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  • Biochemistry and Biotechnology  (1,273)
  • 2005-2009
  • 1990-1994  (1,273)
  • 1994  (670)
  • 1990  (603)
  • 1982
  • 1981
  • 1980
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  • 1
    Electronic Resource
    Electronic Resource
    Fast inferential adaptive optimization of a continuous yeast culture based on carbon dioxide evolution rate (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 8-14 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fast inferential, multivariable adaptive optimization algorithm based on a fast responding off-gas data, the carbon dioxide evolution rate (CER), has been developed and applied to a continuous baker's yeast culture to maximize the cellular productivity in simulation and experimental studies. In the simulation study the process was optimized based on CER measurements using readily available steady-state data on the ratio between the cellular productivity and the CER. It was shown that the algorithm is two to three times faster than the algorithm based on cell mass concentration measurements. In the experimental study the CER was maximized without any information on the relationship between the cellular productivity and the CER. It took about 40 h for the process to converge, while about 80 h was required when the optimization was based on cell mass measurements. The attained steady state was found to be different but fairly close to that obtained with cell measurements. Briefly discussed is a switching to the cell-mass-based algorithm at the final stage of the optimization to overcome a potential inaccuracy.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350103
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen transfer rates in a mammalian cell culture bioreactor equipped with a cell-lift impeller (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 43-49 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Measurements of kLa were carried out in 1. 5- and 5-L New Brunswick Scientific CelliGen® bioreactors. The measured kLa in water were identical for both vessel sizes operated in similar condition. The mass transfer rate increased with temperature, mixing speed, and aeration rate, with this last parameter being the most significant. Surface aeration alone gave kLa values of 0. 4 to 1. 6 h-1. A 25% decrease in kLa was observed above an aeration rate of 1. 6 vvm. This was caused by the particular foam breaker of the CelliGen bioreactor. Measurements of kLa using a mammalian cell culture medium supplemented with 5% fetal calf serum (FCS) have confirmed the negative effect of the foam breaker on kLa The measured value in this medium was 1. 2 h-1 for all aeration rates, more than 60% of which was attributed to surface aeration.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350107
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  • 3
    Electronic Resource
    Electronic Resource
    An active insoluble aggregate of E. coli β-galactosidase (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 94-98 
    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: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350113
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  • 4
    Electronic Resource
    Electronic Resource
    In situ glucose monitoring in fermentation broth by “sandwiched” glucose-oxidase electrode (SGE) (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 103-107 
    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: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350115
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  • 5
    Electronic Resource
    Electronic Resource
    In situ methane enrichment in anaerobic digestion (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 73-86 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A major cost consideration in the use of anaerobic digestion to convert biomass and waste to utility-grade gas is the expense of separating CO2 from the product gas. Anaerobic digestion has a number of inherent properties that can be exploited to increase the methane content of the gas directly produced by the digester, the most important of which is the high solubility of CO2(40-60 times that of methane) in water under digestion conditions. The methane enrichment concept examined in this study involved the recirculation of a liquid stream from the digester through a CO2 desorption process and the return of the liquid stream back to the digester for absorption of additional CO2 produced by the conversion of organic materials. A steady-state equilibrium model predicted that a digester gas methane content exceeding 94% could be achieved with this scheme using modest recirculation rates provided a desorption process could be designed to achieve a 60+% CO2 removal efficiency in the degassing of the liquid recycle stream. Using fixed-film laboratory digesters operated on synthetic feedstocks, the technique of methane enrichment was tested under pressurized and unpressurized conditions. A 93 + 2% methane gas stream was produced from a volatile-acid-fed bench-scale digester simulating the methanogenic stage of two-phase digestion under conditions of (1) a pH swing achieved without caustic addition that allowed digestion at pH 7. 5 and air stripping at pH 6. 5-7. 0, (2) digester pressurization to 30 psig, and (3) a recycle rate of 0. 33 L/L reactor/day. Significant but lower levels of methane enrichment were achieved with the single-stage digester at the low experimental recycle rate. However, the narrow range among all experiments of CO2 desorption efficiencies achieved in air stripping the recycle stream (35-60% CO2 removal) suggests that comparable methane enrichment-may be achieved with unpressurized single-stage digestion using greater recycle rates. A materials balance analysis of data from an unpressurized, single-stage digester employing no chemical addition and using laboratory degassing efficiencies indicated that 94% methane could be produced at recycle rates of less than 1. 4 L/L reactor/day with a methane loss of less than 2%.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350111
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  • 6
    Electronic Resource
    Electronic Resource
    Isolation of urokinase by affinity ultrafiltration (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 87-93 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A water-soluble, ligand-bound polymer has been synthesized for the purpose of isolation of urokinase, an important plasminogen activator. The affinity polymer was formed by copolymerizing N-acryloyl-m-aminobenza-midine and acrylamide in the absence of oxygen. An affinity ultrafiltration process was then developed for isolating urokinase from an artificial solution containing peroxidase and urokinase and from a crude urine source. The process yields were determined to be 86% and 49%, respectively. The recovered urokinase exhibited a specfic activity close to that of the highest commercial grade. This article also presents a new technique for assaying urokinase by coupling plasminogen with L-benzoyl arginine-p-nitroanilide (L-BAPNA), an inexpensive chromogenic substrate.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350112
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  • 7
    Electronic Resource
    Electronic Resource
    Reasons for the apparent difference in the effects of produced and added ethanol on culture viability during rapid fermentation by Saccharomyces cerevisiae (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 109-122 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: By feeding ethanol at various high rates to low cell density cultures of Saccharomyces cerevisiae it was shown that the sharp fall in viability when ethanol is produced during rapid fermentations is in part a direct consequence of the high rate of change of extracellular ethanol concentration. Nevertheless, the fall in viability in high cell density rapid fermentations which produced 98 g L-1 ethanol in 3 h considerably exceeded that of control low cell density cultures to which ethanol was added at the same rate. This difference was shown to be not due to intracellular ethanol accumulation or to differences in glucose concentration between the cultures. The concentrations of a range of potentially toxic fatty acids, higher alcohols, and esters were measured during rapid fermentations, but when added at these concentrations to control cultures in the presence of ethanol they had no significant toxic effect. However, when rapid fermentations were conducted in rich medium containing 80 g L-1 yeast extract, the apparent difference in toxicity of produced and added ethanol virtually disappeared. Magnesium was shown to be the component of yeast extract primarily responsible for this effect. The high rate of fall of viability when ethanol is rapidly produced is suggested to be partly due to the inability of the cells to adapt quickly enough to the rising ethanol concentration and partly to an increased demand for magnesium at higher ethanol concentrations which cannot be met in Mg-unsupplemented high cell density fermentations.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350202
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  • 8
    Electronic Resource
    Electronic Resource
    Asymmetric reduction of ketones with resting cells of Sulfolobus solfataricus (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 559-564 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The method of resting cells has been of interest in the development of biocatalysts applied to organic reactions.This article deals with the use of resting cells of a thermophilic archaebacterium Sulfolobus solfataricus, in the asymmetric reduction of acyclic, cyclic, and aromatic ketones. The system allows the continuous regeneration of endogenous coenzyme with the coupled substrate approach. The results indicate that the direction of hydride attack was equatorial on the re face of the carbonyl group of substrates producing (S)-alcohols with a good optical yield. A convenient system for the reuse of resting cells has been set out to synthesize (S)-alcohols on a preparative scale.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350603
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  • 9
    Electronic Resource
    Electronic Resource
    Oxygen transfer enhancement in aqueous/perfluorocarbon fermentation systems: I. experimental observations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 578-585 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new fiber-optic dissolved oxygen sensing technique was applied to the study of two-phase aqueous/perfluorocarbon (pfc) dispersions. These dispersions were examined for their oxygen transfer enhancement capability in the absence and presence of an oxygen-consuming reaction. For the pfc-in-water dispersions, oxygen uptake rate (OUR) enhancements were equal both with and without oxygen-consuming cells present in the aqueous phase. In contrast, for water-in-pfc dispersions, OUR enhancements inthe presence of reaction were limited by oxygen diffusion across the aqueous phase droplets. Nevertheless, enhancement factors of 5-10 on an aqueous phase volume basis were obtained in a 75% pfc dispersion.These oxygen transfer enhancements were directly translatable into enhancements in overall fermenter productivity for actual microbial cultivation systems.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350605
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  • 10
    Electronic Resource
    Electronic Resource
    Stability of two novel serine proteinases in commercial laundry detergent formulations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 650-652 
    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: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350611
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  • 11
    Electronic Resource
    Electronic Resource
    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990) 
    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.260350701
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  • 12
    Electronic Resource
    Electronic Resource
    Kinetics of growth and α-amylase production of immobilized Bacillus subtilis in an airlift bioreactor (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 99-102 
    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: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350114
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  • 13
    Electronic Resource
    Electronic Resource
    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990) 
    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.260350201
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  • 14
    Electronic Resource
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    A model for energy-sufficient culture growth (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 138-145 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pirt's maintenance model has been widely accepted for the effects of growth rate and maintenance on growth yield. However, the interpretation of parameters in Pirt's model as biological constants is difficult for energy-sufficient culture growth. In this study, a mechanistic model for the growth energetics of energy-sufficient chemostat cultures is proposed and verified with literature data. In the model, the overutilization of the energy substrate in energy-sufficient culture growth is attributed to the defective regulation of the energy substrate metabolism and energy uncoupling. The model also uses an “energy surplus” concept to collectively represent the effects of energy excessiveness. The proposed model provides a better quantitative understanding of the maximum growth yield and maintenance of energy-sufficient cultures. It also explains the glucose concentration effect reported in the literature.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350205
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  • 15
    Electronic Resource
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    Adsorption equilibrium in immunoaffnity chromatography with antibodies to synthetic peptides (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 146-151 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of charged residues in peptide antigens on the binding characteristics of polyclonal antipeptide antibodies were studied using immunoadsorbents prepared by coupling the antibodies to CNBr-activated Sepharose 4B. Among the antipeptide antibodies, an antibody to the peptide without charged residues showed the most stable interaction with the peptide to the changes in pH. Conversely, the binding affinity of antibodies to the pep-tides with histidine residues having a unique pKa value of 6.0 decreased steeply with pH at around 6.0. The binding affinity of an antibody to the peptide with many charged residues decreased steeply with an increase in the ionic strength (adjusted by NaCl). Since circular dichroism (CD) spectrum measurements indicate that these peptides show disordered structures in the pH range of adsorption measurement, the dependence of peptide-antibody interaction on environmental conditions is attributed to the characteristics of side chains of the peptides. These results indicate that the dependence of the binding affinity of antipeptide antibodies on pH and the ionic strength is dominantly affected by the number and the pKa values of charged residues in the peptides.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260350206
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  • 16
    Electronic Resource
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    Ballistic disintegration of microorganisms in laboratory disintegrator of new type ML-1 (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 207-210 
    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 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350212
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  • 17
    Electronic Resource
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    Oscillatory behavior of Saccharomyces cerevisiae in continuous culture: II. Analysis of cell synchronization and metabolism (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 28-38 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sustained oscillations of biomass, ethanol, and ammonium concentrations, specific growth rate, and specific uptake rates of ethanol, ammonium, and oxygen were found in continuous cultures of Saccharomyces cerevisiae under controlled dissolved oxygen (DO), pH, and temperature conditions. The period of oscillations was approximately 2.5-3 h at a pH of 5.5 and 2-2.5 h at a pH of 6.5. Oscillations were observed only under conditions of low carbon (glucose below the minimum detectable level), nitrogen nutrient (ammonium concentration varied between 0.00001 and 0.0015M), and ethanol concentration (0.002-0.085 g/L) in the bioreactor.The oscillatory behavior at pH 5.5 was also characterized by partially synchronized cell growth and reproduction. Not only did the total percentage of budding cells oscillate with the same period as observed for the global biomass and nutrient concentrations, but the peaks in the individual subpopulations of initial budding, middle budding, and late budding cells appeared sequentially during the oscillation period. This provides strong evidence of the hypothesis that variations in metabolism during different periods in the cell cycle of a partially synchronized cell population are responsible for the observed oscillatory bioreactor behavior.The specific nutrient uptake rates for ammonium and oxygen as well as the net specific ethanol uptake rate oscillated with the same period as the biomass oscillations. These results show a dramatic increase in the ammonium and oxygen consumption rates prior to the initial budding of the synchronized subpopulation and a decrease in these rates during the late budding phase. At a pH of 5.5, the late budding phase is characterized by high specific ethanol productivity; however, the ethanol productivity lags the late budding phase at a pH pf 6.5. The observed time-varying metabolism in the oscillatory operating regime appears to be the result of the metabolic changes which occur during the cell cycle. Models which can predict the oscillatory biomass concentration and nutrient levels in this regime must be capable of predicting the concentrations and metabolic rates of the subpopulations as well.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260360105
