity ; protein microheterogeneity ; serum-free media ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450202
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  • 8
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    Buffer exchange using size exclusion chromatography, countercurrent dialysis, and tangential flow filtration: Models, development, and industrial application (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 149-157 
    Details
    ISSN: 0006-3592
    Keywords: buffer exchange ; chromatography ; flow filtration ; dialysis, counter current ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: There are three major methods for buffer exchange of proteins at industrial scale: size exclusion chromatography (SEC), tangential flow filtration (TFF), and countercurrent dialysis (CCD). In order to determine the optimal technology for a given process, a study was done to compare these technologies on a technological and economic basis. This comparison required that new mathematical models be developed which enable the common features of each unit operation to be directly compared. The new concept of a diavolume equivalent for SEC, defined as the inverse of the fractional loading, was also introduced to aid in this comparison. Variables that were examined for each unit operation included range of buffer exchange, dilution of protein solution, yield, buffer requirements, total operating time, throughput, plant space, capital, raw materials, and labor costs. It was found that TFF and CCD have a greater range of buffer exchange than SEC. TFF also provides the advantage that concentration of the protein can readily be accomplished in the same step. For processes of equal batch size and yield, TFF and CCD also provide a two- to five- fold improvement in each of the remaining variables. The major economic advantage in using TFF and CCD over SEC is the decreased plant size required for manufacturing and thus the longer term use of existing facilities. Situations where SEC (or CCD) would be favored over TFF are when protein denaturation occurs in TFF but does not occur in SEC. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450209
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  • 9
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    Effect of membrane morphology and operation on protein deposition in ultrafiltration membranes (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 174-180 
    Details
    ISSN: 0006-3592
    Keywords: ultrafiltration membranes ; protein fouling ; BET measurements ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Membrane morphology is compared to protein depostion under passive adsorption and ultrafiltration conditions. Solute resistance of protein deposits for membranes of varying roughness, structure, and permeability can vary dramatically with operating conditions. Using Brunauer-Emmett-Teller adsorption isotherm (BET), study of the internal area and accessibility of several uttrafiltration membranes to protein deposition allows better understanding of the fouling mechanisms and interpretation of adsorbed protein quantities. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260470208
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  • 10
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    Equilibria for the adsorption of antibiotics onto neutral polymeric sorbents: Experimental and modeling studies (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 215-226 
    Details
    ISSN: 0006-3592
    Keywords: adsorption ; penicillin ; tetracycline ; cephalosporin ; polymeric sorbents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The objective of this work was to study the equilibria for adsorption of three antibiotics (penicillin V, tetracycline, and cephalosporin C) from water onto commercially available neutral polymeric sorbents. The pH was observed to be an important factor in adsorption as our results suggest that the neutral forms of penicillin V and cephalosporin C are preferentially adsorbed onto the neutral sorbents. Also, sorbent surface chemistry was observed to be important for adsorption, as the antibiotics adsorbed more favorably (both in terms of affinities and enthalpies) onto the aromatic sorbent as compared to the aliphatic ester sorbent. In addition to these thermodynamic measurements, molecular modeling studies and Monte Carlo simulations suggest that adsorption onto aromatic sorbents may involve specific interactions between the planar regions of the antibiotic molecules and the phenyl rings of the aromatic sorbent. The interaction energies predicted from Monte Carlo simulations were observed to provide qualitative agreement with experimentally determined adsorption affinities. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260470213
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  • 11
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    The influence of electrostatic interactions on partition in aqueous polyethylene glycol/dextran biphasic systems: Part II (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 252-260 
    Details
    ISSN: 0006-3592
    Keywords: aqueous two-phase systems ; polyethylene glycol-dextran systems ; electrostatic potential ; hydrophobicity ; surface tension ; polyelectrolytes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In aqueous polyethylene glycol/dextran two-phase systems, the hydrophobicity, free volume, surface tension, and interfacial tension of the phases in equilibrium were measured as a function of pH and ionic strength. These parameters were found to change with pH, but the pattern and magnitude cannot explain the unusual partition of charged macromolecules, observed previously. The electrostatic potential difference was determined by a new experimental approach based on the measurement of the pH difference between the phases at equilibrium. In polyethylene glycol/dextran systems containing sodium chloride as ionized species, the electrostatic potential is not constant in the pH range 2 to 11. The partition behavior of charged macromolecules and its dependence on pH can be explained by the combined action of charge and phase potential. This conclusion was tested with poly-L-glutamate, which partitioned as predicted and in a pattern opposite to positively charged macro- molecules. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260470217
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  • 12
    Electronic Resource
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    Photosynthetic performance of a helical tubular photobioreactor incorporating the cyanobacterium spirulina platensis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 261-269 
    Details
    ISSN: 0006-3592
    Keywords: photosynthesis ; global warming ; CO2 fixation ; photobioreactor ; Spirulina platensis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The photosynthetic performance of a helical tubular photobioreactor (“Biocoil”), incorporating the filamentous cyanobacterium Spirulina platensis, was investigated. The photobioreactor was constructed in a cylindrical shape (0.9 m high) with a 0.25-m2basal area and a photostage comprising 60 m of transparent PVC tubing of 1.6-cm inner diameter (volume = 12.1 L). The inner surface of the cylinder (area = 1.32 m2) was illuminated with cool white fluorescent lamps; the energy input of photosynthetically active radiation(PAR, 400 to 700 nm) into the photobioreactor was 2920 kJ per day. An air-lift system ncorporating 4%CO2 was used to circulate the growth medium in the tubing. The maximum productivity achieved in batch culture was 7.18 g dry biomass per day [0.51 g · d biomass/L · day, or 5.44 g · d biomass/m2(inner surface of cylindrical shape)/day] which corresponded to a photosynthetic (PAR) efficiency of 5.45%. The CO2 was efficiently removed from the gaseous stream; monitoring the CO2 the outlet and inlet gas streams showed a 70% removal of CO2 from the inlet gas over an 8-h period with almost maximum growth rate. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260470218
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  • 13
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    High-rate continuous biodegradation of concentrated chlorinated aliphatics by a durable enrichment of methanogenic origin under carrier-dependent conditionsDedicated to the memory of Jean-Baptiste Boucquey (1970-1994). (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 298-307 
    Details
    ISSN: 0006-3592
    Keywords: anaerobic biodegradation ; polychlorinated aliphatics ; acclimation ; enrichment ; polyurethaneactivated carbon carrier ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The simultaneous biodegradation of toxic compounds in mixtures is a major current concern. To bioremediate a toxic mixture, we designed a strategy combining an ad-sorbent carrier with an ecological and nutritional system which allowed work close to heavily polluted conditions in nature. Starting from a methanogenic community, we developed a microbial consortium acclimated to a mixture of about 30 chlorinated aliphatics in a fixed-film stationary-bed bioreactor. Prior to the establishment of a durable period of dechlorination, an interval of progressive dechlorination of the toxic mixture was observed during which the excess of the toxic compounds was stored on the carrier. The latter, consisting of activated carbon in a polyurethane foam, allowed us to work at concentrations far above the solubility of the toxic compounds (apparent concentrations of about 10 g/L). The complete disappearance of hexachloroethane as well as its lower homologues, penta-, tetra-, and trichloroethane, present in the toxic mixture, was observed. Additionally, octachlorocyclopentene, carbon tetrachloride, trichloro-ethylene, tetrachloroethylene, and hexachloro-1,3-butadiene also completely disappeared. For the four latter compounds, from mass balances in the bioreactor, degradation rates around 10 μmol/L per day were determined with total dechlorination. The enrichment culture thus developed exhibited high degradation performances similar to those reported in the literature for pure or enriched anaerobic microbial cultures in contact with a single toxic compound. The results demonstrate the possibility of concurrent high-rate degradation of several highly chlorinated toxic compounds, under conditions approximating field situations.© 1995 John Wiley & Sons, Inc
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260470304
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  • 14
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    A structured metabolic model for anaerobic and aerobic stoichiometry and kinetics of the biological phosphorus removal process (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 277-287 
    Details
    ISSN: 0006-3592
    Keywords: phosphorus removal ; biological ; kinetics ; metabolic model ; polyphosphate ; PHB ; glycogen ; batch reactor, sequenced ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A structured metabolic model is developed that describes the stoichiometry and kinetics of the biological P removal process. In this approach all relevant metabolic reactions underlying the metabolism, considering also components like adenosine triphosphate (ATP) and nic-otinamide-adenine dinucleotide (NADH2) are describedbased on biochemical pathways. As a consequence of the relations between the stoichiometry of the metabolic reactions and the reaction rates of components, the required number of kinetic relations to describe the process is reduced. The model describes the dynamics of the storage compounds which are considered separately from the active biomass. The model was validated in experiments at a constant sludge retention time of 8 days, over the anaerobic and aerobic phases in which the external oncentrations as well as the internal fractions of the relevant components involved in the P-removal process were monitored. These measurements include dissolved acetate, phosphate, and ammonium; oxygen consumption; poly-β-hydroxybutyrate (PHB); glycogen; and active biomass. The model satisfactorily describes the dynamic behavior of all components during the anaerobicand aerobic phases.© 1995 John Wiley & Sons, Inc
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    URL: http://dx.doi.org/10.1002/bit.260470302
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  • 15
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    Mathematical modeling and analysis of glucose and glutamine utilization and regulation in cultures of continuous mammalian cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 334-346 
    Details
    ISSN: 0006-3592
    Keywords: mammalian cells ; glycolysis ; glutarninolysis ; regulation ; kinetic model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A number of factors have been shown to affect the metabolism of glucose and glutamine in mammalian cells and their mechanisms have been partially elucidated. Despite these efforts, a quantitative knowledge of the significance of these factors, the regulation of glucose and glutamine utilization, and particularly the interactions of these two nutrients is still lacking. Controversies exist in the literature. To clarify some of these controversies, mathematical models are proposed in this work which enable to separate and identify the effects of individual factors. Experimental data from five cell lines obtained in batch, fed-batch, and continuous cultures, both under steady-state and transient conditions, were used to verify the model formulations. The resulting kinetic models successfully describe all these cultures. According to the models, the specific consumption rate of glucose (QGlc) of continuous animal cells under normal culture conditions can be expressed as a sum of three parts: a part owing to cell growth; a part owing to glucose excess; and a part owing to glutamine regulation. The specific consumption rate of glutamine (qGlc7) can be expressed as a sum of only two parts: a part owing to cell growth; and a part owing to glutamine excess. Using the kinetic models the interaction and regulation of glucose and glutamine utilizations are quantitatively analyzed. The results indicate that, whereas qGlc is affected by glutamine, qGln appears to be not or less significantly affected by glucose. It is also shown that the relative utilizations of glucose and glutamine by anabolism and catabolism are mainly affected by the residual concentrations of the respective compounds and are less sensitive to growth rate and the nature of growth limitation.© 1995 John Wiley & Sons, Inc
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260470308
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  • 16
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    Fluorophore-labeled carbohydrate analysis of immunoglobulin fusion proteins: Correlation of oligosaccharide content with in vivo clearance profile (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 405-405 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/bit.260470314
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  • 17
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470401
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  • 18
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    Amplification of toluene dioxygenase genes in a hybrid Pseudomonas strain to enhance the biodegradation of benzene, toluene, and p-xylene mixture (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 488-494 
    Details
    ISSN: 0006-3592
    Keywords: biodegradation ; gene amplification ; hybrid strain ; benzene ; toluene ; xylene ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A hybrid metabolic pathway through which benzene, toluene, and p-xylene (BTX) mixture could be simultaneously mineralized was previously constructed in Pseudomonas putida TB101 (Lee, Roh, Kim, Biotechnol. Bioeng 43: 1146-1152, 1994). In this work, we improved the performance of the hybrid pathway by cloning the todC1C2BA genes in the broad-host-range multicopy vector RSF1010 and by introducing the resulting plasmid pTOL037 into P. putida mt-2 which harbors the archetypal TOL plasmid. As a result, a new hybrid strain, P. putida TB103, possessing the enhanced activity of toluene dioxygenase in the hybrid pathway was constructed. The degradation rates of benzene, toluene, and p-xylene by P. putida TB103 were increased by about 9.3-, 3.7-, and 1.4-fold, respectively, compared with those by previously constructed P. putida TB101. Apparently, this improved capability of P. putida TB103 for the degradation of BTX mixture resulted from the amplification of the todC1C2BA genes. Furthermore, a relatively long lag period for benzene degradation observed when P. putida TB101 was used for the degradation of BTX mixture at low dissolved oxygen (DO) tension disappeared when P. putida TB103 was employed. © 1995 John Wiley & Sons, Inc.
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    Quantitative analysis of biofilm thickness variability (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 503-510 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; thickness ; heterogeneity ; roughness ; microscopy ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The thickness variability of biofilms of Pseudomonas aeruginosa, Klebsiella pneumoniae, and the binary population combination of these two species was quantified. The experimental method involved cryoembedding biofilms with a commercial tissue embedding agent, sectioning, and applying image analysis to construct thickness profiles along linear transects (up to 1 cm in length) across the substratum. Biofilms embedded and sectioned by this method were locally as thin as a single cell attached to the surface (〈5 μm) and as thick as 1000 μm. Week-old biofilms of three different species compositions displayed distinct structural features as indicated by their mean thicknesses and by a roughness coefficient. Monopopulation biofilms of P. aeruginosa (29 μm mean thickness) or K. pneumoniae (100 μm mean thickness) were thinner than the binary population biofilm (400 μm mean thickness). A roughness coefficient developed in this investigation corroborated the qualitative visual characterization of P. aeruginosa biofilms as relatively uniformly thick (mean roughness coefficient 0.15), K. pneumoniae biofilms as patchy (mean roughness coefficient 1.14), and the binary population biofilm as intermediate (mean roughness coefficient 0.26). Whereas P. aeruginosa and binary population biofilms covered the substratum completely, significant areas of essentially bare substratum were apparent in K. pneumoniae biofilms. The patchiness of K. pneumoniae biofilms may be due to the fact that this organism is nonmotile. A spatial correlation analysis of the thickness data indicated that thickness measurements were still correlated even when separated by distances that exceeded the mean biofilm thickness. Cell aggregates, some of them hundreds of microns in size, were observed in the effluent of K. pneumoniae and binary population biofilm reactors. Measurements of thickness variability and other observations reported in this article provide a quantitative basis for analysis of microscale structural heterogeneity of biofilms. © 1995 John Wiley & Sons, Inc.
