Effect of growth rate on ethanol tolerance ofSaccharomyces cerevisiae

Δ^5,7 Saccharomyces cerevisiae cells growing in chemostat at a specific growth rate of 0.075/h exhibited higher ethanol tolerance measured as ethanol-induced death and anaerobic growth inhibition than the cells growing at 0.2/h, the difference being dependent on the carbon-to-nitrogen molar proportion in the medium. The observed difference in sensitivity to ethanol of anaerobic growth between the slowly and rapidly-growing cells was completely reversed as a result of a block in sterol synthesis causing a negligible synthesis of Δ^5,7. Two physiological parameters, budding frequency and membrane composition, evidently affected ethanol tolerance. Differences between the Δ^5,7 and deficient strains documented a profound effect of the quality of the sterol present on the physiological state of the cell.