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  • 18
    Electronic Resource
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    Formation of C—C bonds by mandelonitrile lyase in organic solvents (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 39-46 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mandelonitrile lyase (EC 4.1.2.10) catalyzes the formation of D-mandelonitrile from HCN and benzaldehyde. Mandelonitrile lyase was immobilized by adsorption to support materials, for example, Celite. The enzyme preparations were used in diisopropyl ether for production of D-mandelonitrile. In order to obtain optically pure D-mandelonitrile it was necessary to use reaction conditions which favor the enzymatic reaction and suppress the competing spontaneous reaction, which yields a racemic mixture of D, L-mandelonitrile. The effects of substrate concentrations, water content, and support materials on both the spontaneous and enzymatic reactions were studied. The enzymatic reaction was carried out under conditions where the importance of the spontaneous reaction was negligible and high enantiomeric purity of D-mandelonitrile was achieved (at least 98% enantiomeric excess). The operational stability of the enzyme preparations was studied in batch as well as in continuous systems. It was vital to control the water content in the system to maintain an active preparation. In a packed bed reactor the enzyme preparations were shown to be active and stable. The reactors were run for 50 h with only a small decrease in product yield.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260360106
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  • 19
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    Production of L-phenylacetyl carbinol by immobilized yeast cells: II. Semicontinuous fermentation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 55-63 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cyclic, semicontinuous production of L-phenylacetyl carbinol (L-PAC) from a benzaldehyde substrate by Saccharomyces cerevisiae ATCC 834 immobilized in calcium alginate beads was substantially enhanced to about 4.5 g/L in a second cycle by reactivation in fresh medium for 24 h, following an earlier 24-h period of production from substrate. Intermittent feeding of benzaldehyde was employed (four doses in 3 h). In subsequent similar cycles, however, the production returned to that produced in the first cycle, viz. L-PAC concentration of 2-3 g/L in the medium. Production of L-PAC was also increased by adaptation of the cells over 200 h of exposure to the benzaldehyde substrate (compared to wild-type cells) and by continuous (as compared to intermittent) feeding of the substrate. A liter as great as 10 g/L was obtained with wild-type cells by continuous feeding of benzaldehyde over 6 h. Immobilization not only protected the cells from toxic effects of substrate but also permitted them to be used during 7 cycles of semicontinuous operation over more than 200 h.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260360108
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  • 20
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    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990) 
    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.260360201
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  • 21
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    A bioenergetic model of a mixed production fermentation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 142-148 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bioenergetic model has been developed for the fermentation of glucose by Bacillus polymyxa. This model uses energy balances to determine which pathways are utilized by the substrate. The model can predict substrate consumption, biomass formation, and the product distribution for this fermentation. The products are carbon dioxide, water, 2,3-butanediol, and ethanol, where ethanol represents lumped anaerobic products.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260360206
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  • 22
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    Effect of regulatory mechanism on hyperbolic reaction network properties (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 166-178 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The notion that the regulated and flux-controlling enzyme in a metabolic network need not correspond suggests that the purpose of regulation may not be flux homeostasis under all physiological circumstances. Additionally, the fact that diversity in the function of intact metabolic networks exists suggests that in addition to time constant separation, other kinetic structure/regulatory mechanism patterns exist. In order to compliment and expand prior work on identifying kinetic structure-property relationships in networks, the present work explores in a general way how the control, dynamic, and energetic properties of metabolic networks depend on operating point, kinetic structure, and regulatory mechanism. The basic feature of trade-offs between properties is illustrated and used as a basis for indicating how particular subsets of structure, regulatory mechanism, and operating point emphasize certain properties that can be associated with a physiological function. Examples of scavenging trace metabolites and amphibolite coordination are proposed. Microstructure logic in terms of turnover number distributions as well as a potential mixed polynomial network analysis approach are also discussed.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260360209
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  • 23
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    Kinetic analysis of the growth of Chlorella vulgaris (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 198-206 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The energy of the total transmitted light was subtracted from that of the incident light in a culture vessel and the difference was divided by the weight of cells. The value thus obtained was defined as the amount, Ex, of light energy absorbed per unit cell weight per unit time.Batch and continuous cultures of Chlorella vulgaris were carried out at 30°C in the pH range of 6.4-6.7 while restricting illumination. Next the specific growth rate, μ, in the batch culture and the fixed dilution rate, D, in the continuous culture were plotted against Ex. The results showed that the relation between D and Ex can be expressed in a Michaelis-Menten equation, where the maximal specific growth rate is 0.24 h -1 and the saturation constant is 6.58 kcal/g · h.Cell concentration calculated by substituting the apparent concentration, Xe, of incubated cells and the apparent maintenance constant, Me, for this equation agreed with that observed in almost all growth phases. Furthermore, from the change of chlorophyll productivity and the relationship between D and Ex expressed in this equation, it is assumed that Ex involves the light energy directly utilized in photosynthesis in the cells and that which is converted into, e.g., heat. This equation also indicated that a maximum in the growth yield existed. Then the growth yield of 0.029 g/kcal obtained at the incident light of 1.46 or 2.63 cal/cm2 · h was maximum (maximal conversion efficiency of light energy, 15.6%).These results indicate that this method of deriving the equation for the growth rate from this study is a useful procedure for obtaining bioengineering findings.
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    Analysis of pBR322 replication kinetics and its dependency on growth rate (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 233-242 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Accurate estimates of plasmid copy number in a cell are a prerequisite for predicting plasmid stability and protein production. A refined version of a structured model for the pBR322 plasmid replication mechanism is described. The model is capable of accurately predicting pBR322 plasmid copy number in Escherichia coli B/r for a wide range of growth rates. The refinements include better estimates of promoter strength, the degradation rate of RNA species, binding constant of RNAI-RNAII reaction, and dependency of promoter strength on growth rate. The predictions of the model are verified by recent experimental observations but differ from some previous reports. This model can also be used to predict the binding constant of the RNAI-RNAII reaction of ColE1 type plasmids. At 37°C, the binding constant is estimated to be 77 ± 11 × 10-13 mL/molecule-h for pBR322.
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    Solvent selection for biocatalysis in mainly organic systems: Predictions of effects on equilibrium position (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 691-701 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Predictions may be made for the influence of solvent choice on the equilibrium position of biocatalyzed reactions, based on data for the liquid-liquid distribution of the reactants. The most reliable predictions are probably for dilute systems, based on partition coefficients or correlations derived from them. The effective equilibrium constant for esterification reactions is predicted to alter by more than four orders of magnitude on changing between different water-immiscible solvents. The equilibrium constant correlates well with the solubility of water in the solvent, and is most favorable for synthesis in the least polar solvents (aliphatic hydrocarbons). Similar effects seem to apply for other reactions, including oxidation of alcohols and hydrolysis of chlorides. Predictions can be made for nondilute systems using the UNIFAC system of group contributions, but the reliability of these is more questionable.
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    Optimum ph and temperature conditions for xylose fermentation by Pichia stipitis (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 727-731 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pichia stipitis NRRL Y-7124 is a xylose-fermenting yeast able to accumulate ca. 57 g/L ethanol. Because optimum process conditions are important, data were collected to determine the effects of temperature and pH on growth and fermentation rates and product accumulations. Temperatures (26-35°C) providing optimum biomass and ethanol productivities did not necessarily provide maximum ethanol accumulation. Xylitol and residual xylose concentrations increased with temperature. Maximum ethanol selectivity was achieved at 25-26°C with minimal sacrifice to production rates. The temperature optimum for xylose could not be generalized to glucose fermentations, in which ethanol productivity and accumulation were optimum at 34°C. The optimum pH range for growth and fermentation on xylose was 4-7 at 25°C.
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    Enzyme production by genetically engineered Streptomyces strains: Influence of culture conditions (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 719-726 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Production of various extracellular enzymes (the β-lactamases from Streptomyces albus G, Streptomyces cacaoi, Actinomadura R39, and the DD-carboxypeptidase from Streptomyces R61) by genetically engineered Streptomyces lividans TK24 in Lennox broth medium reached a maximum after 36 to 48 h. Subsequently, the enzyme activity drastically decreased probably due to an increased pH value and the production of an inactivator by Streptomyces lividans. Protease activity did not seem to play a major role. The increased pH and inactivator synthesis are related to amino acid catabolism and generally result in cellularlysis. The use of a medium where the catabolism of amino acids was made less likely by the presence of glucose and NH4Cl and by buffering at pH 7.4 considerably inproved the yield. Furthermore, the water activity of the medium seemed to be an important parameter for the production of extracellular proteins by genetically engineered Streptomyces. Better production was observed when the water activity was decreased to 0.96-0.98 by addition of sucrose.Under those conditions, the concentration of extracellular enzyme reached about 0.3 g (1 g in the best case)/L of culture supernantant.
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    Characterization of an immobilized cell, trickle bed reactor during long term butanol (ABE) fermentation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 207-217 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Acetone-butanol-ethanol (ABE) fermentation was performed continuously in an immobilized cell, trickle bed reactor for 54 days without, degeneration by maintaining the pH above 4.3. Column clogging was minimized by structured packing of immobilization matrix. The reactor contained two serial glass columns packed with Clostridium acetobutylicum adsorbed on 12- and 20-in.-long polyester sponge strips at total flow rates between 38 and 98.7 mL/h. Cells were initially grown at 20 g/L glucose resulting in low butanol (1.15 g/L) production encouraging cell growth. After the initial cell growth phase a higher glucose concentration (38.7 g/L) improved solvent yield from 13.2 to 24.1 wt%, and butanol production rate was the best. Further improvement in solvent yield and butanol production rate was not observed with 60 g/L of glucose. However, when the fresh nutrient supply was limited to only the first column, solvent yield increased to 27.3 wt% and butanol selectivity was improved to 0.592 as compared to 0.541 when fresh feed was fed to both columns. The highest butanol concentration of 5.2 g/L occurred at 55% conversion of the feed with 60 g/L glucose. Liquid product yield of immobilized cells approached the theoretical value reported in the literature. Glucose and product concentration profiles along the column showed that the columns can be divided into production and inhibition regions. The length of each zone was dependent upon the feed glucose concentration and feed pattern. Unlike batch fermentation, there was no clear distinction between acid and solvent production regions. The pH dropped, from 6.18-6.43 to 4.50-4.90 in the first inch of the reactor. The pH dropped further to 4.36-4.65 by the exit of the column. The results indicate that the strategy for long term stable operation with high solvent yield requires a structured packing of biologically stable porous matrix such as polyester sponge, a pH maintenance above 4.3, glucose concentrations up to 60 g/L and nutrient supply only to the inlet of the reactor.
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    The pH-auxostat as a tool for studying microbial dynamics in continuous fermentation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 224-232 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: If a microorganism has a growth coupled production or consumption of acid or alkali, it is possible to use the pH-auxostat as a means of control in continuous fermentation. In using the pH-auxostat, it is possible to separate the inlet substrate flow in two different streams. These will both be pH controlled, with one main flow, consisting of nutrients and a second minor but concentrated flow, of acid or alkali. Hereby, it is possible to vary the difference in pH between the fermentor and the inlet medium. This pH difference is proportional to the steady-state cell mass concentration.1,2 It is shown that by separating the inlet flow in two different streams and cultivating without any substrate limitation, the maximum growth rate may be obtained while the cell mass concentration will be controlled. This will also give the possibility to reach high cell mass concentrations at μmax without the risk of wash-out. A modified expression, based on hydrogen, of the steady-state bio-mass concentration, X, is developed as \documentclass{article}\pagestyle{empty}\begin{document}$$ X = Y_{X/H} \cdot [F_{{\rm Hin}} /(F_{{\rm Hin}} + F_{{\rm Min}} )] \cdot (C_{{\rm Hin}} - C_{{\rm HFERM}} ) $$\end{document} where YX/H is the yield coefficient of cell mass per acid produced. The indexes Hin and Min refer to the inflows of alkali and medium, respectively; CHin is the inlet concentration of hydrogen ions. The boundary condition for the cell mass shows that Sin 〉 X/YX/S, where Sin is the medium substrate concentration and YX/S is the yield of biomass per consumed substrate. It is shown that when the cell mass concentration exceeds this value, the flow stops. The applicability of the pH-auxostat method is then verified from different experiments. It is hereby used to detect a deviation from the maximal growth rate showing effects on the microbial physiology. With Escherichia coli used as the model organism, the effect on the growth rate of temperature and high concentration of ammonia were investigated.