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    Purification of an L-asparaginase - atrial natriuretic peptide fusion protein expressed in Escherichia coli (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 483-491 
    Details
    ISSN: 0006-3592
    Keywords: fusion protein ; protein purification ; affinity chromatography ; cation exchange chromatography ; L-asparagine ; α-human natriuretic peptide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel fusion protein designed to facilitate protein purification was expressed in Escherichia coli and purified separately by two different chromatography methods. L-Asparaginase from Erwinia chrysanthemi is fused to the N-terminus of a model peptide, α-human atrial natriuretic peptide (α-hANP). L-Asparaginase was chosen because of its selective affinity for L-asparagine and because of its unusually high isoelectric point(8.6). A gene construction without the L-asparaginase native signal sequence caused expression at a level of 8% of total cell protein, while gene construction with the native signal sequence resulted in over five time less expression. The hybrid protein expressed without the signal sequence was purified from clarified cell lysate byeither L-asparagine affinity chromatography or cation exchange chromatography. After digestion of the fusion protein with factor Xa protease, a peptide with a molecular weight corresponding to the theoretical molecular weight of α-hANP was observed by coupled HPLC/mass spectrometry. © 1995 John Wiley & Sons Inc.
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    The effective diffusion coefficient and the distribution constant for small molecules in calcium-alginate gel beads (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 492-500 
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    ISSN: 0006-3592
    Keywords: alginate ; diffusion ; gel ; saccharides ; organic acids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effective diffusion coefficient, De, and the distribution constant, Ki, for selected mono- and disaccharides and organic acids were determined in homogeneous calcium-alginate gel with and without entrapped bacteria. Results were obtained from transient concentration changes in well-stirred solutions of limited volume, in which the gel beads were suspended. The effective diffusioncoefficients and the distribution constants were estimated by fitting mathematical model predictions to the experimental data using a nonlinear model fitting program (MODFIT). Both single solute diffusion and multiple solute diffusion were performed. A small positive effect was obtained onthe values of De for the system of multiple solute diffusion; however, the values of Ki were not significantly influenced. For the nine solutes tested, De for 2% Ca-alginate gel beads was found to be approximately 85% of the diffusivity measured in water. The effects on De and Ki, for lactose and lactic acid were determined for variations of alginate concentration, pH, temperature, and biomass content in the beads. De decreased linearly for both lactose and lactic acid with increasing cell concentration in the Ca-alginate gel. Ki, was constant for both lactose and lactic acid with increasing cell concentration. De was significantly lower at pH 4.5 than at pH 5.5 and 6.5 for both lactose and lactic acid. Furthermore, De seemed to decrease with increased alginate concentration in the range of 1% to 4%. The diffusion rate increased with increasing temperature, and the activation energy for the diffusion process for both lactose and lactic acid was constant in the temperature range tested. © 1995 John Wiley & Sons Inc.
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    The role of glucose in ajmalicine production by catharanthus roseus cell cultures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 525-534 
    Details
    ISSN: 0006-3592
    Keywords: glucose ; osmotic pressure ; ajmalicine production ; catharanthus roseus ; kinetic model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The role of glucose in ajmalicine production by Catharanthus roseus was investigated in the second stage of a two-stage batch process. Activities of tryptophan decar-boxylate (TDC) and anthranilate synthase (AS), two enzymes In the pathway leading to ajmalicine, were higher after induction with 40 g/L glucose than after induction with 60 or 80 g/L glucose. Experiments with different media containing mixtures of glucose and the nonpermeating osmotic agent xylose, and using an already induced culture as inoculum, revealed that a minimum amount of glucose is required to support ajmalicine production after enzyme induction. This requirement was not an osmotic effect. The relation between the glucose concentration and the specific ajmalicine production rate, qp, was investigated in seven (fed-)batch cultures with constant glucose concentrations: 23, 29, 35, 53, 57, 75, and 98 g/L. In the cultures with a low glucose concentration (23, 29, and 35 g/L) the qp was 2.7-times higher than the cultures with 53 and 57 g/L, and almost six times higher than the cultures with a high glucose concentration (75 and 98 g/L). A glucose perturbation experiment (from 53 to 32 g/L) demonstrated that the ajmalicine production rate was adjusted without much delay. A kinetic equation is proposed for the relationship between the glucose concentration and qp. Differences in enzyme induction and ajmalicine production at different glucose levels could not be explained by the intracellular concentrations of glucose, fructose, sucrose, or starch. © 1995 John Wiley & Sons Inc.
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    Determination of the respiration quotient in mammalian cell culture in bicarbonate buffered media (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 524-535 
    Details
    ISSN: 0006-3592
    Keywords: respiration quotient ; carbon dioxide evolution rate ; continuous culture ; cell metabolism ; bicarbonate buffer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The determination of the respiration quotient (RQ = CER/OUR) has not been used so far as a tool for understanding animal cell metabolism. This is due to problems in measuring the carbon dioxide evolution rate (CER) rather than the oxygen uptake rate (OUR). The determination of the CER is complicated by the use of bicarbonate in the medium. Using liquid and gas balances we have derived an equation for continuous culture to quantify the amount of CO2 that comes from the bicarbonate in the feed. Under cell-free conditions, values predicted by this equation agree within 4% with the experimental results. In continuous culture using hybridoma cells, the CO2 from the feed, as determined by an IR-gas analyzer, was found to represent a significant amount of the total measured CO2 in the off-gas (50% in a suboptimal, and 30% in high-growth medium). Furthermore, the problem of CO2 loss from the medium during medium preparation and storage was solved using both a theoretical and an experimental approach. RQ values in continuous culture were evaluated for two different growth media. Small but significant differences in RQ were measured, which were matched by differences in specific antibody rates and other metabolic quotients. In a medium with Primatone RL, an enzymatic hydrolysate of animal cell tissue that causes a more than twofold increase in cell density, the RQ was found to be 1.05, whereas in medium without Primatone RL (but containing amino acids equivalent in composition and concentration to Primatone RL) the RQ was found to be 0.97. We suggest the RQ to be a useful parameter for estimating the physiological state of cells. Its determination could be a suitable tool for both the on-line control of animal cell cultivations and the understanding of cell metabolism. © 1995 John Wiley & Sons, Inc.
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    Effect of cDNA copy number on secretion rate of activated protein C (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 22-27 
    Details
    ISSN: 0006-3592
    Keywords: cDNA copy number ; gene dosage ; recombinant protein production ; posttranslational modification ; BHK ; secretion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The secretion rate of activated protein C (APC) by BHK cells was increased 35-fold by increasing the cDNA copy number per cell from 50 to 240. In this range, the relation between APC secretion and cDNA copy number was not linear and the rate of APC secretion per cDNA copy increased sevenfold. This apparent cooperative effect of multiple cDNA copies could be related to their integration in tandem. For cDNA copy numbers higher than 240, the APC secreation rate per cDNA and per cell decreased dramatically. The γ-carboxylation of glutamic acid residues, a posttranslational modification required for APC biological activity, was also investigated. The proportion of APC that was fully γ-carboxylated decreased as the secretion rate of APC increased. © 1995 John Wiley & Sons, Inc.
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    Occurrences at mineral-bacteria interface during oxidation of arsenopyrite by Thiobacillus ferrooxidans (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 13-21 
    Details
    ISSN: 0006-3592
    Keywords: arsenopyrite ; Thiobacillus ferrooxidans ; adhering bacteria ; surface-oxidized phases ; ferric arsenate ; sulfur ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The combination of an improved bacterial desorption method, scanning electron microscopy (SEM), diffuse reflectance and transmission infrared Fourier transform spectroscopy, and a desorption-leaching device like high-pressure liquid chromatography (HPLC) was used to analyze bacterial populations (adhering and free bacteria) and surface-oxidized phases (ferric arsenates and elemental sulfur) during the arsenopyrite biooxidation by Thiobacillus ferrooxidans. The bacterial distribution, the physicochemical composition of the leachate, the evolution of corrosion patterns, and the nature and amount of the surface-oxidized chemical species characterized different behavior for each step of arsenopyrite bioleaching. The first step is characterized by a slow but strong adhesion of bacteria to mineral surfaces, the appearance of a surface phase of elemental sulfur, the weak solubilization of Fe(II), As(III), and As(V), and the presence of the first corrosion patterns, which follow the fragility zones and the crystallographic orientation of mineral grains. After this short step, growth of the unattached bacteria begins, while ferrous ions in solution are oxidized by them. Ferric ions produced by the bacteria can oxidize the sulfide directly and are regenerated by Fe(II) bacterial oxidation. At this time, a bioleaching cycle takes place and a coarse surface phase of ferric arsenate (FeAsO4 · xH2O where x ≈ 2) and deep ovoid pores appear. At the end of the bioleaching cycle, the high concentration of Fe(III) and As(V) in solution promotes the precipitation of a second phase of amorphous ferric arsenate (FeAsO4 · xH2O where x ≈ 4) in the leachate. Then the biooxidation process ceases: The bacteria adhering to the mineral sufaces are coated by the ferric arsenates and the concentration of Fe(III) on the leachate is found to have decreased greatly. Both oxidation mechanisms (direct and indirect oxidation) have been stopped. © 1995 John Wiley & Sons, Inc.
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    Properties of microfiltration membranes: Mechanisms of flux loss in the recovery of an enzyme (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 28-35 
    Details
    ISSN: 0006-3592
    Keywords: microfiltration ; membrane ; enzyme ; fouling ; atomic force microscopy ; photon correlation spectroscopy ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transmission and rate of filtration of the enzyme yeast alcohol dehydrogenase (YADH) has been studied at capillary pore microfiltration membranes. Photon correlation spectroscopy (PCS) with nanometer resolution showed that the enzyme existed as discreate molecules only for a narrow range of pH and ionic strength. Under such conditions, the transmission of the enzyme was high. However, the rate of filtration still decreased continuously with time. Analyssis of the time dependence of the rate of filtration indicated that this decrease was due to in-pore enzyme deposition at low concentration (“standard blocking model”) and suface depositon at high concentration (“cake filtration model”). Use of atomic force microscopy (AFM) gave unequivocal and quantitative confirmation of these inferences. The work shows the great advantage of using advanced physical characterization techniques, both for the identification of the optimum conditions for filtration (PCS) and for the elucidation of mechanisms giving rise to inefficiencies in the filtration process (AFM). © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1002/bit.260480101
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    Kinetic model of disaccharide oxidation by Agrobacterium tumefaciens (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 12-16 
    Details
    ISSN: 0006-3592
    Keywords: hexopyranoside:cytochrome c oxidoreductase ; disaccharide oxidation ; oxidation ; kinetic model ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Disaccharides were microbaially transformed to their corresponding 3-keto-derivatives by resting cells of Agrobacterium tumefaciens NCPPB 396. The kinetics and yield of this highly specific oxidation depend on several factors. The oxygen concentration especially has a major influence on the production of 3-keto-derivatives and was investigated kinetically with respect to low stationary oxygen concentrations in solution. Experiments showed unconventional results that conflicted with normal Michaelis-Menten kinetics. A kinetic model was developed and the kinetic constants were calculated. The model and experimental data for sucrose, maltose, iso-maltulose (palatinose), and leucrose are in good agreement with each other. Initial reaction rates with different sugars using constant oxygen concentrations resulted in a Michaelis-Mentent type function. The complete kinetics, including the effect of disaccharide and oxygen concentrations, are presented. © 1995 John Wiley & Sons, Inc.
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    A modeling study of anaerobic biofilm systems: II. Reactor modeling (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 54-61 
    Details
    ISSN: 0006-3592
    Keywords: anaerobic biofilm ; CSTR ; reactors, nonide ; pH ; plug-flow reactors ; biofilm modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rigorous steady-state model of anaerobic biofilm reactors taking into account acid-base and gas-phase equilibria in the reactor in conjunction with detailed chemical equilibria and mass transfer in acetate-utilizing methanogenic biofilms is presented. The performances of ideal completely stirred tank reactors (CSTRs) and plug-flow reactors, as well as reactors with nonideal hydraulic conditions, are simulated. Decreasing the surface loading rate increases the acetate removal efficiency, while decreasing the influent pH and increasing the buffering capacity improves the removal efficiency only if the bulk pH of the reactor shifts toward more optimal values between 6.8 to 7.0. The reactor can have negative or positive removal efficiencies depending on the start-up conditions. The respiration coefficient plays a critical role in determining the minimum influent pH required for reactor recovery after failure. Having multiple CSTRs-in-series generally increases the overall removal efficiency for the influent conditions investigated. Monitoring of the influent feed quality is critical for plug-flow reactors, becasue failure of the initial sections of the reactor may cause a cascading effect that may lead to a rapid reactor failure. © 1995 John Wiley & Sons, Inc.
