Brewer's Yeast as a New Source of Palmitoleic Acid-Analysis of Triacylglycerols by LC-MS

We identified both fatty acids and TAG in waste yeast from seven breweries employing both top and bottom fermentation. Brewer's yeast was found to contain FA exhibiting a broad range of acyl chain lengths, with a high proportion of the nutritionally and biotechnologically important palmitoleic acid. Analysis of FA by GC-MS and of TAG by LC-MS with APCI provided information on the type of brewer's yeast and technology of fermentation. The composition of TAG containing major FA such as palmitic, palmitoleic and oleic acid was found to depend not only on the type of yeast strain, i.e. Saccharomyces pastorianus or S. cerevisiae, but also on brewing fermentation process, i.e. top versus bottom fermentation. Top and bottom yeast can readily be distinguished by the ratios of some regioisomers of TAG since, e.g., the ratio of regioisomers PoOPo and PoPoO is always > 1 in top fermenting yeast and < 1 in bottom yeast. The ratios can thus be used as markers for determining the yeast type and beer-producing technology in a given brewery.