Studies On Production Technology And Properties Of Polysaccharide From Soybean Curd Residue Fermented By Morchella Esculenta

With soybean curd residue (SCR) as raw material, this paper discussed the semisolid fermentation by Morchella esculenta to produce polysaccharide. In addition, the physicochemical properties, structure and biological activities of polysaccharide from fermented SCR were researched.The optimal parameters of the semisolid fermentation were: feed liquid ratio 1:9(g/mL), inoculum size 3.0% and fermentation time 9 d. When the content of polysaccharide was considered as the primary index, three factors including fermentation time, feed liquid ratio and inoculum size in sequence had important influence. The polysaccharide content of fermented SCR was 8.86% under the optimal conditions. There was the significant change between unfermented SCR and fermented SCR through the scanning electron microscopy.Hot water extraction was included in the extraction technology. The product (CMP) is the faint yellow powder and the biological activities of CMP were studied. The test of anti-microbial activities in vitro indicated that CMP had anti-microbial activities against E.coli. and salmonella. The results on the abilities of bile salt-binding showed that CMP had binding capacities for three kinds of cholates, which demonstrated that CMP had hypolipidemic effect.PMP was purified from CMP by ethanol fractional precipitation, which was a kind of acid sugar. The purity of PMP was calculated to be 92.5% and the average molecular weight (Mw) was estimated to be 3.07 × 106 Da. According to the SEM image, the morphological properties of PMP were observed as sheet=shape fragments with irregular shape and its surface exhibited smooth outside. PMP did not contain starch, reducing sugar and polyphenols but with uronic acid (15%, w/w) and protein (3%, w/w). The PMP showed strong thermal stability. The PMP was composed of rhamnose, arabinose, xylose, mannose,glucose and galactose, with the molar ratio of 0.080: 0.251: 0.163: 0.071: 0.284: 1.000.Using FTIR to analyze primary structure, the result showed that PMP had several typical absorption peaks of polysaccharide. Applying congo red test to analyze its structure, the result showed that PMP existed in a triple-helical conformation in aqueous solution. Then,the result of XRD indicated that PMP was semi-crystalline substance. We could corroborate that the glycosidic bonds of PMP possessed mainly ?-configuration and partly?-configuration through NMR. The AFM results demonatrated that the microcosmic morphology of PMP was a three-dimensional complex network structure.Antioxidant assays in vitro demonstrated that PMP had good antioxidant capacities which could be explored as a natural antioxidant for use in functional foods or medicine.