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  • 1
    ISSN: 1573-0778
    Keywords: fixed bed reactor ; immobilization ; dialysis technique ; hybridoma cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An industrial scale reactor concept for continuous cultivation of immobilized animal cells (e.g. hybridoma cells) in a radial-flow fixed bed is presented, where low molecular weight metabolites are removed via dialysis membrane and high molecular products (e.g. monoclonal antibodies) are enriched. In a new “nutrient-split” feeding strategy concentrated medium is fed directly to the fixed bed unit, whereas a buffer solution is used as dialysis fluid. This feeding strategy was investigated in a laboratory scale reactor with hybridoma cells for production of monoclonal antibodies. A steady state monoclonal antibody concentration of 478 mg l-1 was reached, appr. 15 times more compared to the concentration reached in chemostat cultures with suspended cells. Glucose and glutamine were used up to 98%. The experiments were described successfully with a kinetic model for immobilized growing cells. Conclusions were drawn for scale-up and design of the large scale system. Abbreviations: cGlc – glucose concentration, mmol l-1; cGln – glutamine concentration, mmol l-1; cAmm – ammonia concentration, mmol l-1; cLac – lactate concentration, mmol l-1; cMAb – MAb concentration, mg l-1; D – dilution rate, d-1; Di – dilution rate in the inner chamber of the membrane dialysis reactor, d-1; D0 – dilution rate in the outer chamber of the membrane dialysis reactor, d-1; q*FB,Glc – volume specific glucose uptake rate related to the fixed bed volume, mmol lFB -1 h-1; q*FB,Gln – volume specific glutamine uptake rate related to the fixed bed volume, mmol lFB -1 h-1.
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  • 2
    ISSN: 1573-0778
    Keywords: monoclonal antibody ; immobilization ; collagen gel ; BHK ; productivity ; recombinant ; high density culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Animal cell perfusion high density culture is often adopted for the production of biologicals in industry. In high density culture sometimes the productivity of biologicals has been found to be enhanced. Especially in immobilized animal cell culture, significant increase in the productivity has been reported. We have found that the specific monoclonal antibody (MAb) productivity of an immobilized hybridoma cell is enhanced more than double. Several examples of enhancing productivities have been also shown by collagen immobilized cells. Immobilized cells involve some different points from non-immobilized cells in high density culture: In immobilized culture, some cells are contacted together, resulting in locally much higher cell concentration more than 108 cells/ml. Information originating from a cell can be easily transduced to the others in immobilized culture because the distance between cells is much nearer. Here we have performed collagen gel immobilized culture of recombinant BHK cells which produce a human IgG monoclonal antibody in a protein-free medium for more than three months. In this high density culture a stabilized monoclonal antibody production was found with around 8 times higher specific monoclonal antibody productivity compared with that in a batch serum containing culture. No higher MAb productivity was observed using a conditioned medium which was obtained from the high density culture, indicating that no components secreted from the immobilized cells work for enhancing monoclonal antibody production. The MAb productivity by the non-immobilized cells obtained by dissolving collagen using a collagenase gradually decreased and returned to the original level in the batch culture using a fresh medium. This suggests that the direct contact of the cells or a very close distance between the cells has something to do with the enhancement of the MAb productivity, and the higher productivity is kept for a while in each cell after they are drawn apart.
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  • 3
    ISSN: 1573-0972
    Keywords: Biodegradation ; immobilization ; laccase ; olive oil mill wastewater ; white rot fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The biodegradation of olive oil mill wastewater (OOMW) by Coriolus versicolor and Funalia trogii was investigated. Initial COD concentration, agitation and inoculum size were all found to be significant for biodegradation. Adding glucose, sulphate or nitrogen had no effect on biodegradation. During growth in optimum conditions, C.versicolor removed approximately 63% COD, 90% phenol and 65% colour within 6 days and F. trogii removed approximately 70% COD, 93% phenol and 81% colour of the OOMW used. The fungi also excreted large amounts of extracellular laccase into the medium. High biodegradation yields were also obtained by fungi immobilized in calcium alginate gels.
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  • 4
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    World journal of microbiology and biotechnology 14 (1997), S. 107-111 
    ISSN: 1573-0972
    Keywords: Glutaraldehyde ; immobilization ; monochloroacetic acid ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 5
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 252-260 
    ISSN: 0006-3592
    Keywords: lipase ; chemical modification ; stability ; esterification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Semipurified lipase of Candida rugosa (CRSL) was subjected to chemical modification, and the activities of the modified lipase, in hydrolysis and esterification reactions, were examined. The esterification reactions were carried out in the absence and presence of isooctane. When the enzyme was modified with polyethylene glycol (PEG), two methodologies were studied. The activation of PEG with p-NO2-phenylchloroformate gives better biocatalysts than those obtained with cyanuric chloride-PEG. The chemical modification with PEG increases the stability of pure lipases in isooctane at 50°C (extreme conditions). The chemically modified enzymes are useful for biotransformations in organic solvents. In addition the nitration of tyrosines with tetranitromethane was also studied. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 252-260, 1997.
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  • 6
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    Biotechnology and Bioengineering 55 (1997), S. 565-570 
    ISSN: 0006-3592
    Keywords: hybridoma ; hypoosmotic stress ; specific antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To investigate the response of hybridoma cells to hypoosmotic stress, S3H5/γ2bA2 and DB9G8 hybridomas were cultivated in the hypoosmolar medium [Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% serum] resulting from sodium chloride subtraction. Both hybridomas showed similar responses to hypoosmotic stress in regard to cell growth and antibody production. The cell growth and antibody production at 276 mOsm/kg were comparable to those at 329 mOsm/kg (standard DMEM). Both cells grew well at 219 mOsm/kg, though their growth and antibody production were slightly decreased. When the osmolality was further decreased to 168 mOsm/kg, the cell growth did not occur. When subjected to hyperosmotic stress, both cells displayed significantly enhanced specific antibody productivity (qAb). However, the cells subjected to hypoosmotic stress did not display enhanced qAb. Taken together, both hyperosmotic and hypoosmotic stresses depressed the growth of S3H5/γ2bA2 and DB9G8 hybridomas. However, their response to hypoosmotic stress in regard to qAb was different from that to hyperosmotic stress. © 1997 John Wiley & Sons, Inc. Biotechnol Biong 55: 565-570, 1997.
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  • 7
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    Biotechnology and Bioengineering 55 (1997), S. 547-555 
    ISSN: 0006-3592
    Keywords: ethanol ; cellulose ; hemicellulose ; endoglucanase ; cellulase ; lignocellulose ; biomass ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study demonstrates a new approach to reduce the amount of fungal cellulase required for the conversion of cellulose into ethanol. Escherichia coli KO11, a biocatalyst developed for the fermentation of hemicellulose syrups, was used to produce recombinant endoglucanase as a co-product with ethanol. Seven different bacterial genes were expressed from plasmids in KO11. All produced cell-associated endoglucanase activity. KO11(pLOI1620) containing Erwinia chrysanthemi celZ (EGZ) produced the highest activity, 3,200 IU endoglucanase/L fermentation broth (assayed at pH 5.2 and 35°C). Recombinant EGZ was solubilized from harvested cells by treatment with dilute sodium dodecyl sulfate (12.5 mg/ml, 10 min, 50°C) and tested in fermentation experiments with commercial fungal cellulase (5 filter paper units/g cellulose) and purified cellulose (100 g/L). Using Klebsiella oxytoca P2 as the biocatalyst, fermentations supplemented with EGZ as a detergent-lysate of KO11(pLOI1620) produced 14%-24% more ethanol than control fermentations supplemented with a detergent-lysate of KO11(pUC18). These results demonstrate that recombinant bacterial endoglucanase can function with fungal cellulase to increase ethanol yield during the simultaneous saccharification and fermentation of cellulose. © 1997 Wiley & Sons, Inc. Biotechnol Bioeng 55: 547-555, 1997.