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    Production of essential L-branched-chain amino acids in bioreactors containing artificial cells immobilized multienzyme systems and dextran-NAD+ (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 263-269 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We prepared artificial cells each containing leucine dehydrogenase (EC 1.4.1.9), urease (EC 3.5.1.5), soluble dextran-NAD+, and one of the following coenzyme regenerating dehydrogenases: glucose dehydrogenase (EC 1.1.1.47); yeast alcohol dehydrogenase (EC 1.1.1.1); malate dehydrogenase (EC 1.1.1.37); or lactate dehydrogenase (EC 1.1.1.27). Artificial cells were packed in small columns. L-Leucine, L-valine, and L-isoleucine were continuously produced with simultaneous dextran-NADH regeneration. The maximum production ratios depended on the coenzyme regenerating systems used: 83-93% for D-glucose and glucose dehydrogenase system; 90% for ethanol and yeast alcohol dehydrogenase system; 45-55% for L-malate and malate dehydrogenase system; and 64-78% for L-lactate and lactate dehydrogenase system. Kinetic experiments were also carried out. The apparent Km values are as follows: 0.33 mM for α-ketoisocaproate (KIC); 0.51 mM for α-ketoisovalerate (KIV); 0.58 mM for DL-α-keto-β-methyl-n-valerate (KMV); 3.52 mM for urea; 27.82 mM for D-glucose; 3.89 mM for ethanol; 3.02 mM for L-malate; and 16.67 mM for L-lactate. Kinetic analysis showed that KIC, KIV, and KMV were all competitive inhibitors in the reactions catalyzed by leucine dehydrogenase. Their inhibitor constants were the corresponding Km values.
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    Group contributions for estimating standard gibbs energies of formation of biochemical compounds in aqueous solution (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1070-1082 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method is presented for the estimation of the standard Gibbs energies of formation of biochemical compounds (and hence the Gibbs energies and equilibrium constants of biochemical reactions) from the contributions of groups. The method employs a large set of groups and special corrections. The contributions were estimated via multiple linear regression, using screened and weighted literature data. For most of the data employed, the error is less than 2 kcal/mol. The method provides a useful first approximation to Gibbs energies and equilibrium constants in biochemical systems.
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    Decrease in iron oxidizing activity of Thiobacillus ferrooxidans adsorbed on activated carbon (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1105-1109 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It was observed that about 90% of free-swimming Thiobacillus ferrooxidans in 9 K medium was adsorbed on added activated carbon when the concentration of the cultivated bacteria reached about 4 × 1013 cells m-3. The oxidation of ferrous iron and the leaching of copper ore were carried out in shake flasks and in aerated columns. The rates of oxidation and leaching increased when bacteria adsorbed on activated carbon were used. However, the evaluation of the reaction rates by eliminating the catalytic effect of activated carbon showed that the contribution to the reaction by the adsorbed microorganism was very small.
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    High-level recombinant protein production in bioreactors using the baculovirus-insect cell expression system (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1133-1140 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to develop an efficient process for large-scale production of recombinant protein, various factors were studied which affect the productivity of Sf-9 (Spodoptera frugiperda) insect cells when using the baculovirus expression system. It was shown that upon infection with the Bac-BRV6L recombinant baculovirus, the level per cell of VP6 (a bovine rotavirus nucleocapsid protein) would drop 10-fold when host cell density at the time of infection increased from 2 × 106 to 3 × 106 cells/mL. The decrease was found to be totally reversible by culture medium renewal after infection, even when cells were infected at the stationary phase. Recombinant protein production was 4-6 times higher using TNMFH medium supplemented with 10% fetal bovine serum (FBS) than in IPL/41 serum-free medium. Fine-tuning of infection parameters in a 4-L surface-aerated bioreactor resulted in the production of typically 350 mg/L of VP6 protein, representing more than 25% of total cell proteins.
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    Kinetic studies and unstructured models of lymphocyte metabolism in fed-batch culturePresented in part at the 80th annual meeting of the American Institute of Chemical Engineers, Washington, DC, November 27-December 2, 1988. (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 797-807 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth of two lymphocyte cell lines, a hybridoma cell line and a human cutaneous T cell lymphoma (HuT78), was studied in fed-batch culture, and unstructured models of growth developed. A criteria was established to insure that the growth rate varied by less than a specified tolerance throughout the culture period. Glutamine and serum were growth-limiting nutrients for both cell lines with half-maximal growth rates at 0. 53 mM glutamine and 0. 55%(v/v) serum for the hybridoma cells and 0. 21 mM glutamine and 1. 5% serum for the HuT-78 cells. Over the range of glucose concentrations from 5. 5 mM to 28 mM, the specific growth rate of hybridoma cells was independent of glucose concentration, whereas glucose concentrations above 5. 5 mM inhibited HuT-78 growth. For both cell lines, the growth rate was significantly inhibited by the addition of ammonium, although the hybridoma cell line was more affected by ammonia than was the HuT-78 cell line. Growth of HuT-78 cells increased in the presence of interleukin-2. Unstructured models for the hybridoma cells were similar to other models presented in the literature. Applications of these models to adoptive immunotherapy are discussed.
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    A stochastic model to simulate the growth of anchorage dependent cells on flat surfaces (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 547-562 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A stochastic model is proposed to simulate the growth of anchorage dependent cells on a flat surface. The model, based on representing the cell shapes on the surface as external irregular polygons with the nuclei distributed as a set of Poisson points (producing a modified Voronoi tessellation of 2 space) and incorporating a distribution function to describe cell division of the perimeter cells of the colony, provides data not only on population dynamics but also on the patterns produced by clusters of cells in the colony. These patterns produced by the model are qualitatively similar to observations reported for some cell cultures. The periods of induction, rapid growth, and decreasing growth asymptoting to zero as confluence is reached are predicted by the model. Quantitative comparison with published experimental data for this is good. The specific growth rate computed for the period of rapid growth predicted by the model is dependent on the distribution function describing the cell division time. As the standard deviation of this increases, the specific growth rate decreases as with a consequent increase in time to achieve confluence. The removal of cells from the colony by shear forces or death is considered in the model. As the probability for removal increases, the cell density at confluence and specific growth rate decrease. The clusters of cells, patterns, in the colony are very sensitive to cell removal. By analyzing these patterns in experiments, an estimate of cell removal can be made. The areas covered by cells on a substrate are fractal patterns. The fractal dimension is always greater than 1 and is a function of the removal probability.
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    Lipoprotein lipase immobilization onto polyacrolein microspheres (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 593-600 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A lipoprotein lipase (LPL) was made water insoluble by immobilizing onto the surface of polyacrolein (PAA) microspheres with and without oligoglycines as spacer. The activity of the immobilized LPL was found to remain high toward a small ester substrate, p-nitrophenyl laurate (pNPL). The relative activity of the immobilized LPL without spacer decreased gradually with the decreasing surface concentration of the immobilized LPL on the PAA microsphere. On the contrary, the immobilized LPL with oligoglycine spacers gave an almost constant activity for the substrate hydrolysis within the surface concentration region studied and gave a much higher relative activity than that without any spacer. The Michaelis constant Km and the maximum reaction velocity Vm were estimated for the free and the immobilized LPL. The apparent Km was larger for the immobilized LPL than for the free one, while Vm was smaller for the immobilized LPL. The pH, thermal, and storage stabilities of the immobilized LPL were higher than those of the free one. The initial enzymatic activity of the immobilized LPL maintained almost unchanged without any leakage and inactivation of LPL when the batch enzyme reaction was performed repeatedly, indicating the excellent durability of the immobilized LPL.
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    Effects of cell density and glucose and glutamine levels on the respiration rates of hybridoma cells (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 630-635 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of cell density as well as the concentration levels of glucose and glutamine on the specific respiration rate of a hybridoma cell line were investigated. The experimental oxygen consumption rate was found to be constant over a wide range of dissolved oxygen levels if the suspension medium contained glutamine. In glutamine-free medium, however, the rate of oxygen consumption decreased slowly with time.In a stationary flask batch culture, the specific respiration rate decreased from about 7 to 2.9 μmol/min per 109 cells as the cell density increased exponentially from 1 × 105 to 1.2 × 106/mL. To isolate the effect of cell density, cells were re suspended in fresh culture medium so that nutrient concentrations were the same for all experiments. The specific respiration rate decreased with increasing cell density in the same manner as in the stationary flask culture, falling from 8 to 4 μmol/min per 109 cells as the cell density increased from 105 to 106 cells/mL, then declining to 2 μmol/min per 109 cells when the cell density reached 107 cells/mL.Cells suspended in Hanks balanced sale solution (HBSS) were used to elucidate the effect of glucose and glutamine levels on respiration. The addition of glucose in concentrations of 0.25, 0.50, and 0.75 g/L had no observable effect on the specific oxygen uptake rate; however, a glucose concentration of 1 g/L reduced the uptake rate by 22%. Glutamine in a concentration of 0.30 g/L increased the specific respiration rate in HBSS containing 0 and 1 g/L glucose by approximately 13%.
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    Aerosol release from aerated broths (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 970-973 
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    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.260360913
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    Cell growth and death rates as factors in the long-term performance, modeling, and design of immobilized cell reactors (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 983-992 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The viable fraction of immobilized cells in a bioreactor may be critical in predicting long-term or steady-state reactor performance. The assumption of near 100% viable cells in a bioreactor may not be valid for portions of immobilized cell reactors (ICRs) characterized by conditions resulting in appreciable death rates. A mathematical model of an adsorbed cell type ICR is presented in which a steady-state viable cell fraction is predicted, based on the assumptions of no cell accumulation in the reactor and a random loss of cells from the reactor. Data on cell death rates, cell growth rates, and productivity rates as functions of temperature, substrate, and ethanol concentration for the lactose utilizing yeast K. fragillis were incorporated into this model. The steady-state reactor viable cell fraction as predicted by this model is a strong function of both temperature and ethanol concentration. For example, a stable 20% viable fraction of the immobilized cells is predicted in ICR locations experiencing continuous conditions of either 30 g/L ethanol at 40°C, or 95 g/L ethanol at 25°C. Steady-state ICR “plug flow” concentration profiles and column productivities are predicted at three operating temperatures, 20, 30, and 40°C using two different models for ethanol inhibition of productivity. These profiles suggest that the reactor operating temperature should be low if higher outlet ethanol concentrations are desired. Three reactor design strategies are presented to maximize the viable cell fraction and improve long-term ethanol productivity in ICR's: (1) reducing outlet ethanol concentrations, (2) rotating segments of an ICR between high and low ethanol environments, and (3) simultaneous removal of the ethanol produced from the reactor as it is formed.
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    Physiological, biochemical, and mathematical studies of micro-aerobic continuous ethanol fermentation by Saccharomyces cerevisiae. I: Hysteresis, oscillations, and maximum specific ethanol productivities in chemostat culture (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1006-1019 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth and metabolism of Saccharomyces cerevisiae was studied in steady-state chemostat cultures under conditions of scarce oxygen and excess glucose. The specific ethanol productivity and specific glucose uptake rate were stimulated by 50% within a narrow range of air/nitrogen mixtures to the fermentor. Fermentation was inhibited at slightly higher and lower air/nitrogen ratios, confirming similar results by previous investigators. This stimulation could not be caused by obvious mechanisms, such as the Pasteur or Crabtree effects. Since this maximum in the fermentation rate occurred in a steady-state chemostat and at a constant dilution rate, the ATP yield of the culture necessarily attained a minimum. Thus, changes in the energetic efficiency of growth or the degree of wasting of ATP were surmised. The steady-state biomass concentration at various oxygenation rates exhibited hysteresis phenomena. Ignition and extinction of the biomass concentration occurred as critical oxygen feed rates were passed. The hysteresis was prevented by adding yeast extract to or reducing the antifoam concentration in the medium. These medium alterations had the simultaneous effect of stimulating the fermentation rate, suggesting that ATP has a critical role in dictating the biomass concentration in micro-aerobic culture. Silicone polymer antifoam was found to stimulate glycerol production at the expense of ethanol production, having consequences for the energy generation and the biomass concentration of the culture.
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    Immobilization can improve the stability of hybridoma antibody productivity in serum-free media (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1049-1055 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hybridoma cells (S3H5/γ2bA2) were cultivated in spinner flasks with 1% serum media and serum-free media. Monoclonal antibody productivity was maintained in 1% serum media. However, cells in serum-free media showed a decrease in antibody productivity, and it completely disappeared in IMDM-based low protein medium. This loss of antibody productivity was not observed when the cells were immobilized in alginate beads. In fact, immobilization enhanced the specific MAb productivity.