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    Effects of substrate branching characteristics on kinetics of enzymatic depolymerization of mixed linear and branched polysaccharides: II. Amylose/glycogen α-amylolysis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 36-42 
    Details
    ISSN: 0006-3592
    Keywords: depolymerization ; polysaccharides ; amylose ; glycogen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enzymatic depolymerization of polysaccharides with α-amylase has been studied in mixed aqueous dimethylsulfoxide (DMSO)/water solvents. Polysaccharide substrate chemical compositions, configurational structures, and bonding pattersn are known to affect observed enzymatic reaction kinetics. The branching structures of polysaccharides and their effects on the kinetic mechanisms of depolymerization reactions via endo-acting hydrolyzing enzyme was studied via size exclusion chromatography coupled to low angle laser light scattering (SEC/LALLS). The glycogen branching structure is a heterogeneously distributed “cluster” structure rather than a homogeneously distributed “treelike” structure. The action pattern of α-amylase on glycogen, which is composed of highly branched clusters, as end-products, has a “pseudo-exo-attack” in contrast to an expected “endoattack” as seen in the hydrolysis of amylose or amylopectin substrates. These effects of branched substrates for mixed amylose/glycogen α-amylolysis have been predicted and demonstrated by both experimental and theoretical analysis using the kinetic model presented in this report. The “lumped” kinetic model employed, assumes that the enzyme simultaneously attacks both linear and branched substrates. In general, excellent agreement between the model predictions and the experimental observations, both qualitatively and quantitatively, was obtained. © 1995 John Wiley & Sons, Inc.
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    Genetically engineered charge modifications to enhance protein separation in aqueous two-phase systems: Charge directed partitioning (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 62-68 
    Details
    ISSN: 0006-3592
    Keywords: aqueous two-phase systems ; β-galactosidase ; T4 lysozyme ; partitioning ; charge modifications ; genetic engineering ; polymers ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This report continues or examination of the effect of genetically engineered charge modifications on the partitioning behavior of proteins in aqueous two-phase extration. The genetic modifications consisted of the fusion of charged peptide tails to β-galactosidase and charge-change point mutations to T4 lysozyme. Our previous article examined the influence of these charge modifications on partitioning as a function of interfacial potential difference. In this study, we examined charge directed partitioning behavior in PEG/dextran systems containing small amounts of the charged polymers diethylaminoethyl-dextran (DEAE-dextran) or dextran sulfate. The best results were obtained when attractive forces between the protein and polymer were present. Nearly 100% of the β-galactosidase, which carries a net negative charge, partitioned to the DEAE-dextran-rich phase regardless of whether the phase was dextran or PEG. In these cases, cloudiness of the protein-rich phases suggest that strong charge interactions resulted in protein/polymer aggregation, which may have contributed to the extreme partitioning. Unlike the potentialdriven partitioning reported previously, consistent partitioning trends were observed as a result of the fusion tails, with observed shifts in partition coefficient (Kp) of up to 37-fold. However, these changes could not be solely attributed to charge-based interactions. Similarly, T4 lysozyme, carrying a net positive charge, partitioned to the dextran sulfate-containing phase, and displayed four- to sevenfold shifts in Kp as a result of the point mutations. These shifts were two to four times stronger than those observed for potential driven partitioning. Little effect on partitioning was observed when the protein and polymer had the same charge, with the exception of β-galactosidase with polyarginine tails. The high positive charge density of these tails provided for a localized interaction with the dextran sulfate, and resulted in 2- to 15-fold shifts in Kp. © 1995 John Wiley & Sons, Inc.
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    Comparison of hydrolysis and esterification behavior of Humicola lanuginosa and Rhizomucor miehei lipases in AOT-stabilized water-in-oil microemulsions: II. Effect of temperature on reaction kinetics and general considerations of stability and productivity (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 190-196 
    Details
    ISSN: 0006-3592
    Keywords: hydrolysis ; esterification ; Humicola lanuginosa ; Rhizomucor miehei ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Humicola lanuginosa lipase (HIL) and Rhizomucor miehei lipase (RrnL), isolated from commercial preparations of Lipolase and Lipozyme, respectively, were solubilized in AOT-stabilized water-in-oil (w/o) microemulsions in n-heptane and aspects of their hydrolysis and condensation activity examined. The temperature dependence of HIL hydrolysis activity in unbuffered R = 10 microemulsions matched very closely that for tributyrin hydrolysis by Lipolase in an aqueous emulsion assay. Apparent activation energies were measured as 13 ± 2 and 15 ± 2 kJ mol / respectively. Condensation activity, however, was essentially independent of temperature over the range 5° to 37°C. The stability of HIL over a 30-day period was very good at all pH levels (6.1, 7.2, 9.3) and R values studied (5, 7.5, 10, 20), except when high pHs and low R values were combined. The excellent stability was reflected by the linearity of the productivity profiles which facilitate system optimization. The temperature dependence of RmL hydrolysis activity toward pNPC4 showed a maximum at 40°C and an apparent Eact = 20 ± 2 kJ mol-1 was calculated based on the linear region of the profile (5° to 40°C). RmL esterification activity showed only a slight dependence on temperature over the studied range (0° to 40°C) and an apparent Eact = 5 ± 1 kJ mol-1 was measured for octyl decanoate synthesis. Both RmL and HIL, therefore, have potential for application in low temperature biotransformations in microemulsion-based media. The stability of RmL over a 30-day period was good in R = 7.5 and R = 10 microemulsions containing pH 6.1 buffer, and this was reflected in the linearity of their respective productivity profiles. RmL stability was markedly poorer at more alkaline pH, however, and proved to be sensitive to relatively small changes in the R value. © 1995 John Wiley & Sons, Inc.
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    Enzymatic preparation of biosurfactants from sugars or sugar alcohols and fatty acids in organic media under reduced pressure (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 214-221 
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    ISSN: 0006-3592
    Keywords: sugar esters ; lipase ; nonaqueous media ; Candida antarctica ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biosurfactants were prepared by enzymatic esterification of sugars and sugar alcohols in nonaqueous media. Sorbitol monooleate was produced in pure molten substrates, with reduced pressure to remove water. The results were compared to synthesis in organic solvent, with and without water removal. Synthesis in organic solvent with water removal, obtained by refluxing through a desiccant under reduced pressure, proved to be the most efficient method in terms of total yield and side-products formation. This process was applied to the production of different surfactants, by changing the nature of the hydrophilic and hydrophobic moieties. Yields above 90% of monoesters were obtained after 24 h when the reaction was carried out in 2-methyl-2-butanol with Novozym 435 (Type B lipase from Candida antarctica) with an excess of hydroxyl donor. © 1995 John Wiley & Sons, Inc.
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    Kinetics of phase separation for polyethylene glycol-phosphate two-phase systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 246-256 
    Details
    ISSN: 0006-3592
    Keywords: polyethylene glycol ; phosphate ; phase separation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phase separation times for polyethylene glycol (PEG)-4000-phosphate aqueous two-phase systems were studied, for small scale (5-g) and large scale (1300-g) systems, as a -function of the stability ratio. Profiles of dispersion height for both large and small scale systems were represented as a fraction of the initial height and were found to be independent of the geometrical dimensions of the separator. Furthermore, by plotting time as a fraction of the initial height the total time of separation can be calculated for a given height of system at a particular stability ratio. This generalization is important for the design of large scale aqueous two-phase separators. Phase separation times were also found to be dependent on which of the phases is continuous. A characteristic change in phase separation time was also observed at the phase inversion point (i.e., where the dispersed phase changes to a continuous phase and vice versa) and this point tends toward higher volume ratios as the tie-line length (TLL) is increased. Furthermore, the phase inversion point at each TLL corresponds to a fixed phosphate concentration. © 1995 John Wiley & Sons, Inc.
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    Hydrodynamic, physiological, and morphological characteristics of Fusarium moniliforme in geometrically dissimilar stirred bioreactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 266-277 
    Details
    ISSN: 0006-3592
    Keywords: Fusarium moniliforme ; hydrodynamics ; image analysis ; kinetic energy ; morphology stirred bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of two mixing geometries (at the same scale) with different flow energy distributions on the performance of the gibberellic acid fermentation and on the morphology of the producing fungus Fusarium moniliforme was investigated. Fermentations were performed using a turbine mixing system (TMS) and a counterflow mixing system (CMS), which were high and low power number mixing systems, respectively. Different agitator speed rate profiles were maintained to obtain equal specific power inputs to both mixing systems. Substantial differences in morphology and productivity of F. moniliforme were found. To investigate the causes of these differences, local values and spectra of the kinetic energy of flow fluctuations were measured during the fermentations using a stirring intensity measuring device (SIMD) and a frequency spectrum analyzer. Biomass and gibberellic acid concentrations were found to be higher in the TMS, where the energy distribution was less even, and Vi/here the main part of the energy was at small frequencies (large eddies). An automated image analysis method was used for quantitative characterization of F. moniliforme freely dispersed mycelia and clump morphology. A higher proportion of clumped mycelia with clumps of larger area, perimeter, and roughness was observed in the TMS. A correlation between the morphology and productivity was found, and TMS favored the development of more productive mycelia with longer and thinner hyphae. Introduced power was not a good parameter to characterize different impellers, even at a given scale. © 1995 John Wiley & Sons, Inc.
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    Recovery and purification of bioproducts: I (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 301-301 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1002/bit.260480402
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    Novel function of guanidine hydrochloride in reverse micellar extraction of lysozyme from chicken egg white (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 333-340 
    Details
    ISSN: 0006-3592
    Keywords: reverse micelle ; guanidine hydrochloride ; extraction ; lysozyme ; chicken egg white ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The efficiency of guanidine hydrochloride (GuHCl) addition in the suppression of gel formation and the extraction of lysozyme during reverse micellar extraction from chicken egg white was investigated. A low concentration of GuHCl in the feed permitted the successful extraction of lysozyme in its native form without gel formation, which is perceived as a novel function of GuHCl. The highest recovery and specific activity of lysozyme were obtained at a GuHCl concentration of 0.06 M in 25 mM AOT reverse micellar extraction from 20-fold-diluted natural chicken egg white. Lysozyme and ovalbumin CD spectra in the corresponding GuHCl aqueous solutions revealed no changes in the higher order structures of the proteins. Furthermore, the specific activity of lysozyme in the feed was well preserved in the GuHCl system. © 1995 John Wiley & Sons, Inc.
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    Correlation between steady-state cell concentration and cell death of hybridoma cultures in chemostat (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 18-26 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; cell death ; chemostat ; autoinhibitor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present study, the steady-state cell density (X) of chemostat cultures of murine hybridoma was varied by the concentration of glucose and glutamine in culture medium and the dissolved oxygen partial pressure. Except at low glutamine and low oxygen levels, the specific death rate (kd) of the cultures was found to decrease with increasing dilution rate (D). However, the plot of kd vs. X/D yielded linear relation, which suggests that cell death was due to a non-growth-linked inhibitory product of the cells. The kd value measured at low glutamine and low oxygen levels remained practically unchanged over a wide range of D between 0.020 and 0.029 h-1. The kd for low oxygen cultures was always lower than the values obtained in low glucose and low glutamine cultures. A low-molecular-weight component of possibly less than 3000 MW was detected to be cell-death-inducing in the supernatant of exponentially growing cultures. It was neither lactate nor ammonium. The autoinhibitor was not cell-line specific. © 1995 John Wiley & Sons, Inc.
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    On-line gas analysis in animal cell cultivation: I. Control of dissolved oxygen and pH (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 42-53 
    Details
    ISSN: 0006-3592
    Keywords: oxygen uptake rate ; animal cell cultivation ; dissolved oxygen and pH ; state space controller ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To monitor gas reaction rates in animal cell culture at constant dissolved oxygen concentration (DO) and constant pH it was necessary to develop improved control methods. Decoupling of both controllrs was obtained by manipulation of molar fractions of oxygen and carbon dioxide in the gas phase. Two pairs of DO and pH controllers were designed and tested both in simulation and exprimental runs. The first controller pair was developed for headspace aeration only, whereas the second controller pair was designed for bubble aeration using a microsparger and flushing the headspace with helium. pH was controlled by a conventional discrete PID controller in its velocity form. For DO control two linear state space feedback controllers with parameter adaptation were established. In these controllers the oxygen uptake rate (OUR) was considered as a disturbance and was not included in the mathematical model. The feedback gain adaptation was based on the difference between the actual molar fraction of oxygen at time step n and the initial molar fraction. This difference is related to OUR and was used to increase or decrease the state feedback controller gain (k and k1, respectively) in a slow manner. With these controllers it was possible to get an excellent online estimate of OUR. In the case of bubble aeration a simple gas phase mass balance was sufficient, whereas during the headspace aeration a liquid phase balance was required. It has been shown that determination of OUR using gas balance requires a significantly better controller performance compared to just keeping DO and pH within reasonable limits. © 1995 John Wiley & Sons, Inc.
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    Parametric sensitivity of stoichiometric flux balance models applied to wild-type Escherichia coli metabolism (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 69-79 
    Details
    ISSN: 0006-3592
    Keywords: E. coli ; linear optimization ; metabolic fluxes ; stoichiometry ; sensitivity analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Stoichiometrically based flux balance models provide a method to quantify the metabolic pathway fluxes within a living cell. Predictions of flux balance models are expected to have applications in pathway engineering as well as in bioprocess design and control. These models utilize optimality principles applied to metabolic pathway stoichiometry along with the metabolic requirements for growth to determine the flux distribution in a metabolic network. A flux balance model has been developed for Escherichia coli W3110 using five experimentally determined strain-specific parameters. In this report, we determine the sensitivity of the predictions of the flux balance model to these five strain-specific parameters. Model predictions are shown to be sensitive to the two parameters describing metabolic capacity, while they are relatively insensitive to the three parameters that describe the metabolic requirements for growth. Thus, when stoichiometrically based models are formulated for additional strains one needs to measure the metabolic capacity (maximum rates of nutrient and oxygen utilization) accurately. Determination of metabolic capacity from batch experiments is relatively easy to perform. On the other hand, the harder to determine maintenance parameters need not be as accurately determined. © 1995 John Wiley & Sons, Inc.
