Purification, characterization and bioactivity of exopolysaccharides produced by Lactobacillus plantarum KX041.

A novel crude exopolysaccharide (EPS) produced by Lactobacillus plantarum KX041 possessed prominent antioxidant activity which was proved in our previous study. In our present study, the further purifications were conducted to obtain EPS fractions, which were called as EPS-1-1, EPS-2-1 and EPS-3. The structures and conformational characterizations were determined through FT-IR, UV, GC, HPLC, NMR, SEM and Congo red test analysis. The Mw of EPS-1-1, EPS-2-1 and EPS-3 were estimated to be 57,201, 70,734, and 26,387 Da, respectively. EPS-1-1 and EPS-2-1 had the similar structure, composed of arabinose, mannose, glucose and galactose with a ratio of 1.09:88.53:3.99:6.39 and 0.58:94.11:3.55:1.76, and both were α-type configurations. Whereas EPS-3 contained rhamnose, fucose, arabinose, xylose, mannose, glucose, galactose and galacturonic acid in a molar ratio of 2.01:2.65:10.95:4.62:4.07:27.81:44.16:3.73 and possessed a triple helical structure. SEM results indicated EPS-1-1 and EPS-2-1 appeared flake shapes piling up into compact structures with a rough surface. In addition, these purified EPS fractions all possessed the immune activity, DPPH/ABTS radicals scavenging activities and DNA damage protective effect.