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    Lipolytic activities of a lipase immobilized on six selected supporting materials (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 132-137 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Six different types of materials including PVC, chitosan, chitin, agarose, Sepharose, and Trisacryl were evaluated for their lipase-coupling efficiencies. Among those tested, chitosan yielded the highest amount of lipase (79 mg/mL packed gel) immobilized but with lowest oil hydrolytic activity (0.03 mg eq/mL gel). The amount of lipase immobilized was affected by the length of the hydrocarbon chain attached to the PVC matrix but not by the pore size of the supports used. On the other hand, the specific activity of the immobilized lipase was affected by the pore size but not by the chain length of the hydrocarbon attached to the support. After immobilization, the optimal reaction pH was shifted from 7.5 to 8.5 and the optimal reaction temperature from 35 to 45-55°C. Lipase immobilized on PVC exhibited higher thermal stability than that on agarose. The half-life of the PVC immobilized lipase operating at 30°C in a packed-bed reactor was estimated to be about 400 h.
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    Enzymatic production of hydrogen peroxide and acetaldehyde in a pressure reactor (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 834-838 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alcohol oxidase, an enzyme which exhibits relatively weak substrate specificity among short chain alcohols, forms the corresponding aldehyde and hydrogen peroxide as coproduct. The ability of alcohol oxidase from Pichia pastoris yeast to convert ethanol to acetaldehyde and hydrogen peroxide was examined in an oxygen pressure reactor under conditions, such that oxygen availability was sufficient to permit rapid catalysis. Hydrogen peroxide levels of ∼1.8/M (6% w/w) were attained in 2-3 h with 2.8 μM enzyme, corresponding to a productivity of ∼30 g peroxide/g enzyme. Optimal conditions (within equipment limitations) were 900 psi oxygen, 2.6M ethanol, at 4 °C. Similar levels of products were reached in the reactor using enzyme immobilized covalently on controlled pore glass and noncovalently on an anion exchange support. Recycle of covalently immobilized enzyme was not possible as a result of enzyme inactivation after a single run. Limited recycle of noncovalently immobilized enzyme was accomplished with substantial decreases in levels of product attainable on each cycle.
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    Micromixing in fermentors: Metabolic changes in Saccharomyces cerevisiae and their relationship to fluid turbulence (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 854-864 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Even when microorganisms are grown in highly agitated fermentors, calculation predicts a mismatch between the microscale of the turbulence (where the smallest eddy is typically 50-300 μm diameter) and the cellular dimensions (1-5 μm). The cell thus spends substantial portions of time in an apparently stagnant eddy, depleted of nutrients. The local fluid microscales were measured in a laboratory fermenter to confirm this. Using S. cerevisiae in continuous culture, it is shown that the local microscales influence cell metabolism dramatically. The issues addressed in this study are thus micromixing and microsegregation of reactants and how they influence cell yield.
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    Diffusional limitations of immobilized Escherichia coli in hollow-fiber reactors: Influence on 31P NMR spectroscopy (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 887-901 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Escherichia coli cells were immobilized and grown in hollow-fiber reactors allowing simultaneous NMR spectroscopy and perfusion with nutrient medium. The extent to which the cells were starved due to inadequate mass transfer was predicted using a mathematical model of reaction and diffusion. Reactors were experimentally characterized using 35S autoradiography to visualize spatial variations in protein synthesis rates and transmission electron microscopy to indicate spatial variations in cell morphology. Mass transfer limitations in reactors operated at 37 °C were shown to be severe, with regions of starved cells occupying up to 80% of the cell-containing region. Phosphorus-31 nuclear magnetic resonance (NMR) spectra of the immobilized, perfused cells revealed abnormally low volume-averaged concentrations of sugar phosphates, NTP, and ratios of NTP/NDP in these reactors. Intracellular pH was also depressed in the cells. In order to overcome mass transfer limitations in the cell layer, the reactor growth temperature was decreased. Sulfur-35 autoradiographs of a reactor operated at 16°C did not indicate the presence of starved cells. The NMR spectra obtained from this reactor showed near-normal intracellular pH, metabolite concentrations, and NTP/NDP ratios. The presence of significant mass transfer limitations in a perfused cell sample during NMR spectroscopy is generally undesirable since the resulting spectra can be ambiguous and difficult to interpret. The strategy adopted in this work, namely estimation of the relative rates of reaction and diffusion in the cell mass and appropriate changes in reactor design and operating parameters, should prove generally applicable for the design of perfused cell samples for NMR spectroscopic experiments.
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    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990) 
    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.260351001
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    Enzyme loading in a solid support with nonuniform pore size distribution (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 976-982 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The concept of pore size distribution is incorporated into the Clark model of enzyme immobilization in the present study. This refined model predicted that in the case of small harmonic pore radius with the same surface area and porosity of the support, more enzyme could be loaded in a support with nonuniform pores than that with uniform pores. In comparing the enzyme loading efficiency of the support with two different pore size distributions, the one with Gaussian distribution had the greater amount of enzyme immobilized than the other one with Rajagopalan's distribution. Furthermore, more enzyme could be loaded in a support with wider Gaussian pore size distribution than that with narrower distribution. The immobilized enzyme profile in the solid support with pore size distribution displayed a stepwise pattern which differed appreciably from the sigmoidal profile predicted for the support with uniform pore size. This stepwise enzyme distribution profile became sigmoidal with decreasing hT or increasing k. The new model could be used for designing protocols for an enzyme immobilization process.
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    New method of immobilization of microbial cells by capture on the surface of insoluble pyridinium-type resin (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1000-1005 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method for the immobilization of microbial cells has been developed. Whole cells of Escherichia coli with aspartase activity were immobilized by capture on the surface of cross-linked poly(N-benzyl-4-vinylpyridinium bromide) containing styrene (BVPS resin), an insoluble pyridinium-type resin. When a suspension of the bacterial cells in buffer solution was passed through a glass column containing beads of BVPS resin, the cells were captured on the resin surface and formed an immobilized cell system. A fixed-bed column reactor containing 300 mg of the bacterial cells immobilized by capture on 10 g of BVPS resin beads was used for the preparation of L-aspartic acid from ammonium fumarate. Continuous operation of tne bioreactor produced L-aspartic acid in a quantitative yield when the influent substrate concentration was 0.1M and the flow rate was 0.41-0.83 bed volumes per hour at pH 7.4-7.7 at 30°C.
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    Effects of spatial heterogeneity on the dynamics of a microbial feeding interaction (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1024-1033 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model for an ideal chemostat in which one microbial population feeds on another and where Monod's model is used for the specific growth rates of both populations predicts a less stable behavior for the system than the one observed experimentally. Various factors have been proposed as being the reason for the increased stability of such systems. In this work, the effect of spatial heterogeneity on the dynamics of the microbial feeding interaction is studied. It is concluded that spatial heterogeneity has a stabilizing effect on the system. This effect combined with other factors could be the reason for the increased stability observed in systems where a microbial feeding interaction occurs.
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    Use of an oxygen microsensor for the determination of intrinsic kinetic parameters of an immobilized oxygen reducing enzyme (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1078-1087 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An oxygen microsensor was used to measure internal oxygen profiles in biocatalyst particles of different diameter and activity. The particles were made of agarose gel and contained an oxygen reducing enzyme, L-lactate mono-oxygenase. The kinetics of the enzyme could be well described by the Michaelis-Menten equation. From the internal substrate concentration profile the intrinsic kinetic parameters were determined by means of fitting a simulated profile to the measurements, using Marquardt's algorithm. The intrinsic kinetic parameters found following this procedure appeared to be independent of particle radius or enzyme loading used, proving the method to be reliable. These parameters were also compared with the kinetic parameters of the free enzyme which were determined in a biological oxygen monitoring system. The intrinsic kinetic parameters showed a decrease with a factor 2.3 for Vm value and with a factor 2.7 for the Km value compared to the parameters for the free enzyme. From this the conclusion can be drawn that the immobilization as such or the carrier material not only can have an effect on the maximum intrinsic conversion rate (Vm) but also on the affinity of the enzyme (Km) for oxygen.
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    Production of S-adenosyl-L-methionine by Saccharomyces cerevisiae cells carrying a gene for ethionine resistance (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1120-1124 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A gene for ethionine resistance isolated from the yeast Saccharomyces cerevisiae DKD-5D-H conferred on the yeast cells resistance to seleno-L-methionine and capability to produce S-adenosyl-L-methionine in the cells. An enzymatic study of the L-methionine synthetic pathway of L-methionine proto- and auxotrophs and in dried yeast cells with or without the gene suggested that the cloned gene for ethionine resistance is responsible for the activity of S-adenosyl-L-methionine synthase. To produce S-adenosyl-L-methionine by yeast cells transformed with the ethionine resistance gene, some culturing conditions were determined.
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    Increased mass transfer to microorganisms with fluid motion (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1135-1144 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of fluid flow and laminar shear on bacterial uptake was examined under conditions representative of the fluid environment of unattached and attached cells in wastewater treatment bioreactors. Laminar shear rates below 50 s-1 did not increase leucine uptake by suspended cultures of Zoogloea ramigera. However, leucine uptake by cells fixed in a flow field of ∼ 1 mm s-1 was 55-65% greater than uptake by suspended cells. Enhanced microbial uptake with advective motion is consistent with mass transfer rates calculated using Sherwood number correlations. Advective flow increases microbial uptake by increasing collisions between substrate molecules and cells through compression of the concentration boundary layer surrounding a cell. The rate of leucine uptake suggests that binding proteins used to transport leucine into the cell can occupy approximately 1% of the cell surface area.
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    Quantitative assay for low levels of L-threonine in amino acid fermentation broths (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1169-1173 
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    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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    Production of recombinant human growth hormone in Escherichia coli: Expression of different precursors and physiological effects of glucose, acetate, and salts (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1-11 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The constitutive cytoplasmic expression in E. coli of human growth hormone (hGH) with different N-terminal extensions (3 or 4 amino acids) has been studied. These hGH precursors were used for in vitro cleavage to obtain the mature, authentic hormone. Small changes in the amino acid extensions of the hGH precursors led to three-fold differences in specific expression rates. The specific expression rate of the hGH precursors was inversely proportional to the ratios of the specific growth rates of plasmid containing and plasmid free cells (μ+/μ-) and also to the genetic stability. To ensure a satisfactory genetic stability in production fermentors, an hGH precursor with a moderate expression efficiency was chosen.The medium composition and growth conditions were studied, resulting in the choice of a glucose fed batch fermentation process using a complex medium. In this process a yield of 2000 mg/L of met-ala-glu-hGH (MAE-hGH) was obtained. The fermentation process comprised a glucose-limited growth phase followed by a second phase with increased glucose feed and exhaustion of phosphate from the medium. The second phase is characterized by an MAE-hGH production, whereas further biomass formation is blocked. High concentrations of glucose led to reduced specific expression of MAE-hGH - the specific and total yield in batch glucose fermentations is only about 30% of the yield in optimized fed batch fermentations. The physiological background for this was investigated. Chemostat experiments showed that the glucose concentration and the metabolic condition of the cells - i.e. with or without formation of acetate - was not critical per se in order to obtain a high specific yield of MAE-hGH. Therefore it is unlikely that formation of MAE-hGH is catabolite repressed by glucose. Furthermore it was shown that the specific production rate of MAE-hGH was independent of the specific growth rate and it was further demonstrated that the decrease in expression efficiency in glucose batch fermentation was a result of an inhibitory effect of acetic acid. In batch fermentations this inhibitory effect was enhanced by a salt effect caused by increased consumption of acid and base used to control pH. The identity of the acid and the base used are not important in this context.From studies of the expression of other proteins in E. coli. with constitutive as well as inducible promoters we conclude that glucose fed batch processes are often superior to batch processes in the production of heterologous proteins E. coli.
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    Production of L-phenylacetyl carbinol by immobilized yeast cells: I. Batch fermentation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 47-54 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Immobilization of Saccharomyces cerevisiae ATCC 834 within alginate beads enhances microbiological conversion of benzaldehyde to L-phenylacetyl carbinol (L-PAC), a precursor employed for synthesis of L-ephedrine. Yields of 90% L-PAC on benzaldehyde (initially 0.6% in medium) were obtained with immobilized cells, in contrast to about 10% with free cells which tend to form pellets in the presence of benzaldehyde. The predominant favorable action of immobilization appears to be a reduction in the toxic or inhibitory effects of benzaldehyde. With an initial benzaldehyde concentration of about 0.6% in the medium the optimum cell mass concentration was observed to be about 28 g cell mass (immobilized) per liter of medium.
