Mechanism of Fermented-Litchi Polysaccharide Promoting Exopolysaccharide Production by Weissella confusa

Fermented-litchi polysaccharide (Lzp) has been demonstrated to enhance the production of exopolysaccharides (EPS) in Weissella confusa in our previous study. To elucidate the underlying mechanisms, the resulting EPS was identified as a homopolysaccharide primarily composed of →6)-α-d-Glcp-(1→. Integrated metabolomics and transcriptomics analyses identified 19 differential metabolites and 60 differential genes associated with the effects of Lzp. Specifically, 13 extracellular metabolites were enriched in ABC transporters, starch and sucrose metabolism, and glycerophospholipid metabolism, while 6 intracellular metabolites were linked to aminoacyl-tRNA biosynthesis and pyrimidine metabolism. Transcriptomics revealed upregulation of key genes in the ABC transporter pathway (msmX, ugpA, ugpE, and pstS) and sucrose synthase-dependent pathway (sacA and sucA), facilitating the transport of EPS precursors and their extracellular assembly. Notably, Lzp-derived galactose and arabinose were transformed into UDP-glucose via the Leloir pathway and the pentose phosphate pathway, respectively, thus enhancing the availability of UDP-glucose for EPS synthesis. Validation via qRT-PCR confirmed the regulatory roles of these genes. Furthermore, genes involved in pyrimidine metabolism (pyrB, pyrE, etc.) were modulated to regulate nucleotide synthesis, indirectly supporting EPS polymerization. This study unveils Lzp's multi-target mechanism, coordinating carbohydrate metabolism, transporter activity, and transcriptional regulation to enhance EPS production, offering a foundation for industrial optimization using natural polysaccharides.