Harnessing exogenous AI-2 to improve ethanol tolerance in Lactobacillus plantarum R: Insights from transcriptome and metabolome

Lactobacillus plantarum R is the predominant bacterium widely used in food fermentation. However, it has a low tolerance to ethanol during fermentation, which restricts its broader application in the food industry. Although biofilm formation enhances bacterial resistance to various stresses, regulating biofilm formation in L. plantarum R remains challenging. In this study, we established a pathway for producing autoinducer 2 (AI-2), a quorum-sensing (QS) signaling molecule, by heterologously expressing pfs and LuxS in L. plantarum R. This approach aimed to modulate cell membrane structure and improve bacterial ethanol resistance. The findings showed that exogenous AI-2 significantly enhanced the growth of L. plantarum R under high-ethanol concentration and improved its biofilm formation at different ethanol concentrations. Furthermore, a multi-omics analysis revealed potential mechanisms by which AI-2 improved the tolerance of L. plantarum R to ethanol. Notably, the upregulation of the crr gene, a component of the phosphotransferase system (PTS), enhanced biofilm formation in response to ethanol stress. In addition, differential metabolites enriched in cysteine and methionine metabolic pathways further supported the role of QS in enhancing the tolerance of L. plantarum R to ethanol. These findings lay the groundwork for enhancing the fermentation performance of strains applied in the food fermentation industry, presenting a novel method for expanding the utilization of L. plantarum R in high-ethanol fermentation.