Accumulation of sulphite by Saccharomyces cerevisiae and Zygosaccharomyces bailii as affected by phospholipid fatty-acyl unsaturation and chain length.

Analyses were made of the fatty-acyl composition of phospholipids from each of two strains of Saccharomyces cerevisiae and Zygosaccharomyces bailii grown aerobically. Residues of C16:0, C16:1 and C18:1 predominated in phospholipids from strains of the first yeast, while phospholipids from Z. bailii contained mainly C16:0, C18:1 and C18:2 residues. S. cerevisiae NCYC 431, grown anaerobically in media supplemented with ergosterol and C14:1, C16:1, C18:1, C18:2, C18:3 or C20:1 fatty acids, contained phospholipids enriched with residues of the exogenously provided acid, to a greater extent with shorter chain than longer chain acids. A plot of the permeability coefficient for sulphite, derived from Woolf-Eadie plots, against the degree of unsaturation in phospholipids (expressed as delta mol-1 value) showed that the coefficient was greater the lower the degree of unsaturation in the phospholipids. A plot of the permeability coefficient against values for the mean fatty-acyl chain length divided by the delta mol-1 value, which is an approximation of the cross-section surface area of a phospholipid molecule, showed that the permeability coefficient tended to increase the greater the surface-area value.