Abstract: In order to elucidate the relationship between the sterol composition and halotolerance of Saccharomyccs cerevisiae, strain Bs-1 was constructed by knocking out the key gene ERG3 involved in ergosterol synthesis. The growth of Bs-1 was inhibited on YPD (yeast extract, peptone and dextrose) plates containing 60 g/L NaCl as compared with wild type strain BY4741. It was unable to survive on YPD containing 80 g/L. Using gas chromatography-mass spectrometry (GC-MS), we found that Bs-1 could synthesize 5,6-dihydroergosterol rather than ergosterol. In addition, the metabolites of Bs-1 and BY4741 were analyzed. The maximum OD600 nm of Bs-1 was 5.56 ± 0.30 in YPD containing 60 g/L NaCl, which was 45% lower than that of BY4741; the maximum ethanol yield of Bs-1 was (4.20 ± 0.00) g/L, which was 35% lower than that of BY4741; and Bs-1 produced larger amount of extracellular glycerol than did BY4741, but its ability to retain glycerol was weakened. These results indicate that changes in sterol composition could affect metabolic characteristics and membrane fluidity of yeast cells, resulting in increased intracellular glycerol efflux and decreased yeast salt tolerance.

Key words: Saccharomyccs cerevisiae, halotolerant, ergosterol, ERG3