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  • 8
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    Biotechnology and Bioengineering 55 (1997), S. 577-580 
    ISSN: 0006-3592
    Keywords: mRNA stability ; hairpins ; gene expression control ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An expression system has been developed for the introduction of DNA cassettes into the region between the transcription and translation start sites of a gene of interest. This cassette system was used to engineer mRNA stability through the introduction of hairpins at the 5′ end. A synthetic DNA cassette was designed so that the resulting mRNA hairpin would be positioned one nucleotide from the 5′ mRNA end. The hairpin-containing mRNA exhibited a half-life 3 times that of the mRNA with no hairpin, resulting in increases in both mRNA and protein levels. These results indicate that it is possible to engineer mRNA stability as an additional means of controlling gene expression. © 1997 John Wiley & Sons Inc. Biotechnol Bioeng 55: 557-580, 1997
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  • 9
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    Biotechnology and Bioengineering 55 (1997), S. 581-591 
    ISSN: 0006-3592
    Keywords: adsorptive membranes ; oscillatory flow ; integrated processes ; in situ product recovery ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Preferential transport in adsorptive membranes can be used to selectively remove biochemicals directly from fermentation broths. During preferential transport, an adsorbing solute is selectively transported across the membrane while nonadsorbing solutes and cells are retained by the membrane. This technique was used to separate lysozyme directly from a feed containing lysozyme, myoglobin, and yeast cells. We found that because the oscillatory flows used in preferential transport involve strokes that are close to symmetric, they are very efficient in alleviating cake formation due to cell deposition on the membrane surface. Theoretical results suggest that, by optimizing process variables, preferential transport can lead to a continuous concentrated stream of the adsorbing protein. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 581-591, 1997.
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  • 10
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    Biotechnology and Bioengineering 55 (1997), S. 592-608 
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; metabolic modeling ; sensitivity analysis ; glycolysis ; compartmentation ; transient response ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model of glycolysis in Saccharomyces cerevisiae is presented. The model is based on rate equations for the individual reactions and aims to predict changes in the levels of intra- and extracellular metabolites after a glucose pulse, as described in part I of this study. Kinetic analysis focuses on a time scale of seconds, thereby neglecting biosynthesis of new enzymes. The model structure and experimental observations are related to the aerobic growth of the yeast. The model is based on material balance equations of the key metabolites in the extracellular environment, the cytoplasm and the mitochondria, and includes mechanistically based, experimentally matched rate equations for the individual enzymes. The model includes removal of metabolites from glycolysis and TCC for biosynthesis, and also compartmentation and translocation of adenine nucleotides. The model was verified by in vivo diagnosis of intracellular enzymes, which includes the decomposition of the network of reactions to reduce the number of parameters to be estimated simultaneously. Additionally, sensitivity analysis guarantees that only those parameters are estimated that contribute to systems trajectory with reasonable sensitivity. The model predictions and experimental observations agree reasonably well for most of the metabolites, except for pyruvate and adenine nucleotides. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 592-608, 1997.
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  • 11
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    Biotechnology and Bioengineering 55 (1997), S. 609-615 
    ISSN: 0006-3592
    Keywords: interacting populations ; membrane reactor ; induced metabolic changes ; elicitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The design of a reactor in which two interacting cell populations (microorganisms and plants) could grow under controlled conditions was considered. In this reactor, the cell populations are separated by a membrane which permits semi-in vivo study of induced interaction-specific changes in metabolism. In this paper, the interaction of suspension culture of Nicotiana tabacum (tobacco) and the Oomycete, Phytophthora nicotiana was simulated. The results of the computer simulation show the induced metabolic changes as a consequence of the biological interaction. The paper introduces a novel approach in the strategy for the study of interacting population in suspension cultures. This type of system has potential applications in studies of the regulation of secondary metabolism and for the production of high values pharmaceuticals. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 609-615, 1997.
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  • 12
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    Biotechnology and Bioengineering 55 (1997), S. 616-629 
    ISSN: 0006-3592
    Keywords: cell adhesion ; radial-flow chamber ; hydrodynamic shear ; detachment kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The strength of adhesion and dynamics of detachment of murine 3T3 fibroblasts from self-assembled monolayers were measured in a radial-flow chamber (RFC) by applying models for fluid mechanics, adhesion strength probability distributions, and detachment kinetics. Four models for predicting fluid mechanics in a RFC were compared to evaluate the accuracy of each model and the significance of inlet effects. Analysis of these models indicated an outer region at large radial positions consistent with creeping flow, an intermediate region influenced by inertial dampening, and an inner region dominated by entrance effects from the axially-oriented inlet. In accompanying experiments patterns of the fraction of cells resisting detachment were constructed for individual surfaces as a function of the applied shear stress and evaluated by comparison with integrals of both a normal and a log-normal distribution function. The two functions were equally appropriate, yielding similar estimates of the mean strength of adhesion. Further, varying the Reynolds number in the inlet, Red, between 630 and 1480 (corresponding to volumetric flow rates between 0.9 and 2.1 mL/s) did not affect the mean strength of adhesion. For these same experiments, analysis of the dynamics of detachment revealed three temporal phases: 1) rapid detachment of cells at the onset of flow, consistent with a first-order homogeneous kinetic model; 2) time-dependent rate of detachment during the first 30 sec. of exposure to hydrodynamic shear, consistent with the first-order heterogeneous kinetic model proposed by Dickinson and Cooper (1995); and 3) negligible detachment, indicative of pseudo-steady state after 60 sec. of flow. Our results provide rigorous guidelines for the measurement of adhesive interactions between mammalian cells and prospective biomaterial surfaces using a RFC. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 616-629, 1997.
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  • 13
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    Biotechnology and Bioengineering 55 (1997), S. 693-700 
    ISSN: 0006-3592
    Keywords: glucose ; lactate ; real-time determination ; hematopoietic cell culture ; colony-forming cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucose and lactate metabolic rates were evaluated for cultures of cord blood (CB) mononuclear cell (MNC), peripheral blood (PB) MNC, and PB CD34+ cell cultures carried out in spinner flasks and in T-flasks in both serum-containing and serum-free media. Specific glucose uptake rates (qgluc, in micromoles per cell per hour) and lactate generation rates (qlac) correlated with the percentage of colony-forming cells (CFC) present in the culture for a broad range of culture conditions. Specifically, the time of maximum CFC percentage in each culture coincided with the time of maximum qgluc and qlac in cultures with different seeding densities and cytokine combinations. A two-population model (Qlac = α[CFC] + β([TC] - [CFC]), where [TC] is total cell concentration; Qlac is volumetric lactate production rate in micromoles per milliliter per hour; α is qlac for an average CFC; and β is qlac for an average non-CFC) was developed to describe lactate production. The model described lactate production well for cultures carried out in both T-flasks and spinner flasks and inoculated with either PB or CB MNC or PB CD34+ cells. The values for α and β that were derived from the model varied with both the inoculum density and the cytokine combination. However, preliminary results indicate that cultures carried out under the same conditions from different samples with similar initial CD34+ cell content have similar values for β and β. These findings suggest that it should be possible to use lactate production data to predict the harvest time that corresponds to the maximum number of CFC in culture. The ability to harvest ex vivo hematopoietic cultures for transplantation when CFC are at a maximum has the potential to speed the rate at which immunocompromised patients recover. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 693-700, 1997.
