Sulphur Dioxide Resistance in Saccharomyces cerevisiae and Saccharomycodes ludwigii

SUMMARY: Saccharomyces cerevisiae was unable to grow in media containing above about 1·5 mm free sulphite at pH 4·0, whereas Saccharomycodes ludwigii grew at the same pH value in the presence of 7·8 mm free sulphite. Expressed in terms of μl of intracellular water, the initial velocity of sulphite accumulation by S'codes ludwigii was approximately twice that of S. cerevisiae, although the former yeast accumulated at equilibrium only about one-third of the amount of sulphite accumulated by S. cerevisiae. A Woolf-Hofstee plot for accumulation of SO2 by S'codes ludwigii at pH 3·0 and 30°C gave a vertical line. Incorporation of sulphite in growth media induced excretion of acetaldehyde by both yeasts, the rate being greater by S'codes ludwigii than S. cerevisiae. Acetaldehyde excretion was accompanied by release of lower concentrations of pyruvate. Excretion of 2-oxoglutarate was barely detectable. It is suggested that the greater resistance of S'codes ludwigii to sulphite, compared with S. cerevisiae, may be explained partly by its decreased capacity to accumulate the compound, and partly by its ability to produce more acetaldehyde.