Study on the optimization of liquid fermentation of Lepista Nuda and the structure and functional activity of its alkaline- and water-extracted polysaccharides

• 1、Jiangnan University,Wuxi 214122

Abstract：Lepista Nuda is a kind of rare edible wild fungus, which has very high antioxidant, anticancer and antiviral activities. In this study, the liquid fermentation medium of Lepista Nuda was optimized by single factor and orthogonal optimization. The optimal fermentation medium was 3% (w/v) glucose, 1% yeast powder, 0.05% potassium dihydrogen phosphate and 0.25% magnesium sulfate. The biomass of Lepista Nuda under this condition was 22.3g/L. Water-extracted polysaccharide (WLNP) and alkali-extracted polysaccharide (ALNP) were extracted from the mycelium of Lepista Nuda by hot water and hot alkali. The structure of polysaccharides was characterized by FT-IR, HPGPC, ion chromatography and SEM. The results showed that WLNP (1532kDa) was larger than ALNP (767kDa), and WLNP was more regular under scanning electron microscope, while ALNP was a large flake. WLNP is mainly composed of GlcN, Glc and Man, ALNP is mainly composed of Glc, Man and Fru, and Glc is the main dominant monosaccharide. In the study of antioxidant activity, WLNP showed more powerful antioxidant activity than ALNP, and the highest DPPH free radical clearance was 88.34±2.47%(WLNP). The results of cell experiments showed that WLNP had a significantly higher inhibition rate on Hep-G2 than ALNP, and WLNP had the lowest IC50 (317.9 μg/mL), indicating the strongest anticancer activity. Based on the above research, polysaccharides from Lepista Nuda are expected to become a new member of functional food, WLNP has more development potential in functional food or medicine industry.

Keywords： Lepista Nuda；Liquid fermentation；Polysaccharides；Structural characterization；Functional activity