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    Kinetics of CO2 hydration in fermentors: pH and pressure effects (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 92-96 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluctuations in pH and head-space pressure in a fermentor introduce temporary changes in off-gas CO2 concentrations. These changes are quantified using a simple model based on kinetics of CO2 hydration and gas-liquid mass transfer. The model is verified experimentally. An eigenvalue analysis of the model indicates that mass transfer is the parameter which controls the dynamics of CO2 equilibration.
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    Wall-Growth hollow-fiber reactor for tissue culture: II. A theoretical model (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 104-108 
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    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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    A comparison of mathematical model predictions to experimental measurements for growth and recombinant protein production in induced cultures of Escherichia coli (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 124-134 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant cell growth and protein synthesis by a recombinant Escherichia coli under various inducing conditions are compared to the predictions of a mathematical model. The mathematical model used was a combination of two literature models: (1) an empirical kinetic model for recombinant growth and product formation and (2) a genetically structured model of the lac promoter-operator on a multicopy plasmid. The experimental system utilized was recombinant E. coli CSH22 bearing the temperature-sensitive plasmid pVH106/172, which codes for the synthesis of β-galactosidase and the other lac operon genes under the control of a lac promoter. Mathematical model predictions for recombinant β-galactosidase yield and specific growth rate were compared with fermentation measurements of these same quantities for conditions of chemical induction with cyclic AMP and IPTG, copy number amplification (by shifting culture temperature), and combined chemical induction and copy number amplification. The model successfully predicted experimental product yields for most cases of chemical induction even though the product yields varied from 0.34 × 103 to 1500 × 103 units/g cell mass. The kinetic model also correctly predicted a decline in the specific growth rate with increasing levels of plasmid and recombinant protein. The model was less successful at predicting product amplification at high copy numbers. A comparison of model predictions and experimental results was also used to investigate some of the assumptions used in constructing the mathematical models.
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    Continuous hydrolysis of oil by immobilized lipase in a countercurrent reactor (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 617-622 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lipase from Pseudomonas fluorescens biotype I was immobilized by adsorption of anion exchange resin using glutaraldehyde to enhance the adsorption. The activity yield of the immobilized lipase was very low (below 1%) when lipase activity was measured using emulsion substrate. The activity yield was 10-70% when lipase activity was measured using non-emulsion substrate. Countercurrent reactors for hydrolysis of oil using non-emulsion substrate were studied. A fluidized bed reactor was found to be superior to a fixed bed one since in a fixed bed reactor the separation rate of the two layers was slow and the flow rate of the reactor had to be slower than the separation rate. A fluidized bed reactor system equipped with settling compartments and stirring compartments was devised. Continuous lipolysis at 60 °C and continuous separation of oily product and water soluble product were performed. After continuous operation for more than 3 months, 70% of the initial activity of the immobilized lipase was observed at the end of the reaction.
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    Continuous production of maltotetraose using a dual immobilized enzyme system of maltotetraose-forming amylase and pullulanase (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 790-796 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to produce a product with a high content of maltotetraose, dual-enzyme systems composed of immobilized maltotetraose-forming amylase (G4-forming amylase) and pullulanase were studied. The thermostability of individually immobilized enzymes was examined in continuous operation; studies revealed that the enzyme immobilized on “Chitopearl” was much more stable than that immobilized on Diaion HP-50. The effects of operating conditions on the stability of G4 forming amylase immobilized on “Chitopearl” were examined to confirm that the apparent half-life data could be arranged using the immobilized enzyme stability factor, fs. As for the dual immobilized enzyme system, six methods of usage were considered, with five yielding a 7-10% (w/w) higher content of maltotetraose product than the single-enzyme system. The effects of operating conditions on the maltotetraose production reaction were examined to confirm that the maltotetraose content of the products could be analyzed using the specific space velocity,SSV. In dual immobilized enzyme systems, pullulanase immobilized on the same carrier as the G4-forming amylase was found to be more stable than pullulanase immobilized on separate carriers. The effectiveness of using immobilized pullulanase along with the G4-forming amylase was confirmed from constant-conversion operations in which the maltotetraose content in the product was kept at 50% (w/w) in laboratory-scale experimentation.
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    The process utility of thermotolerant methylotrophic bacteria: II. An evaluation of transient responses (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 821-825 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In Part II, the process utility of a thermotolerant methylotrophic bacterium is evaluated with respect to its dynamic response when various substrate or nutrient pulses are imposed on it while growing under steady-state conditions in a chemostat. The pulses investigated were methanol pulses on methanol-, methanol/formaldehyde-, and dual methanol/ammonia-limited cultures and an ammonia pulse on a severely nitrogen (ammonia)-limited culture. The results obtained, although exemplifying the complex biochemistry of such bacteria, clearly demonstrate the bacteriums flexibility and versatility in handling process transients. Its lack of fastidiousness in unsteady state continuous culture make it a most promising candidate for inclusion in process cultures for elevated temperature industrial wastewater treatment.
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    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990) 
    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.260360901
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    A hollow-fiber reactor design for NMR studies of microbial cells (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 879-886 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A hollow-fiber membrane reactor was designed and constructed to allow perfusion of entrapped, dense Escherichia coli cells with nutrient medium during examination of cell metabolism using nuclear magnetic resonance (NMR) spectroscopy. Phosphorus-31 NMR spectra of the perfused cells included peaks for nucleoside di- and triphosphates, sugar phosphates, and pH-sensitive peaks for inorganic phosphate. The observed intensity of the lumenal inorganic phosphate peak was found to depend on flow rate, ruling out the use of this peak as a concentration reference. Absolute intracellular pH values obtained from NMR measurements were found to be accurate to 0.2 pH units due to uncertainties in intracellular ionic concentrations. Relative pH values, however, were found to be sensitive to cell energetic status. The response of E. coli intracellular pH following a shift to carbon starvation medium was monitored with a resolution of 3 min. Use of a hollow-fiber reactor for cell containment and perfusion during NMR spectroscopy enables metabolic experiments of longer duration and of greater variety than is possible using standard, nonperfused sample tubes.
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    The use of a metabolically structured model in the study of growth, nitrification, and denitrification by Thiosphaera pantotropha (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 921-930 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thiosphaera pantotropha is capable of aerobic heterotrophic nitrification and both aerobic and anaerobic denitrification. These phenomena have been studied in acetate-limited aerobic and anaerobic continuous cultures supplied with ammonia and nitrate. The internal reaction rates were defined, based on biochemical knowledge. The observable external conversion rates are related through a linear equation on the basis of the specified internal reaction rates. The linear equation is a Pirt relation extended for microbial systems with multiple electron donors (acetate and ammonia) and electron acceptors (oxygen and nitrate). The coefficients in this equation were estimated from the continuous culture measurements, and are composed of parameters involved in ATP production and consumption by the microorganism. It is shown that with realistic values for these parameters, the metabolically structured model describes the aerobic as well as the anaerobic experiments.
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    Determination of growth and coupled nitrification/denitrification by immobilized Thiosphaera pantotropha using measurement and modeling of oxygen profiles (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 931-939 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An oxygen microsensor in combination with mathematical modeling was used to determine the behavior of immobilized Thiosphaera pantotropha. This organism can convert ammonia completely to nitrogen gas under aerobic conditions (coupled nitrification/denitrification) and denitrifies nitrate at highest rates under anaerobic conditions. Immobilization of T. pantotropha can result in aerobic and anaerobic zones inside the biocatalyst particle which will be advantageous for the conversion of ammonia and nitrate from wastewater. However, information of the effects of immobilization on the physiology of T. pantotropha is necessary for the development of such a system. This article gives the extension of a model developed to describe the behavior of chemostat cultures of T. pantotropha so that it can be used for immobilized cells. The original model was based on metabolic reaction equations. Kinetic and diffusion equations have now been added. Experimental verification was carried out using a stirred tank reactor and a Kluyver flask. After immobilization in agarose, the cells were grown in the particles under continuous culture conditions for 3 days. After 24 h the oxygen penetration depth showed a constant value of 100 μ, indicating that a steady state was reached. Scanning electron micrographs showed that large colonies of cells were present in this 100-μm aerobic layer.From the dynamics of the start-up phase, several parameters were determined from measurements of the oxygen concentration profiles made every few hours. The profiles simulated by the model were fitted to the measured data. The average value for the maximum specific growth rate was 0.52 h-1, and the maximum oxygen conversion rate was 1.0 mol Cmol-1 h-1. The maximum specific acetate uptake rate was 2.0 mol Cmol-1 h-1, and the Monod constant for acetate was 2.9 × 10-2 mol m-3. The maximum specific nitrification rate was 0.58 × 10-1 mol Cmol-1 h-1, and the amount of oxygen necessary for nitrification was 11% of the total oxygen uptake rate. Most of the kinetic parameters determined for the immobilized cells were in good agreement with those for the suspended cells. Only the maximum specific growth rate was significantly higher, and the maximum specific nitrification rate was some what lower than for suspended cells. The experimental results clearly show that an oxygen microsensor, in combination with mathematical modeling, can successfully be used to elucidate the kinetic behavior of immobilized, oxygen-consuming, cells.
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    The long-term effects of ethanol on immobilized cell reactor performance using K. fragilis (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 975-982 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of ethanol on reactor performance were studied in a small, 5-cm packed height, “differential” type immobilized cell reactor. Lactose utilizing yeast cells, Kluyveromyces fragilis, were absorbed to a porous adsorbant sponge matrix in a gas continuous reactor. Step changes in the feed ethanol concentration to the column (10-130 g/L) were used to test the reactor response over extended periods of time (about 30-50 h per dosage level) followed by a return to basal zero inlet ethanol feed. Effluent cell density and effluent cell viability were measured at intervals. An inhibitory response in ethanol productivity to feed dosage ethanol levels above 20 g/L was detected almost immediately, with a near steady state response noted within 2.5 h of initiating the dosage. Feed ethanol levels above 50 g/L resulted in a subsequent gradual decrease in reactor productivity over time, which was associated with a decrease in the fraction of viable shed cells in the reactor effluent. The reactor response to a step removal of the ethanol inhibition was also monitored. Quick and complete rebounding of the fermentation rate to the original basal rate was noted following dosage concentrations of under 50 g/L ethanol. Recovery rates slowed following ethanol dosage levels above 50 g/L. Viable shed cell density improved overtime during the slow recovery periods. Growth rates (as determined by shed cell density) were more strongly inhibited than productivity. Growth responded more slowly to changes in ethanol environment as growth rates at 30 h fell to about 40% of the rates measured 7.5 h after initiation of a dosage level. It is concluded that ethanol contributions to cell injury and death (and consequent ICR performance degradation) may be more important than ethanol inhibition of productivity rates in the long-term operation of immobilized cell reactors at ethanol concentrations over 50 g/L.
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    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990) 
    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.260361101
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    Characterization of E. coli cell disintegrates from a bead mill and high pressure homogenizers (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1083-1089 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The protein releases, the particle size distribution and the viscosity of disrupted E. coli suspensions from Dyno Mill KDL, Manton Gaulin 15 M-8TA and Microfluidizer M-110 were determined. The effects of these parameters on separation of the cell debris from the protein solution by centrifugation and by filtration were also examined. All three disintegration methods investigated give approximately the same protein and enzyme releases but considerably different physical properties of the cell disintegrates which influences centrifugation and filtration. The separation degree of biomass during centrifugation is only slightly affected by increasing degree of disruption (increasing protein releases) in the bead mill, while an increase in the degree of disruption in the two high pressure homogenizers drastically reduces the centrifugal degree of separation. However, increasing degrees of disruption result in shorter filtration times during filtration for all three disintegration methods. The results show further that the cell concentration only has a minor influence on protein releases in the Microfluidizer high-pressure homogenizer, while an increase in the biomass content reduces the separability of the cell disintegrate both in filtration and in centrifugation.
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    Enhancing penicillin fermentations by increased oxygen solubility through the addition of n-hexadecane (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1110-1118 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: n-Hexadecane was added to fermentation media to increase the medium oxygen solubilities, thus enhancing oxygen transfer rates in penicillin fermentations. For shake flask fermentations, cells were found to grow faster in the flasks with n-hexadecane than those without. The addition of n-hexadecane to penicillin fermentations was shown to significantly increase cell growth and penicillin production and reduce formation of mycelial pellets. The result was attributed to the enhancement of oxygen transfer in mycelial fermentations due to the higher oxygen solubilities of fermentation media achieved by adding n-hexadecane.
