Study On The Novel Pattern Of Grifola Frondosa Cultivation And Fermentation And Polysaccharide Products

Grifola frondosa is a rare edible and medicinal fungus.Both the mycelium and fruit body of G.frondosa are rich in nutrients and active ingredients,especially its polysaccharide has various physiological functions such as antioxidant,antihyperglycemic and antitumor.As the main by-products of rice and wheat processing in China,rice bran and wheat bran have a high annual output,but further research is needed for deep processing and exploitation.Corn flour is made by directly grinding corn and contains many nutrients.In this study,a cultivation medium with the addition of rice bran,wheat bran and corn flour was optimized for the cultivation and production of G.frondosa fruit body.In addition,the quality of fruit body produced by transforming rice bran,wheat bran and corn flour was analyzed.In the liquid fermentation of G.frondosa,a pilot test of 200 L fermentor was conducted to provide reference for the fermentation of rice bran,bran and corn flour by G.frondosa from laboratory research to factory production.The polysaccharides of G.frondosa were purified and structures were analyzed to gain a preliminary understanding of the activity in vitro of the polysaccharides,with the aim of providing a theoretical basis for the subsequent development of polysaccharide healthy food or pharmaceuticals.The main research contents and results are as follows.（1）Optimization of G.frondosa cultivation medium.The uniform U₁₁（11³）experiment was designed with rice bran,wheat bran and corn flour additions as variables.The results of fruit body fresh weight,fruit body dry weight,biotransformation rate,polysaccharide content,total polysaccharide yields were analyzed to obtain regression model equations,from which the optimal medium composition were determined.The highest fresh weight of fruit body was achieved when rice bran,wheat bran and corn flour were added at 3%,4%and 23%,respectively,reached 190.58 g per package.The highest dry weight of fruit body was achieved when rice bran,wheat bran and corn flour were added at 3%,5%and 22%respectively,reached 18.61 g per package.The highest biotransformation rate was achieved when rice bran,wheat bran and corn flour were added at 10%,13%and 7%respectively,reached 58%.The highest polysaccharide content of fruit body was achieved when rice bran,wheat bran and corn flour were added at 4%,12%and 14%respectively,reached79.51 mg/g.The highest total polysaccharide yields of fruit body was achieved when rice bran,wheat bran and corn flour were added at 7%,12%and 11%respectively,reached 282.14 g.In addition,The quality of fruit body was analyzed,and the results show that all of them fit in industry standards.（2）Pilot trial of fermented rice bran,bran and corn flour from G.frondosa was carried out.A total of 10.686 kg of rice bran,bran and corn flour was added into the200 L fermentor and water was added to 140 L.After 14 days of fermentation,14.15kg of wet mycelium and 75 L of fermentation broth were harvested.During the fermentation process,changes of biomass,p H,polysaccharide content and the activity of three enzymes were observed.The results showed that mycelial growth was most active at 2 to 8 days,and fermentation could be terminated and the product harvested at 8 to 10 days.Besides,In vitro antioxidant tests were conducted on polysaccharides which obtained from mycelial and fermentation,and the results showed that the polysaccharides have certain antioxidant activity in vitro.（3）G.frondosa fruit body and mycelium obtained from the previous study were used as materials for the extraction and purification of G.frondosa polysaccharides.Two purified polysaccharides,GPZ-0 and GPZ-1,were obtained by extraction and purification from the fruit body,and two purified polysaccharides,GPF-0 and GPF-1,were obtained by extraction and purification from the mycelium.Characterization of the structures of the four purified polysaccharides led to the conclusion:GPF-0 had the lowest molecular weight of 4.690×10⁵ Da,while GPF-1,GPZ-0 and GPZ-1 had molecular weights of 1.242×10⁷,4.116×10⁷ and 2.000×10⁷ Da,respectively.GPZ-1 is a typical glucan,while the other three polysaccharides are glucose-based heteroglycans.The two polysaccharides obtained from mycelium containedα-type glycosidic bonds,while the two polysaccharides obtained from fruit body had bothαandβ-type glycosidic bonds;Among the four purified polysaccharides only GPF-0 may contain a triple helix structure.（4）In vitro hypolipidemic and hypoglycemic activities of four purified polysaccharides were investigated.In terms of in vitro hypolipidemia,the highest binding rate with sodium glycocholate was GPF-0 from mycelium with 42.19%,and the highest binding rate with sodium taurocholate was GPZ-0 from fruit body with38.48%.The inhibition rate of lipase by the four purified polysaccharides was basically around 18.00%.In terms of in vitro hypoglycemia,GPF-0 inhibited the activity ofα-amylase up to 60.23%,while GPZ-0 inhibited the activity ofα-glucosidase up to48.92%.The results showed that all four purified polysaccharides showed outstanding antihyperglycemic and hypolipidemic activities in vitro.