Metabolomics Reveals the Regulatory Mechanisms of Antioxidant Dipeptides Enhancing the Tolerance of Lager Yeast against Ethanol Stress

The antioxidant dipeptides (Ala-His, AH; Thr-Tyr, TY; and Phe-Cys, FC) significantly enhanced the lager yeast tolerance of ethanol stress. The enhancement mechanisms were further elucidated through physiological responses and metabolomics analysis. The results indicated that antioxidant dipeptides significantly increased the lager yeast biomass and budding rate. The primary mechanisms by which antioxidant dipeptides improved lager yeast tolerance involved decreasing intracellular reactive oxygen species (ROS) levels and increasing energy metabolism. Specifically, the addition of FC resulted in a 27.44% reduction in intracellular ROS content and a 26.14% increase in the ATP level compared to the control. Metabolomics analysis further explored the potential mechanisms underlying the protective effects of FC, identifying 63 upregulated and 103 downregulated metabolites. The analysis revealed that FC altered intracellular metabolites related to glutathione metabolism, purine metabolism, starch and sucrose metabolism, and ABC transporters, thereby enhancing yeast stress tolerance. The results suggest that FC is an effective enhancer for improving lager yeast tolerance to ethanol stress.