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    Rheologies and morphologies of three actinomycetes in submerged culture (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 80-85 
    Details
    ISSN: 0006-3592
    Keywords: rheology ; morphology ; actinomycete ; Saccharopolyspora erythraea ; Actinomadura roseorufa ; Streptomyces rimosus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The broth rheologies and morphologies of three actinomycetes (Saccharopolyspora erythraea, Actinomadura roseorufa, and Streptomyces rimosus) in submerged culture have been examined. The rheology of all the broths became pseudoplastic as soon as significant growth occurred with the power law index, n, falling to 0.20 to 0.25. The consistency index, K, rose with biomass concentration although in some instances it fell later in the fermentation. The mean main hyphal lengths of all cultures were in the range, 15 to 25 μm, and did not alter greatly even when large changes in K were occurring. © 1995 John Wiley & Sons, Inc.
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    Synthesis of protein-containing polymers in organic solvents (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 10-17 
    Details
    ISSN: 0006-3592
    Keywords: proteins ; enzymes ; immobilization ; biopolymers ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Subtilisin has been modified with polyethylene glycol (PEG) monomethacrylate (MW 8000) by reductive alkylation, and incorporated into polymethyl methacrylate durring free-radical initiated polymerization. The activity and stability of the PEG-modified enzymes have been determined in aqueous buffer and organic solvents. The Km and Vmax values for unmodified, singly and doubly modified subtilisin were compared in these environments, and the half-lives of both modified enzymes were remarkably high (up to 2 months). The protein-containing polymer was analyzed for activity and polymer properties, and our results indicate that active subtilisin can be incorporated into polymethyl methacrylate during polymerization in organic solvents while retaining its activity and stability. © 1995 John Wiley & Sons, Inc.
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    Enzymatic interesterification of triglyceride with surfactant-coated lipase in organic media (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 27-32 
    Details
    ISSN: 0006-3592
    Keywords: esterification ; lipase ; glycerides ; organic solvent ; surfactant ; bioconversion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several surfactant-coated enzymes have been prepared by coating lipases of various origins with a nonionic surfactant, glutamic acid dioleylester ribitol (2C18Δ9GE). Enzymatic interesterification of tripalmitin with oleic acid using the surfactant-coated lipase was carried out in organic media. The surfactant-coated lipases could effectively catalyze the interesterification of glycerides better than did the powder lipases. A suitable organic solvent was an aliphatic hydrocarbon such as isooctane. The enzymatic activity for the interesterification strongly depended on the origin of the lipase. The surfactant-coated lipase prepared by Mucor javanicus showed the highest enzymatic activity for the interesterification of glycerides, although its powder lipase did not show enzymatic activity. Selective interesterification of glycerides could be performed by adjusting the concentration ratio of oleic acid to tripalmitin in isooctane. Di-substituted glyceride could be selectively produced when the concentration ratio of carboxylic acid to glycerides was 7. © 1995 John Wiley & Sons, Inc.
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    On-line gas analysis in animal cell cultivation: II. Methods for oxygen uptake rate estimation and its application to controlled feeding of glutamine (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 54-62 
    Details
    ISSN: 0006-3592
    Keywords: oxygen uptake rate ; animal cell cultivation ; hybridoma ; monoclonal antibody ; glutamine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Different methods for oxygen uptake rate (OUR) determinations in animal cell cultivation were investigated using a high quality mass spectrometer. Dynamic measurements have considerable disadvantages because of disturbances of the growing cells by the necessary variations of dissolved oxygen concentration. Only infrequent discrete measurements are possible using this method. Stationary liquid phase balance yielded better results with much higher frequency. Gas phase balancing has the advantage of not requiring dissolved oxygen measurement and knowledge of KLa, both of them are easily biased. It was found that simple gas phase balancing is either very inaccurate (error larger than expected signal) or very slow, with gas phase residence times of several hours. Therefore, a new method of aeration was designed. Oxygen and CO2 transfer are mainly achieved via sparging. The gas released to the headspace is diluted with a roughly 100-fold stream of an inert gas (helium). Through this dilution, gas ratios are not changed for O2, CO2, Ar, and N2. The measurement of lower concentrations (parts per million and below) is easy using mass spectrometry with a secondary electron multiplier. With this new method an excellent accuracy and sufficient speed of analysis were obtained. All these on-line methods for OUR measurement were tested during the cultivation of animal cells. The new method allowed better study of the kinetics of animal cell cultures as was shown with a hybridoma cell line (HFN 7.1, ATCC CRL 1606) producing monoclonal antibodies against human fibronectin. With the aid of these methods it was possible to find a correlation between a rapid decrease in oxygen uptake rate (OUR) and glutamine concentration. The sudden decrease in OUR can be attributed to glutamine depletion. This provided a basis for the controlled addition of glutamine to reduce the formation of ammonia produced by hydrolysis. This control method based on OUR measurement resulted in increased cell concentration and threefold higher product concentration. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450201
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  • 46
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    Starvation-induced programmed death of hybridoma cells: Prevention by amino acid mixtures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 86-90 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; nutrition ; cell death ; apoptosis ; monoclonal antibody ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Association of the availability of nutrients with the phenomenon of programmed cell death - apoptosis - was investigated using hybridoma cells cultured in protein-free medium under conditions of starvation, i.e., in RPMl-1640 medium diluted to 50% with saline. Amino acid mixtures, such as MEM essential amino acids or MEM nonessential amino acids were found to prevent starvation death significantly when added to the diluted medium in 1 to 2 mM concentrations, the MEM vitamin mixture was ineffective, and glutamine displayed a moderate growth-supporting effect. The specific monoclonal antibody production rate in cultures supplemented with amino acid mixtures was strikingly low, whereas supplementation with glutamine alone or simultaneously with other amino acids resulted in a specific antibody production rate comparable with the rate observed in undiluted medium. © 1995 John Wiley & Sons, Inc.
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    On-line calibration of a computerized biosensor system for continuous measurements of glucose and lactate (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 122-128 
    Details
    ISSN: 0006-3592
    Keywords: on-line calibration ; continuous monitoring ; biosensor system ; enzyme reactor ; glucose ; lactate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An on-line calibration procedure for application in continuous monitoring systems has been developed. Control of the calibration value and recalibration on-line during monitoring is possible without having to disrupt the sample withdrawal. The calibration procedure has been applied and evaluated in a continuous biosensor system based on the detection of oxygen depletion during enzymatic substrate conversion by immobilized oxidases. Evaluation included on-line calibration during continuous measurements of glucose and lactate in bovine blood samples. Calibration of the complete system consisting of a sampling device, a sample handling step, a biocatalytic step, a detection step, and a data processing unit is performed by the on-line addition of a calibration solution to a blank sample which is fed through the system. The calibration cycle is completed within 5.5 min. When recalibration is carried out during monitoring, the calibration solution is added to the sample, instead of to a blank sample, and the increase in outlet singl is registered. The major advantage of this internal standard principle is that the calibration solution is fed through the whole system according to the same path as the sample solution and thus takes into account all parameters influencing the sample. © 1995 John Wiley & Sons, Inc.
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    Real-time fuzzy-knowledge-based control of Baker's yeast production (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 135-143 
    Details
    ISSN: 0006-3592
    Keywords: baker's yeast; ; knowledge-based system ; fuzzy logic ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
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    A mathematical model for the leukocyte filtration process (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 158-164 
    Details
    ISSN: 0006-3592
    Keywords: depth filtration ; mathematical model ; leukocyte filtration ; filter efficiency ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Leukocyte filters are applied clinically to remove leukocytes from blood. In order to optimize leukocyte filters, a mathematical model to describe the leukocyte filtration process was developed by modification of a general theoretical model for depth filtration. The model presented here can be used to predict the time-dependent leukocyte filtration as a function of cell-cell interaction in the filter, filter efficiency, filter capacity, filter dimensions, and leukocyte concentration in the suspension applied to the filter. The results of different leukocyte filtration experiments previously reported in the literature could be well described by the present model. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450301
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    A study of mass transfer in yeast in a pulsed baffled bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 165-175 
    Details
    ISSN: 0006-3592
    Keywords: pulsed baffled bioreactor ; baffle ; yeast resuspension ; oscillation ; power density ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We report experimental data of mass transfer of oxygen into yeast resuspension in a pulsed baffled bioreactor. The bioreactor consists of a 50-mm-diameter column with the presence of a series of either wall (orifice) or central (disc) baffles or a mixture of both where fluid oscillation can also be supermposed during the experiments. Air bubbles are sparged into the bottom of the pulsed baffled bioreactor, and the kinetics of liquid oxygen concentration in the yeast solution is followed using a dissolved oxygen probe with a fast response time of 3 s together with the dynamic gassing-out technique. Among the three different baffle geometries investigated, the orifice baffles gave the highest and sharpest increase in the oxygen transfer rate, and the trends in the kLa measurements are consistent with the fluid mechanics observed within both the systems and previous work. In addition, we have also compared the kLa values with those obtained in a stirred tank; an 11% increase in the KLa is reported. © 1995 John Wiley & Sons, Inc.
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    Cultivation of hybridoma cells in an inclined bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 176-186 
    Details
    ISSN: 0006-3592
    Keywords: animal cell ; hybridoma cell ; shear ; cell damage ; bioreactor design ; inclination ; bubble column ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Murine hybridoma cells were grown in a bubble column that was inclined up to 45° from vertical. Inclining the column by a few degrees separated the rising bubbles against the upper surface, leaving the bulk of the liquid bubble free. The liquid was circulated well by the rising bubbles, but collection of cells by rising bubbles and exposure of cells to bursting bubbles were minimized. Maximum viable cell count and exponential growth of the cells were not affected by inclination, but an inclination of 30° gave an antibody titer of 42 mg/L, which more than doubled the yield of 17 mg/L in the vertical position. By comparison, the culture gave yields of 30 mg/L when grown in spinner flasks. The enhanced antibody production in the inclined bioreactor corresponded to a prolonged stationary phase of 45 h. © 1995 John Wiley & Sons, Inc.
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    Surfactant-Modified lipase for the catalysis of the interesterification of triglycerides and fatty acids (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 187-195 
    Details
    ISSN: 0006-3592
    Keywords: interesterification reaction ; surfactant-modified lipase ; modified lipase Saiken ; triglycerides ; fatty acids ; biocatalyst ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The lipase-catalyzed intresterification of triglycerides and fatty acids in n-hexane was studied. Initially, lipase Saiken was modified with a surfactant of sorbitan esters so that its dispersibility in hydrophobic organic media was improved. The surfactant-modified lipase formed in the modification process carried out in a buffer solution has 1,3-positional specificity and predominantly catalyzed the interesterification reaction in a microaqueous n-hexane system. The modification technique converted inactive lipases to very active biocatalysts for the interesterification of triglycerides and fatty acids. The pH and the weight ratio of surfactant to enzyme used during the lipase modification process have shown significant effects in determining the recoveries of the protein and enzyme activity from the buffer solution, the protein content of the modified lipase complex after being freeze dried, and the interesterification activity of the complex. The water content in the reaction solution has strongly influenced the enzyme activity as well as the distribution of the products. © 1995 John Wiley & Sons, Inc.
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    Effects of calcium on development of anaerobic acidogenic biofilms (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 212-218 
    Details
    ISSN: 0006-3592
    Keywords: biofilms ; calcium ; anaerobic digestion ; acidogenesis ; lactose ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anerobic biofilms with dominantly acidogenic bacteria were grown in fixed-bed recycle reactors. The influence of calcium concentration in the culture medium on biofilm mass accumulation, immobilized calcium concentration, and biofilm-specific activity was investigated. The results indicate that the biofilm mass accumulation was increased by the presence of calcium in the growth medium when calcium concentration was not higher than 120mg/L. Calcium accumulated in the biofilms increased in proportion to the calcium level in the feed. The biofilms for an increased input calcium concentration showed a trend of decrease in specific activity. The biofilms with a thickeness of less than 0.5 mm had the highest specific activity. The optimum calcium concentration for substrate consumption by the biofilms was 100 to 120 mg/L. The biofilms transferred from higher calcium medium to lower calcium medium were more susceptible to sloughing from their support surfaces, which indicates calcium's role in the stability of the biofilm structure. © 1995 John Wiley & Sons, Inc.
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    Purification of monoclonal antibodies from whole hybridoma fermentation broth by fluidized bed adsorption (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 205-211 
    Details
    ISSN: 0006-3592
    Keywords: monoclonal antibodies ; fermentation ; fluidized bed adsorption ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To achive the coarse purification of a monoclonal antibody from whole hybridoma fermentation broth a fluidized bed cation exchange process was used. The procedure consisted of application of the crude sample and washing of the bed in a fluidized mode and elution in a fixed bed mode. A completely clarified eluate was obtained with purification factors between 4 and 8 and a concentration of the desired product (monoclonal antibody) by a factor of more than 3 was achived. Thus, a combination of the three early steps of the downstream process clarification, concentration and coarse purification was possible. Two different materials were tested: a commercially available agarose-based matrix (Stream-line-SP), and a self-derivatized material based on controlled-pore glass (Bioran). Initial experiments were performed to describe the fluidization of the glass material. Comparison with the agarose material showed several differences, the agarose matrix allowing liquid flow closer to plug flow than the glass material. Increased backmixing in the liquid phase was detected when fluidizing the glass adsorbent compared with the agarose-based matrix. Despite this fact, comparison of the two materials with respect to antibody binding and elution demonstrated a similar performance. © 1995 John Wiley & Sons, Inc.
