The AI-2/LuxS quorum sensing system enhances stress tolerance and enological performance of Lactiplantibacillus plantarum during malolactic fermentation.

Although Lactiplantibacillus plantarum shows potential for malolactic fermentation (MLF), its stress sensitivity compared to Oenococcus oeni limits its enological applications. This study reveals the critical role of the AI-2/LuxS quorum sensing (QS) system in the wine stress adaptation of L. plantarum XJ25 through targeted luxS gene manipulation. Deletion of luxS did not impact growth or acid production of L. plantarum XJ25 in optimal conditions (no stress) but significantly decreased AI-2 signal molecule activity. However, under simulated wine stress conditions, including low pH and high ethanol concentrations, the wild-type strain exhibited significantly higher L-malic acid degradation rate and culturable cell viability compared to the luxS deletion mutant, although comparable cell activity as detected by flow cytometry. Notably, a strong positive correlation was found between culturable cell counts and malate metabolism efficiency (r = 0.978, p < 0.001). Integrated transcriptome analysis revealed that the AI-2/LuxS QS system modulates key metabolic pathways associated with folic acid, methionine, and purine metabolism, as well as substance transport, thereby enhancing L. plantarum's stress resilience during the later stages of MLF. In MLF of Marselan wine, the wild-type strain outperformed the luxS deletion mutant, exhibiting higher growth activity, faster L-malic acid degradation, and improved wine quality, as evidenced by more stable wine color and elevated concentrations of varietal aroma compounds. These results highlight the critical contribution of AI-2/LuxS QS system to the stress resistance and enological performance of L. plantarum.