Phospholipid Desaturation in Candida Lipolytica as a Function of Temperature and Growth

Abstract

Changes in the phospholipid fatty acids of a mesophilic yeast, Candida lipolytica, strain NRRLY 1094, were followed during growth at 10 °C or 25 °C. Total lipids were separated by thin-layer chromatography into phosphatidylcholine, phosphatidylinositol + phosphatidylserine, phosphatidylethanolamine, and neutral lipid fractions, and the fatty acids from each fraction were analyzed by gas–liquid chromatography. Unsaturation of all components was greater at 10 °C than at 25 °C, and was maintained at a higher level later into the active phase of growth at the lower temperature. A reciprocal relationship between percentages of oleic and linoleic acids during growth at either temperature was observed in all of the phospholipids, but was most pronounced in phosphatidylcholine. Positional distribution studies showed that desaturation during growth at either temperature occurred in fatty acids esterified both at the 1- and 2-positions of phosphatidylcholine, but specifically in the 2-position of phosphatidylethanolamine. Argentation chromatography indicated the existence in cells grown at either temperature of molecular species of lecithin containing four, three, two, and one double bonds. Calculations of the probable distribution of molecular species during growth suggest that desaturation of lecithin to a tetraenoic species occurs at both temperatures by stepwise desaturation of dienoic and trienoic molecular species. A similar pathway, with some modifications, is envisioned for phosphatidylethanolamine.