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  • 14
    ISSN: 0006-3592
    Keywords: tubular photobioreactors ; light distribution ; average solar irradiance ; light attenuation ; microalgae mass culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model to estimate the solar irradiance profile and average light intensity inside a tubular photobioreactor under outdoor conditions is proposed, requiring only geographic, geometric, and solar position parameters. First, the length of the path into the culture traveled by any direct or disperse ray of light was calculated as the function of three variables: day of year, solar hour, and geographic latitude. Then, the phenomenon of light attenuation by biomass was studied considering Lambert-Beer's law (only considering absorption) and the monodimensional model of Cornet et al. (1900) (considering absorption and scattering phenomena). Due to the existence of differential wavelength absorption, none of the literature models are useful for explaining light attenuation by the biomass. Therefore, an empirical hyperbolic expression is proposed. The equations to calculate light path length were substituted in the proposed hyperbolic expression, reproducing light intensity data obtained in the center of the loop tubes. The proposed model was also likely to estimate the irradiance accurately at any point inside the culture. Calculation of the local intensity was thus extended to the full culture volume in order to obtain the average irradiance, showing how the higher biomass productivities in a Phaeodactylum tricornutum UTEX 640 outdoor chemostat culture could be maintained by delaying light limitation. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 701-714, 1997.
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  • 15
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    Biotechnology and Bioengineering 55 (1997), S. 715-726 
    ISSN: 0006-3592
    Keywords: fungal morphology ; pellets ; hyphae ; hair of pellets ; agitation intensity ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Both parallel fermentations with Aspergillus awamori (CBS 115.52) and a literature study on several fungi have been carried out to determine a relation between fungal morphology and agitation intensity. The studied parameters include hyphal length, pellet size, surface structure or so-called hairy length of pellets, and dry mass per-wet-pellet volume at different specific energy dissipation rates. The literature data from different strains, different fermenters, and different cultivation conditions can be summarized to say that the main mean hyphal length is proportional to the specific energy dissipation rate according to a power function with an exponent of -0.25 ± 0.08. Fermentations with identical inocula showed that pellet size was also a function of the specific energy dissipation rate and proportional to the specific energy dissipation rate to an exponent of -0.16 ± 0.03. Based on the experimental observations, we propose the following mechanism of pellet damage during submerged cultivation in stirred fermenters. Interaction between mechanical forces and pellets results in the hyphal chip-off from the pellet outer zone instead of the breakup of pellets. By this mechanism, the extension of the hyphae or hair from pellets is restricted so that the size of pellets is related to the specific energy dissipation rate. Hyphae chipped off from pellets contribute free filamentous mycelia and reseed their growth. So the fraction of filamentous mycelial mass in the total biomass is related to the specific energy dissipation rate as well.To describe the surface morphology of pellets, the hyphal length in the outer zone of pellets or the so-called hairy length was measured in this study. A theoretical relation of the hairy length with the specific energy dissipation rate was derived. This relation matched the measured data well. It was found that the porosity of pellets showed an inverse relationship with the specific energy dissipation rate and that the dry biomass per-wet-pellet volume increased with the specific energy dissipation rates. This means that the tensile strength of pellets increased with the increase of specific energy dissipation rate. The assumption of a constant tensile strength, which is often used in literature, is then not valid for the derivation of the relation between pellet size and specific energy dissipation rate. The fraction of free filamentous mycelia in the total biomass appeared to be a function of the specific energy dissipation in stirred bioreactors. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 715-726, 1997.
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  • 16
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    Biotechnology and Bioengineering 55 (1997), S. 921-926 
    ISSN: 0006-3592
    Keywords: green fluorescent protein ; sensor ; on-line monitoring ; quantitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We present an intensity based sensor designed for on-line monitoring of green fluorescent protein, a revolutionary marker of protein expression. The device consisted of a blue light emitting diode as the excitation source. A band pass excitation filter cut off light longer than 490 nm. The light was directed into a bifurcated optical fiber bundle with the common end inserted into a stainless steel housing equipped with a quartz window. The fiber bundle and stainless steel housing are steam sterilizable. The emission radiation was collected through a long wave pass filter to reject the excitation light shorter than 505 nm and was detected by a photomultiplier tube. The signal was amplified and sent to a computer for recording time course data. The sensor was tested in an Escherichia coli fermentation of JM105 transformed with pBAD-GFP. The on-line signal was compared to off-line fluorescence spectrophotometer measurements. The on-line profile closely followed the off-line. Western blot data showed that with a time shift, the sensor was able to both continuously and quantitatively monitor expression of green fluorescent protein on-line in real time. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55:921-926, 1997.
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  • 17
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    Biotechnology and Bioengineering 55 (1997), S. 909-920 
    ISSN: 0006-3592
    Keywords: baculovirus ; insect cells ; metabolism ; Sf-9; high five™ ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nutrient utilization and byproduct accumulation were monitored in Spodoptera frugiperda Sf-9 and Trichoplusia ni BTI-Tn-5B1-4 (High Five™) cell lines during growth and following viral infection in suspension cultures in order to develop a better understanding of cell metabolism and to acquire information relevant to large scale fed-batch bioreactors. The utilization of glucose, dissolved oxygen, and amino acids were monitored in Sf-9 cell cultures grown in Sf-900 II serum-free medium (SFM) and in High Five™ cell cultures grown in both Sf-900 II and Express Five SFM. Using the optimal medium for each cell line, i.e., Sf-900 II SFM for Sf-9 cells and Express Five SFM for High Five™ cells, the cell growth rate, maximum cell density, specific glucose and glutamine utilization rates, and specific alanine production rate were comparable during cell growth. In addition, the expression level of recombinant human tissue plasminogen activator was comparable in the two cell lines on a per cell basis. It was found, however, that lactate and ammonia accumulated in High Five™ cell cultures, but not in Sf-9 cell cultures. In addition, High Five™ cells utilized asparagine more rapidly than glutamine, whereas Sf-9 cells consumed only minimal asparagine, and the oxygen utilization rate was significantly higher in High Five™ cell cultures. It was also found that the medium had a significant effect on High Five™ cell metabolism, e.g., the specific glucose utilization rate and the specific lactate and alanine production rates were significantly higher in Sf-900 II SFM than in Express Five SFM. In addition, the maximum cell density and specific asparagine utilization rate were significantly higher in Express Five SFM. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55:909-920, 1997.
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  • 18
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    Biotechnology and Bioengineering 55 (1997), S. 940-940 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No abstract.
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  • 19
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    Biotechnology and Bioengineering 56 (1997), S. 1-8 
    ISSN: 0006-3592
    Keywords: transesterification ; hydrolysis ; water activity ; cutinase ; gas ; bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fusarium solani cutinase supported onto Chromosorb P was used to catalyze transesterification (alcoholysis) and hydrolysis on short volatile alcohols and esters in a continuous gas/solid bioreactor. In this system, a solid phase composed of a packed enzymatic preparation was continuously percolated with carrier gas which fed substrates and removed reaction products simultaneously. A kinetic study was performed under differential operating conditions in order to get initial reaction rates. The effect of the hydration state of the biocatalyst on the kinetics was studied for 3 conditions of hydration (aw = 0.2, aw = 0.4 and aw = 0.6), the alcoholysis of propionic acid methyl ester with n-propanol, and for 5 hydration levels (from aw = 0.2 to aw = 0.6) for the hydrolysis of propionic acid methyl, ethyl or propyl esters. F. solani cutinase was found to have an unusual kinetic behavior. A sigmoid relationship between the rate of transesterification and the activity of methyl propionate was observed, suggesting some form of cooperative activation of the enzyme by one of its substrate. For the hydrolysis of short volatile propionic acid alkyl esters, threshold effects on the reaction rate, highly depending on the water activity and the substrate polarity, are reported. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 1-8, 1997.
