Mechanisms of Antioxidant Dipeptides Enhancing Ethanol-Oxidation Cross-Stress Tolerance in Lager Yeast: Roles of the Cell Wall and Membrane

High concentrations of ethanol could cause intracellularoxidativestress in yeast, which can lead to ethanol-oxidation cross-stress.Antioxidant dipeptides are effective in maintaining cell viabilityand stress tolerance under ethanol-oxidation cross-stress. In thisstudy, we sought to elucidate how antioxidant dipeptides affect theyeast cell wall and membrane defense systems to enhance stress tolerance.Results showed that antioxidant dipeptide supplementation reducedcell leakage of nucleic acids and proteins by changing cell wall componentsunder ethanol-oxidation cross-stress. Antioxidant dipeptides positivelymodulated the cell wall integrity pathway and up-regulated the expressionof key genes. Antioxidant dipeptides also improved the cell membraneintegrity by increasing the proportion of unsaturated fatty acidsand regulating the expression of key fatty acid synthesis genes. Moreover,the addition of antioxidant dipeptides significantly (p < 0.05) increased the content of ergosterol. Ala-His (AH)supplementation caused the highest content of ergosterol, with anincrease of 23.68 & PLUSMN; 0.01% compared to the control, followed byPhe-Cys (FC) and Thr-Tyr (TY). These results revealedthat the improvement of the cell wall and membrane functions of antioxidantdipeptides was responsible for enhancing the ethanol-oxidation cross-stresstolerance of yeast.