Effect of Initial Substrate Concentration on Two Wine Yeasts: Relation Between Glucose Sensitivity and Ethanol Inhibition

Fermentation of glucose in ethanol by both Saccharomyces cerevisiae and S. bayanus was studied anaerobically in batch cultures. Studies were made of kinetic and stoichiometric parameters — specific growth rate, rate of ethanol production, biomass, and ethanol yields — as a function of initial substrate concentration. Taking into account results previously obtained on the intracellular ethanol accumulation in S. cerevisiae, we discussed the substrate-inhibition on the basis of intracellular ethanol accumulation, and we made the comparison between S. cerevisiae and S. bayanus. The higher tolerance to glucose and ethanol of S. bayanus apparently is not related to a higher growth rate or a higher specific ethanol production rate: glucose and ethanol sensitivity, more pronounced in S. cerevisiae, is likely due to a higher intracellular accumulation of ethanol.