Biochemistry and Biotechnology
Wiley InterScience Backfile Collection 1832-2000
Process Engineering, Biotechnology, Nutrition Technology
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.
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