A comparative study of the lipid composition of yeasts with different fermentative capacities

Summary The lipid composition of a classical yeast and a poor fermenter, at low and high sugar concentrations, was compared. Polyunsaturated fatty acids (18:2, 18:3) were found in the osmotolerant weak fermenter, Saccharomyces mellis, their content decreasing with an increase of glucose levels, while the highly fermenting yeast S. cerevisiae had no polyunsaturated fatty acids at all sugar concentrations examined. Also total unsaturation of fatty acids ( mol^–1) was significantly higher with S. mellis. The sterol content varied considerably, being higher with the highly fermenting yeasts and low with S. mellis and the film yeast Pichia sp. The ratio of free sterols/phospholipids was high in S. cerevisiae (1:7) and low in S. mellis (1:177). Hybrid yeasts (S. cerevisiaexS. mellis) which were the best fermenting organisms in our study, also showed a high ratio of free sterols/phospholipids (1:6–1:8). A correlation between the fermentative capacity of yeasts and the fluidity of their membranes is suggested.