Novel exopolysaccharide from Limosilactobacillus fermentum A10: Biosynthesis, physicochemical properties and...

In this study, the biosynthesis, physicochemical properties and antioxidant activity of novel EPS from Limosilactobacillus fermentum A10 were investigated. Whole genome sequencing and functional annotation were employed to identify genes involved in the EPS synthesis and the Wzx/Wzy-dependent pathway. After being purified by a DEAE-52 cellulose column, the main component EPS-1, which consisted of rhamnose, galactose, glucose, mannose, and glucuronic acid, was isolated and prepared. Structural analysis indicated that EPS-1 was a heteropolysaccharide containing a pyranose ring with a zeta potential of -18 mV and a particle size of 146 nm. EPS-1 had a loose, porous, crystalline structure and had thermal stability of up to 257.80 °C. EPS-1 exhibited high radical scavenging activity and cytoprotective effect against H₂O₂-induced HepG2 cellular oxidative damage and significantly increased the activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT). Moreover, EPS-1 induced antioxidant mechanisms by activating the Keap1-Nrf2/ARE signaling pathway. Molecular docking results indicated that the main interactions between Keap1 protein and rhamnose, galactose, glucose, mannose, and glucuronic acid are hydrogen bonds (NH and OH) and electrostatic interactions (amide bonds). These results demonstrated that EPS-1 can potentially be used in functional food to target Keap1 inhibitors/Nrf2 activators.