Research On Antioxidant Function And Antibacterial Activity Of Extract From Wheat Bran Liquid-state Fermented By Ganoderma Lucidum And Its Active Components

As a by-product of wheat processing,bran is rich in carbohydrate,protein and dietary fiber.It comes from a wide range of sources and has a huge yield,but its comprehensive utilization rate is low.Ganoderma lucidum is a precious medicinal material with a long history of medicinal use.It has strong biological activities such as antioxidant,bacteriostasis and immune regulation.In this study,the bran was used as liquid substrate for Ganoderma lucidum fermentation,and the optimal preparation conditions of wheat bran liquid-state fermented by Ganoderma lucidum were studied.The antioxidant and antibacterial activities of crude polysaccharides and alcohol extracts from Ganoderma lucidum were compared before and after the fermentation.By analyzing the structure of crude polysaccharides from fermented bran and the composition of polyphenols,flavonoids and alkaloids in the alcohol extract,the thesis is at the first phase of exploring into the reasons of antioxidant and antibacterial activities of crude polysaccharides and alcohol extract from fermented bran.The thesis mainly includes the following four parts:(1)Preparation of Ganoderma lucidum fermented wheat branThe polysaccharide,polyphenols,flavonoids,alkaloids and biomass were used as the indexes to select the best fermentation conditions.The results showed that adding 10%wheat bran over 40 mesh in liquid medium for liquid Ganoderma lucidum fermentation had the best effect.(2)Antioxidant and antibacterial activities of crude polysaccharides and alcohol extracts from fermented branThe fermented bran was centrifuged and the supernatant was vaporized and freeze-dried to obtain the supernatant(GWBS),after the precipitation was immersed in boiling water for 4 h,the water extract was rotated and freeze-dried to obtain ganoderma wheat bran precipitate(GWBP).The crude polysaccharides in the supernatant and precipitate of fermented bran were extracted by alcohol precipitation and deproteinization method,the crude polysaccharides from ganoderma wheat bran supernatant(GWBS-2)and the crude polysaccharides from ganoderma wheat bran precipitation(GWBP-2)were obtained.The alcohol-soluble substances in the supernatant and precipitate of ganoderma wheat bran were extracted by 90%ethanol,the alcohol extract from ganoderma wheat bran supernatant(GWBS-1)and the alcohol extract from ganoderma wheat bran precipitation(GWBP-1)were obtained.Using DPPH scavenging rate,hydroxyl radical scavenging rate,reducing power,the minimum inhibitory concentration as indexes,the antioxidant activities and antibacterial activities of crude polysaccharides and alcohol extracts from fermented bran before and after fermentation were compared and analyzed.The results showed that the antioxidant and antibacterial activities of fermented bran were significantly higher than those of unfermented bran(P<0.05).The hydroxyl radical scavenging rate of crude polysaccharides in the supernatant of fermented bran was higher,and the DPPH radical scavenging ability,reducing power and antibacterial activity of crude polysaccharides precipitated by fermented bran were higher.The antioxidant activity of alcohol extract precipitated from fermented bran was higher,and the antibacterial activity of alcohol extract in the supernatant of fermented bran was higher.(3)Composition and structure analysis of crude polysaccharide from fermented branThe monosaccharide composition of crude polysaccharides in the supernatant and precipitation of fermented bran was analyzed by HPLC.Glucose,arabinose,galactose,mannose,rhanose,glucuronic acid and galacturonic acid were found in the supernatant and precipitated crude polysaccharides of fermented bran,but the molar percentage of each monosaccharide was different.The molecular weight of GWBS-2 was 5.199×10~3Da,the molecular weight of GWBP-2 was 4.172×10~3Da.The polysaccharide structures of GWBS-2 and GWBP-2 were analyzed by infrared spectroscopy,both GWBS-2 and GWBP-2 are pyranose.The crude polysaccharides in the supernatant of fermented bran combined with more flavonoids,and the crude polysaccharides precipitated by fermented bran attached more binding proteins in the sugar chain.(4)Based on metabonomics analysis of polyphenols,flavonoids and alkaloids compounds from fermented branThrough metabolomic analysis,a total of 494 metabolites were detected in fermented bran,including 170 phenolic acids,139 flavonoids,110 alkaloids,24 terpenoids and 51other metabolites.The content of phenolic acids in the most substances are vanillin,diisobutyl phthalate,dibutyl phthalate.The substances with the highest content of flavonoids are sarcorin B,sarcorin A and alfalfa(tricin).The most abundant alkaloids are betaine,choline and spermine.A total of 171 different metabolites(149 up-regulated and 22down-regulated)were detected in the superclear and precipitated alcohol extracts of fermented bran,including 45 phenolic acids,67 flavonoids,39 alkaloids,4 terpenoids and16 other metabolites.The contents of polyphenols,flavonoids and alkaloids in the alcohol extract of fermented bran precipitation were more abundant.In conclusion,this study provide an effective way for the resource utilization of wheat bran,and to provide a theoretical basis for the application of Ganoderma lucidum fermented bran as a natural anti-active substance in animal production,the biological activity and main active substances of the bran were prepared and analyzed.