SUMMARY: When was cultivated in continuous culture, it exhibited the typical growth behaviour of a glucose-sensitive yeast. Metabolic changes related to glucose-repressed growth were assessed by an analysis of overall culture parameters (biomass formation, ethanol and acetate production and gas exchange rates) and by measuring the mitochondrial cytochrome content. These functions were mainly affected by the glucose effect; the steady state values of these variables were first established in the chemostat as a function of dilution rate.

The short- and long-term regulation taking place when the cells were submitted to repression was assessed by administering glucose pulses and by shifts in the dilution rate. The primary response of the cells to the initiation of repressed growth was the formation of ethanol and acetate. Since there was no repression of oxygen uptake rate or cytochrome content prior to this response, it was concluded that ethanol and acetate formation was not the consequence of repression of respiratory activity, but resulted from the regulation of pyruvate dehydrogenase and pyruvate decarboxylase activities. Long-term adaptation of the cells occurred within 24 to 48 h of the initiation of repressed growth as manifested by a decrease of mitochondrial cytochrome content to the steady state value corresponding to that of repressed growth.


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