Optimization And Structure Identification Of Extracellular Polysaccharide From Inonotus Obliquus Based On ?-glucosidase Inhibitory Rate

Inonotus obliquus polysaccharide has obvious effect on treating diabetes.In this study,inonotus obliquus was used as material through optimized culture medium and fermentation kinetic study to improve the polysaccharide yield which can inhibit?-glucosidase activity during fermentation conversion.Polysaccharide purification and structural analysis were conducted to provide new basis for the development of hypoglycemic drug.Specific research contents and conclusions are as follows:1.Optimization of culture medium.Based on single-factor experiments of carbon sources,nitrogen sources,inorganic salts,and growth factorss,L₉?3?⁴orthogonal experiment was designed to optimize the media formulation and to research the extracellular polysaccharide content and the?-glucosidase inhibition rate of inonotus obliquus.The results showed that the optimal medium formula was:glucose 2%,tryptone 0.5%,inorganic salt Mg Cl₂ 0.05%and VB₆ 0.0005%.Comparison between IC₅₀0 of the?-glucosidase half-inhibition rate measured at this time and IC₅₀0 of the half-inhibition rate of Inonotus obliquus?-glucomannan cultured by the un-optimized medium showed that the biomass increased by 0.6 g/L,polysaccharide content increased by 4.028 mg/mL,and?-glucosidase half-inhibition ratio IC₅₀0 decreased from 59.856 to 13.946.2.Fermentation kinetic study.The changes in biomass,substrate consumption,and product during the fermentation process were studied.Three mathematical models were obtained. Cell growth model:??? substrate consumption model:???and product formation model:???3.IOEP1 and IOEP2 polysaccharide structure analysis.Two high-efficiency polysaccharides,IOEP1 and IOEP2 were finally obtained.The study found that IOEP1 is mainly composed of mannose,rhamnose,glucose,galactose,xylose,and arabinose with the percentages of 7.968%,17.226%,28.540%,13.955%,32.105%,and 33.753%respecrively.IOEP2 is mainly composed of rhamnose,glucose,galactose,xylose,arabinose,and fucose,with the percentages of 11.183%,26.154%,12.229%,8.810%,37.053%,and 11.190%respectively.The content of arabinose is the highest in both two components.Nuclear magnetic structure scanning analysis showed that IOEP1 and IOEP2 both contain?-configuration glycosidic bond and?-configuration glucosidic bond.Results of FT-IR scanning analysis showed that both IOEP1 and IOEP2 are pyranose,and IOEP1 has mannose,but IOEP2 does not have mannose.UV spectrum scanning analysis showed that the two polysaccharides still contained a small amount of protein after removing protein by servage treatment.It can be presumed that there exist a certain amount of binding protein in IOEP1 and IOEP2.