Preparation and in Vitro Hypoglycemic Activity Analysis of Selenoexopolysaccharides from Weizmannia coagulans P-L1

To develop a method for the preparation of selenium exopolysaccharide (Se-EPS) with high yield, the heat-resistant Weizmannia coagulans P-L1 was selected to produce Se-EPS through fermentation, with the addition of sodium selenite at a concentration of 20 mg/L, using anion exchange resins. In addition, Se-EPS was characterized using infrared spectroscopy, and in vitro hypoglycemic activity of Se-EPS was investigated. The results showed that the initial bacterial concentration, the employment of anion exchange resins and the fermentation time all had a significant impact on the yield of Se-EPS. With an initial bacterial concentration of 1×10⁶ CFU/mL, the yield of Se-EPS achieved up to 19.1 g/L after 8 days of fermentation, which was increased by 5.4-fold as compared to the yield of Se-EPS obtained with an initial bacterial concentration of 1×10⁵ CFU/mL, and was increased by 19.5-fold as compared to the yield of exopolysaccharide (EPS) obtained by conventional fermentation (without using anion-exchange resin). The selenium content of the Se-EPS reached up to 213 μg/g. Infrared spectroscopy analysis revealed that selenium was probably incorporated into the EPS via Se-O and Se=O bonds. Both EPS and Se-EPS derived from Weizmannia coagulans P-L1 exhibited good in vitro hypoglycemic activity, with Se-EPS showing significantly higher activity than EPS. At a concentration of 1 mg/mL, the inhibition of Se-EPS against α-glucosidase and α-amylase were 28% and 16% higher than those of EPS, respectively. The study provides theoretical support and technical references for the development and application of Se-EPS products derived from Weizmannia coagulans.