MAXIMIZATION OF CANDIDA-UTILIS CYTOCHROMES BY PULSE ADDITIONS OF ETHANOL TO CONTINUOUS CULTURES

Candida utilis was grown with glucose as growth‐limiting carbon source in batch culture, steady‐state continuous culture, and non‐steady‐state continuous culture. High cytochrome concentrations were routinely recorded in cells harvested in the latter stages of batch culture. They were occasionally recorded in cells from imprecisely controlled steady‐state cultures, but precise control of the steady‐state dissolved oxygen tension stabilized the cytochromes at relatively low levels. Controlled non‐steady‐state continuous cultures, imposed by pulse additions of ethanol, routinely produced cells with high cytochrome concentrations. A mechanism is proposed whereby maintenance of cytochrome derepression in continuous culture is dependent upon indefinitely prolonging an “overshoot” response in gene expression. Copyright © 1979 John Wiley & Sons, Inc.