Characterization of novel exopolysaccharide of Enterococcus faecium WEFA23 from infant and demonstration of its in vitro biological properties

In this study exopolysaccharide (EPS) of Enterococcus faecium WEFA23 from healthy infant's feces was yielded as high as 130 mg/L by fermentation. By purification the EPS was further fractioned into A23-1, A23-2, A23-3 and A23-4 on HiTrap Q HP and Superdex G-200 column. As the major purified fractions, A23-2 and A23-4 were analyzed for the preliminary structures and investigated for the biological properties in vitro. The molecular weight of A23-2 and A23-4 was 2.50 × 10 4  Da and 3.23 × 10 4  Da, respectively. A23-2 was composed of mannose, glucose and galactose with a ratio of 1.38:1.00:1.42, while A23-4 consisted of only mannose. The antioxidant ability of A23-2 was significantly higher than that of A23-4, as proved by scavenging test of DPPH radical, hydroxyl radical and superoxide radical. Both A23-2 and A23-4 exhibited strong inhibition against the adhesion of L . monocytogenes CMCC54007 on HT-29 cells no matter for the styles of competition, displacement and exclusion. Notably, for exclusion they had a maximal inhibition rate of 89.85 ± 0.46% and 90.81 ± 2.29%, respectively, at 200 μg/mL.