Optimization Of The Fermentation Condition And Secondary Metabolites Of Endophytic Fungi HND5from Brachiaria Brizantha

Investigation on the endophytic fungi of the plants has been widespread concern in recent years. Endophytic fungi not only can enhance plant stress tolerance and pest resistant ability, but also improve plant photosynthesis and promote plant growth. Fungi produce secondary metabolites in host or induce host to produce. Based on this multiple metabolites, endophytic fungi has a symbiotic relationship with host plant. Isolation, purification and identification of secondary metabolites from endophytic fungi were help to reveal the mechanism of interaction between plants and microorganisms. A hot research of endophytic fungi is separation of the substance with the novel structure.In earlier stage work, a endophytic Acremonium sp. fungi strain HND5has been isolated from the leaves of the Brachiaria brizantha. According to the evaluation results of indoor and outdoor activity, the strain broth and volatile gas have strong antagonistic for a variety of tropical crops common pathogenic fungi. This study optimized fermentation conditions of HND5to increase the strains biomass. The secondary metabolites from ethyl acetate extract components of the mycelium and fermentation broth were isolated and identificated. Obtained the following results:In this paper, the optimal culture meidium was determined by one factor experimental design and orthogonal experimental design. The results indicated that the best culture medium contained4.1%sucrose,2.24%yeast extract,0.005%ZnSO4-7H2O,0.05%K2HPO4,0.05%MgSO4-7H2O and the proportion of C/N was10:1. One factor experimental design was used to determine the optimal culture condition. The results showed that28℃, the initial pH8.0,120r/min,10%initial inoculation amount were the best culture conditions for HND5.In this study, the fementation broth of HND5was extracted with ethyl acetate, and the compounds from the extract were isolated by column chromatography, then the structures of all the compounds were elucidated by physicochemical and spectral data (UV, IR, MS,1D NMR and2D NMR).Four known compounds were isolated from mycelium extract. They were elucidated as: Peroxide of ergosterol (1),(22E,24R)-ergosterol-27,22-diene-6β-methoxy-3β,5a-diol (2), a-Ethyl-fructofuranosidase (3), Daucosterol (4).Eight known compounds were isolated from the extract of the fementation liquid. They were elucidated as:Cyclo-(L-Pro-L-Tyr)(5), Cyclo-(L-Pro-L-Phe)(6), Cyclo-(L-Pro-L-Leu)(7), Cyclo-(L-Pro-L-Ile)(8), Cyclo-(L-Pro-L-Ala)(9), Cyclo-(L-Pro-L-Val)(10),3’-deoxyinosine (11), Uracil (12). Among them, compound5-10are isolated from Acremonium sp. for the first time.