Zn2+ supplementation-mediated IZH4 enhances acid tolerance in Saccharomyces cerevisiae via membrane lipid remodeling: A multi-omics study

Zinc is an essential micronutrient that serves as a vital cofactor in multiple metabolic pathways, including the mechanism mediated by <i>IZH</i> (Implicated in Zinc Homeostasis) genes and lipid biosynthesis. Previous studies revealed that <i>Saccharomyces cerevisiae</i> ET008-c54 (WT) exhibited excellent fermentation performance at low pH for acidic fruit wines, with <i>IZH4</i> identified as a key gene. This study investigated the specific role of <i>IZH4</i> mediated under Zn²⁺ supplementation in low-pH tolerance, using greengage plum wine as a model. Based on fermentation time and sensory evaluation, the optimal Zn²⁺ supplementation level was preliminarily determined to be 2 mg/L. Further metabolomics and flavoromics confirmed that Zn²⁺ supplementation at 2 mg/L was an effective strategy for enhancing the quality of greengage plum wine. On this basis, the effects of <i>IZH4</i> deletion on the growth behavior and membrane composition of the WT strain under Zn²⁺ supplementation were evaluated. The experimental findings revealed that the knockout strain WT-ΔIzh4 showed reduced growth at pH 2.5. Regarding the cellular lipid composition, WT-ΔIzh4 exhibited notably reduced levels of unsaturated fatty acids and ergosterol compared to WT, which resulted in less fluid membranes. Zn²⁺ supplementation increased the growth rate by 20.1 % and elevated ergosterol content by 15.2 % compared with WT-ΔIzh4, and further adjusted the ratio of unsaturated to saturated fatty acids to a level comparable to that of the WT strain. These results demonstrated the significant role of <i>IZH4</i> mediated under Zn²⁺ supplementation in the low pH tolerance of yeast by remodeling the cell membrane structure. This investigation offers fresh insights into the biological function of <i>IZH4</i> against low pH stress, and allows a better-defined target for subsequent genetic improvement of yeast.