ALCOHOL FERMENTATION - EFFECT OF TEMPERATURE ON ETHANOL ACCUMULATION WITHIN YEAST-CELLS

Abstract

During fermentation, yeast growth is rapidly stopped when the concentration of alcohol in the medium increases but fermentive activity is not entirely inhibited until high alcohol concentrations are reached. The rate of alcohol accumulation within the cells and certain kinetic parameters were simultaneously determined in such fermentative processes using Saccharomyces carlsbergensis cells. The growth inhibitory effect of alcohol was related to its retention within the cells; i.e., yeast multiplication is stopped when intracellular alcohol concentration reaches a maximum value. Moreover, the higher the temperature, the deeper the inhibitory effect of ethanol and the higher the maximal intracellular alcohol concentration. Activation energy determinations showed that ethanol accumulation within the cells was a consequence of the resistance to its diffusion through the cell wall from within to outside the cell.