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    Characterization of tryptic casein phosphopeptides prepared under industrially relevant conditions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 196-204 
    Details
    ISSN: 0006-3592
    Keywords: tryptic casein phosphopeptides ; peptides ; casein phosphopeptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anticariogenic casein phosphopeptides (ACPP) contain the cluster sequence -Ser(P)-Ser(P)-Ser(P)-Glu-Glu- and have commercial potential as toothpaste, mouthwash, and food additives for the prevention of dental caries. In an approach to develop a commercial-scale process for the production of ACPP we have comprehensively characterized casein phosphopeptides (CPP) produced under industrially relevant conditions. Sodium caseinate (10% w/v) was hydrolyzed by Novo trypsin (commercial grade) at 50°C for 2 h and CPP were purified from the acid clarified hydrolysate by a single-step selective precipitation procedure involving Ca2+ (20 mol/mol casein) and ethanol (50% v/v) at pH 4.6 or 8.0. The individual peptides of the CPP preparations were purified by reversed-phase high-performance liquid chromatography (HPLC) and then identified by amino acid composition and sequence analyses. The yield of the pH 8.0 precipitate (13.85 ± 0.48 wt % of the caseinate) was slightly higher than that of the pH 4.6 precipitate (11.04 ± 0.30 wt % of the caseinate). However, the pH 4.6 precipitate contained predominantly (86.4 mol %) ACPP cluster peptides with small amounts of the diphosphorylated peptides (13.6 mol %), αs1(43-58) and αs2(126-136). In the pH 8.0 precipitate the cluster peptides represented a smaller proportion of the total peptides (61.9 mol %) due to increased recoveries of the diphosphorylated peptides (24.4 mol %) as well as the additional recovery of the monophosphorylated peptide β(33-48) (13.7 mol %) indicating increased cross-linking by Ca2+ at the higher pH. The recovery of the ACPP from the original caseinate was similar for both the pH 4.6 and 8.0 precipitates. Slight chymotryptic activity was detected in the industrial-grade enzyme, resulting in minor truncation of some peptides. Also some deamidation and methionine oxidation of one peptide, αs1(59-79), were detected. In conclusion, ACPP can be produced under industrially relevant conditions with only minor modifications such as slight truncation, deamidation, and methionine oxidation. However, in order to prepare casein phosphopeptides predominantly containing the cluster sequence -Ser(P)-Ser(P)-Ser(P)-Glu-Glu-, the single-step selective precipitation with Ca2+/ethanol should be performed at pH 4.6 rather than pH 8.0. © 1995 John Wiley & Sons, Inc.
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    High cell density fermentation of recombinant Vibrio cholerae for the production of B subunit of Escherichia coli enterotoxin (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 245-250 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli enterotoxin ; fed batch ; high cell density ; fermentation ; purification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High cell density fermentation studies were performed to produce the B subunit of Escherichia coli heat-labile enterotoxin (LTB) from a Vibrio cholerae culture that carries a recombinant plasmid with an ampicillin resistance gene, tac promoter, and the gene encoding LTB. Upon induction with isopropyl-β-D-thiogalactopyranoside (IPTG) the culture secreted the protein into the extracellular milieu. Fed-batch fermentation with stepwise addition of a total of 5 mM of IPTG during the active growth phase of the organism resulted in the production of 400 mg/L of LTB in 9 h and a cell optical density (OD) of 24. The LTB was purified to homogeneity with 70% recovery from the fermentation broth and was found to be chemically and biologically identical to the native protein by N-terminal amino acid sequencing and receptor binding assay. © 1995 John Wiley & Sons, Inc.
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    Effect of surfactant and particle size reduction on hydrolysis of deinking sludge and nonrecyclable newsprint (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 239-244 
    Details
    ISSN: 0006-3592
    Keywords: cellulase ; newsprint ; deinking sludge ; surfactant ; hydrolysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Disposal of sludge from deinking mills represents a significant proportion of operating costs. Bioconversion of the cellulosic fraction of deinking sludge (DIS) to ethanol greatly reduces disposal costs while producing an environmentally friendly fuel. In this study, the cellulosic fraction of newsprint and deinking sludge was hydrolysed to produce fermentable sugars. For newsprint, a particle size of 1 to 1.5 mm provided optimal reaction rates in batch reactors over practical hydrolysis times, and reducing sugar concentrations as high as 35 g/L could be achieved using a fed-batch reactor configuration. For both newsprint and DIS, the hydrolysis rate increased nonlinearly with enzyme loading. Tween-80 only marginally improved sugar production but was able to release sugars from cellulosic substrates in the absence of lytic enzymes, in an amount proportional to the surfactant concentration and the substrate particle size. DIS was relatively recalcitrant to enzymatic hydrolysis, possibly due in part to inhibition by hydrophobic constituents. © 1995 John Wiley & Sons, Inc.
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    Modeling of anaerobic formate kinetics in mixed biofilm culture using dynamic membrane mass spectrometric measurement (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 219-228 
    Details
    ISSN: 0006-3592
    Keywords: formate conversion ; mass spectrometer ; anaerobic conversion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamics of the anaerobic conversion of formate in a microbial mixed culture taken from an anaerobic fluidized bed reactor was studied using a new stirred micro reactor equipped with a membrane mass spectrometer. The microreactor with a toroidally shaped bottom and pitched blade turbine and a cylindrical flow guide was thermostated and additionally equipped with a pH electrode and pH control. During fed-batch experiments using formate, the dissolved gases (methane, hydrogen, and carbon dioxide), as well as the acid consumption rates for pH control were monitored continuously. Initially and at the end of each experiment, organic acids were analyzed using ion chromatography (IC). It was found that about 50% of the formate was converted to methane via hydrogen and carbon dioxide, 40% gave methane either directly or via acetate. This was calculated from experiments using H13CO3- pulses and measurement of 12CH4 and 13CH4 production rates. About 10% of the formate was converted to lactate, acetate, and propionate, thereby increasing the measured CO2/CH4 production ratio. The nondissociated formic acid was shown to be rate determining. From the relatively high Ks value of 2.5 mmol m-3, it was concluded that formate cannot play an important role in electron transfer. During dynamic feeding of formate, hydrogen concentration always increased to a maximum before decreasing again. This peak was found to be very discriminative during modeling. From the various models set up, only those with two-stage degradation and double Monod kinetics, both for CO2 and hydrogen, were able to describe the experimental data adequately. Additional discrimination was possible with the IC measurement of organic acids. © 1995 John Wiley & Sons, Inc.
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    Batch cultivation of Methylosinus trichosporium OB3B: IV. Production of hydrogen-driven soluble or particulate methane monooxygenase activity (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 229-238 
    Details
    ISSN: 0006-3592
    Keywords: methanotroph ; methane monooxygenase ; nitrogenase ; hydrogenase ; batch culture conditions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch culture conditions were established for the formation of H2-driven whole-cell soluble or particulate methane monooxygenase (sMMO or pMMO) activity in the obligate methanotroph, Methylosinus trichosporum Ob3b, to expand its potential uses in groundwater bioremediation and the production of specific chemicals. Addition of either Ni and H2 to a nitrate-containing minimal salts growth medium or Ni and Mo to a nitrate-lacking growth medium (induces a nitrogenase that generates intracellular H2) markedly enhanced both the hydrogenase and the accompanying washed-cell H2-driven MMO activities of shake-flask cultured cells. For sMMO containing cells, H2 provided in vitro reducing power for the oxidation of chlorinated solvents such as chloroform and trichloroethylene. Cell cultivations under N2-fixing conditions in a 5-L bioreactor, however, required an initial nitrate concentration of at least 1 to 2 mM to achieve high biomass yields (5 to 7 g of dry cell wt/L) for cells producing H2-driven sMMO or pMMO activity. Elevation of the initial medium nitrate concentration to 20 mM shortened the culture time for pMMO producing cells by 40%, yet still generated an equivalent growth yield. High nitrate also shortened the culture time for sMMO containing cells by ∼25%, but it lowered their biomass yield by 26%. Upon storage for 5 weeks at room temperature, washed resting-state cells retained 90% and 70% of their H2-driven sMMO and pMMO activity, respectively. This makes their practical use quite feasible. © 1995 John Wiley & Sons, Inc.
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    Photolithotrophic cultivation of Laminaria saccharina gametophyte cells in a stirred-tank bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 251-260 
    Details
    ISSN: 0006-3592
    Keywords: macroalgal cells ; stirred-tank bioreactor ; photolithotrophic cultivation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Filamentous cell cultures derived from female gametophytes of the temperate brown macroalga Laminaria saccharina were photolithotrophically cultivated in artificial seawater medium within an illuminated 1.3-L stirred-tank bioreactor at 13°C using CO2 in air as the carbon source. A Monod model adequately described light-saturated growth. The apparent half-saturation constant (Ko) was 23 μE/m2-s, and maximum specific growth rate was 0.15 day-1. At a constant inoculation cell density of 50 mg DCW/L, biomass productivity after 26 days of cultivation increased from 630 mg DCW/L at 18 μE/m2-s to 890 mg DCW/L at 228 μE/m2-s. At 98 μE/m2-s, 1.1 vvm aeration rate, and 250 rpm impeller speed, the CO2 transfer rates (CO2 TRs) and CO2 consumption rates (rco2) were determined over the cultivation period. At peak CO2 demand, the maximum CO2 TR was 0.19 mmol CO2/L-h, but rco2 was only 0.15 mmol CO2/L-h, implying that the culture was not CO2 transport limited. This is the first reported bioreactor cultivation study of cell cultures derived from a macrophytic marine alga. © 1995 John Wiley & Sons, Inc.
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    Enzyme catalyzed biotransformations in aqueous two-phase systems with precipitated substrate and/or productTo Professor Joachim Klein on the occasion of his 60th birthday. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 261-267 
    Details
    ISSN: 0006-3592
    Keywords: Biotransformations in aqueous suspensions ; chymotrypsin ; penicillin amidase ; immobilized enzyme ; peptide synthesis ; D-phenylglycine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biotransformations catalyzed by free and immobilized enzymes have been carried out in aqueous suspensions with up to 25% (w/w) precipitated substrate or product. For the kinetically controlled synthesis of N-Acetyl-Tyr-Arg-NH2 with up to 0.8 M insoluble activated substrate N-Acetyl-TyrOEt catalyzed by α-chymotrypsin (EC3.4.21.1) the dipeptide yield was found to be 〉90%. This and the space-time yields were higher than those observed for one-phase aqueous systems and much higher than in systems where the insoluble substrate had been solubilized by addition of organic solvents. In the equilibrium controlled hydrolysis of 0.4 M D-phenylglycine-amide catalyzed by immobilized penicillin amidase (EC 3.5.1.11) the product precipitates. The enzyme immobilized in the support with the smallest pores could be reused without reduction in the rate due to precipitation in the pores. This decreases the number of immobilized enzyme molecules that can be used as biocatalysts. The latter was observed for supports with larger pores as the solubility decreases with increasing particle size. These results demonstrate that biotransformations with insoluble substrates or products using free or immobilized enzymes can be easily carried out in aqueous two-phase systems, without organic solvents, provided that the pore sizes of the supports are sufficiently small and that the rate of mass transfer from the precipitated substrate is large. The latter increases with decreasing particle size. © 1995 John Wiley & Sons, Inc.
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    Enzymic peptide synthesis in microaqueous, solvent-free systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 276-278 
    Details
    ISSN: 0006-3592
    Keywords: enzymic peptide synthesis ; solvent free system, chymotrypsin ; thermolysin ; peptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermolysin-catalyzed (EC 3.4.24.4) and chymotrypsin-catalyzed (EC 3.4.21.1) peptide synthesis reactions were accomplished without any organic solvent in the presence of low amounts of water under sonication and fluidization. The systems used are considered to be microaqueous solvent-free ones. The influence of several reaction parameters, such as time, the amount of enzyme, the amount of water in free form or bound as hydration water, and the N/C component ratio, on the vield of the thermolysin-catalyzed synthesis of Z-Phe-Leu-NH2 (up to 87% yield) was investigated in a sonicated system. Besides Z-Phe-Leu-NH2, the tripeptide derivatives Ac-Xaa-Trp-Leu-NH2, (Xaa = Gly, Ala) were also obtained in good yields of 79 and 71% respectively. In the latter case, no hydrolytic side reactions were observed. Using a fluidized-bed reactor, chymotrypsin- and thermolysin-catalyzed syntheses of N-protected di- and tripeptide amides could be perfromed with yields in the range of 10 to 40%. © 1995 John Wiley & Sons, Inc.
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    Production of poly(D-3-hydroxybutyrate) from CO2, H2, and O2 by high cell density autotrophic cultivation of Alcaligenes eutrophus (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 268-275 
    Details
    ISSN: 0006-3592
    Keywords: poly(D-3-hydroxybutyrate) ; P(3HB) ; Alcaligenes eutrophus ; gas explosion ; autotroph ; hydrogen oxidizing bacterium ; carbon dioxide fixation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrogen-oxidizing bacterium, Alcaligenes eutrophus autotrophically produces biodegradable plastic material, poly(D-3-hydroxybutyrate), P(3HB), from carbon dioxide, hydrogen, and oxygen. In autotrophic cultivation of the microorganism, it is essential to eliminate possible occurrence of gas explosions from the fermentation process. We developed a bench-plant scale, recycled-gas, closed-circuit culture system equipped with several safety features to perform autotrophic cultivation of A. eutrophus by maintaining the oxygen concentration in the substrate gas phase below the lower limit for a gas explosion (6.9%). The culture vessel utilized a baskettype agitator, resulting in a KL a value of 2970 h-1. Oxygen gas was also directly fed to the fermentor separately from the other gases. As a result, 91.3 g · dm-3 of the cells and 61.9 g · dm-3 of P(3HB) were obtained after 40 h of cultivation under this oxygen-limited condition. The results compared favorably with those reported for mass production of P(3HB) by heterotrophic fermentation. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450401
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    Kinetics of nitrate inhibition of carbon tetrachloride transformation by a denitrifying consortia (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 279-284 
    Details
    ISSN: 0006-3592
    Keywords: carbon tetrachloride ; nitrate inhibition ; biodegradation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of nitrate inhibition of carbon tetrachloride (CT) transformation were examined using a denitrifying consortium. Comparison of data from fed-batch experiments to the model reported by Hooker et al. indicate that the inhibition constant ranges between 3.2 and 21 mg/L, with an average of 8.8 mg/L. This range is much lower than the previously reported value of 169 mg/L. Simulations using the corrected parameter accurately reflect this new data and the data reported by Hooker et al. In contrast, the earlier reported coefficient value does not reflect the data reported in this work. © 1995 John Wiley & Sons, Inc.
