Lipid composition of mitochondria of aerobically grown baker’s and brewer’s yeast ABSTRACT The mitochondria of baker’s yeast (obtained as the end-product of industrial production) and bottom-fermenting brewer’s yeast (obtained at the end of propagation in industrial beer production) were analysed in this work. It was determined that the main phospholipid of baker’s yeast mitochondria was phosphatidylcholine, accounting for more than 47% of total phospholipids, followed by phosphatidylethanolamine, phosphatidylinositol and cardiolipin. In the neutral lipid composition, ergosterol was the main component, accounting for 0.039 mg/mg proteins. The fatty acid composition was characterised by high predominance of monounsaturated fatty acids (79%). In the mitochondria of brewer’s yeast, the phospholipid classes were almost evenly represented accounting between 23 and 16%. Ergosterol was the main neutral lipid accounting for 0.016 mg/mg protein, but significant amount of squalene was also determined (0.007 mg/mg proteins) despite the aerobic conditions. Fatty acid composition was characterised by small predominance of unsaturated acids (55%) and high predominance of C16-acids (69%). The results led to the conclusion that estimation of the lipid composition of industrial yeasts based on the results obtained in laboratory conditions is uncertain and that the analysis of the yeast grown in specific conditions should be performed. KEYWORDS: baker’s yeast, brewer’s yeast, lipids, squalene, mitochondria, Saccharomyces cerevisiae, aerobic conditions ABBREVIATIONS PtdCho : phosphatidylcholine PtdEtn : phosphatidylethanolamine PtdIns : phosphatidylinositol PtdSer : phosphatidylserine PtdOH : phosphatidic acid CL : cardiolipin PLs : phospholipids Erg : ergosterol FAs : fatty acids SE : steryl esters TAGs : triacylglycerols INTRODUCTION During production processes and applications, industrial yeasts are exposed to various stressors. These stressors may occur simultaneously or sequentially and moreover with high fluctuations [1]. To survive, they must activate adaptive responses, such as changes in the composition of cell components, including lipids. The goal of baker’s yeast producers is to maximise growth and minimize fermentation, whereas the goal of bakers is opposite. Therefore, baker’s yeast is required to exhibit efficient respiratory metabolism during its production and to leaven bread efficiently by producing considerable quantities of carbon dioxide (mostly via ethanolic fermentation of various sugars in dough), plus 1 Department of Chemistry and Biochemistry, Faculty of Medicine, University of Rijeka, Braće Branchetta 20; 2 Department of Quality, Teaching Institute of Public Health, Primorsko-Goranska County, Krešimirova 52A, Rijeka, Croatia. Gordana Čanadi Jurešić 1 , Suzana Šegota 1 , Marin Glad 2 and Branka Blagović 1, * *Corresponding author: branka.blagovic@medri.uniri.hr Current Trends in Microbiology Vol. 10, 2016