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  • 1
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of four pH steps and one dilution rate step are described for an ammonia-nitrogen-limited continuous culture of Escherichia coli B/r. Two of the pH steps, 6.06-5.49 and 5.96-5.60, led to prolonged transients in both cell density and rate-limiting nutrient concentration. The other two pH steps, 6.20-5.96 and 5.60-6.20, had almost no effect on the culture. The dilution rate step led to a sharp transition in the steady-state external pyruvate concentration. Monitoring of the external pyruvate concentration for the pH 5.96-5.60 step revealed that the transient phase continued long after the cell density and rate-limiting nutrient concentration returned to steady-state values. The implications for industrial and laboratory fermentations are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fed-batch cultures were performed to maximize the α-amylase activity in a bioreactor. Kinetic equations containing a catabolite repression effect were used to model the enzyme formation from Bacillus amyloliquefaciens. Fed-batch culture experiments were performed using maltose to implement the optimal feeding strategy. Optimal fed-batch culture based on sequential parameter estimation was performed successfully using off-line analysis while the fermentation was in progress. The enzyme activity from the fed-batch culture employing maltose was higher than that of the batch culture by 60%. Enzyme production using starch showed similar trends to those obtained using maltose.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 22 (1980), S. 89-106 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Three feedback strategies for the on-line control of cell densities in a mixed-culture system have been examined. A competitive mixed-culture system of Candida utilis and Corynebacterium glutamicum grown on glucose as the limiting carbon source was modeled using Monod growth kinetics. First-order time constants were added to simulate transient growth effects. Multivariable feedback control of cell densities by manipulation of substrate feed and dilution rate was investigated. Feedback strategies directed to minimizing control interactions were found to be superior to classical feedback. Transients in the growth-rate response produced oscillations in cell density and required retuning of control constants. The relative time constants of the two species were important, with the largest oscillations resulting when the faster growing organism had the faster time constant.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The yeast Candida utilis and the bacterium Escherichia coli B/r were evaluated as a candidate experimental, continous, competitive mixed culture system under ammonia-nitrogen limited conditions at 30°C. High dilution rates favored yeast dominance, while low dilution rates favored bacterial dominance. The hydrogen ion concentration was also demonstrated to be an effective manipulative variable for control of the yeast-bacterial mixed culture. Through trial-and-error manipulation of the pH for the mixed culture operating at constant dilution rate, it was possible to locate a metastable equilibrium point and to operate in the vicinity of that point for more than 24h. The reproducible emergence of a variant E. coli was also noted in this study.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Techniques are reviewed for the identification and enrichment of fimbriae-positive and fimbriae-negative Escherichia coli. Fimbriae-positive E. coli were observed to form a semistable suspension of pH 7.0 which settled at a rate much slower than the fimbriae-negative bacteria. Intense autoflocculation of fimbriae-positive E. coli was noted at pH values below 5.2.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The microbial production of α-amylase from Bacillus amyloliquefaciens was investigated. The microorganism was grown using media containing glucose or maltose at 37°C and under aerobic conditions in a 16-L fermentor. The α-amylase synthesis from maltose was not found to be inducible but was found to be subject to catabolite repression. The maltose uptake rate was observed to be the rate-limiting step compared to the conversion rate of maltose to glucose by intracellular α-glucosidase. The α-amylase activity achieved with maltose as a substrate was higher than that achieved with glucose. A slower growth rate and a higher cell density were obtained with maltose. The enzyme production pattern depended upon the nutrient composition of the medium.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The control of the continuous, competitive mixed culture of the yeast Candida utilis (ATCC 8205) and the bacterium Escherichia coli B/r (ATCC 12407) was examined. A modified version of the dynamic matrix control (DMC) algorithm was tested in simulation and then was successfully implemented. This represents the first report of the location and stabilization of a competitive mixed culture at a metastable equilibrium point using automatic control.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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