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    Microbial production of (+)-trans-isochorismic acid (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 285-291 
    Details
    ISSN: 0006-3592
    Keywords: Klebsiella pneumoniae 62-1 ; isochorismate hydroxymutase (E.C. 5.4.99.6) ; affinity immobilization ; isochorismate excretion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two methods are described for the preparation of enantiomerically pure (+)-trans-isochorismic acid, an important metabolite of the postchorismate pathway. Both methods can be employed to prepare isotopically labeled isochorismic acid. One of the two methods is suitable to prepare bulk quantities of isochorismic acid using a recombinant strain of Klebsiella pneumoniae 62-1. © 1995 John Wiley & Sons, Inc.
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    Intracellular flux analysis in hybridomas using mass balances and in vitro 13C nmr (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 292-303 
    Details
    ISSN: 0006-3592
    Keywords: fluxes ; intracellular fluxes ; hybridoma cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Intracellular fluxes are important in defining cellular physiology and its changes in response to environmental variations. Stoichiometric balances combined with extra cellular metabolite measurements were applied to the estimation of intracellular fluxes and the study of energy metabolism in the hybridoma cell line ATCC CRL 1606. Redundant measurements allowed the evaluation of the consistency of the stoichiometry, measurements, and pseudo-steady-state assumption leading to refinement of the assumed biochemistry and identification of measurement errors. To validate the flux estimates, two batch experiments were performed with glucose labeled in the 1 position with 13C. The distribution of 13C in secreted lactate was measured via nuclear magnetic resonance spectroscopy (NMR) and compared to that predicted from the estimated intracellular fluxes. There was good agreement between the measured and estimated isotope distributions, demonstrating the validity of the flux estimates obtained from stoichiometric balances. © 1995 John Wiley & Sons, Inc.
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    Removal of phenols and aromatic amines from wastewater by a combination treatment with tyrosinase and a coagulant (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 304-309 
    Details
    ISSN: 0006-3592
    Keywords: phenol ; substituted phenol ; tyrosinase ; immobilization ; chitosan ; coagulant ; immobilized enzyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Removal of phenols and aromatic amines from industrial wastewater by tyrosinase was investigated. A color change from colorless to darkbrown was observed, but no precipitate was formed. Colored products were found to be easily removed by a combination treatment with tyrosinase and a cationic polymer coagulant containing amino group, such as hexamethylenediamine-epichlorohidrin polycondensate, polyethleneimine, or chitosan. The first two coagulants, synthetic polymers, were more effective than chitosan, a polymer produced in crustacean shells. Phenols and aromatic amines are not precipitated by any kind of coagulants, but their enzymatic reaction products are easily precipitated by a cationic polymer coagulant. These results indicate that the combination of tyrosinase and a cationic polymer coagulant is effective in removing carcinogenic phenols and aromatic amines from an aqueous solution. Immobilization of tyrosinase on magnetite gave a good retention of activity (80%) and storage stability i.e., only 5% loss after 15 days of storage at ambient temperature. In the treatment of immobilized tyrosinase, colored enzymatic reaction products were removed by less coagulant compared with soluble tyrosinase. © 1995 John Wiley & Sons, Inc.
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    Development of optimized transfectoma cell lines for production of chimeric antibodies in hollow fiber cell culture systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 310-319 
    Details
    ISSN: 0006-3592
    Keywords: chimeric antibodies ; transfectoma cells ; hollow fiber fermentor ; immunoglobulin enhancer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Methods for the selection of transfectoma cells that express large quantities of mouse-human chimeric antibodies have been develped. SP2/0 mouse myeloma cells were transfected with pSV2-gpt and pSV2-neo based immunoglobulin expression vectors. Double transfectants were selected using the xanthine-guanine phosphoribosyl transferase (gpt)and the neomycin (neo) selection marker genes. ELISA-based screening of transfectoma clones resulted in the isolation of IgG-producing transfectomas. Introduction of the kappa light-chain 3′-enhancer into the light-chain expression vector significantly increased immunoglobulin expression, but only when the enhancer was located at its physiological site, 9 kb downstream of the kappa constant region exon. With some of the transfectomas, final yields of up to 80 mg/L of chimeric IgG were obtained in conventional flask cultures using serum-free growth medium. A pilot-scale AcuSyst Maximizer hollow fiber cell culture system was used for the production of gram amounts of chimeric IgG. Results obtained with different transfectoma clones in conventional culture were not fully predictive for yields in the hollow fiber system. In contrast, differences in productivity between individual clones in the laboratory-scale Tecnomouse cell culture unit were comparable with those in the Maximizer system. Up to 200 mg of chimeric IgG were produced per day in one Maximizer bioreactor. © 1995 John Wiley & Sons, Inc.
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    Evaluation of cellulase recycling strategies for the hydrolysis of lignocellulosic substrates (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 328-336 
    Details
    ISSN: 0006-3592
    Keywords: cellulase recycling ; lignin ; lignocellulose hydrolysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recycling of cellulases should lower the overall cost of lignocellulosiic bioconversion processes. In this study, three recycling strategies were evaluated to determine their efficiencies over five successive rounds of hydrolysis. The effect of lignin on recycling was examined by comparing water-washed, steam-exploded birch (WB; 32% lignin) and WB which had been further extracted with alkali and peroxide (PB; 4% lignin). When the cellulases were recovered from the residual substrates after partial hydrolysis of both substrates, the recovered cellulase activity toward the mixture of fresh and residual substrates decreased after each recycling step. When the cellulases in the supernatants were also recycled, up to 20% more activity could be recovered. In both of these cases, the recovered activities did not correspond to the activities expected from the amount of cellulase protein recovered during recycling. The best recovery was obtained when the cellulases were recovered from both the residue and the supernatant after complete hydrolysis of the PB substrate. In this case, all of the originally added cellulase activity could be recovered for four consecutive hydrolysis rounds. However, when the same recycling strategy was carried out using the WB substrate, the recovered cellulase activity declined quickly with each recycling round. In all three of the recycling strategies, lower cellulase activities were recovered from the substrates with higher lignin contents. © 1995 John Wiley & Sons, Inc.
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    Dielectrophoretic separation of cells: Continuous separation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 337-343 
    Details
    ISSN: 0006-3592
    Keywords: dielectrophoresis ; cells, separation of ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dielectrophoresis is the movement of particles in non-uniform alternating and direct current (AC, DC) electric fields. When nonuniform electric fields are created between microelectrodes, cells will redistribute themselves around the electrodes, the force holding the cells in place dependig on the local electric field and on the electrical properties of the cells themselves and the suspending medium. Steric drag forces produced by a gentle fluid flow in the chamber can be used to separate cells by selectively lifting cells from potential energy wells produced by the electric field. The technique is demonstrated in the batch separation of bacteria, yeast cells, and plant cells. Continuous separation and extraction of two cell types can be achieved by repeated reversing of the fluid flow direction in phase with the switching on and off of the applied voltage, and the efficacy of the technique is demonstrated for viable and nonviable (heat-treated) yeast cells. © 1995 John Wiley & Sons, Inc.
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    Operational patterns affecting lactic acid production in ultrafiltration cell recycle bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 320-327 
    Details
    ISSN: 0006-3592
    Keywords: cell recycle reactor ; ultrafiltration tubular membranes ; high lactic acid productivities ; best operational conditions ; different dilution rates ; start-up strategy ; membrane permeability ; long-term fermentations ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lactic acid production with cell recycling on an ultrafiltration tubular membrane reactor was studied; higher lactic acid concentrations as well as productivities were obtained under long-term fermentations compared with other high cell density systems. Different operational conditions, namely dilution rates and start-up modes, were assessed. Performances were very different at the three different dilution rates tested (D = 0.20 h-1, D = 0.40 h-1, or D = 0.58 h-1). The different behaviours are discussed and factors responsible for them are presented. The best way to operate for lactic acid production is chosen, the dilution rate of D = 0.40 h-1 being the one providing the best overall performance. On the other hand, results show that of the two start-up modes tested, continuous start (membrane open) permits higher permeabilities throughout the operational runs than batch start (membrane closed). Operational stability was found to be directly associated with membranes that work at “steady state,” the membrane permeability being kept around 15 L/m2 h. Optimized cell bleed can improve time of operation if such membrane permeability can be maintained for a longer time. A comparison of results with those obtained in other lactic acid production systems is presented; such comparison shows that this tubular ultrafiltration membrane cell recycle reactor presents three important advantages: (1) concomitant lactic acid concentrations and productivities; (2) long periods of operation at reasonable permeabilities; and (3) good mechanical stability permitting the use of steam sterilization. © 1995 John Wiley & Sons, Inc.
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    Esterification reactions catalyzed by Chromobacterium viscosum lipase in CTAB-based microemulsion systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 344-355 
    Details
    ISSN: 0006-3592
    Keywords: esterification ; Chromobacterium viscosum ; lipase ; microemulsions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chromobacterium viscosum (CV) lipase solubilized in water-in-oil (w/o) microemulsions based on the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) have been used for multigram-scale ester synthesis, including the kinetic resolution of a secondary alcohol. The stability of CV lipase in all the CTAB microemulsions studied was excellent and was superior to that observed in aqueous buffer at the same pH and temperature. Kinetic studies were performed using the synthesis of ethylhexadecanoate as a model reaction. Under pseudo-first-order conditions, the synthesis rates were linearlydependent on the enzyme and fatty acid concentrations and the R dependence shows the characteristic bell-shaped curve (where R = [H2O]/[surfactant]). The dependence of enzyme activity toward octyldecanoate synthesis on the pH of the dispersed buffer phase is in marked contrast to that observed for the pH dependence of CV lipase toward p-nitrophenylbutyrate hydrolysis. In the former case, the pH-activity profile is approximately sigmoidal, which may reflect the ionization state of the fatty acid substrate. In the latter case, the pH dependence is minimal at both R = 10 and R = 50, suggesting the enzyme does not experience a changed pH environment. Inclusion of a pH-sensitive probe molecule into those incubations containing fatty acid clearly demonstrates that the probe molecule experiences a changed environment consistent with that expected for the selected buffer. An in situ Fourier transform nuclear magnetic resonance (FT-NMR) assay has been developed which allows continuous monitoring of the esterification reactions, thereby providing an additional means of determining initial rates. The method may be of general value for lipase assays in microemulsions since it may provide, at the same time, information regarding enzyme regioselectivity. © 1995 John Wiley & Sons, Inc.
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    Kinetics of ethanol production by recombinant Escherichia coli KO11 (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 356-365 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli KO11 ; ethanol production ; kinetic model ; lignocellulosic hydrolysate ; fermentation, mixed sugar ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fermentation kinetics for separate as well as simultaneous glucose and xylose fermentation with recombinant ethanologenic Escherichia coli KO11 are presented. Glucose and xylose were consumed simultaneously and exhibited mutual inhibition. The glucose exhibited 15 times stronger inhibition in xyclose fermentation than vice versa. The fermentation of condensate from steampretreated willow (Salix) was investigated. The kinetics were studied in detoxified as well as in nondetoxified condensate. The fermentation of the condensate followed two phases: First the glucose and some of the pentoses (xylose in addition to small amounts of arabinose) were fermented simultaneously, and then the remaining part of the pentoses were fermented. The rate of the first phase was independent of the detoxification method used, whereas the rate of the second phase was found to be strongly dependent. When the condensate was detoxified with overliming in combination with sulfite, which was the best detoxification method investigated, the sugars in the condensate, 9 g/L, were fermented in 11 h. The same fermentation took 150 h in nondetoxified condensate. The experimental data were used to develop an empirical model, describing the batch fermentation of recombinant E. coli KO11 in the condensate. The model is based on Monod kinetics including substrate and product inhibition and the sum of the inhibition exerted by the rest of the inhibitors, lumped together. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1002/bit.260450501
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    Development of effective modified cellulase for cellulose hydrolysis process (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 366-373 
    Details
    ISSN: 0006-3592
    Keywords: enzymatic hydrolysis ; cellulase ; polyoxyalkylene ; adsorption ; reactive two-phase partition ; solubilization in organic solvent ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cellulase was modified with amphilic copolymers made of α-allyl-ω-methoxy polyoxyalkylene (POA) and maleic acid anhydride (MAA) to improve the cellulose hydrolytic reactivity and cellulase separation. Amino groups of the cellulase molecule are covalently coupled with the MAA functional groups of the copolymer. At the maximum degree of modification (DM) of 55%, the modified cellulase activity retained more than 80% of the unmodified native cellulase activity. The modified cellulase shows greater stability against temperature, pH, and organic solvents, and demonstrated greater conversion of substrate than native cellulase does. Cellulase modification is also useful for controlling strong adsorption of cellulase onto substrate. Moreover, cellulase modified with the amphiphilic copolymer displays different separation characteristics which are new. One is a reactive two-phase partition and another is solubility in organic solvents. It appears that these characteristics of modified cellulase work very effectively in the hydrolysis of cellulose as a total system, which constitutes the purification of cellulase from culture broth, hydrolysis of cellulose, and recovery of cellulase from the reaction mixture. © 1995 John Wiley & Sons, Inc.