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  • 20
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    Biotechnology and Bioengineering 56 (1997), S. 9-22 
    ISSN: 0006-3592
    Keywords: condensation reactions ; disaccharides ; equilibria ; glucoamylase ; kinetics ; monosaccharides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Arabinose, fructose, galactose, myo-inositol, lyxose, mannose, ribose, and xylose were incubated individually and with glucose in the presence of Aspergillus niger glucoamylase at pH 4.5 and 45°C. Glucoamylase condenses galactose, glucose, and mannose individually into disaccharides. It also produces mixed disaccharides when each of the eight carbohydrates is incubated with glucose. Many products were identified by gas chromatography of the derivatized reaction mixtures followed by mass spectroscopy of the individual chromatographic peaks. Galacto-, gluco-, or mannopyranosyl rings appear to be present at the nonreducing ends of all the disaccharides produced. Molecules linked through primary hydroxyl groups have the highest equilibrium constants of all products formed, since these bonds are thermodynamically favored. However, glucoamylase is capable of forming bonds with many available hydroxyl groups, as previously demonstrated when it was incubated with glucose alone. Formation rates of different bonds linking different residues vary widely. These results demonstrate that glucoamylase has a wide selectivity toward residues it will condense into disaccharides and toward bonds it will form between them. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 9-22, 1997.
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    World journal of microbiology and biotechnology 13 (1997), S. 597-598 
    ISSN: 1573-0972
    Keywords: Glucose isomerase ; immobilization ; production ; purification ; Streptomyces olivochromogenes PTCC 1457
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Production of glucose isomerase from Streptomyces olivochromogenes PTCC 1457 was followed by its purification and immobilization. Different immobilization methods including the use of a hydrophobic support were investigated.
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  • 22
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    World journal of microbiology and biotechnology 14 (1997), S. 247-250 
    ISSN: 1573-0972
    Keywords: Baker's yeast ; 18-crown-6 ; imines ; immobilization ; oximes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Immobilized baker's yeast entrapped in calcium alginate beads efficiently reduces N-benzylidinemethylamine to N-methylbenzylamine in hexane at 37°C and tetrahydrofuran (THF) at 30°C in the presence of 18-crown-6, while in the presence of water as cosolvent and glucose as an additive N-benzylidinemethylamine undergoes decomposition. Benzaldoxime in a hexane–water (1:9) solvent system containing glucose as an additive is reduced to N-benzylhydroxylamine. On using an ethanol–water (1:1) solvent system, benzaldoxime is converted to benzyl alcohol and in hexane, benzene, THF, hexane–water (1:1) or acetonitrile–water (1:1) solvent systems, or using dried baker's yeast in different solvent systems, transformation of benzaldoxime does not occur.
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    World journal of microbiology and biotechnology 13 (1997), S. 469-473 
    ISSN: 1573-0972
    Keywords: 2-Deoxy-d-glucose ; hydroxylation ; immobilization ; polyoxin ; protoplasts ; steroids
    Source: Springer Online Journal Archives 1860-2000
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  • 24
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    Biotechnology and Bioengineering 18 (1976), S. 15-35 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The criterion for the oxygen limitation of substrate uptake in microbial film fermenters is expressed in terms of diffusion coefficients, utilization coefficients, and the free solution concentrations of substrate and oxygen. It is proposed that the ideal film thickness in such fermenters is equal to the penetration depth of the limiting substrate. The ideal film thickness is calculated, in terms of the parameters contained in the criterion for oxygen limitation, for three separate kinetic rate expressions. It is found that for the air-glucose-microbe system a simplified kinetic rate expression can be used and the region of dependence on two substrates is shown to be very limited. This is not true for other systems. Maximum uptake rates are calculated for a range of concentrations. Finally, it is shown that the procedure used can be generalized to determine the limiting substrate in a multisubstrate system and to calculate ideal film thickness and uptake rates for any pair of substrates where the kinetics of substrate uptake are known for the individual microorganism.
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    Biotechnology and Bioengineering 18 (1976), S. 95-104 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The apparent activation energy of N-α-benzoyl-L-arginine-ethyl ester (BAEE) hydrolysis by immobilized trypsin varies with the bulk substrate concentration from its maximum value, comparable to that of the free enzyme, to considerably lower values. Thus, with a concentration change from 3 × 10-2 to 10-4 M the apparent activation energy diminishes from 9.5 to 4.5 kcal/mol. This experimental finding is interpreted to be due to Michaelis-type kinetics in a heterogeneous system, in one case reflecting the temperature dependence of the maximal enzyme reaction rate, in another case illustrating the diffusion limited overall reaction at low substrate concentrations. As a consequence it may not be feasible to operate a reaction at elevated temperatures in a high conversion range, since diffusion limitation may restrict the enhancement of the overall reaction rate. Some further data are given concerning the buffer effect on the reaction rate, which should occur due to its limitation by proton transfer in the buffer-free system.
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    Biotechnology and Bioengineering 18 (1976), S. 145-165 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The applicability of the model derived by Ramanathan and Gaudy (Biotechnol. Bioeng., 11, 207, (1969)) for completely mixed activated sludge treatment holding the recycle solids concentration as a system constant was investigated using an actual industrial organic wastewater. Short-term experiments were conducted at various dilution rates (1/8, 1/6, 1/4, 1/2, 1/1.5 hr-1) for two recycle solids concentration values (5000 and 7000 mg/liter). The influent substrate concentration was maintained at 1000 mg/liter COD and the hydraulic recycle ratio, α, was kept at 0.3. It was found that for bottling plant (Pepsi Cola) waste-waters, a steady state with respect to reactor biological solids and effluent COD, at different dilution rates, could be attained, lending experimental evidence to the assumption that a steady state could be reached in developing the model and also affecting the applicability of the model in industrial organic wastewater. The reactor biological solids and effluent COD calculated from the model closely agreed with the observed values at dilution rates lower than 0.5 hr-1. Operation at dilution rates higher than 0.5 hr-1 will washout the biological solids from the reactor and the recycle substrate concentration will be apparent if the concentration of XR were not increased.
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    Biotechnology and Bioengineering 18 (1976), S. 63-80 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient experiments were conducted on a Pseudomomas utilizing phenol in a continuous culture by disturbing the influent substrate concentration and dilution rate. Two stable steady states existed for some ranges of the parameters. Highly damped oscillations were observed in approaching a new high conversion steady state or in returning to a new high conversion steady state following a small disturbance. When a large disturbance was applied there was a smooth (overdamped) approach to a new low conversion steady state.The observed oscillatory behavior for small disturbances was predicted by a modified Powell-Ierusalemskii bottleneck model, but could not be predicted by a Monod-Haldane model; neither model was accurate for predicting the effect of large disturbances.A constant wall growth factor was used to account for microbial film activity, and the existence of two stable states was directly due to the presence of the film.
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    Biotechnology and Bioengineering 18 (1976), S. 129-132 
    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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    Biotechnology and Bioengineering 18 (1976) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 18 (1976), S. 189-198 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Utilizing a chemostat with a dual nutrient limitation of nitrogen and phosphate, we examined the transient response of the culture following a pulse of one of the limiting nutrients (ammonia). This method provided quantitative evidence that cells can be grown under dual nutrient limitation. Furthermore, the pattern of response was consistent with the hypothesis that phosphate limitation restricts nucleic acid synthesis in the cell and that nitrogen limitation restricts protein synthesis. The net result is that under a phosphate limitation there is a restricted biosynthetic capacity which we feel is closely associated with the RNA content of the cell.
