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

Abstract

Fermentation of glucose in ethanol by both <i>Saccharomyces cerevisiae</i> and <i>S. bayanus</i> 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 <i>S. cerevisiae</i>, we discussed the substrate-inhibition on the basis of intracellular ethanol accumulation, and we made the comparison between <i>S. cerevisiae</i> and <i>S. bayanus</i>. The higher tolerance to glucose and ethanol of <i>S. bayanus</i> apparently is not related to a higher growth rate or a higher specific ethanol production rate: glucose and ethanol sensitivity, more pronounced in <i>S. cerevisiae</i>, is likely due to a higher intracellular accumulation of ethanol.