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    Preferential release of one daughter cell during division of immobilized chinese hamster ovary cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 374-378 
    Details
    ISSN: 0006-3592
    Keywords: cell culture ; patterened surfaces ; cell adhesion ; hydrogel ; polyHEMA ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chinese hamster ovary (CHO) cells were attached to tiny adhesive sites in poly-2-hydroxyethyl methacrylate(polyHEMA-) coated glass, and their divison properties were examined. The adhesive sites were produced by placing a metal mask, containing 8-μm-diameter holes arranged in a regular pattern, on top of the coated glass and exposing the sandwich to glow discharge treatment. This treatment produced an ordered array of circular cavities in the polyHEMA down to the glass. These adhesive sites were smaller in diameter than a newborn CHO cell, so that, upon division, there would theoretically be room for only one of the two new daughter cells to remain attached. It was found that individual CHO cells attached to, and grew upon, the sites, and that division normally resulted in the releas of one of the two new daughters. It is concluded that this culture technique has applications in research on the mammalian cell cycle, cell partitioning, and cellular senescence. © 1995 John Wiley & Sons, Inc.
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    Working at controlled water activity in a continuous process: The gas/solid system as a solution (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 387-397 
    Details
    ISSN: 0006-3592
    Keywords: transesterification ; water activity ; lipolytic enzymes ; gas ; bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fusarium solani cutinase and Candida cylindracea lipase were used to catalyze a transesterification reaction in a continuous gas/solid bioreactor. In this system, a solid phase composed of a packed enzymatic preparation was continuously percolated with carrier gas which fed substrate and removed reaction products simultaneously. Different conditions of immobilization were used and compared to the results obtained with a nonsupported enzyme. The enzymatic activity was found to be highly dependent of a key parameter: water activity (aw). Biocatalyst stability was greatly influenced by water activity and the choice of immobilization technique for the enzymatic material. For free and adsorbed enzymes, water requirements exhibited optima which corresponded to the complete hydration coverage of the protein. These optima presented a good correlation with the isotherm sorption curves obtained for the different preparations. In this work are reported the results concerning the possibility of using a continuous system able to operate at controlled water activity in a heterogeneous medium. Lipolytic enzyme in such a system appears to be a new process for the biotransformation of volatile esters. © 1995 John Wiley & Sons, Inc.
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    Performances of a full-scale novel multiplate anaerobic reactor treating cheese whey effluent (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 398-405 
    Details
    ISSN: 0006-3592
    Keywords: anaerobic digestion ; full-scale ; granule activity ; multiplate reactor ; solid retention ; whey permeate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A 450-m3 multiplate anaerobic reactor (MPAR) has been started-up in April 1992 for treating wastewater (whey permeate and domestic wastewater) at the Nutrinor (Lactel) cheese factory in Chambord (Québec, Canada). The MPAR consists of four superimposed sections. The liquid flows upwards from one section to the next, while the gas is collected below each plate and evacuated through side-outlets. The wastewater is concurrently distributed at the bottom of the first, second, and third sections, as 50%, 33%, and 17% of the total influent stream, respectively. Granular anaerobic sludge at an initial concentration of 30 kg of volatile suspended solids (VSS) per cubic meter of reactor liquid volume was used to inoculate the reactor. Under normal operation of the factory, the chemical oxygen demand (COD) concentration of the influent ranged from 20 to 37 kg COD m-3. The reactor organic loading rate (OLR) fluctuated between 9 and 14.7 kg COD m-3 d-1 for hydraulic retention times (HRT) maintained between 55 and 68 h. At the highest OLR, the MPAR showed an efficiency of 98% and 92% for soluble and total COD removal, respectively, and a methane production rate averaging around 4 m3 m-3 d-1.Biomass-specific activities ranged between 7 and 51, 1.3 and 8.5, 5.3 and 12.2, 60 and 119, and 119 and 211 mmol g-1 VSS d-1 for glucose, propionate, acetate, formate, and hydrogen, respectively. Average equivalent-diameter of the granules was around 0.65 mm. The MPAR reactor generally showed a large capacity for solid retention with a biomass content between 32 and 37 kg VSS m-3. © 1995 John Wiley & Sons, Inc.
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    A novel recycle batch immobilized cell bioreactor for propionate production from whey lactose (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 379-386 
    Details
    ISSN: 0006-3592
    Keywords: propionic acid fermentation ; Propionibacterium acidipropionici ; immobilized cell bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recycle batch fermentations using immobilized cells of Propionibacterium acidipropionici were studied for propionate production from whey permeate, de-lactose whey permeate, and acid whey. Cells were immobilized in a spirally wound fibrous sheet packed in a 0.5-L column reactor, which was connected to a 5-L stirred tank batch fermentor with recirculation. The immobilized cells bioreactor served as a breeder for these recycle batch fermentations. High fermentation rates and conversions were obtained with these whey media without nutrient supplementation. It took ∼55 h to ferment whey permeate containing ∼45 g/L lactose to ∼20 g/L propionic acid. Higher propionate concentrations can be produced with various concentrated whey media containing more lactose. The highest propionic acid concentration obtained with the recycle batch reactor was 65 g/L, which is much higher than the normal maximum concentration of 35 to 45 g/L reported in the literature. The volumetric productivity ranged from 0.22 g/L · h to 0.47 g/L · h, depending on the propionate concentration and whey medium used. The corresponding specific cell productivity was 0.033 to 0.07 g/L · g cell. The productivity increased to 0.68 g/L · h when whey permeate was supplemented with 1% (w/v) yeast extract. Compared with conventional batch fermentation, the recycle batch fermentation with the immobilized cell bioreactor allows faster fermentation, produces a higher concentration of product, and can be run continually without significant downtime. The process also produced similar fermentation results with nonsterile whey media. © 1995 John Wiley & Sons, Inc.
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    Fluid shear effects on suspension cultures of Morinda citrifolia (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 415-425 
    Details
    ISSN: 0006-3592
    Keywords: plant cell suspension culture ; capillary shear loop ; Morinda citrifolia ; shear susceptibility ; morphology ; stirred tank reactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The shear susceptibility of cell suspension cultures of the plant cell Morinda citrifolia was investigated by subjecting the cells to the well-defined shear field generated in turbulent flow through a capillary. Suspensions were circulated using a peristaltic pump and average shear stresses between 25 and 350 N m-2 were generated in the capillary test section. Control experiments were performed to assess the possible contribution of the peristaltic pump to the observed cell damage. There was clear evidence of pump-induced damage at the more severe test conditions and all viability measurements were corrected accordingly. Both shake flask suspension cultures (aged between 9 and 15 days) and repeated batch fermentation cultures, grown in a stirred tank reactor (STR) under a variety of controlled agitation conditions, were tested in the capillary shear loop. The cell damage incurred was evaluated in terms of suspension viability, as determined by a dye exclusion technique. Viability loss was found to conform closely to a first-order model in which the rate constant was observed to increase with the imposed shear stress. Furthermore, a linear relationship was identified between the specific death constant and the cumulative energy dissipated. Post-shear morphological measurements showed that the chain length distribution is shifted toward markedly lower values. In comparison with shake flask cultures, repeated batch fermentation cultures exhibited a marked increase in sensitivity to capillary shear. Based upon the determined morphological characteristics, this result is primarily attributable to the increased chain lengths characteristic of the repeated batch cultures. © 1995 John Wiley & Sons, Inc.
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    Effects of sorbitol addition on the action of free and immobilized hydrolytic enzymes in organic media (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 406-414 
    Details
    ISSN: 0006-3592
    Keywords: chymotrypsin ; differential scanning calorimetry ; ligands ; lipase ; organic media ; sorbitol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of the addition of sorbitol on the activity and stability of enzymes was examined by monitoring transesterification reactions performed in organic media at various water activities (aw = 0.08 to 0.97). Lipases from Chromobacterium viscosum and Candida rugosa immobilized on celite, and chymotrypsin, free or immobilized on celite, were used. When the sorbitol-containing enzymes were employed, higher reaction rates and less hydrolysis were observed. Immobilization of chymotrypsin resulted in high activity and operational stability, while the nonimmobilized enzyme was stable only in the presence of sorbitol. The activity of all preparations diminished after washing them with pyridine to remove sorbitol. Furthermore, severe stability problems occurred in the preparations lacking sorbitol. Sorbitol treatment, even after removal of the sorbitol itself, improved the activity of nonimmobilized chymotrypsin relative to the washed control. On the other hand, washing to remove sorbitol had a negative effect on the activity of both coimmobilized lipase and coimmobilized chymotrypsin. Addition of a substrate analogue, N-acetyl-L-phenylalanine, to chymotrypsin yielded a preparation that exhibited higher activity than both the control and its sorbitol-containing counterpart. Differential scanning calorimetry measurements revealed that the chymotrypsin-sorbitol complex was stable against thermal denaturation, undergoing transition at a high temperature (89°C). The transition temperatures of the substrate-containing chymotrypsin and of the control were identical (72°C). © 1995 John Wiley & Sons, Inc.
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    Relation between dissolved oxygen concentration and ajmalicine production rate in high-density cultures of Catharanthus roseus (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 435-439 
    Details
    ISSN: 0006-3592
    Keywords: Catharanthus roseus ; ajmalicine production rate ; dissolved oxygen concentration ; kinetic model ; high-density culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The relation between dissolved oxygen (DO) and the ajmalicine production rate of Catharanthus roseus was investigated in 15-L tank reactors at constant stirrer speed and gas flow rate. Below a DO concentration of 29% of air saturation the ajmalicine production rate was less than 0.06 μmol/g/d. Above a DO of 43% the ajmalicine production rate was constant at 0.21 μmol/g/d. Between a DO of 29% and 43% there was a strong relation between the ajmalicine production rate and the DO concentration. After a period of at least 12 days at DO ≤29% the culture lacked the ability to adapt to a DO ≥57%. A kinetic equation is proposed for the relation between DO and the specific ajmalicine production rate. © 1995 John Wiley & Sons, Inc.
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    Controlling enzyme-catalyzed regioselectivity in sugar ester synthesis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 426-434 
    Details
    ISSN: 0006-3592
    Keywords: regioselectivity of enyzmatic catalysis ; sucrose acylation in organic solvents ; molecular modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rational control over enzyme-catalyzed regioselectivity has been studied using sucrose acylation by vinyl esters in organic media as a model. Subtilisins BPN' and Carlsberg preferentially acylate at the 1′-hydroxyl of sucrose with some acylation observed at the 6-hydroxyl. The preference for the 1′-hydroxyl is strongly affected by the hydrophobicity of the organic solvent and the chain length of the vinyl ester. Increasingly hydrophobic solvents and longer chain lengths lower the favorable formation of the 1′-acylation and improve 6-acylation. Molecular modeling of sucrose in the binding pocket of subtilisin BPN' shows that the 1′-acylation is favored in solvents that can solvate sugars (such as pyridine) as the glucose moiety is exposed to the medium, whereas 6-acylation leaves the entire sucrose molecule buried within the enzyme's binding pocket. Thus, 1′-acylation is sterically more favorable than 6-acylation. Increasingly hydrophobic solvents affect regioselectivity by changing the degree of solvation of the glucose moiety in the medium and forcing the sucrose 1′-ester completely into the binding pocket. In a related modeling, the vinyl ester chain length was shown to modulate regioselectivity by controlling the bond angles between the resulting acylenzymes and the sucrose thereby affecting the positioning of the sucrose in the binding pocket of subtilisin BPN'. This study shows that control over enzymic regioselectivity can be achieved by rational choices of substrate and solvent. © 1995 John Wiley & Sons, Inc.
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    Diffusion of Cu2+ in calcium alginate gel beads: Further analyses (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 454-457 
    Details
    ISSN: 0006-3592
    Keywords: copper ; diffusion ; alginate gel beads ; diffusion models ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The diffusivity of Cu2+, as determined by previous authors from analysis of experimental data in terms of the shrinking core (SCM) and linear absorption (LAM) models, is examined in light of the ability of the models to curve fit all the data. It is concluded from this further analysis that previous conclusions depicting the LAM to have an advantage over the SCM for predictive value are not justified. It is also shown that equally good curve fits can be obtained with a recent absorption/desorption model of diffusion which considers directly, through distribution theory, the effect of heterogeneity of material properties on the rate of diffusion. © 1995 John Wiley & Sons, Inc.
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    Metal recognition by in-vitro selection (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 458-462 
    Details
    ISSN: 0006-3592
    Keywords: molecular recognition ; in vitro selection ; metal-binding protein ; molecular process engineering ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We propose an in vitro selection strategy to identify bacteriophage variants that recognize metal ions in solution. In 6 M urea, phage T7 loses 99.9% of its activity in less than 5 min. Inactivation is accelerated by gold, but slowed by zinc and magnesium. Selection of phage over five generations in the presence of gold, zinc, and magnesium increases phage half-lives 4-, 10-, and 70-fold, respectively. As selections are repeated, phage become increasingly dependent on the specific metal employed in the selection, indicating the suitability of the strategy for optimization of metal-ion recognition. © 1995 John Wiley & Sons, Inc.
