Characterization and bioactivities of an exopolysaccharide produced by Lactobacillus plantarum YW32

The exopolysaccharide (EPS) produced by Lactobacillus plantarum YW32 was purified and characterized, and the in vitro bioactivities of the purified EPS were also evaluated. The EPS had a molecular weight of 1.03 × 105 Da, and it consisted of mannose, fructose, galactose and glucose in an approximate molar ratio of 8.2:1:4.1:4.2. Microstructural studies of the EPS demonstrated a web-like structure composed of compact ropes, and presence of many homogeneous rod-shaped lumps. The EPS also showed high thermal stability with a degradation temperature of 283.5 °C. Furthermore, the EPS at a dose of 5 mg/ml had strong scavenging abilities toward hydroxyl (77.5%) and superoxide radicals (66.5%). The EPS exhibited a concentration-dependent inhibitory effect on the formation of biofilms by several pathogenic bacteria, including Escherichia coli O157, Shigella flexneri CMCC (B), Staphylococcus aureus AC1 and Salmonella typhimurium S50333. In vitro antitumor assay of the EPS showed that it had good inhibitory activity against colon cancer HT-29 cells. These characteristics and bioactivities of the EPS would make it a promising candidate for use as a potential food adjunct in foods with healthy properties.