Purification and characterization of an exopolysaccharide produced by Lactobacillus plantarum HY isolated from home-made Sichuan Pickle

In the present study, the exopolysaccharide (EPS) producing strain HY was isolated from home-made Sichuan Pickle and identified as Lactobacillus plantarum. The EPS was purified by ethanol precipitation, and fractionation by column chromatography, and the yield of purified HY EPS was 1.423 g/L. The molecular weight of the purified HY EPS was 9.549 × 104 Da and composed of mannose, galactose, glucuronic acid and glucose in a mass percentage of 72.99%, 17.27%, 6.99% and 2.75%, respectively. FT-IR spectrum exhibited the existence of carboxyl and hydroxyl group. Partial sugar residues and glycosidic bond present in HY EPS could be identified by NMR spectroscopy, i.e. α-d-glucose and α-d-mannose residues. The degradation temperature (320 °C) and melting point (122.78 °C) of the HY EPS were determined by thermogravimetric analysis (TGA) and differential scanning calorimeter analysis (DSC). A highly porous structure of EPS was observed by SEM, and the AFM analysis of the EPS revealed presence of spherical lumps. Meanwhile, the in vitro biological activity assays of HY EPS showed considerable antioxidant and α-amylase inhibitory activities, suggesting its promising potential to be applied in the food and pharmaceuticals industry.