Isolation and characterization of an antioxidant exopolysaccharide produced by Bacillus sp. S-1 from Sichuan Pickles

•An exopolysaccharide BS-2 were extracted from Bacillus sp. S-1 in Sichuan Pickles.•The primary structure of BS-2 was identified by HPSEC, FT-IR, GC–MS, NMR.•The exopolysaccharide BS-2 exhibited potent antioxidant activity in vitro. It is urgent to explore food-grade EPSs from edible microorganism. In this study, a new type of exopolysaccharide (EPS) secreted by Bacillus sp. S-1 from Sichuan Pickles was isolated and fractioned on anion-exchange and gel-filtration chromatography. As indicated by monosaccharides components analysis, the major component BS-2 mainly consisted of galactose, glucose, and mannose with average molecular weight (Mw) of 1.765 × 104 Da. Moreover, the characterization of EPS was investigated by FT-IR and NMR Spectroscopy. In vitro antioxidant activity assay, it proved that the EPSs possessed potent quenching capacities on superoxide, hydroxyl, and DPPH radicals in a dose-dependent way. Furthermore, the major component BS-2 showed potent protection against oxidative injury by inhibiting H2O2-induced apoptosis in RAW264.7 cells. As suggested by the results, BS-2 might serve as a promising antioxidant agent to be applied in nutraceutical and pharmaceutical industries.