Phospholipids and fatty acyl composition of Saccharomyces cerevisiae as affected by oxygen and low growth temperature.

A strain of Saccharomyces cerevisiae, previously shown to be able to complete the fermentation of grape must at low temperature, was grown in the presence and in the absence of oxygen at 10 and 25 degrees C in order to investigate about the effects of low growth temperature on the phospholipids (PLs) and on the fatty acyl (FA) composition of the yeast cells. Both anaerobic and aerobic cells grown at the lower temperature showed a much higher amount of total PLs due to the increased amount of phosphatidylethanolamine, phosphatidylinositol and phosphatidylcholine, whereas the cellular concentration of the other PLs, namely phosphatidylglycerol and phosphatidylserine, was not significantly modified. The amount of unsaturated FAs of whole cells was almost unaffected by the lower growth temperature, but a very significant increase of their quantity was observed in the phospholipidic fraction of cells grown at 10 degrees C. No significant modifications in the mean fatty acid chain length of both whole cells and PLs were observed, demonstrating that this parameter is practically temperature-independent. These results point out that low growth temperatures stimulate both the synthesis of PLs and the increase of their unsaturation degree, without significantly affecting the amount of unsaturated FAs of whole cells.