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    Biotechnology and Bioengineering 18 (1976) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 37-51 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Little is known about techniques for applying untreated microbial cells containing enzymes directly to industrial processes as a biocatalyst. The kinetic behavior of α-galactosidase-containing spherical pellets which are formed naturally under given conditions in a submerged culture of Mortierella vinacea was studied on the hydrolysis of PNPG (p-nitrophenyl-α-D-galactopyranoside). The effect of intraparticle diffusion on the overall reaction rate was assessed by the use of an effectiveness factor, which was calculated by the approximate solution to the equation derived from the mass balance within a pellet. The experimental effectiveness factors were found to be represented as a single function of the modified Thiele modulus, including such parameters as pellet size, enzyme concentration in the pellet, and substrate concentration. As the diffusional effect became more significant, the marked substrate inhibition as seen for a five enzyme disappeared gradually. The effect of product inhibition on the pellets was much weaker than that for a free enzyme at a given substrate concentration. In the region of diffusion controlled reaction, it was found that the rate is proportional to the square root of the enzyme concentration in the pellet. In addition, similarly to what was reported previously for a free enzyme, the reaction in a batch system was found to be approximately representable as simple first-order kinetics in which the rate constant was dependent on the initial substrate concentration.
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    Biotechnology and Bioengineering 18 (1976), S. 105-118 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Trypsin was covalently immobilized on porous glass in the presence and absence of a specific substrate and reacted in various organic solvents of different dielectric constants. Optimum solvent concentration, pH profile, Km(app), Vmax(app), productivity versus temperature, activity, and reaction rates were determined. Reaction rates of six lysyl dipeptides were compared. Crystalline trypsin was dansylated for studies by nanosecond fluorescence techniques to determine the effects of introducing high concentrations of organic solvents on the molecule. The results indicated that greater reaction rates were observed with dipeptides having more acidic carboxyl terminal groups. The data also indicated that greater reaction rates were observed in higher concentrations of solvents of lower dielectric constants. Nanosecond fluorescence spectroscopy of trypsin in high concentrations of a low dielectric constant solvent indicated major dehydration even though maximal enzyme-activity was achieved under these conditions.
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    Biotechnology and Bioengineering 18 (1976), S. 141-142 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 18 (1976), S. 179-187 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The glucose oxidase and catalase activities immobilized to the γ-aminopropyltriethoxysilane derivative of nickel-impregnated silica alumina was controlled by several factors. The most important of these was enzyme concentration. In constructing the dual immobilized enzyme catalyst, competition between the two enzymes for available binding sites was observed. The order of addition of the various reactants during immobilization was also important. Higher glucose oxidase activities were immobilized when glutaraldehyde was added concurrently with the enzyme, while maximal coupling of catalase occurred if glutaraldehyde was first added to react with the amino derivative of the silica alumina support, excess reagent washed away, and then the catalase added. Bovine serum albumin, which aids in the crosslinking of glucose oxidase, hindered the coupling of the enzyme to the support particles.
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    Biotechnology and Bioengineering 18 (1976), S. 239-252 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Monod's model is often assumed to describe the kinetics of feeding of a protozoan population on a bacterial population in a chemostat. An earlier study (J. L. Jost et al., J. Bacteriol, 113, 84 (1973)) of the feeding of Tetrahymena pyriformis on either Escherichia coli or Azotobacter vinelandii found that this model correctly predicted the occurrence of sustained oscillations of population densities but made predictions of minimum bacterial population densities that were much smaller than those observed. The earlier study removed the discrepancy between the model and data by replacing Monod's model with a different model. It is shown in the present study that the discrepancy can be explained equally as well if Monod's model for the feeding relation is retained and if, in addition, growth of bacteria on the chemostat walls is allowed for in the model equations.
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    Biotechnology and Bioengineering 18 (1976), S. 269-272 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 18 (1976), S. 273-279 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 18 (1976), S. 285-286 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 281-284 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 18 (1976) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 289-295 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: The influence of pH and temperature on the substrate yield coefficient for growth of Saccharomyces cerevisiae in a chemostat under limited organic substrate conditions was studied.Mathematical analysis of the substrate yield coefficient as a function of pH and temperature in the near-optimal area was made. It was shown that the location of pH and temperature optima were independent of each other. The maximum substrate yield coefficient had the following coordinates: pH = 4.1, temperature = 28.5°C.
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    Biotechnology and Bioengineering 18 (1976), S. 297-309 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Cells of Candida utilis grown in a single-stage chemostat at D = 0.05, 0.1, 0.25, and 0.35 hr-l were separated into a fraction of scar-bearing mother cells and a fraction of scar-free daughter cells. The scar-free cells were transferred into small batch cultures where the length of the maturation phase, changes in length and width of cells, specific growth rate, and specific rate of RNA and protein synthesis were examined for 5 hr. The daughter cells grown at D = 0.05 hr-1 were very small at the moment of separation from the mother cells (about one-third of the mother cell). Their maturation phase (in a batch culture), at the beginning of which they attain the specific growth rate approaching the μmax of the strain used, lasts for 3 hr. On the other hand, daughter cells grown at D = 0.35 hr-1 are almost the same size as the mother cells at the moment of separation. After transfer to a batch culture they begin to bud almost immediately. Similarly, in their other morphological and physiological parameters they differ strikingly from immature daughter cells which are formed at low specific growth rates. The importance of these differences from the point of view of mathematical modeling of growth processes is discussed.
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    Biotechnology and Bioengineering 18 (1976), S. 311-332 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Grazing of the ciliate Colpoda steinii on the blue-green alga Anacystis nidulans has been studied in batch and chemostat type laboratory cultures. Growth of the populations, grazing of the ciliates on the algae, hydrodynamic washout of the populations (in chemostat cultures), encystment of Colpoda, and transfer of cysts from the liquid culture to the vessel wall and their attachment thereto were all found to have significant effects on the dynamics of this system. In addition, reinoculation of the liquid with ciliates excysted from the wall and with algae detached from the wall may be important. The interaction of all of these processes produces quite complex dynamical phenomena which at present cannot be predicted by a model. The results obtained differ from those found earlier for feeding of ciliates or slime mold amoebas on bacteria in that steady states of coexistence, rather than sustained oscillations, were exhibited by the present system.
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    Biotechnology and Bioengineering 18 (1976), S. 333-348 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Experiments on the grazing of the ciliate Colpoda steinii on the blue-green alga Anacystis nidulans showed, among other things, that declines of the algal population initiated by grazing often continued for several days after grazing pressure had been released. In addition, long lags were observed when this alga was inoculated into sterile culture medium. Evidence presented in this study indicates that both phenomena were due to cellular damage caused by exposure of algal cells to a sudden increase of light intensity (“light shock”). The occurrence of light shock appeared to exert a destabilizing influence on the grazing relation between Colpoda and Anacystis.
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    Biotechnology and Bioengineering 18 (1976), S. 349-362 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Enzymes are generally sensitive to temperature changes. Porous glass particles used for glucoamylase immobilization are poor thermal conductors and a non-uniform temperature distribution can conceivably develop in a packed bed reactor of immobilized glucoamylase on porous beads. This study was made to determine experimentally the temperature and concentration profiles in an immobilized glucoamylase column. This work provides a procedure for examining possible heat effects on reactor column performance in enzyme applications.
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    Biotechnology and Bioengineering 18 (1976), S. 383-387 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A proposed substrate inhibition model (M. C. Tseng and M. Wayman, Can. J. Microbiol., 21, 994 (1975)), (1)\documentclass{article}\pagestyle{empty}\begin{document}$$\mu = \mu _{\max} S/\left[{K + S} \right],{\rm when}S 〈 S_\theta $$\end{document} (2)\documentclass{article}\pagestyle{empty}\begin{document}$$\mu = \mu _{\max} S/\left[{K + S} \right] - i\left[{S - S_\theta} \right],{\rm when}S 〉 S_\theta $$\end{document} derived from yeast growth rates has been applied to data for bacterial growth: Pseudomonas methanica grown on methanol and Arthrobacter AK19 grown on n-butanol. The model represents the experimental data very well.