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    Transformation capacities of chlorinated organics by mixed cultures enriched on methane, propane, toluene, or phenol (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 440-449 
    Details
    ISSN: 0006-3592
    Keywords: transformation capacity ; product toxicity ; oxygenase enzymes ; chlorinated organics ; trichloroethylene ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The degradation of trichloroethylene (TCE), chloroform (CF), and 1,2-dichloroethane (1,2-DCA) by four aerobic mixed cultures (methane, propane, toluene, and phenol oxidizers) grown under similar chemostat conditions was measured. Methane and propane oxidizers were capable of degrading both saturated and unsaturated chlorinated organics (TCE, CF, and 1,2-DCA). Toluene and phenol oxidizers degraded TCE but were not able to degrade CF, 1,2-DCA, or other saturated organics. None of the cultures tested were able to degrade perchloroethylene (PCE) or carbon tetrachloride (CC4). For the four cultures tested, degradation of each of the chlorinated organics resulted in cell inactivation due to product toxicity. In all cases, the toxic products were rapidly depleted, leaving no toxic residues in solution. Among the four tested cultures, the resting cells of methane oxidizers exhibited the highest transformation capacities (Tc) for TCE, CF, and 1,2-DCA. The Tc for each chlorinated organic was observed to be inversely proportional to the chlorine carbon ratio (Cl/C). The addition of low concentrations of growth substrate or some catabolic intermediates enhanced TCE transformation capacities and degradation rates, presumably due to the regeneration of reducing energy (NADH); however, addition of higher concentrations of most amendments reduced TCE transformation capacities and degradation rates. Reducing energy limitations and amendment toxicity may significantly affect Tc measurements, causing a masking of the toxicity associated with chlorinated organic degradation. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260450509
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450601
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    Enhancing effect of albumin hydrolysate on ethanol production employing Saccharomyces sake (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 450-453 
    Details
    ISSN: 0006-3592
    Keywords: ethanol production ; albumin hydrolysate ; plasma membrane ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enhancing effect of albumin hydrolysate on ethanol production was investigated in ethanol fermentations using Saccharomyces sake. In batchwise ethanol production, addition of supplemental albumin hydrolysate and phosphatidylcholine, or albumin hydrolysate alone, brought about a more than 60% increase in final ethanol concentration (148 or 144 g/L compared with 88 g/L with no supplementation [control] after 72 h). The effect of the supplements is believed to be due to an enhanced alcohol tolerance of cells grown in media containing the supplements. Cells grown in media containing albumin hydrolysate were enriched in phenyalanine, tyrosine, and methionine in their plasma membranes. All three amino acids were also present in considerable amounts in the albumin hydrolysate. This fact suggests that the three amino acids, which are present in albumin hydrolysate, are incorporated into the plasma membranes of cells. Under ethanol production conditions in which only one amino acid among the components of albumin hydrolysate was excluded, namely phenlalanine, tyrosine, or methionine, significant reductions in ethanol production resulted. © 1995 John Wiley & Sons, Inc.
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    Dynamics of biofilm detachment in biofilm airlift suspension reactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 481-487 
    Details
    ISSN: 0006-3592
    Keywords: biofilms ; detachment ; substrate loading ; airlift reactor ; abrasion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamic change in the overall detachment rate of spherical biofilms in a biofilm airlift suspension reactor was measured after a downshift of the substrate loading rate to zero while all other conditions remained constant. In contrast to the expectations, the overall detachment rate decreased rapidly to a nearly stable level. Correlations available from literature were not able to describe this phenomenon. Concepts were formulated which can describe the observations from this study. Research under dynamic conditions and careful monitoring of the biofilm surface area and biofilm morphology are necessary to elucidate and discriminate biofilm detachment mechanisms. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260450604
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    The protective effect of specific medium additives with respect to bubble rupture (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 473-480 
    Details
    ISSN: 0006-3592
    Keywords: cell adhesion ; protective additives ; interfacial tensions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A significant degree of cell damage is observed during suspension cell culture with air sparging. Protective agents can be added to the culture medium to protect the cells from damage. It has been observed that cells tend to adhere to air-medium interfaces and cell damage is mainly due to this cell-bubble interaction; protective additives have been found to prevent this cell adhesion to the bubble surfaces. In this article, it is demonstrated that the interfacial tension between the air and medium is related to the effectiveness of the protective additives to prevent adhesion of cells to this interface. Five different types of additives (Pluronic F-68, Methocels, dextran, Polyvinyl alcohol, and polyethylene glycols) were studied in an effort to determine their protective characteristics. Liquid-vapor interfacial tensions of the culture medium, with and without the additives, were measured by two different techniques (maximum bubble pressure method and Wilhelmy plate method). In addition, visualization techniques showed that in the presence of certain protective additives cells do not adhere to the bubble surface. Results obtained from these experiments indicate that the additives which rapidly lower the liquid-vapor interfacial tension of the culture medium also prevent adhesion of cells to the bubble surface. Experiments have also been conducted to determine the number of cells killed due to bubble rupture, and it was observed that this number is related to the amount of cells adhering to the bubble surface. © 1995 John Wiley & Sons, Inc.This article is a US Government Work and, as such, is in the public domain in the United States of America.
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    URL: http://dx.doi.org/10.1002/bit.260450603
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    Death mechanisms of animal cells in conditions of intensive agitation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 463-472 
    Details
    ISSN: 0006-3592
    Keywords: apoptosis ; animal cell death ; hybridoma cells ; agitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The question is addressed as to whether cells which are subject to high-energy dissipation rates in agitated bioreactors show an apoptotic response. Murine hybridoma cells in batch culture were agitated in bench-scale (1-L) bioreactors without gas sparging. At an energy dissipation rate of 1.5 W m-3 there was no apparent damage. At 320 W m-3 cell viability declined, and increasing proportions of the dead cells displayed the morphological features of apoptosis, but necrosis also remained as a significant mechanism of death. When cells were subjected to the intensive energy dissipation rate of 1870 W m-3 in a bioreactor without gas headspace, the cell number dropped by 50% within 2 h and a subpopulation of smaller-sized cells emerged. This excluded trypan blue but showed some apoptotic characteristics such as reduced and condensed DNA content and low F-actin content. The incidence of apoptotic activity was further demonstrated by the appearance of numerous apoptotic bodies. Analysis of the cell cycles of both small and normal size populations indicated that greater proportions of S and G2 cells had become apoptotic and there was evidence of preferential survival of G1 cells. It is suggested that two mechanisms of cell death are apparent in hydrodynamically stressful situations, but their relative expression depends on the energy dissipation rate. © 1995 John Wiley & Sons, Inc.
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    Evaluation and applications of optical cell density probes in mammalian cell bioreactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 495-502 
    Details
    ISSN: 0006-3592
    Keywords: optical cell density probes ; turbidity probes ; on-line monitoring ; in situ probes ; mammalian cell bioreactors/fermentors ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line optical cell density probes were implemented to continuously monitor the cell densities in mammalian cell bioreactor and to achieve advanced bioreactor controls. We tested cell density probes from six manufacturers in high cell density bioreactors. When externally calibrated, Aquasant and Ingold backscattering probes produced the most linear probe responses (PR) versus cell density (CD), followed by the ASR and Cerex laser probes. Monitek and Wedgewood transmission probes had lower resolutions. All probes were tested in two murine hybridoma fermentations. Cell densities varied between 1 × 106 cells/mL to 20 × 106 cells/mL and the bioreactors were operated for 5 to 7 weeks. For our bioreactors, Aquasant, Ingold, ASR, Wedgewood, and Monitek probes gave satisfactory responses. Little fouling was observed with any probe at the end of 2 weeks. Fouling was a possibility after 3 weeks in one bioreactor but its effect can be easily corrected. Cell density control and specific perfusion control of bioreactors based on the Aquasant probe were achieved. Implementation of cell density probe based perfusion control, instead of “step perfusion adjustments” based on manual hemacytometer control, will result in smoother operation, healthier cultures, increased medium delivery efficiency, and reduced operational excursions. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260450606
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    Cometabolic degradation of trichloroethylene in a bubble column bioscrubber (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 461-469 
    Details
    ISSN: 0006-3592
    Keywords: trichloroethylene ; bioscrubber ; bubble column ; cometabolism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bubble column bioreactor was used as bioscrubber to carry out a feasibility study for the cometabolic degradation of trichloroethylene (TCE). Phenol was used as cosubstrate and inducer. The bioreactor was operated like a conventional chemostat with regard to the cosubstrate and low dilution rates were used to minimize the liquid outflow. TCE degradation measurements were carried out using superficial gas velocities between 0.47and 4.07 cm s-1 and TCE gas phase loads between 0.07 and 0.40 mg L-1 Depending on the superficial gas velocity used, degrees of conversion between 30% and 80% were obtained. A simplified reactor model using plug flow for the gas phase, mixed flow for the liquid phase, and pseudo first order reaction kinetics for the conversionof TCE was established. The model is able to give a reasonable approximation of the experimental data. TCE degradation at the used experimental conditions is mainly limited by reaction rate rather than by mass transfer rate. The model can be used to calculate the reactor volume and the biomass concentration for a required conversion. © 1995 John Wiley & Sons Inc.
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    URL: http://dx.doi.org/10.1002/bit.260470407
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    Recombinant cyclin E expression activates proliferation and obviates surface attachment of chinese hamster ovary (CHO) cells in protein-free medium (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 476-482 
    Details
    ISSN: 0006-3592
    Keywords: cyclin E expression ; CHO cells ; insulin ; fibroblast growth factor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Exogenous growth factors normally required in cell culture activate cell proliferation via the molecular controls of cell-cycle progression. Highly differing influences of mitogenic stimulation of Chinese hamster ovary (CHO) cells by insulin and basic fibroblast growth factor(bFGF) have been clearly observed in a defined protein-free medium. CHO K1 cells stimulated only with insulin grow with flattened cell morphology and extensive cell-cell contact, whereas stimulation with only bFGF or bFGF plus insulin results in loss of cell-cell contact and a transformed and rounded-up morphology. Compared with insulin-stimulated cells, bFGF-stimulated cells exhibit a relatively long G1, and short S phase, and contain higher levels of cyclin E. Observation of elevated levels of cyclin E in wild-type CHO K1 cells mitogenically stimulated by basic fibroblast growth factor motivated transfection of these cells by a cyclin E expression vector. These transfectants grew rapidly in protein-free basal medium and had similar cyclin b levels, distributions of nuclear cell-cycle times, and cell morphologies as bFGF-stimutated CHO K1 culture. Metabolic engineering of cell-cycle regulation thus bypasses exogenous growth factor requirements, addressing a priority objective in economical, reproducible, and safe biopharmaceutical manufacturing. © 1995 John Wiley & Sons Inc.
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    URL: http://dx.doi.org/10.1002/bit.260470409
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470501
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    Sustained and constitutive high levels of protein production in continuous cultures of bacillus subtilis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 520-524 
    Details
    ISSN: 0006-3592
    Keywords: bacillus subtilis ; plasmid ; continuous culture ; CAT ; recombinant cultures ; acid formation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The feasibility of continuous production of proteins in chemostat cultures of Bacillus subtilis was investigated. An expression system consisting of the bacterium B. subtilis BR151 carrying plasmid p602/19 was used. The plasmid contains the cat (chioramphenicol acetyltrans-ferase) gene downstream of a strong vegetative T5 promoter. It was found that, at a dilution rate of 0.2 h-1 production of relatively high levels of CAT protein (about 4% ofcellular protein) can be sustained. But, experiments at a higher dilution rate of 0.4 h-1 were unproductive because of high acidformation and washout. Combination of low cell yield, which results from excessive acid formation, and low dilution rate led to a low volumetric CAT productivity. Our recent work with the nonrecombinant cells, has demonstrated that uptake of small amounts of citrate significantly reduces or entirelyeliminates the acid formation. This superior performance in the presence ofcitrate was hypothesized, based on strong experimental evidence, to be the result of a reduction in glycolysis flux through a sequence of events leading to a reduction in pyruvate kinase and phosphof- ructokinase activities, the regulatory enzymes of glycol-ysis. In this study, it is demonstrated that cofeeding of glucose and citrate substantially reduces theorganic acid formation and significantly increases the recombinant culture productivity. The combination of high specific CAT activity and cell density resulted in a total of six- to tenfold higher culture productivitywhen citrate and glucose were cometabolized than when glucose was the only carbon source. © 1995 John Wiley & Sons Inc.
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    URL: http://dx.doi.org/10.1002/bit.260470503
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    Membrane anchored protein production from spheroid, porous, and solid microcarrier chinese hamster ovary cell cultures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 550-556 
    Details
    ISSN: 0006-3592
    Keywords: spheroids ; porous and solid microcarriers ; CHO ; controlled release ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of the microcarrier type on the performance of a controlled release process used to produce a recombinant glycosyl-phosphatidylinositol anchored protein was investigated. Chinese hamster ovary (CHO) cells expressing the human melanoma tumor antigen (p97) were cultured in 10% serum on Cultispher-GH porous microcarriers and then, for protein production, maintained in 2% serum. Cells were harvested every 48 h and p97 was recovered at 90 μg/mL and 40% purity. Harvested p97 concentrations were increased by harvestingfrom spheroid (241 μg/mL) and smaller porous microcarrier, Cultispher-G (167 μg/mL) cultures. The low total cell specific p97 production of cells cultured on Cultispher-GH was due to necrosis of cells within the beads, decreased p97 expression of the immobilized cells, dilution by the liquid (up to 40% volume) associated with settled beads, and incomplete recovery of p97 from within the beads. Cells cultured on solid microcarriers, Cytodex-1, had the highest cell viability and cell specific p97 production, It is recommended that a two-stage cyclic harvesting process of cells cultured on small Cultispher-G or on Cytodex-1 beads would minimize protein loss and maximize cell specific protein recovery. © 1995 John Wiley & Sons Inc.
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    URL: http://dx.doi.org/10.1002/bit.260470507
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    Modeling of continuous Ph-stat stirred tank reactor with Lactococcus lactis ssp. lactis bv. diacetylactis immobilized in calcium alginate gel beads (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 567-574 
    Details
    ISSN: 0006-3592
    Keywords: immobilized Lactococcus diacetylactis ; alginate beads ; diffusionl/reactionl/growth model ; lactosecitrate cometabolism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic diffusion-reaction-growth model is proposed for the study of lactic fermentation, the bioconversion of citric acid, and cell release in an immobilized cell reactor [pH-stat continuous stirred tank-reactor (CSTR)]. The model correctly simulates the onset of fermentation and colonization of the gel, followed by the steady state. External diffusion is nonlimiting and internal diffusion is limited by high cell densities at the periphery of the gel beads. Lactose-citrate cometabolism in the gel is related to the distribution of active included biomass within the gel and to gradients of substrates (lactose, citrate) and products (lactate, pH) in the beads. The utilization of lactose is limited by reaction, whereas that of citrate is limited by diffusion. Cell release from gel to the liquid medium occurs in the external spherical cap of the beads. In this peripheral zone viability is maintained at around 90%. © 1995 John Wiley & Sons Inc.
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