The lipid compositions of Saccharorrces cerevisiae N.C.Y.C. 366 grown in batch culture at 30°C and 15°C, were compared. The compositions of lipids from cells grown in a chemostat, under glucose limitation and at constant dissolved oxygen tension at two rates at 30°C and one rate at 15°C, were also examined to discover whether the growth temperature-induced changes in the lipid composition of batch-grown cells were caused solely by the change in temperature or whether they were conditioned partially or wholly by the lowering of the growth rate that accompanies a decrease in the growth temperature of batch cultures. Lowering the growth temperature of batch cultures was accompanied by an increase in the contents of total lipids, total fatty acids, triacylglycerols and phospholipid (mainly as phosphatidylcholine), but had little or no effect on the contents of diacylglycerols, free fatty acids, sterols or sterol esters. Analyses of lipids from chonostut-grown cells suggested that the increased synthesis of triacylglycerols was caused mainly by lowering of the growth temperature, but that the increased content of phosphatidylcholine could be attributed mainly to a decrease in growth rate. Lowering the rate at which cells were grown continuously at 30°C caused an increased synthesis of sterol esters whereas lowering the temperature at which cells were grown at a fixed rate was accompanied by a decreased content of both free and esterified sterols. Extracts of all cells examined contained two major sterols, Delta 5,7,22,24(20)-ergostatetraene-3beta-ol and ergosterol. There was little change in either the fatty-acid composition or the degree of unsaturation of the fatty acids in batch-grown or chemostat-grown cells following a change in incubation temperature. Significant proportions of C fatty acids were detected in cells grown in chemostat at 30°C at 0.05h-1. Data on the sterol content obtained by saponification and acid hydrolysis of whole cells are also reported. Preliminary data are reported on the distribution of lipids in fractions obtained by density-gradient centrifugation of lysates of yeast spheroplasts.
|Date of Award||1972|