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    Biotechnology and Bioengineering 18 (1976), S. 389-413 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Partially purified glucose isomerase from a Streptomyces species was immobilized on porous glass particles and studied for various characteristics concerning its use as an industrial catalyst. The activities were investigated in relation to the reaction parameters and the enzyme deactivation was studied systematically under various reaction conditions. The half-life of the immobilized enzyme was found to exceed 200 days at 50°C. The rate equation of the reversible glucose ⇄ fructose reaction was derived and the kinetic constants were determined. The rate equation was found to be in good agreement with experimental data for both forward and reverse reactions. The degree of diffusional effects was experimentally measured and theoretically analyzed.
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    Biotechnology and Bioengineering 18 (1976), S. 363-382 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Five cell lines (BSC-1, CHO, Balb/c 3T3, HeLa, and KB) have been grown in serum-free media for several months with regular schedules of media changing and subculturing. The medium found to be successful in all cases was MEM-α (without the ribosides and deoxyribosides) supplemented with 1% bactopeptone, although simple MEM [minimum essential medium (Eagle)] with bactopeptone (BP) gave fairly good growth in the case of BSC-1 and 3T3 cells. The addition of insulin was necessary for CHO, 3T3, HeLa, and KB cells. Only the BSC-1 cells grew exclusively as a monolayer in the serum-free systems, the CHO, HeLa, and KB cells growing as stationary suspensions and the 3T3 cells growing as a combination of monolayer and suspension depending on the age of the culture and the nature of the growth surface. SV40 was produced in BSC-1 cells grown and infected in the MEM-α, bactopeptone medium and adenovirus-2 was produced in spinners of HeLa and KB cells grown in MEM-α, bactopeptone, PVP-360, and insulin. The yield of virus and infectivity of the viruses produced were about the same as those produced in conventional serum-containing systems.
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    Biotechnology and Bioengineering 18 (1976), S. 421-424 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 415-420 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: A series of baker's yeast continuous cultivations were made using different intensities of aeration. The experimental conditions were such as to eliminate the effects caused by high glucose concentrations in the medium on the formation of enzymes. The variation in activity of several enzymes was investigated and distinct changes were noted. The activities of hexokinase and alcohol dehydrogenase characterize the actual rate of glycolysis in yeast, the same being true, in part, for pyruvate decarboxylase. The activity of phosphofructokinase is nearly insensitive to the oxygen level at normal tensions. The activity of the cell to the phosphofructokinase can be limited in anaerobic conditions by its scarcity. The insensitivity of glucose-6-phosphate dehydrogenase to the oxygen tension together with its low activity suggests that this enzyme plays primarily a biosynthetic role and that the function of the pentose phosphate pathway as an energy-producing route is negligible.
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    Biotechnology and Bioengineering 18 (1976), S. 425-432 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 18 (1976), S. 433-438 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 18 (1976), S. 448-448 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 439-443 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 18 (1976), S. 445-447 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976) 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 449-463 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The disintegration by freeze-pressing of a low concentration of Saccharomyces cerevisiae suspended in aqueous solutions of gelatin and different salts has been studied at different temperatures. In the freeze-pressing process deionized water and salt solutions flow in pulses, whereas samples with increasing concentrations of gelatin or cells tend to flow more smoothly. This smooth flow enhances the disruption efficiency particularly at lower temperatures, which seems to be of great practical importance. The addition of salts also promotes disintegration. The presence of both gelatin and salts works antagonistically on disintegration presumably because of different modes of action at disruption of cells.
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    Biotechnology and Bioengineering 18 (1976), S. 465-471 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Cell survival curves have been obtained for Escherichia coli B (E. coli B) after the sonication of suspensions of the bacteria with continuous wave ultrasound at a fixed frequency of 2 MHz between peak intensities of 8.7 and 2.25 W cm-2. It was found that under suitable conditions the survival curves were reproducible and it also was found that there was a clear relationship between the rate of inactivation and the peak acoustic intensity of the ultrasound. There appeared to be a lower threshold of peak intensity below which no inactivation was observed.
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    Biotechnology and Bioengineering 18 (1976), S. 473-492 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: The relationships between the specific rate of nutrient consumption and biomass growth and between the specific rate of penicillin production and oxygen concentration in the broth are analyzed.The functional dependencies which have been obtained from the experimental data of industrial fermenters are used with the mass balances to develop a model of the behavior of semicontinuous operations. The proposed model allows one to study the influence of some operational parameters.The obtained results agree with the data of industrial processes.
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    Biotechnology and Bioengineering 18 (1976), S. 493-512 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: The role of fundamental parameters in the conduction of penicillin semicontinuous fermentations is analyzed. Biomass concentration, penicillin production, and main nutrient consumption are particularly studied. Furthermore, the conduction of the operation is simulated with regard to conditions of constant specific rate of growth and of constant oxygen concentration in the broth. An intermediate condition is also considered.
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    Biotechnology and Bioengineering 18 (1976), S. 581-585 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 513-526 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: The mixed culture of Lactobacillus plantarum and Propionibacterium shermanii grown anaerobically in glucose minimal medium exhibits features typical of a commensal interaction even though a number of complicating factors, such as a large maintenance requirement of L. plantarum and inhibition of growth of P. shermanii at low pH, are present. A simple mathematical model of the system is presented and is shown to reproduce rather well some of the features of the continuous mixed culture system in both steady-state and transient situations.
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    Biotechnology and Bioengineering 18 (1976), S. 527-543 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The potential of sand as a support for immobilized enzymes was investigated by preparing alkylamine sand and devising methods to measure the total number of amine groups present and the fraction available for immobilization of enzymes. Alcohol dehydrogenase (alcohol:NAD oxidoreductase, EC 1.1.1.1) and lactate dehydrogenase (L-lactate: NAD oxidoreductase, EC 1.1.1.27) were immobilized on alkylamine sand, and the stability of the immobilized protein and dehydrogenase activity was measured. Urease (urea amidohyrdrolase, EC 3.5.1.5) was also immobilized on sand to test the applicability of these methods to larger scale immobilizations. Results suggest that sand shows promise as a support for immobilized enzymes.
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    Biotechnology and Bioengineering 18 (1976), S. 545-580 
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    Notes: Protein solubility can be adequately represented by the classical Cohn equation for the salting-out of alcohol dehydrogenase and fumarase from clarified yeast homogenate with ammonium sulfate. However, the constant β in this equation is a function of the contacting procedure employed. The kinetics of continuous salting-out were similar for alcohol dehydrogenase and fumarase. The overall rate equation for precipitation had a variable order which was high initially, up to 3.1, but approached unity on completion of precipitation. This was followed by a partial resolution stage which was first order with respect to the concentration driving force. Precipitate particle size was estimated as 0.5 to 5 μm with continuous flow precipitation producing the largest particles.
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    Biotechnology and Bioengineering 18 (1976), S. 587-590 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 591-593 
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    Biotechnology and Bioengineering 18 (1976), S. 599-600 
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    Biotechnology and Bioengineering 18 (1976), S. 595-598 
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    Biotechnology and Bioengineering 18 (1976) 
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    Biotechnology and Bioengineering 18 (1976), S. 601-621 
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    Notes: The production of cholesterol oxidase by 3 liter batch cultures of Nocardia rhodocrous growing on a glycerol/yeast extract medium was investigated. Cholesterol was shown to be a good inducer of the enzyme. The optimum time for cholesterol addition and the quantity to be added were determined, resulting in a 15-fold yield increase. Cholesterol oxidase synthesis was influenced by the dissolved oxygen tension. Maximum cholesterol oxidase production was obtained at 30-40% air saturation. The effect of growth conditions on the extraction of cholesterol oxidase by Triton X-100 was investigated. The scale-up of the fermentation to 800 liters in a pilot-plant fermenter is described.
