Proteomics and metabolomics elucidate the biosynthetic pathway of acid stress-induced exopolysaccharides and its impact on growth phenotypes in Lactiplantibacillus plantarum HMX2

Lactiplantibacillus plantarum has been well acknowledged to produce exopolysaccharides (EPS) as a defense mechanism against acid stress. However, the complete biosynthetic pathway of EPS in L. plantarum and its impact on the cell growth and primary metabolism were still unclear. To fill these gaps, we carried out phenotypic, proteomic and metabolomics analysis of L. plantarum HMX2 cultured under different acidic conditions. Component and structure analysis showed that the repeating unit of EPS consisted of N-acetylmannosamine, N-acetylglucosamine, galactose, mannoses and glucoses. Multiomics analysis facilitated the curation and entablement of the complete EPS biosynthetic pathway ready for use in genome-scale metabolic models. Furthermore, proteomics and metabolomics data indicated that compared to the pH 6.5 condition, the acid stress at pH 4.5 significantly accelerated glycolysis and EPS biosynthesis processes while reduced the metabolic fluxes through the TCA cycle and the lactic acid fermentation, which suggested a trade-off between primary and secondary metabolism.