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  • 1
    Electronic Resource
    Electronic Resource
    Cell recycling studies for α-amylase production by Bacillus amyloliquefaciens (1995)
    Springer
    Bioprocess and biosystems engineering 14 (1995), S. 23-31 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Production of α-amylase by a strain of Bacillus amyloliquefaciens was investigated in a cell recycle bioreactor incorporating a membrane filtration module for cell separation. Experimental fermentation studies with the B. amyloliquefaciens strain WA-4 clearly showed that incorporating cell recycling increased α-amylase yield and volumetric productivity as compared to conventional continuous fermentation. The effect of operating conditions on α-amylase production was difficult to demonstrate experimentally due to the problems of keeping the permeate and bleed rates constant over an extended period of time. Computer simulations were therefore undertaken to support the experimental data, as well as to elucidate the dynamics of α-amylase production in the cell recycle bioreactor as compared to conventional chemostat and batch fermentations. Taken together, the simulations and experiments clearly showed that low bleed rate (high recycling ratio) various a high level of α-amylase activity. The simulated fermentations revealed that this was especially pronounced at high recycling ratios. Volumetric productivity was maximum at a dilution rate of around 0.4 h−1 and a high recycling ratio. The latter had to exceed 0.75 before volumetric productivity was significantly greater than with conventional chemostat fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369849
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Enzyme production in a cell recycle fermentation system evaluated by computer simulations (1995)
    Springer
    Bioprocess and biosystems engineering 13 (1995), S. 59-68 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Enzyme production in a cell recycle fermentation system was studied by computer simulations, using a mathematical model of α-amylase production by Bacillus amyloliquefaciens. The model was modified so as to enable simulation of enzyme production by hypothetical organisms having different production kinetics at different fermentation conditions important for growth and production. The simulations were designed as a two-level factorial assay, the factor studied being fermentation with or without cell recycling, repression of product synthesis by glucose, kinetic production constants, product degradation by a protease, mode of fermentation, and starch versus glucose as the substrate carbon source. The main factor of importance for ensuring high enzyme production was cell recycling. Product formation kinetics related to the stationary growth phase combined with continuous fermentation with cell recycling also had a positive impact. The effect was greatest when two or more of these three factors were present in combinations, none of them alone guaranteeing a good result. Product degradation by a protease decreased the amount of product obtained; however, when combined with cell recycling, the protease effect was overshadowed by the increased production. Simulation of this type should prove a useful tool for analyzing troublesome fermentations and for identifying production organisms for further study in integrated fermentation systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00420431
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Production of proteinase A by Saccharomyces cerevisiae in a cell-recycling fermentation system: experiments and computer simulations (1996)
    Springer
    Applied microbiology and biotechnology 44 (1996), S. 724-730 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Overproduction of proteinase A by recombinant Saccharomyces cerevisiae was investigated by cultivations in a cell-recycling bioreactor. Membrane filtration was used to separate cells from the broth. Recycling ratios and dilution rates were varied and the effect on enzyme production was studied both experimentally and by computer simulations. Experiments and simulations showed that cell mass and product concentration were enhanced by high ratios of recycling. Additional simulations showed that the proteinase A concentration decreased drastically at high dilution rates and the optimal volumetric productivities were at high dilution rates just below washout and at high ratios of recycling. Cell-recycling fermentation gave much higher volumetric productivities and stable product concentrations in contrast to simple continuous fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178609
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Production of proteinase A bySaccharomyces cerevesiae in a cell-recycling fermentation system: experiments and computer simulations (1996)
    Springer
    Applied microbiology and biotechnology 44 (1996), S. 724-730 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Overproduction of proteinase A by recombinantSaccharomyces cerevisiae was investigated by cultivations in a cell-recycling bioreactor. Memebrane filtration was used to separate cells from the broth. Recycling ratios and dilution rates were varied and the effect on enzyme production was studied both experimentally and by computer simulations. Experiments and simulations showed that cell mass and product concentration were enhanced by high ratios of recycling. Additional simulations showed that the proteinase A concentration decreased drastically at high dilution rates and the optimal volumetric productivities were at high dilution rates just below washout and at high ratios of recycling. Cell-recycling fermentation gave much higher volumetric productivities and stable product concentrations in contrast to simple continuous fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178609