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    Biotechnology and Bioengineering 18 (1976), S. 633-648 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: Using whole cells containing glucose isomerase, mathematical models for the enzymatic conversion of D-glucose to D-fructose and for the inactivation of the enzyme catalyst have been postulated and verified experimentally. The heat of reaction, the equilibrium constant, and the individual rate constants and their activation energies have been estimated. The model can be used to predict the time course for the enzymatic production of fructose in a batch reactor within the tested experimental range of 40-80°C.
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    Biotechnology and Bioengineering 18 (1976), S. 623-632 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: The authors studied the influence of periodic variations (one cycle per 24 hr) of the feeding mash concentration of a continuous anaerobic culture of Saccharomyces cerevisiae in sugarcane molasses media at constant dilution rate. It was observed that the average yield coefficients during the transient state were practically equal to the yield coefficient obtained during steady-state experiments. It was also observed, in each experiment, that the average specific growth rate during the transient state was equal to the dilution rate.
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    Biotechnology and Bioengineering 18 (1976), S. 649-657 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In view of the advantages which are associated with the use of the BHK monolayer cell for the production of foot-and-mouth disease (FMD) virus, a unit system using glass spheres was developed to grow BHK monolayer cells and to test the susceptibility of such cells to FMD virus. The yield of cells and their susceptibility compares favorably with BHK monolayer cells which have been grown in Roux bottles.
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    Biotechnology and Bioengineering 18 (1976), S. 659-667 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: Methods are described which make possible the production of foot-and-mouth disease (FMD) virus from BHK 21 C13 monolayer cells which have been grown on the surface of serum coated DEAE Sephadex A50 beads. The yield of cells and their susceptibility to infection by FMD virus are equivalent to conventional Roux monolayer systems. The potential for the commercial application of the DEAE Sephadex A50 system is discussed in relation to other unit process monolayer systems and in particular to the system in which cells are cultured in a deep bed of small glass spheres.
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    Biotechnology and Bioengineering 18 (1976), S. 685-699 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Urease from Jack bean was immobilized on nonporous glass beads by covalent bonding and its kinetics were studied in a packed-column differential reactor. To facilitate comparison, the urease was immobilized by both diazo and glutaraldehyde coupling. The kinetic properties of immobilized urease were similar to those of the soluble enzyme and different immobilization methods did not appreciably alter the kinetic properties. The affects of three different amino acid activators appear to follow predictions obtained from a relatively simple competitive model, except at very low substrate levels.
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    Biotechnology and Bioengineering 18 (1976), S. 669-684 
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    Notes: Glucose oxidase from Aspergillus niger was immobilized on nonporous glass beads by covalent bonding and its kinetics were studied in a packed-column recycle reactor. The optimum pH of the immobilized enzyme was the same as that of soluble enzyme; however, immobilized glucose oxidase showed a sharper pH-activity profile than that of the soluble enzyme. The kinetic behavior of immobilized glucose oxidase at optimum pH and 25°C was similar to that of the soluble enzyme, but the immobilized material showed increased temperature sensitivity. Immobilized glucose oxidase showed no loss in activity on storage at 4°C for nearly ten weeks. On continuous use for 60 hr, the immobilized enzyme showed about a 40% loss in activity but no change in the kinetic constant.
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    Biotechnology and Bioengineering 18 (1976), S. 723-727 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 729-735 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: In previous reports from this laboratory it has been shown that the extended aeration process for biological treatment of organically laden municipal and/or industrial waste could be successfully employed for concurrent purification and sludge disposal. Also results using a modified process in which autodigestion was aided and controlled by periodic partial hydrolysis of small portions of the recycle sludge showed that operational control was feasible. There was some question regarding the success of such a process if the original waste contained a large portion of inorganic solids. Accordingly, a 1½ year pilot plant study was made using a waste (hydrolyzed trickling filter sludge) of exceptionally high ash content (50-60%). It was found that the ash content of activated sludge grown on this substrate did not continually increase nor did the high ash content of the waste interfere in any way with the efficiency of removal of organic matter. In general it exceeded 90 percent. Also a highly nitrified effluent was produced. A variety of analyses were performed: COD, BOD, TOC, suspended solids, NH3-N, organic-N, NO3-N, etc. Interrelationships between these important monitoring parameters for assessing plant performance offered useful insight into operational control for hydrolytically assisted extended aeration processes.
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    Biotechnology and Bioengineering 18 (1976), S. 737-739 
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    Biotechnology and Bioengineering 18 (1976), S. 741-743 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976) 
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    Biotechnology and Bioengineering 18 (1976), S. 745-790 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 18 (1976), S. 791-804 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A model is proposed that accounts for the decreases in yield which occur in chemostat cultures of mesophilic yeasts at superoptimal growth temperatures. Two yield depressing effects were identified, one due to increased maintenance requirements by the viable fraction of the population, the other due to energy substrate dissipation by the nonviable fraction. The two effects are functions of the dilution rate, as is the fraction of nonviable cells. Experimental results were obtained on the yield, maintenance, and dissipation of energy substrate in a glucose-limited chemostat culture of a respiration-deficient mutant of Saccharomyces cerevisiae at 39°C. The rates of glucose utilization for maintenance and for dissipation constituted, respectively, 33-28% and 15-9% of the total glucose utilization rate over the range of dilution rates tested (0.038-0.064 hr-1), while the yield varied over this range from 0.066-0.085 g of biomass (dry wt) per gram of glucose.
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    Biotechnology and Bioengineering 18 (1976), S. 805-812 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: The models of Monod and Williams, for the growth of unicellular organisms in chemostats, give strongly damped transients in the biomass and cell number when the flow rate of the chemostat is changed. A simple trick is used to incorporate time delay in these models while still allowing a conventional stability analysis. For long enough time delays the equilibrium point is unstable and limit cycles can be computed. Results obtained using Williams' model, with weakly damped transients as a result of using moderately long time delay, are compared with his data in which cell numbers show weak damping but biomass shows strong damping.
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    Biotechnology and Bioengineering 18 (1976), S. 839-846 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An efficient method to grow Escherichia coli W to high cell concentrations on the pilot scale is described and discussed. The method involves growth linked introduction of glucose; and ammonia to the culture, sparing with oxygen, and maintenance of aerobic conditions by gradually decreasing the temperature in the culture in order to keep the oxygen demand within the limits of the capacity of supply. Under these conditions the linear rate of cell mass production is actually the result of exponential growth with a gradually decreasing growth-rate constant.About 10 kg packed cells were produced in a 50 liter working-volume fermentor in one run of 13 hr. The concentration of the cells at the end of the growth was about 47 g dry cells/liter. The expenditure for nutrients was minimal and the controls were of simple automatic nature. From the determined yield constants for glucose, nitrogen, phosphorus, and oxygen it may be inferred that the cells grown by this method are similar to those grown exponentially at constant temperature.
