EFFECTS OF ETHANOL AND ACETIC-ACID ON THE TRANSPORT OF MALIC-ACID ANDGLUCOSE IN THE YEAST SCHIZOSACCHAROMYCES-POMBE - IMPLICATIONS IN WINEDEACIDIFICATION

Ethanol and acetic acid, at concentrations which may occur during wine -making, inhibited the transport of L-malic acid in Schizosaccharomyce s pombe. The inhibition was non-competitive, the decrease of the maxim um initial velocity following exponential kinetics. Glucose transport was not significantly affected either by ethanol (up to 13%, w/v) or b y acetic acid (up to 1.5%, w/v). The uptake of labelled acetic acid fo llowed simple diffusion kinetics, indicating that a carrier was not in volved in its transport. Therefore, the undissociated acid appears to be the only form that enters the cells and is probably responsible for the toxic effects. Accordingly, deacidification by Ss. pombe during w ine fermentation should take place before, rather than after, the main alcoholic fermentation by Saccharomyces cerevisiae.