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Discontinuities in continuous cultures studied with a recombinant Saccharomyces cerevisiae and two computer models (1997)
    Springer
    Bioprocess engineering 18 (1997), S. 35-39 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Chemostat cultures and other continuous cultures, where the feed to the bioreactor was divided in pulses while maintaining the overall dilutions rate by the increased flow in the pulses, were studied by cultivations with Saccharomyces cerevisiae JG176 and by simulations with two computer models, Yeast model SG176 and Yeast model MC176. All three systems gave interesting response surfaces. Deviations from an ideal chemostat may have significant effects on volumetric productivity, which for production of the recombinant protein, proteinase A by Saccharomyces cerevisiae JG176 was positive, while the productivity of biomass and ethanol decreased. In simulations with both models pulsing caused lower production of biomass and ethanol. In simulations with one of the models the effects of pulsing on productivity of a protein were also negative, whereas simulations with the other model suggested clear positive effects of pulsing on a production of a protein though with a somewhat different response surface than with the experiments with Saccharomyces cerevisiae JG176.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008972
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Enzyme production in a cell recycle fermentation system evaluated by computer simulations (1995)
    Springer
    Bioprocess engineering 13 (1995), S. 59-68 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Enzyme production in a cell recycle fermentation system was studied by computer simulations, using a mathematical model of α-amylase production by Bacillus amyloliquefaciens. The model was modified so as to enable simulation of enzyme production by hypothetical organisms having different production kinetics at different fermentation conditions important for growth and production. The simulations were designed as a two-level factorial assay, the factor studied being fermentation with or without cell recycling, repression of product synthesis by glucose, kinetic production constants, product degradation by a protease, mode of fermentation, and starch versus glucose as the substrate carbon source. The main factor of importance for ensuring high enzyme production was cell recycling. Product formation kinetics related to the stationary growth phase combined with continuous fermentation with cell recycling also had a positive impact. The effect was greatest when two or more of these three factors were present in combinations, none of them alone guaranteeing a good result. Product degradation by a protease decreased the amount of product obtained; however, when combined with cell recycling, the protease effect was overshadowed by the increased production. Simulation of this type should prove a useful tool for analyzing troublesome fermentations and for identifying production organisms for further study in integrated fermentation systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00420431
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Cell recycling studies for α-amylase production by Bacillus amyloliquefaciens (1995)
    Springer
    Bioprocess engineering 14 (1995), S. 23-31 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Production of α-amylase by a strain of Bacillus amyloliquefaciens was investigated in a cell recycle bioreactor incorporating a membrane filtration module for cell separation. Experimental fermentation studies with the B. amyloliquefaciens strain WA-4 clearly showed that incorporating cell recycling increased α-amylase yield and volumetric productivity as compared to conventional continuous fermentation. The effect of operating conditions on α-amylase production was difficult to demonstrate experimentally due to the problems of keeping the permeate and bleed rates constant over an extended period of time. Computer simulations were therefore undertaken to support the experimental data, as well as to elucidate the dynamics of α-amylase production in the cell recycle bioreactor as compared to conventional chemostat and batch fermentations. Taken together, the simulations and experiments clearly showed that low bleed rate (high recycling ratio) various a high level of α-amylase activity. The simulated fermentations revealed that this was especially pronounced at high recycling ratios. Volumetric productivity was maximum at a dilution rate of around 0.4 h-1 and a high recycling ratio. The latter had to exceed 0.75 before volumetric productivity was significantly greater than with conventional chemostat fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369849
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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