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    Biotechnology and Bioengineering 18 (1976), S. 813-837 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An analytical expression for the rate efficiency factor of planar localized enzyme systems is derived. The derivation takes into account the isothermal kinetic effect under the externally imposed perturbation of combined electrostatic and high frequency time-varying fields. The contribution of each individual field to the enzyme reaction is examined through the basic mechanism in which charged substrates interact, with the specific perturbing field. The interaction mechanisms for the electrostatic and for the time-varying fields are found to be different. This difference regulates the different manners in which enzymatic reaction rates are altered. Enzymatic reactions under electrostatic perturbation can be retarded or enhanced depending on the field polarization. At sufficiently high field intensities the reaction rate may approach zero or approach a maximum value equal to the turnover number of the enzyme. Time-varying field perturbations, on the other hand, always enhance the enzymatic reactions if bunching effects are negligible. At sufficiently high field intensities, the reaction may approach a value equal to that of the free enzyme system. Several typical numerical examples on pure electrostatic field perturbations, pure time-varying field perturbations, and combined field perturbations are also presented.
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    Biotechnology and Bioengineering 18 (1976), S. 847-864 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This work is concerned with the optimization study of the semibatch fermentation by which an amino acid is produced. The particular fermentation studied is the synthesis of lysine by the auxotrophic mutant. Applying Green's theorem to the maximization problem was proposed, and it succeeded in determining the feed rate of the substrate that maximized the production rate of the desired product.
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  • 90
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 18 (1976) 
    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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  • 91
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    Biotechnology and Bioengineering 18 (1976), S. 865-883 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The pressure required for initiation of flow when freeze-pressing with the X-press is related to the phase boundaries of water, particularly those between ice I and liquid even at temperatures around -25°C and lower. Widening the orifice of the pressure chamber to diameters larger than 2.5 mm leads to lower pressures and less extensive cell disintegration.Pressing Saccharomyces cerevisiae slowly with the aid of a manual hydraulic jack at -25°C produces a disintegration of 60-75% irrespective of cell concentration. Pressing at -35°C shows no clear differences.Pressing more rapidly with the aid of a motor-driven hydraulic press produces a similar extent of disruption of diluted cell suspensions (5.4 mg/g) as slow pressing. However, freeze-pressing a paste of baker's yeast (270 mg/g) increases the degree of disintegration. Under these conditions the disintegration is further enhanced by a lower temperature, -35°C, and by a high velocity of flow through the orifice, such that more than 95% of the S. cerevisiae is disrupted by one pressing at less than 2 × 108 Pa.Mechanisms for flow through the X-press are suggested and discussed in relation to the phase diagram of water.
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  • 92
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    Biotechnology and Bioengineering 18 (1976), S. 889-890 
    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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  • 93
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    Biotechnology and Bioengineering 18 (1976), S. 885-887 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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  • 94
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    Biotechnology and Bioengineering 18 (1976), S. 909-919 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The characteristic flavor of hard Italian cheeses is associated with the presence of fatty acids, particularly butyric acid, liberated from milk fat during the ripening process. To ensure proper development and control of flavor, animal pregastric esterases or lipases are routinely added to the milk before coagulation of the curd. Such esterases are also used to generate flavor in enzyme modified cheese and other dairy products.Esterases from microbial sources have been investigated as agents to enhance flavor in cheese. We have found that an esterase from Mucor miehei exhibits the type of lipolytic activity needed for this application. Romano and fontina cheeses of excellent quality have been prepared by the use of this esterase. It has also been used successfully in the preparation of enzyme modified cheese, and, in turn, processed American cheese.
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  • 95
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 18 (1976), S. 921-925 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study illustrates approaches using botanical proteinases and a pancreatic lipase to improve the palatability of two types of food. A third example is presented to illustrate the use of a chelating agent in growing corn to increase the sugar content by over 50%, presumably by influencing enzyme activity in the corncob itself. The purpose is to show that one is not limited to using only the microbial approach for producing flavors but to point out the broader concept of food palatability which includes texture and flavor.
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  • 96
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    Biotechnology and Bioengineering 18 (1976), S. 891-907 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: There are four main sources of enzymes in foods - these being the inherent enzymes, enzymes from microbial contaminants, enzymes elaborated by microorganisms added to foods, and specific enzymes added to foods. This study primarily deals with the latter two sources of enzymes in food. Although both plants and animals serve as sources of enzymes, they are not as economical or versatile sources as are enzymes obtained from microorganisms. In the meat industry, proteases are used to tenderize muscle and to obtain flavor precursors. In the preparation of cured meat products such as sausages, lipases, and proteases from bacterial cultures are utilized. Similarly, proteases and lipases are used in the dairy industry to develop flavor compounds. Proteases and amylases also have applications in the baking and milling industries where they are used to produce precursors for the nonenzymatic browning reactions. Carbohydrases such as amylase, amyloglucosidase, and glucose isomerase have found usage in the starch and syrup industry for the production of high dextrose and high fructose syrups. Other enzymes such as glucose oxidase, pectinase, and naringinase are of value to the wine and fruit juice industries. A better understanding of the mode of action of enzymes as well as the mechanisms of development of flavor compounds will further enhance the use of microbial enzymes to develop specific and desired flavors in foods.
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  • 97
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    Biotechnology and Bioengineering 18 (1976), S. 927-938 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The development of the unique flavor of blue type cheese depends on the concerted action of numerous enzymes of Penicillium roqueforti involved in protein and lipid metabolism. Protease(s) by degrading casein modify the texture and background flavor of the ripening cheese. Lipase by hydrolyzing milk triglycerides provides flavorful fatty acids and precursors of methyl ketones. The enzyme complex involved in the partial oxidation of free fatty acids and the properties of β-ketoacyl decarboxylase which generates the major flavor components of blue cheese are discussed. Fermentation of P. roqueforti for the rapid production of methyl ketones is briefly reviewed.
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  • 98
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 19 (1977), S. 1091-1094 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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  • 99
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    Biotechnology and Bioengineering 19 (1977), S. 1115-1123 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Trypsin was coupled on an agarose gel which was modified with a spiropyran compound. The trypsin-spiropyran (agarose) gel showed reverse photochromism. The activity of the trypsin-spiropyran gel in the dark was 12% of that of native trypsin, and it was higher than that under visible light. The apparent Michaelis constant of the trypsin-spiropyran gel in the dark was larger than that under visible light. On the other hand, the maximum velocity in the dark was higher than that under visible light. The optimum pH of the trypsin-spiropyran gel in the dark was the same as that under visible light. Immobilized trypsin was stable in the pH range from 3 to 9. The trypsin-spiropyran gel was more stable against heat than the native trypsin.
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  • 100
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    Biotechnology and Bioengineering 19 (1977), S. 1125-1143 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cell recycle and vacuum fermentation systems were developed for continuous ethanol production. Cell recycle was employed in both atmospheric pressure and vacuum fermentations to achieve high cell densities and rapid ethanol fermentation rates. Studies were conducted with Saccharomyces cerevisiae (ATCC No. 4126) at a fermentation temperature of 35°C. Employing a 10% glucose feed, a cell density of 50 g dry wt/liter was obtained in atmospheric-cell recycle fermentations which produced a fermentor ethanol productivity of 29.0 g/liter-hr. The vacuum fermentor eliminated ethanol inhibition by boiling away ethanol from the fermenting beer as it was formed. This permitted the rapid and complete fermentation of concentrated sugar solutions. At a total pressure of 50 mmHg and using a 33.4% glucose feed, ethanol productivities of 82 and 40 g/liter-hr were achieved with the vacuum system with and without cell recycle, respectively. Fermentor ethanol productivities were thus increased as much as twelvefold over conventional continuous fermentations. In order to maintain a viable yeast culture in the vacuum fermentor, a bleed of fermented broth had to be continuously withdrawn to remove nonvolatile compounds. It was also necessary to sparge the vacuum fermentor with pure oxygen to satisfy the trace oxygen requirement of the fermenting yeast.
    Additional Material: 9 Ill.
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