ETHANOL-INDUCED WATER-STRESS IN YEAST

This review considers the effect of ethanol-induced water stress on ye ast metabolism and integrity. Ethanol causes water stress by lowering water activity (a(w)) and thereby interferes with hydrogen bonding wit hin and between hydrated cell components, ultimately disrupting enzyme and membrane structure and function. The impact of ethanol on the ene rgetic status of water is considered in relation to cell metabolism. E ven moderate ethanol concentrations (5 to 10%, w/v) cause a sufficient reduction of a(w) to have metabolic consequences. When exposed to eth anol, cells synthesize compatible solutes such as glycerol and trehalo se that protect against water stress and hydrogen-bond disruption. Eth anol affects the control of gene expression by the mechanism that is n ormally associated with (so-called) osmotic control. Furthermore, etha nol-induced water stress has ecological implications.