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    A comparison of the Michaelis-Menten and HCH-1 models (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1151-1154 
    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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    Kinetic analysis of microbial sulfate reduction by desulfovibrio desulfuricans in an anaerobic upflow porous media biofilm reactor (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 267-274 
    Details
    ISSN: 0006-3592
    Keywords: microbial souring ; sulfate reduction ; porous media ; kinetics ; stoichiometry ; transport phenomena ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An anaerobic upflow porous media biofilm reactor was designed to study the kinetics and stoichiometry of hydrogen sulfide production by the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans (ATCC 5575) as the first step for the modeling and control of formation souring (H2S) in oil field porous media. The reactor was a packed bed (50 × 5.5 cm) tubular reactor. Sea sand (140 to 375 μm) was used as the porous media. The initial indication of souring was the appearance of well-separated black spots (precipitates of iron sulfide) in the sand bed. The blackened zones expanded radially and upward through the column. New spots also appeared and expanded into the cone shapes. Lactate (substrate) was depleted and hydrogen sulfide appeared in the effluent.Analysis of the pseudo-steady state column shows that there were concentration gradients for lactate and hydrogen sulfide along the column. The results indicate that most of the lactate was consumed at the front part of the column. Measurements of SRB biomass on the solid phase (sand) and in the liquid phase indicate that the maximum concentration of SRB biomass resided at the front part of the column while the maximum in the liquid phase occurred further downstream. The stoichiometry regarding lactate consumption and hydrogen sulfide production observed in the porous media reactor was different from that in a chemostat. After analyzing the radial dispersion coefficient for the SRB in porous media and kinetics of microbial growth, it was deduced that transport phenomena dominate the souring process in our porous media reactor system. © 1994 John Wiley & Sons, Inc.
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    Separation of penicillin G from phenylacetic acid in a supported liquid membrane system (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 309-313 
    Details
    ISSN: 0006-3592
    Keywords: Penicillin G ; phenylacetic acid ; separation process ; Amberlite LA-2 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The separation of penicillin G (Pen G) from phenylacetic acid (PAA) by use of a supported liquid membrane (SLM) system with Amberlite LA-2 dissolved in 1-decanol, supported on a microporous polypropylene membrane, was studied. The results show that the individual permeability of each component in mixture was lower than that in a single compartment system and, it suggests a strong transport competition between Pen G and PAA. The SLM system in this study proved to be a promising process for the selective separation of Pen G from PAA. The maximum separation factor was found to be 1.8 under a liquid membrane resistance controlled mechanism. © 1994 John Wiley & Sons, Inc.
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    Inactivation of enzymes by organic solvents: New technique with well-defined interfacial area (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 331-336 
    Details
    ISSN: 0006-3592
    Keywords: enzyme inactivation ; organic solvents ; urease ; interfacial area ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A liquid-liquid bubble column apparatus allows exposure of enzyme solutions to water-immiscible organic solvents with a known total interfacial area and welldefined time scales and flow. It allows clear distinction of the different classes of inactivation mechanism. With urease as a model enzyme, octan-2-one and butylbenzene act only through the effects of solvent molecules dissolved in the aqueous phase, giving first-order inactivation at 0.34 and 0.21 h-1, respectively. Hexane and tridecane act only through exposure to the interface. The amount of urease inactivated is proportional to the total area of interface exposed, rather than to elapsed time, and may be characterized by a rate of about 0.5 μkat m-2. This is consistent with the formation and (partial) inactivation of a complete adsorbed monolayer of protein. With butan-1-ol, both mechanisms contribute significantly to the observed inactivation. The presence of O2 increases the rate of interfacial inactivation, but not that by dissolved solvent. © 1994 John Wiley & Sons, Inc.
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    Purification of a recombinant protein produced in a baculovirus expression system by immobilized metal affinity chromatography (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 349-356 
    Details
    ISSN: 0006-3592
    Keywords: immobilized metal ion affinity chmotagraphy ; baculovirus expression system ; infectious bursal disease virus ; protein purification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Over the past 10 years, the baculovirus-insect cell system has become a powerful and versatile tool for the expression of a variety of heterologous proteins. In order to simplify separation of a cloned protein from the baculovirus-insect expression system, we have cloned a gene encoding for the protein of interest, a structural protein (VP2) of a strain (E/DEL) of infectious bursal disease virus (IBDV), with a metal ion binding site (His)5 at its C-terminus. This chimeric protein (VP2H) has been expressed and one-step affinity purified with immobilized metal ions (Ni+2). With antigen capture-enzyme-linked immunosorbent assay (AC-ELISA), we determined that the conformation of this chimeric protein was no different from the recombinant wild-type VP2 protein. However, the two proteins (VP2 and VP2H) can be distinguished and resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and detected immunologically following Western blotting. © 1994 John Wiley & Sons, Inc.
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    A mathematical model for the bacterial oxidation of a sulfide ore concentrate (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 357-364 
    Details
    ISSN: 0006-3592
    Keywords: Thiobacillus ferrooxidans ; pyrite/arsenopyrite leaching ; Monod kinetics ; arsenic inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of dilution rate and feed solids concentration on the bacterial leaching of a pyrite/arsenopyrite ore concentrate was studied. A mathematical model was developed for the process based on the steady-state data collected over the range of dilution rates (20 to 110 h) and feed solids concentrations (6 to 18% w/v) studied. A modified Monod model with inhibition by arsenic was used to model bacterial ferrous ion oxidation rates. The model assumes that (i) pyrite and arsenopyrite leaching occurs solely by the action of ferric iron produced from the bacterial oxidation of ferrous iron and (ii) bacterial growth rates are proportional to ferrous ion oxidation rate. The equilibrium among the various ionic species present in the leach solution that are likely to have a significant effect on the bioleach process were included in the model. © 1994 John Wiley & Sons, Inc.
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    Partition coefficients of substrates and products and solvent selection for biocatalysis under nearly anhydrous conditions (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 365-370 
    Details
    ISSN: 0006-3592
    Keywords: biocatalysis in organic media ; partion coefficients of substrate and product ; log P ; water activity ; mushroom tyrosinase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of solvent on the activity of mushroom tyrosinase toward three substrates was studied at a constant water activity of either 0.74 or 0.86. No simple correlation was observed between enzyme activity and log P, but partition coefficients of substrate (Ps) and product (Pp) gave systematic relations with enzyme activity. When initial reaction rates were considered, there was a bellshaped relationship between enzyme activity and Ps with an optimal Ps for each substrate. This can be explained by assuming that the solvent affected the enzyme activity primarily by affecting the substrate concentration in the aqueous layer around the catalyst where the enzymic reaction occurs. When long-term reaction rates were considered, a high Pp/Ps ratio was consistent with preservation of enzyme activity. © 1994 John Wiley & Sons, Inc.
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    Structured model of genetic control via the lac promoter in Escherichia coli (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 399-410 
    Details
    ISSN: 0006-3592
    Keywords: lac-based promoters ; Escherichia coli ; genetic control ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model that describes induction of protein synthesis from lac-based promoters has been developed and incorporated into the single-cell model of Escherichia coli with transcriptional and translational modifications. Unlike previous models of lac-based promoters, this model allows a priori prediction of the intracellular parameters controlling transcription from lac-based promoters with only the extracellular levels of substrate and inducer as inputs. Because of the structural detail of the model, it is possible to simulate different genetic constructions for comparison, such as Laclq strains versus wild-type cells, or including lacl on a multicopy plasmid. Expression from lac to tac promoters is predicted to yield 5% and 30% of the total cellular protein, respectively, with a pBR322-type plasmid. The model predicts the experimental observation that the Laclq strain is not as fully induced as the wild-type strains, even at higher inducer concentrations. Additionally, the model predicts the right order of magnitude of protein production from lac and tac promoters when mechanisms for attenuation of transcription at lower translational efficiency are considered. Finally, the model predicts that for high copy number systems ribosomes become limiting in the synthesis of plasmid-encoded proteins. © 1994 John Wiley & Sons, Inc.
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    Ammonia inhibition of hybridomas propagated in batch, fed-batch, and continuous culture (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 434-438 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; continuous culture ; ammonia ; growth inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The nature and temporal development of ammonia inhbition were investigated in batch, fed-batch, and continuous cultures. Significant inhibition was observed when cells were inoculated in serum-containing or chemically defined medium containing more than 2 mM of ammonia. In contrast, no inhibition was observed at greater than 10 mM when the ammonia concentration was gradually increased over the span of a batch culture by feeding ammonium chloride. Strong growth inhibition was observed after each of five step changes (2.8 → 3.7 → 4.0 → 4.9 → 7.7 → 13.5 mM) in continuous culture. Following a period of adaptation at each higher value, the viable cell density stabilized at a new lower value. The lowering in viable cell density was caused by an increase in specific death rate and a decreased cell yield on glucose, glutamine, and oxygen. Increased ammonia concentration had little or no effect on the steady-state specific growth kinetics or specific antibody productivity. © 1994 John Wiley & Sons, Inc.
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    Extraction of cephalosporin C from whole broth and separation of desacetyl cephalosporin C by aqueous two-phase partition (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 439-445 
    Details
    ISSN: 0006-3592
    Keywords: extraction from whole broth ; aqueous two-phase partition ; separation ; cephalosporin C ; desacetyl cephalosporin C ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cephalosporin C was extracted from diluted or whole broth by PEG/salt aqueous two-phase systems. Parameters such as PEG molecular weight, salt type, pH, and salt concentration were investigated for finding a suitable extraction system. In PEG 600/ammonium sulfate or phosphate systems, Kc (partition coefficienct of cephalosporin C) was observed to be larger than 1, with Kd (partition coefficient of desacetyl cephalosporin C) being smaller than 1. The particular values of these coefficients would imply that the difficult separation of cephalosporin C and desacetyl cephalosporin C could possibly be achieved via the aqueous two-phase extraction. The addition of surfactants, water-miscible solvents, and neutral salts for enhancement of the separation efficiency was also investigated. The addition of surfactants to the system did not affect the separation efficiency substantially. Kc would increase whereas Kd decreased as a result of the addition of acetone, MeOH, EtOH, IPA, and n-BuOH. Meanwhile both Kc and Kd would decrease whenever neutral salts, NaCl, KCl, Kl, or KSCN, were added. The partitioning behavior of cephalosporin C and desacetyl cephalosporin C in filtered, whole, and different batches of broth was notably quite similar to that of diluted broth. The recovery yield of cephalosporin C in whole broth extraction was observed to be a function of centrifugal force used in phase separation. © 1994 John Wiley & Sons, Inc.
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    Stereotypic culture systems for liver and bone marrow: Evidence for the development of functional tissue in vitro and following implantation in vivo (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 810-825 
    Details
    ISSN: 0006-3592
    Keywords: liver cell culture ; bone marrow culture ; stromal cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Stromal cell-associated liver cell and bone marrow (BM) culture on three-dimensiional nylon screen or polyglycolic acid (PGA) felt templates conveys certain functional advantages to the parenchyma of these tissues. Hepatic parenchymal cells (PC) manifest long-term (∼2 month) expression of liver-specific activities including cytochrome P450 enzyme activity and the synthesis of albumin, fibrinogen, transferrin, and other proteins. PC also undergo proliferation in association with stromal cells that were pre-established on these templates. PC mitoses are directly proportional to available space within the template for their expansion indication that geometric or sterotypic parameters influence the growth of these cells in vitro. BM cultured on a similar template exhibits long-term multilineage hematopoietic expression and limited expansion of progenitor cell numbers. Progenitor cell concentration within the cultures can be substantially enhanced if these cells are liberated from co-culture and reseeded onto a template containing fresh stromal cells. BM and liver cel cultures established on felt composed of bioresorbable PGA filaments was grafted into various sites in rats. Liver co-cultures generated sinusoids and other liver-like structures in situ; active hematopoietic blasts were observed at sites of BM co-culture grafts. Biodegradable polymer constructs may prove useful for certain clinical applications as vehicles for the delivery of tissues that were engineered in culture.
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    Leuconostoc mesenteroides growth kinetics with application to bacterial profile modification (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 865-873 
    Details
    ISSN: 0006-3592
    Keywords: Leuconostoc mesenteroides ; dextran ; kinetics ; bacterial profile modification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bacterial profile modification (BPM) is being developed as an oil recovery technique that uses bacteria to selectively plug oil depleted zones within a reservoir to divert displacing fluids (typically water) into oil-rich zones. Leuconostoc mesenteroides, which produces dextran when supplied with sucrose, is a bacterium that is technically feasible for use in profile modification. However, the technique requires controlled bacterial growth to produce selective plugging.A kinetic model for the production of cells and polysaccharides has been developed for L. mesenteroides bacteria. This model, based on data from batch growth experiments, predicts saccharide utilization, cell generation, and dextran production. The underlying mechanism is the extracellular breakdown of sucrose into glucose and fructose and the subsequent production of polysaccharide (dextran). The monosaccharides are then available for growth. Accompanying sucrose consumption is the utilization of yeast extract. The cell requires a complex media that is provided by yeast extract as a source of vitamins and amino acids. Varying the concentration ratio of yeast extract to sucrose in the growth media provides a means of controlling the amount of polymer produced per cell. Consequently, in situ bacteria growth can be controlled by the manipulation of nutrient media composition, thereby providing the ability to create an overall strategy for the use of L. mesenteroides bacteria for profile modification.
