Study On Liquid Fermentation And Metabolites Of Lepista Sordida

Lepista sordida is a rarely edible and medicinal fungi, and it has a great develop potential because of its wonderful nutritional value and biological activity,and extremely expensive price for its scarcely wild resources and low production.In this paper, lepista sordida collected from Laoshan in Qingdao was isolated and identified; Optimization of submerge fermentation indexing of mycelium biomass, mycelium chemical compounds and metabolite analysis were done. Development of functional foods was studied preliminary. The main results are as follows:Lepista sordida anamorph was isolated by tissue isolation and identified as Lepista sordida through the fruiting bodies, colonies, mycelium morphology and ITS sequence analysis, which is named as Lepista sordida LS7.By monofactorial and orthogonal test, optimum medium and fermentation conditions indexing of mycelium biomass had been determined, which are as follows: glucose as carbon source, yeast extract as nitrogen source, initial pH 6.5, temperature 25℃,7% as inoculation,100/250mL medium capacity,120 hours fermentation period. The optimum medium composition is 20% potatoes,3% glucose,0.6% yeast extract,0.1% KH2PO4,0.02% MgSO4·7H2O and 0.01% VB1(m/v). The mycelium biomass was found to increase significantly and the fermentation time was shortened obviously by optimizing. The mycelium biomass can reach 25.40±0.25g/L which is significantly higher than that of the common mushrooms under the optimal medium and fermentation conditions.The contents of nutritional components and bioactive substance of the mycelium of lepista sordida LS7 were determined and the results are as follows:water 12.0±0.9%, protein 30.2±1.2%, crude fat 1.4±0.2%, crude fiber 3.4±0.2%, ash 8.1±0.4%, amino acid 17.8%, nucleosides 1.52% and mannitol 6.25%, which contains high content of protein, low fat and all kinds of amino acid. And these high content essential amino acids and delicious amino acid are in line with the requirement of FAO/WHO for high quality protein. Lepista sordida LS7 was found to be rich in nucleosides, compared with other edible fungi, which includes adenosine, guanosine and uridine and their contents were 0.62%,0.17% and 0.73% respectively. The results indicate that Lepista sordida is a kind of high-quality fungi resources, which is nutritious, delicious and with a variety of physiological activity.Metabolites of Lepista sordida LS7 were studied in this study. Exopolysacchari-de(EPS) and Intracellular polysaccharide (IPS) of Lepista sordida were prepared by the complex process of liquid fermentation, ethanol precipitation and water resolution. EPS contains 93.5% total sugar,4.25% reducing sugar and trace amounts of protein; The molecular weight of EPS is about 77kDa, and it was composed of mannose, glucose and galactose by the molar ratio of 3.9:1:0.1. IPS contains 91.3% total sugar, 4.5% reducing sugar and 3.96% protein; The molecular weight of EPS is about 84kDa, and it has the same composition as EPS but with the molar ratio of 1.8:1:0.1; Infrared spectrum (IR) shows that glycosidic bond configuration of EPS is mainly P-configuration, and that of IPS is a-configuration. Studies on antioxidant activity of polysaccharide show that EPS and IPS can scavenge hydroxyl free radicals, and the ability of scavenging hydroxyl enhances with the increasing of the concentration; both of which can not clear the superoxide anion; The reducing power increased with the increasing concentration of EPS and IPS. Antibacterial activity experiments showed that EPS and IPS had no antibacterial activity; extracellular metabolites with small molecule were found to have a broad antibacterial activity against Gram-positive bacteria, Gram-negative bacteria, yeasts and molds, and effects on Fusarium oxysporum and Colletotrichum capsicibutl significantly.Based on the research of lepista sordida on nutrition and metabolic activity, development on various kinds of functional foods was preliminary studied. Optimal formulation was defined by orthogonal experiment,1) beverage:mycelium extract concentration 50%, sweeteners (sucrose) 2%, acid (citric acid) 0.06%, the stabilizer (sodium alginate) 0.05%; 2) sauce jam:salt 1.5%, sugar 1.25%, pepper power 0.5%, ginger powder 0.5%, starch 1%; 3) condiment ingredient:salt 15%, pepper 3%, MSG 2%. Functional foods developed from lepista sordida have a kind of unique aroma and flavor of mushrooms and a variety of physiological activity ingredients.