Purification, characterization and biological activities of exopolysaccharides from Lactobacillus rhamnosus ZFM231 isolated from milk

Exopolysaccharides (EPS) produced by Lactobacillus rhamnosus ZFM231 isolated from milk were purified by DEAE Cellulose-52 and Sephadex G-100 chromatography in sequence, obtaining four purified fractions EPS-1, EPS-2, EPS-3 and EPS-4. Among them, EPS-1 was a neutral polysaccharide and the others were acidic polysaccharides. The four factions were characterized by chemical composition analysis, molecular weight measurement, and UV, IR, 1H and 13C NMR spectra analysis. The antioxidant activity assays indicated that the purified fractions possessed appreciable ferric iron reducing power, free radical (DPPH, hydroxyl and superoxide anion radicals) scavenging ability and ferrous iron chelating ability. These purified exopolysaccharides were also found to possess marked hypolipidemic activity in vitro. The results showed that they were able to effectively inhibit lipase activity, and possessed remarkable activity in reducing cholesterol and triglyceride levels in the HepG2 cell models. Therefore, Lactobacillus rhamnosus ZFM231 and EPS produced by this probiotic strain may find application in food and pharmaceutical industries.