Release of polysaccharides by three strains of Saccharomyces cerevisiae during alcoholic fermentation in synthetic medium and red wine was studied. Polysaccharides after isolation from media by ethanol precipitation were quantified by a colourimetric method as well as by HPLC assay in wines. Yeast strains differed in their capacity to release polysaccharides into the medium and a maximum concentration of 100mg/L was observed. For all strains, release varied according to metabolic phase, with greater release occurring when the yeast mortality rate was high. Mannose was the main component (90%) of these polysaccharides, with the exception of yeast strain BM45 which contained approximatively 50% glucose and 50% mannose. This composition may be related to cell wall composition. The results suggest that polysaccharides can combine with anthocyanins and tannins in wine. This combination seems to increase colour stability and decrease astringency.

Accumulation of ethanol in supernatants from anaerobic cultures of Saccharomyces cerevisiae NCYC 43 1 closely paralleled growth during the early exponential phase of batch growth, and continued after growth had ceased. During the 8-64 h period of the fermentation, the intracellular ethanol concentration was greater than the extracellular concentration. Ethanol was very rapidly extracted from organisms by washing with water. During growth up to 32 h, there was a progressive decrease in fatty-acyl unsaturation in phospholipids, and a corresponding proportional increase in saturation. Thereafter, the trend was very slightly reversed. Supplementing cultures with ethanol (0.5 or 1.0 M) after 8 h incubation retarded growth rate, while supplementation with 1.5 M-ethanol immediately stopped growth. In cultures supplemented with 0.5 or 1 SO M-ethanol, viability was not lowered, but supplementation with 1 -5 M-ethanol caused a rapid decline in viability.Supplementation of cultures with ethanol at any of the three concentrations led to an increase in the proportion of mono-unsaturated fatty-acyl residues in cellular phospholipids, especially in CI8 residues, which was accompanied by a decrease in the proportion of saturated residues.

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Decanoic acid, a lipophilic agent, inhibited in w i b o the plasma membrane H+-ATPase of Sacchammyces cemwisiae grown in YPD medium. Conversely, when decanoic acid (35 pM) was present in the growth medium, the measured H+-ATPase activity was four times higher than that of control cells. Kw and pH and orthovanadate sensitivity were the same for the two growth conditions, which indicated that H+-ATPase activation was not due to conformational changes in the enzyme. The activation process was not entirely reversible which showed that plasma membrane H+-ATPase activation is due t o several mechanisms. 1,6-diphenyl-l,3,5-hexatriene anisotropy performed on protoplasts from cells grown in YPD revealed that as decanoic acid concentration was increased, anisotropy significantly decreased, i.e. membrance fluidity increased. Cells grown in media containing decanoic acid exhibited greater membrane fluidity compared with control cells. Furthermore, these cells did not show any fluidifying effect when increased concentrations of decanoic acid were added. Chemical analysis of cell membrane lipid composition revealed a modification in the distribution of the phospholipid fatty acids and sterols in cells grown in the presence of 35 pM decanoic acid compared with control cells. Our results support the view that the plasma membrane H+-ATPase activation induced by decanoic acid is correlated with an alteration in membrane lipid constituents.