Cellular mechanism for the improvement of multiple stress tolerance in brewer's yeast by potassium ion supplementation

The ethanol fermentation efficiency was affected by multiple stress tolerance of yeast during brewing and bioethanol industry. The effect of KCl on the multiple stress tolerance of yeast cells was examined.Results showed that KCl addition significantly enhanced the tolerance of yeast cells to osmotic and etha-nol stress, which correlated with the decreased membrane permeability, the increased intracellular ergos-terol and ATP content, and the improved activity of complex II and complex III in yeast cells. Biomassand viability of yeast cells under osmotic and ethanol stress were increased significantly by KCl addition.Supplementation of 4 and 10 g L⁻¹ KCl exhibited the best promotion activity for yeast cells present inmedium with 500 g L⁻¹ sucrose and 10% (v v⁻¹) ethanol, respectively. These results suggested that exoge-nous potassium addition might be an effective strategy to improve yeast tolerance and fermentation effi-ciency during industrial very-high-gravity (VHG) fermentation