Effect of cadmium on lipid composition of Aureobasidium pullulans grown with added extracellular polysaccharides

Effect of cadmium on the growth and lipid composition in three Aureobasidium pullulans strains grown in the presence and absence of extracellular polysaccharides was studied. Strains tolerated up to 1 mM Cd2+ in medium, but addition of either pectin or pullulan to medium increased tolerance to up to 2 mM Cd2+. While cadmium enhanced lipid accumulation notably only in strains of CCY 27-1-98 and CCY 27-1-111, strain CCY 27-1-115 displayed considerably high levels of sterols. Cadmium increased fatty acid unsaturation rapidly in phosphatidylethanolamine in all strains, owing to elevated levels of linoleic acid in this lipid fraction. On the other hand, Cd2+ ions significantly lowered conversion of oleic acid to linoleic acid in phosphatidylcholine only in the strain CCY 27-1-115. Nevertheless, addition of either pullulan or pectin amplified the ratio of C18:C16 fatty acids and the degree of fatty acid unsaturation in all membrane lipids as a result of induced biotransformation of stearate to oleate and linoleate. It was concluded that more saturated membranes with preferred C18 fatty acyl chains and high sterol amounts in the strain CCY 27-1-115 might be connected with its lower capacity to form pullulan as a protective metabolite against heavy metals compared with the other two strains.