Yeast lipids and fatty acids (FA) were analyzed in Saccharomyces pastorianus from seven breweries and in the dietary yeast supplement Pangamin. GC-MS identified more than 30 FA, half of which were very-long chain fatty acids (VLCFA) with hydrocarbon chain lengths of ≥22 C atoms. Positional isomers ω-9 and ω-7 were identified in FA with C18-C28 even-numbered alkyl chains. The most abundant ω-7 isomer was cis-vaccenic acid. The structure of monounsaturated FA was proved by dimethyl disulfide adducts (position of double bonds and cis geometric configuration) and by GC-MS of pyridyl carbinol esters. Ultra-high performance liquid chromatography-tandem mass spectrometry with negative electrospray ionization identified the phospholipids phosphatidylethanolamine, phosphatidylinositol and phosphatidylcholine, with more than 150 molecular species. Wild-type unmutated brewer's yeast strains conventionally used for the manufacture of food supplements were found to contain VLCFA.
Keywords: Negative electrospray ionization; Phospholipids; Very long chain fatty acids; Yeast.