Salt-dependent osmoadaptation and metabolic responses of Lactiplantibacillus plantarum BS3-1 in fermented bamboo shoots.

Salt concentration shapes the growth and metabolism of lactic acid bacteria in vegetable fermentations, yet the effects of salt gradients on the fermentation performance of suansun-derived Lactiplantibacillus plantarum BS3-1, together with associated temporal transcriptional changes in BS3-1 and metabolite variation in the fermentation broth, remain insufficiently characterized. Here, BS3-1 was evaluated across a 0-7% (w/w) salt gradient during suansun fermentation. The 0%, 3%, and 5% treatments were selected for time-series transcriptomic analysis of fermentation-derived cell pellets and untargeted metabolomic analysis of fermentation-broth supernatants. The 3% treatment yielded the highest sensory score (79.0/100 versus 72.2/100 in the no-added-salt treatment). On day 7, total acidity was 8.16 g/L at 1% salt and 3.60 g/L at 7%, and viable cells at 7% fell below the detection limit. BS3-1 transcriptional profiles and fermentation-broth metabolite compositions differed among salt treatments. In the 3% versus 0% comparison, 119 differentially expressed genes were shared across four time points, while an average of 598 differential metabolites was identified per time point. WGCNA identified 17 co-expression modules with significant module-trait associations. Association analysis integrating 126 candidate hub genes from four phenotype-associated modules with 30 shared differential metabolites retained 1100 gene-metabolite associations (|r| ≥ 0.65, global BH-FDR < 0.05). Overall, under the tested conditions, 3% salt provided the most favorable balance among viable-cell persistence, acidification, and sensory quality, while multi-omics analysis revealed covariation among BS3-1 transcriptional responses, fermentation traits, and fermentation-broth metabolite variation.