| Endophytic fungi have rich diversity.It has formed a unique metabolic pathway during the long-term evolution of the same host.It can not only produce the same or similar chemical composition as the host,but also produce other compounds with novel structure,which is to obtain new medicinal use a treasure trove of chemical ingredients.In order to make better use of this microbial resource,this paper takes walnut endophytic fungus as the research object,cultures and ferments the strains isolated in the early stage of the laboratory,and selects the strains with antioxidant and antifungal activities.The fermentation process of this strain was optimized,the activities of different components were compared,and the activities of highly active components were analyzed by HPLC-MS/MS.The main results are as follows:(1)Taking 29 walnut endophytic fungi isolated and preserved in the laboratory as the research object,its antioxidant activity was evaluated by DPPH· clearance rate and total reducing power(FRAP method),and its antifunal activities were evaluated by the inhibition rate of 6 plant pathogenic fungi To screen out highly active strains with research value.The results showed that the endophytic fungus LTS-6-6 isolated from walnut green skin showed good antioxidant activity and antifungal effect.At a concentration of 1 mg/m L,the total reducing power of the fermentation broth was at 130.47 mg VC/g,the DPPH· clearance rate reached 96.47%;under experimental conditions,the inhibition rate against wheat scab and apple rot pathogens reached 100%,and the inhibition rate against Thanatephorus cucumeris pathogen was 94.87%.(2)Using the dry weight of mycelium,total reducing power(FRAP method)and the inhibition rate of Thanatephorus cucumeris as the evaluation index,the cultivation conditions of the highly active strain LTS-6-6 were optimized through single factor experiments and orthogonal experiments.Single-factor experiment results show that taking fructose as the carbon source,peptone as the nitrogen source can significantly improve the antioxidant and antifungal activities of LTS-6-6 fermentation broth.Orthogonal experiment results show that the number of fermentation days is the main factor affecting the dry weight of the mycelium,and the initial p H of the medium is the main factor affecting the antioxidant and antifunal activities of the fermentation broth.The fermentation process that maximizes mycelium yield and the best antifunal activity is 23 ?,15 d,p H 8.5;Thefermentation process that maximizes the total reducing power of the fermentation broth is24?,15 d,p H 8.5.(3)The concentrated fermentation broth LTS-6-6 was extracted to study the antioxidant and antifungal activities of different solvent extracts.The test results showed that the antioxidant activity of the ethyl acetate extract is significantly higher than that of other solvent extracts,and the antifungal active substances are concentrated in the ethyl acetate and n-butanol extract.Different pathogens respond to the same extract differently.The correlation coefficients between the total reducing power of different solvent extracts and total phenolic total flavonoids were 0.8771 and 0.9177,respectively.HPLC-MS/MS analysis results showed that the most active ethyl acetate extract contained multiple phenolic substances.It is speculated that the presence of benzoic acid is the main reason for the antifungal activities of the extract,and the free radical scavenging ability is the result of the combined action of various phenolic substances such as quercetin and myricetin.(4)The acid value and peroxide value were used as indicators to investigate the effect of ethyl acetate extract on the oxidative stability of rapeseed oil and lard.The results showed that the addition of ethyl acetate extracts with different concentrations will decrease the acid value and peroxide value of rapeseed oil and lard at the same storage time.Tert-butyl hydroquinone is equivalent.After adding 0.02% ethyl acetate extract,the oxidation kinetic model of rapeseed oil is that it can be predicted that the shelf life of rapeseed oil at 20? is 99 d and the shelf life at 25? is 75 d. |
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