Production of intracellular selenium-enriched polysaccharides from thin stillage by Cordyceps sinensis and its bioactivities

BACKGROUND: Thin stillage was used as the substrate to produce intracellular selenium-enriched polysaccharides (ISPS) from Cordyceps sinensis to increase the value of agricultural coproducts. METHODS: Fermentation parameters were optimized using response surface methodology (RSM) to improve the production of ISPS. Then, the effects of ISPS on the antioxidant activities in vitro, as well as the glycosylated serum protein concentration, malondialdehyde level, and total antioxidant capacity of streptozotocin-induced diabetic rats were studied. RESULTS: The optimized conditions were as follows: sodium selenite concentration, 33.78 µg/L; incubation time, 8.24 days; and incubation temperature, 26.69°C. A maximum yield of 197.35 mg/g ISPS was obtained from the validation experiments, which was quite close to the predicted maximum yield of 198.6839 mg/g. FT-IR spectra indicated that ISPS has been successfully selenylation modified with similar structure to polysaccharide of intracellular polysaccharides. The in vitro scavenging effects of 1.0 mg/mL ISPS on hydroxyl, superoxide, and 1,1-diphenyl-2-picrylhydrazyl radicals were 74.62±4.05, 71.45±3.63, and 79.48±4.75%, respectively. The reducing power of ISPS was 0.45±0.01 (absorbance at 700 nm). Fasting blood glucose and glycosylated serum protein of group C (rats with diabetes that received drinking water with ISPS) were significantly lower than those of group B (rats with diabetes) (P<0.01) after treatment was administered for 2 and 4 weeks. Serum malonaldehyde content of group C was significantly lower than that of group B at 4 weeks (P<0.01). At 4 weeks, malonaldehyde contents in heart, liver, and kidney tissues of group C were significantly lower than those of group B; however, malonaldehyde content in pancreas tissue of group C was not significantly different. Total antioxidant capacities in liver, pancreas and kidney tissues of group C were significantly higher than those of group B, but total antioxidant capacity in heart tissue was not significantly different. Serum total antioxidant capacity was also increased compared with that of group B. CONCLUSION: The result of these experiments indicated that RSM is a promising method for the optimization of ISPS production, and the ISPS of C. sinensis can reduce blood glucose level and improve antioxidant capacity of rats with diabetes induced by streptozotocin.