Different concentrations of exopolysaccharides enhance the freeze resistance of Lactobacillus plantarum: Transcriptomics and metabolomics.

The study aimed to investigate the regulatory effects of exopolysaccharides (EPS) derived from Pediococcus acidilactici S1 on the cell physiological functions of Lactobacillus plantarum FQR during the freezing process. Results demonstrated that the addition of 70 mg/mL EPS as a cryoprotectant achieved a maximum survival rate of 91.99 ± 3.52%. The EPS effectively mitigated cell wall and membrane damage, reduced membrane permeability, and stabilized membrane fluidity. Furthermore, EPS decreased the freezing point of the solution from -17.37°C ± 0.19°C to -17.08°C ± 0.20°C, thereby inhibiting ice crystal formation and maintaining post-freeze-drying stability in DNA structure, membrane structure, cell wall protein structure, and unsaturated fatty acid composition within cells. Notably, there was a significant increase in intracellular salicylic acid levels among differential metabolites observed through metabolomic analysis. Combined with transcriptomic analysis, it was revealed that purine metabolism, pyruvate metabolism, and galactose metabolism were the main metabolic pathways involved in this process.