Production, fractionation, characterization of extracellular polysaccharide from a newly isolated Trametes gibbosa and its hypoglycemic activity

The submerged fermentation for extracellular polysaccharide (EPS) production from Trametes gibbosa was optimized. An optimal medium for EPS production was obtained through central composite design (CCD) as follows: 53.12 g/L maltose and 4.21 g/L polypeptone in distilled water. Furthermore, four groups of EPSs (designated as Fr-I, Fr-II, Fr-III and Fr-IV) were obtained from the culture filtrates by size exclusion chromatography (SEC), and their molecular characteristics were examined by a multiangle laser-light scattering (MALLS) and refractive index (RI) detector system. The weight-average molar mass of Fr-I was determined to be 3.872 x 105 g/mol and its molecular shape was revealed to be a rigid rod in an aqueous solution. Finally, the hypoglycemic effect of the EPS, investigated in streptozotocin induced diabetic mice, decreased plasma glucose, total cholesterol and triacylglycerol concentrations by 17.4%, 14.0% and 12.6%, respectively. The results indicate the potential of this EPS to prevent hyperglycemia in diabetic patients.