Physiological, biochemical, and mathematical studies of micro‐aerobic continuous ethanol fermentation by Saccharomyces cerevisiae. II: Intracellular metabolite and enzyme assays at steady state chemostat cultures

Intracellular metabolite concentration and enzyme activity measurements were made to explain the new metabolic and growth phenomena seen in the micro‐aerobic, continuous yeast cultures described in Part I. The results of these assays suggested mechanisms for the observed maximum in the specific ethanol productivity as a function of the oxygen feed rate, changing ATP yields, the effects of antifoam, and the sharp changes in the biomass concentration with small changes in the oxygenation. Measured were the intracellular concentrations of ATP, NADH, glucose 6‐phosphate, pyruvate, glycerol, and ethanol, and the activities of hexokinase and alcohol dehydrogenase. Rate‐limiting steps were identified by the accumulation of metabolites upstream and the depletion of metabolites downstream of the step.

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