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    Ammonia affects the glycosylation patterns of recombinant mouse placental lactogen-I by chinese hamster ovary cells in a pH-dependent manner (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 505-514 
    Details
    ISSN: 0006-3592
    Keywords: glycosylation ; recombinant protein expression ; CHO cells ; ammonia ; pH ; placental lactogen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The N-linked glycosylation of the recombinant protein mouse placental lactogen-I (mPL-I) expressed by Chinese hamster ovary (CHO) cells under nongrowth conditions was inhibited by increasing levels of ammonium chloride (3 and 9 mM) in a serum-free, protein expression medium. The effect of ammonia on glycosylation was dependent on the extracellular pH (pHe). In media containing 0 and 9 mM ammonium chloride, the percentage of the most heavily glycosylated forms of secreted mPL-I decreased from ca. 90% to ca. 25% at pHe 8.0, and from ca. 90% to ca. 65% at pHe 7.6, respectively. However, at pHe 7.2, the most heavily glycosylated forms of secreted mPL-I decreased from ca. 90% to ca. 80% in media containing 0 and 9 mM ammonium chloride, respectively. Inhibition of mPL-I glycosylation was found to correlate with the calculated concentrations of the ammonia species (NH3). Control experiments showed that the ammonia effect on mPL-I glycosylation could not be attributed to increased chloride concentration or osmolarity, or to extracellular events after secretion of the recombinant protein into the supernatant. Ammonium chloride, 9 mM, inhibited the expression rate of MPL-I by CHO cells at low pHe. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260430611
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    Sorption and precipitation of metals in activated sludge (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 874-880 
    Details
    ISSN: 0006-3592
    Keywords: sludge ; sorption ; precipitation ; metals ; adsorption ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A conceptual model describing the relative roles of sorption and precipitation processes for metals in solid-solution suspensions is presented. The model performance is demonstrated using experimental data on sorption and precipitation of metals in samples of activated sludge mixed liquor. Based on the experimental results presented here, it appears that, at total metal and mixed liquor suspended solids concentrations and pH values generally encountered in full-scale municipal (or combined municipal/industrial) activated sludge systems, metals are primarily removed by sorption processes.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260430906
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    Mammalian cell damage in a novel membrane bioreactor (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 899-906 
    Details
    ISSN: 0006-3592
    Keywords: membrane bioreactor ; mammalian cell damage ; critical shear rate ; power dissipation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The experimental study has assessed a novel membrane bioreactor for mammalian cell culture. In the absence of a gas phase, the key features of cell damage associated with laminar and turbulent flow have been identified. The bioreactor employs a dimpled membrane in order to enhance transverse mixing in a narrow channel, but a fall in viable cell density has been observed at Reynolds numbers above Re = 83. In the laminar flow regime wall shear is the critical mechanism and an accurate calculation of shear rate in a complex channel has been achieved using the Reynolds analogy. Flow generating a wall shear rate in excess of 3000 s-1 has been shown to cause damage. Power dissipation measurements have been used to distinguish between laminar and turbulent flow and also to predict Kolmogorov eddy lengths. An additional turbulent bulk stress damage mechanism at higher Reynolds numbers (Re 〉 250) results in a very rapid fall in viable cell density.
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    URL: http://dx.doi.org/10.1002/bit.260430909
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    Importance of solute partitioning in biphasic oxidation of benzyl alcohol by free and immobilized whole cells of pichia pastoris (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 918-924 
    Details
    ISSN: 0006-3592
    Keywords: biphasic oxidation ; immobilized whole cells ; organic solvent ; reagent partitioning ; benzyl alcohol ; Pichia pastoris ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using free and immobilized whole cells of Pichia pastoris, the biocatalytic oxidation of benzyl alcohol was investigated in different two-phase systems. This reaction was strongly influenced by both the substrate and product inhibitions, and the production rate of benzaldehyde in the aqueous system became maximum at the initial substrate concentration of ca. 29 g/L with the aldehyde formation less than 4 to 5 g/L even after a longer reaction period. The reaction rates in the two-liquid phase systems were predominantly determined by the partitioning behaviors of the substrate and product between the two phases rather than by enzyme deactivation by the organic solvents. In the two-liquid phase systems, consequently, the organic solvent acted as a reservior to reduce these inhibitory effects, and it was essential to select the organic solvent providing the optimal partitioning of the substrate into the aqueous phase as well as the preferential extraction of the product into the organic phase. The whole cells immobilized in a mixed matrix composed of silicone polymer [〉50% (v/v)] and Ca alginate gel (〈50%) worked well in the xylene and decane media, providing comparable activities with the free cells. The production rate of aldehyde was also influenced by the solute partitioning into the hydrophilic alginate phase where the cells existed. © 1994 John Wiley & Sons, Inc.
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    Biodegradation of pesticides in nonionic water-in-oil microemulsions of tween 85: Relationship between micelle structure and activity (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 946-959 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; phosphotriesterase ; reversed micelles ; microemulsions ; nonionic surfactants ; organophosphorus hydrolase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Water-in-oil microemulsion systems have been studied in recent years for a number of applications in protein separation and enzymology. Although it is well established that reversed micelle systems provide an excellent medium for nonaqueous biocatalytic studies, there is still much speculation as to the interaction of the enzyme with the surfactant interface. Polyoxyethylene sorbitan trioleate (Tween 85) is a nonionic surfactant which has some interesting properties for microemulsion formation and protein solubilization. In conjunction with a separate article describing the structural features of Tween 85 reversed micelles in hexane with isopropanol as a cosurfactant, this work describes the activity of an enzyme, organophosphorus hydrolase, for degrading organophosphorus pesticides in this microemulsion system. Ternary phase diagrams were constructed to outline the phase boundaries at different temperatures and isopropanol concentrations, which elucidate the role of the cosurfactant alcohol, as well as some features of micelle structure. Kinetic and stability studies with organophosphorus hydrolase show the effect of enzyme partitioning between the micelle surfactant layer and aqueous core. © 1994 John Wiley & Sons, Inc.
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    Pervaporative butanol fermentation by Clostridium acetobutylicum B18 (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 978-986 
    Details
    ISSN: 0006-3592
    Keywords: butanol ; fermentation ; Clostridium acetobutylicum ; acetone ; ethanol ; pervaporation ; fed batch ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Extractive acetone-butanol-ethanol (ABE) fermentation was carried out successfully using pervaporation and a low-acid-producing Clostridium acetobutylicum B18. A pervaporation module with 0.17 m2 of surface area was made of silicone membrane of 240 μm thickness. Pervaporation experiments using make-up solutions showed that butanol and acetone fluxes increased linearly with their concentrations in the aqueous phase. Fickian diffusion coefficients were constants for fixed air flow rates, and increased at higher sweep air flow rates. During batch and fed-batch fermentations, pervaporation at an air flow rate of 8 L/min removed butanol and acetone efficiently. Butanol concentration was maintained below 4.5 g/L even though Clostridium acetobutylicum B18 produced butanol steadily. Pervaporation could not remove organic acids efficiently, but organic acids did not accumulate because strain B18 produced little organic acid and recycled added organic acids efficiently. With pervaporation, glucose consumption rate increased compared to without pervaporation, and up to 160 g/L of glucose was consumed during 80 h. Cell growth was not inhibited by possible salt accumulation or oxygen diffusion through the silicone tubing. The culture volume was maintained relatively constant during fed-batch operation because of an offsetting effect of water and product removal by pervaporation and addition of nutrient supplements. © 1994 John Wiley & Sons, Inc.
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    Cadmium removal in a biosorption column (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1010-1015 
    Details
    ISSN: 0006-3592
    Keywords: biosorption ; column sorption ; trickle column ; toxicity removal ; cadmium ; cadmium removal ; wastewater treatment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New biosorbent material derived from a ubiquitous brown marine alga Ascophyllum nodosum has been examined in packed-bed flow-through sorption columns. It effectively removed 10 mg/L of cadmium down to 1.5 ppb levels in the effluent, representing 99.985% removal. The experimental methodology used was based on the early Bohart and Adams sorption model, resulting in quantitative determination of the characteristic process parameters which can be used for performance comparison and process design. An average metal loading of the biosorbent (N0) determined was 30 mg Cd/g, corresponding closely to that observed for the batch equilibrium metal concentration of 10 mg Cd/L. The critical bed depth (Dmin) for the potable water effluent quality standard (0.005 mgg Cd/L) varied with the column feed flow rate (2.4 to 9.6 L/h · cm2) from 20 to 50 cm. The sorption column mass transfer and dispersion coefficients were determined, which are also required for solving the sorption model equations. © 1994 John Wiley & Sons, Inc.
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    Cybernetic model for synthesis of poly-β-hydroxybutyric acid in Alcaligenes eutrophus (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1043-1051 
    Details
    ISSN: 0006-3592
    Keywords: cybernetic model ; poly-β-hydroxybutyric acid ; Alcaligenes eutrophus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The pathway of poly-β-hydroxybutyric acid (PHB) exhibits a mode of transcriptional control induced by environmental stress. A new cybernetic model for coordinated regulation of stress-induced metabolism was developed to predict the growth and the synthesis of PHB in Alcaligenes eutrophus. A plausible objective for this control is optimization of acetyl-CoA utilization so that the cells have a high degree of flexibility in their catabolism. The state equation for key protein synthesis was assumed to have a dependence on the nonlinear control variable. The proposed model can demonstrate the mixed-growth-associated synythesis of PHB. Reported unstructured models were compared statistically with the result of the simulation derived from the proposed model using the experimental data of this study and the literature. The proposed model appeared to provide an excellent description for the overall fermentation range. © 1994 John Wiley & Sons, Inc.
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    Overproduction of glycogen in Escherichia coli blocked in the acetate pathway improves cell growth (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 132-139 
    Details
    ISSN: 0006-3592
    Keywords: glycogen ; Escherichia coli ; cell growth ; acetate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Excessive production of acetate is a problem frequently encountered in aerobic high-cell-density fermentations of Escherichia coli. Here, we have examined genetic alterations resulting in glycogen overproduction as a possible means to direct the flux of carbon away from the acetate pool. Glycogen overaccumulation was achieved either by using a regulatory glgQ mutation or by transforming cells with a plasmid containing the glycogen biosynthesis genes glgC (encoding ADPG pyrophosphorylase) and glgA (encoding glycogen synthase) under their native promoter. Both strategies resulted in an approximately five-fold increase in glycogen levels but had no significant effect on acetate excretion. The glgC and glgA genes were then placed under the control of the isopropyl---D-thiogalactopyranoside (IPTG) inducible tac promoter, and this construct was used to stimulate glycogen production in a mutant defective in acetate biosynthesis due to deletion of the ack (acetate kinase) and pta (phosphotransacetylase) genes. If glycogen overproduction in the ack pta strain was induced during the late log phase, biomass production increased by 15 to 20% relative to uninduced controls. Glycogen overaccumulation had a significant influence on carbon partitioning: The output of carbon dioxide peaked earlier than in the control strain, and the levels of an unusual fermentation byproduct, pyruvate, were reduced. Exogenous pyruvate was metabolized more rapidly, suggesting higher activity of gluconeogenesis or the tricarboxylic acid (TCA) cycle as a result of glycogen overproduction. Potential mechanisms of the observed metabolic alterations are discussed. Our results suggest that ack pta mutants over producing glycogen may be a suitable starting point for constructing E. coli strains with improved characteristics in high-cell-density fermentations. © 1994 John Wiley & Sons, Inc.
