Studies On Submerged Fermentation Culture And Hypoglycemic Activity Of Selenium-enriched Mycelia Of Coprinus Comatus

In this paper, the submerged fermentation process of selenium-enriched mycelia of C. comatus and the effect of selenium-enriched products on hypoglycemic activity in diabetic mice were studied.(1) The mycelia biomass and the ability of selenium accumulation of four strains of C. comatus were firstly investigated. Although the strain of C. comatus III did not show the highest production of mycelia biomass, but it showed the highest ability of selenium accumulation among them according to the orthogonal experimental design. Thus C. comatus III were further selected to test the characters of selenium tolerance and accumulation. The result showed that the highest concentration of selenium tolerance in solid and liquid medium were 10μg/mL and 4μg/mL, respectively. The production of mycelia biomass was 4.11 g/L when the concentration of selenium is 2μg/mL. While the ratio of selenium accumulation and organic selenium were 50.57% and 92.95% respectively under the same condition.(2) The effects of the nutrition factor on the biomass and selenium accumulation of C. comatus mycelia were studied. An optimum medium was selected through orthogonal test. The medium composition was as follows: 2.0% glucose, 4% maize power, 0.4% peanut meal, 0.2% KH2PO4, 0.1% MgSO₄·7H₂O, 10×10^-3 g/L VB1, 4.4×10^-3 g/L Na₂SeO₃. The results showed that under these conditions, the production of mycelia biomass and the ratio of selenium accumulation were 18.14 g/L and 56.35% respectively, when the mycelia had been cultured about 5 d in the shaking flask.(3) Plackett-Burman design combined with the path of steepest ascent method and responses surface methodology were adopted to optimization of fermentation conditions for the selenium accumulation of C. comatus. The results indicated that fungus age, initial pH and the filling volume of shaking flask were the major factors.The optimized fermentation conditions were filling volume 70 mL in 250 mL shaking flask, fungus age 133 h, inoculum 3%, initial pH 5.8, 25℃, 100 r/min, 5 d. Under the optimized conditions, the production of mycelia biomass and the ratio of selenium accumulation were 24.51 g/L and 81.03% respectively, 35.12% and 43.80% higher than the control one respectively.(4) We investigated the effect of selenium-enriched mycelia of C. comatus (SMCC) and the selenium-polysaccharide (SPS) isolated from selenium-enriched mycelia of C. comatus on hypoglycemic and antioxidant activities in alloxan-induced diabetic mice. After induction of diabetes, Treatment of diabetic mice with SMCC for 3 weeks resulted in a significant reduction (p<0.05) in blood glucose and the injuries of pancreas. In addition, a significant increase (p<0.05) in the activities of SOD and GSH-Px and a significant decrease (p<0.05) in the content of malondialdehyde (MDA) were observed in serum, liver and kidney. The administration of SPS for 20 days caused a significant decrease (p<0.05) in blood glucose levels. Simultaneously, the alteration in lipid metabolism was partially attenuated as evidenced by decreased serum total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL) levels and by increased high-density lipoprotein cholesterol (HDL) concentration in diabetic mice(p<0.05). In addition, the SPS caused a significant decrease (p<0.05) in the level of malondialdehyde (MDA) and a significant increase (p<0.05) in the activities of enzymic antioxidants and the levels of non-enzymic antioxidants in liver and kidney of diabetic mice. The results showed that SMCC and SPS may be able to inhibit hyperglycemia, and may be helpful in the prevention of diabetic complications associated with oxidative damage. We concluded that SMCC and SPS possess potent antioxidant activity, which may be directly or indirectly responsible for its hypoglycemic properties.