Revealing the Response Mechanism of Under Acid and Alcohol Stresses via a Combined Transcriptomic and Metabolomic Analysis.

, an important lactic acid bacterium in the brewing of Chinese (liquor), usually encounters environmental stresses including ethanol and lactic acid, which severely impact cellular growth and metabolism. In this study, a combined physiological and omics analysis was employed to elucidate the response mechanisms of under ethanol and lactic acid stress conditions. The results showed that the biomass of cells decreased by about 40% under single-stress conditions and 70% under co-stress conditions. Analysis of the differentially expressed genes revealed that the cells adjusted various cellular processes to cope with environmental stresses, including modifications in cell wall synthesis, membrane function, and energy production pathways. Meanwhile, the increased expression of genes involved in DNA repair system and protein biosynthesis ensured the normal physiological function of cells. Notably, under ethanol stress, upregulated genes involved in unsaturated fatty acid biosynthesis, enhancing membrane stability and integrity. Conversely, under lactic acid stress, cells downregulated F-type ATPase, reducing H influx to maintain intracellular pH homeostasis. The metabolomic analysis revealed DNA damage under co-stress conditions and further validated the transcriptomic results. Our findings elucidate the molecular and physiological strategies of under acid and ethanol stress, providing a foundation for optimizing fermentation processes and enhancing microbial resilience in industrial settings.