Separation, Purification, Structural Characterization, and Anticancer Activity of a Novel Exopolysaccharide from sp.

sp. has a wide range of applications in the food fermentation industry. In this study, a novel exopolysaccharide, labeled MSEPS, was separated from sp. fermentation broth through ethanol precipitation and was purified by ion-exchange chromatography, as well as gel filtration column chromatography. MSEPS was composed mostly of mannose, galactose, fucose, arabinose, and glucose with a molar ratio of 0.466:0.169:0.139:0.126:0.015 and had a molecular weight of 7.78 × 10 Da. The analysis of methylation and nuclear magnetic resonance results indicated that MSEPS mainly consisted of a backbone of →3,6)-α-d-Man-(1→3,6)-β-d-Gal-(1→, with substitution at O-3 of →6)-α-d-Man-(1→ and →6)-β-d-Gal-(1→ by terminal α-l-Ara residues. MTT assays showed that MSEPS was nontoxic in normal cells (HK-2 cells) and inhibited the proliferation of carcinoma cells (SGC-7901 cells). Additionally, morphological analysis and flow cytometry experiments indicated that MSEPS promoted SGC-7901 cell death via apoptosis. Therefore, MSEPS from sp. can be developed as a potential antitumor agent.