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    Genetically engineered charge modifications to enhance protein separation in aqueous two-phase systems: Electrochemical partitioning (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 147-153 
    Details
    ISSN: 0006-3592
    Keywords: aqueous two-phase systems ; β-galactosidase ; T4 lysozyme ; partitioning ; charge modifications ; genetic engineering ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have examined the effect of genetically engineered charge modifications on the partitioning behavior of proteins in dextran/polyethylene glycol two-phase systems containing potassium phosphate. By genetically altering a protein's charge, the role of charge on partitioning can be assessed directly without the need to modify the phase system. The charge modifications used are of two types: Charged tails of polyaspartic acid fused to β-galactosidase and charge-change point mutations of T4 lysozyme which replace positive lysine residues with negative glutamic acids. The partition coefficient Kp for these proteins was related to measured interfacial potential differences Δφ using the simple thermodynamic model, In Kp = In Ko + (F/RT)Zp δφ. The protein net charge Zp was determined using the Henderson-Hasselbalch relationship with modifications based on experimentally determined titration and isoelectric point data. It was found that when the electropartitioning term Zp δφ was varied by changing the pH, the partitioning of T4 lysozyme was quantitatively described by the thermodynamic model. The β-galactosidase fusions displayed qualitative agreement, and although less than predicted, the partitioning increased more than two orders of magnitude for the pH range examined. Changes in the partitioning of lysozyme due to the various mutations agreed qualitatively with the thermodynamic model, but with a smaller than expected dependence on the estimated charge differences. The β-galactosidase fusions, on the other hand, did not display a consistent charge based trend, which is likely due either to the enzyme's large size and complexity or to nonelectrostatic contributions from the tails. The lack of quantitative fit with the model described above suggests that the assumptions made in developing this model are oversimplified. © 1994 John Wiley & Sons, Inc.
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    Heterogeneity of biofilms in rotating annular reactors: Occurrence, structure, and consequences (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 194-204 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; biofilm reactors ; structure ; heterogeneity ; kinetics ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rotating annular reactor (Roto Torque) was used for qualitative and quantitative studied on biofilm heterogeneity. In contrast to the classic image of biofilms as smooth, homogeneous layers of biomass on a substratum, studies using various pure and mixed cultures consistently revealed more-dimensional structures that resembled dunes and ridges, among others. These heterogeneities were categorized and their underlying causes analyzed. Contrary to expectations, motility of the microorganisms not a decisive factor in determining biofilm homogeneity. Small Variations in substratum geometry homogeneity. Small variations in substratum geometry and flow patterns were clearly reflected in the biofilm pattern. Nonhomogeneous flow and shear patterns in the reactor, together with inadequate mixing resulted in significant, position-dependent differences in surface growth. It was therefore not possible to take representative samples of the attached biomass. Like many other types of reactors, the Roto Torque reactor is valuable for qualitative and morphological biofilm experiments but less suitable for quantitative physiological and kinetics studies using attached microorganisms. © 1994 John Wiley & Sons, Inc.
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    Adsorption of BSA on strongly basic chitosan: Equilibria (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1087-1093 
    Details
    ISSN: 0006-3592
    Keywords: adsorption ; ion exchange ; chitosan ; equilibrium ; BSA ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Equilibrium isotherms for adsorption of bovine serum albumin (BSA) on a new adsorbent, a strongly basic crosslinked chitosan (Chitopearl 2503), which is hard and is not compressed by pressure in a column, have been presented and compared with diethylaminoethyl (DEAE) Sepharose Fast Flow (hard gel). In Chitopearl 2503, when only buffer existed in the BSA solution, the isotherm was not affected by the initial concentration of BSA but it was affected by pH considerably. The isotherm was favorable when pH ≥ pl (≅ 4.8). When NaCl existed in the BSA solution, the amount of BSA absorbed on the resin decreased with increasing concentration of NaCl. When the concentration of NaCl was 200 mol/m3, the resin did not adsorb BSA at all. The equilibrium data were correlated by the Langmuir equation reasonably well. The BSA may be adsorbed mainly by electrostatic attraction between negatively charged BSA and positively charged quanternary ammonium groups at pH 〉 pl and by protonation reaction of the primary ammonium groups by weak acid groups of BSA at pH = pl. These are confirmed by measuring the amount of inorganic ion exchanged for BSA. In DEAE Sepharose Fast Flow, the isotherm was favorable when pH 〉 pl but unfavorable ar pH = pl. The saturation capacity of BSA on Chitopearl 2503 is about 1.3 to 2.2 times larger than that on DEAE Sepharose Fast Flow. © 1994 John Wiley & Sons, Inc.
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    Synthesis of aspartame precursor with an immobilized thermolysin in tert-amyl alcohol (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1118-1123 
    Details
    ISSN: 0006-3592
    Keywords: enzymatic synthesis ; peptide synthesis ; thermolysin ; immobilized enzyme ; aspartame precursor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: N-(Benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methyl ester (Z-AspPheOMe), a precursor of the synthetic sweetner asparatame, was synthesized from N-(benzyloxycarbolyl)-L-aspartic acid (Z-Asp) and L-phenylalanine methyl ester (PheOMe) with an immobilized thermolysin in various organic solvents. We found that in tert-amyl alcohol containing a small amount of water the immobilized enzyme showed a high activity comparble to that in ethyl acetate with quite a high stability. The immobilized enzyme was fully stable up to 70°C in tert-amyl alcohol in the absence of the subatrate, and up to 50°C in the presence of the substrate. The high stability in the presence of the substrate was found due to the fact that the release of calcium ions, the stabilizing factor of thermolysin, is suppressed.The substrate concentration dependence of the initial synthetic rate with the immobilized enzyme was quite different from that with the free enzyme in the biphasic system, in contrast to that in ethyl acetate. Finally, Z-AspPheOMe was continuously synthesized in a column reactor using 200 mM PheOMe and 120 mM Z-Asp as the substrate for over 300 h at 45°C and a space velocity of 1 h-1 without any loss of acivity. © 1994 John Wiley & Sons, Inc.
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    Protein fractionation using fast flow immobilized metal chelate affinity membranes (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 21-36 
    Details
    ISSN: 0006-3592
    Keywords: affinity sorption ; microporous membrane ; metal chelate ; protein fractionation ; radial dispersion model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new group-specific affinity membrane using metal chelates as ligands and inorganic glass hollow fiber microfiltration membranes as support matrices is developed and tested. The study focused on developing the optimum activation and coupling procedures to bind the chelating agent (iminodiacetic acid, IDA) to the surface of the microporous glass hollow fiber membrane and testing the resultant affinity membrane. Starting with three different glass surfaces, five modification reactions were evaluated. All the modified “active surfaces” were first tested for their protein adsorptive properties in batch mode with suspended microporous glass grains using model proteins with known binding characteristics with Cu-IDA systems. The metal loading capacities of the surfaces exhibiting favorable fractionation were then measured by atomic absorption spectroscopy.The results were compared with the results obtained with a commercial material used in immobilized metal affinity column chromatography. The protein binding characteristics of the hollow fiber affinity membranes were also evaluated under conditions of convective flow. This was performed by flowing single solute protein solutions through the microporous membrane at different flow rates. These results were then used to estimate the optimum loading and elution times for the process. A mathematical model incorporating radial diffusion was solved using a finite difference discretization method. Comparison between model predictions and experimental results was performed for four different proteins at one flow rate. These results suggested that the kinetics of adsorption was concentration dependent. Finally, the hollow fiber affinity membranes were challenged with two component mixtures to test their ability to fractionate mixed protein solutions. Efficient separation and good purity were obtained.The results presented here represent the development of a new fast flow affinity membrane process-immobilized metal affinity membranes (IMAM). © 1994 John Wiley & Sons, Inc.
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    Rapid renaturation of denatured and aggregated proteins using liquid paraffin as a pseudolipid bilayer membrane (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 57-63 
    Details
    ISSN: 0006-3592
    Keywords: protein renaturation ; liquid paraffin ; BSA ; ribonuclease ; myoglobin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A means of rapidly renaturing denatured protein was devised and evaluated. Three liquids were laminarly layered in a centrifuge tube, in which two solutions sandwiched liquid paraffin so as to form a pseudolipid bilayer. Denatured and aggregted protein placed on the upper surface of liquid paraffin was renatured as it passed through liquid-paraffin layer into the renaturation buffer during the centrifugation. The aggregated and denatured protein selectively passed through the liquid-paraffin layer, whereas other solutions, such as chaotropic agents or organic solvent, could not. This means that a rapid dilution condition favorable for protein renaturation was realized in a small scale. Aggregated and denatured BSA and ribonuclease A were renatured and resolubilized as they passed through the liquid-paraffin layer into an appropriate renaturation buffer solution. This method was also applied to the rapid heme reconstitution of myoglobin from Feprotoporphyrin IX to Zn-protoporphyrin IX. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430108
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    The influence of polyalcohols and carbohydrates on the thermostability of α-amylase (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 107-114 
    Details
    ISSN: 0006-3592
    Keywords: polyols and carbohydrates ; protein thermostability ; heat inactivation kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of polyhydric alcohols and carbohydrates on the thermostability, i.e., the heat inactivation kinetics, of Bacillus licheniformis α-amylase was studied in the temperature range 96° to 130°C. High concentrations (from 9 to 60 weight percent) of glycerol, sorbitol, mannitol, sucrose, or starch can markedly decrease the inactivation rate constant, k, and in the studied cases, this stabilizing effect grows stronger with increasing additive concentration. Statements about stabilization should, however, be specified carefully with respect to temperature, because EA is mostly altered likewise. For dissolved enzyme EA was almost always decreased in the presence of polyol or carbohydrate, whereas for immobilized enzyme it was augmented in each studied instance. The inactivation of dissolved enzyme can, in all the studied cases, be adequately described as a firstorder process. Immobilized enzyme, however, shows biphasic then first-order inactivation kinetics, depending on the additive concentration and temperature. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260430202
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    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994) 
    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.260440801
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  • 99
    Electronic Resource
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    Solids retention time in spherical biofilms in a biofilm airlift suspension reactor (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 867-879 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; microbeads ; solids retention time ; airlift reactor ; particulates ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluorescent microparticles were used as tracer beads to measure the dynamics of solids in spherical biofilms in a biofilm airlift suspension reactor. Attachment to, release from, and penetration into the biofilms of the tracer beads were measured. The coverage of the biofilm surface was low and the steady state particle concentration on the surface was dependent on the biofilm surface characteristics. The measured attachment rate constant was identical in both experiments and appeared to be determined by the hydrodynamic conditions in the turbulent reactor. The attachment rate was much faster than the release rate of the tracer beads and, therefore, the solidsretention time in the biofilm particle is not due to a simple reversible adsorption-desorption process. The heterogeneity of the distribution oftracer beads on different sectors on the biofilm surface decreased duringthe attachment period. Due to random detachment processes the heterogeneity of the tracer bead distribution increased during the release periodThe tracer beads quickly penetrated into the biofilm and became distributed throughout the active layer of the biofilm. The observed penetration into biofilms, the nonuniform distribution on the biofilm surface, and the fast uptake and slow release of tracer beads cannot be described by a simple model based on a reversible adsorption-desorption mechanism, nor withexisting biofilm models. These biofilm models, which balance growth and advection assuming a uniform biofilm with a homogeneous surface, are inadequate for the description of the observed solids retention time in biofilms. Therefore, a new concept of biofilm dynamics is proposed, in which formation of cracks and fissures, which are rapidly filled with growing biomass, combined with nonuniform local detachment, explains the observed fast penetration into the biofilm of tracer beads, the long residence time, and the nonuniform distibution of fluorescent microparticles. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440802
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  • 100
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    Improved taxol yield by aromatic carboxylic acid and amino acid feeding to cell cultures of taxus cuspidata (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 967-971 
    Details
    ISSN: 0006-3592
    Keywords: taxol production ; Taxus cuspidata ; cell culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cell culture of Taxus cuspidata represents an alternative to whole plant extraction as a source of taxol and related taxanes. Feeding phenylalanine to callus cultures was previously shown to result in increased taxol yields, probably due to the involvement of this amino acid as a precursor for the N-benzoylphenylisoserine side chain of taxol. Inthis study, we have examined the effect of various concentrations of phenylalanine, benzoic acid, N-benzoylglycine, serine, glycine, alanine, and 3-amino-3-phenyl-propionic acid on taxol accumulation in 2-year-old cell suspensions of Taxus cuspidata, cell line FCL1F, and in developing callus cultures of T. cuspidata. All compounds tested were included in media at stationary phase (suspensions) or after the period of fastest growth (calli). Alanine and 3-amino-3-phenyl-propionicacid were tested only in callus cultures and did not affect taxol accumulation. Significant increases or trends toward increases in taxol accumulationin callus and suspensions were observed in the presence of phenylalanine, benzoic acid, N-benzoylglycine, serine, and glycine. The greatest increases in taxol accumulation were observed in the presence of various concentrations of phenylalanine (1 mM for callus; 0.05, 0.1, and 0.2 mM for suspensions) and benzoic acid (0.2 and 1 mM for callus and 0.05, 0.1, and 0.2 mM for suspensions). Increases in taxol yields of cell suspensions in the presence of the most effective precursors brought taxol amounts at stationary phase from 2 μg · g-1 to approximately 10 μg . g-1 of the extracted dry weight. The results are discussed in termsof possible implications to taxol biosynthesis and in terms of practical applications to large-scale cell culture systems for the production ofthis drug. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260440813
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