Rearch On The Bio-characteristic Of Actinomycetes LA5 Strain In Fermentation And Antibiotic High Yield Mutation Breeding

The Actinomycetes strain LA5 was isolated from the capsicum plant in Hainan Province, China. The antibiotic produced by LA5 strain has strongly inhibitory to Phytophthora capsici, Fusarium oxysporum f. sp. Cubense, Colletotrichum musae, Colletotrichum gloeosporioides and Magnaporthe grisea in carrot agar plate. The fermentation liquid of LA5 had 90% control effect against capsicum blight in greenhouse. The antibiotic consists of hydrosoluble and fat-soluble components, in which the hydrosoluble component is yellowish, columelliform crystal, and the liposoluble component is brown and syrupy crystal. This antibiotic can maintain antifungal activity under environment of light, heat, and cold storage that indicates antibiotic LA5 can well match stability requirement of pesticide. The main absorption peak to UV light appears around 270 nm. It may be a multi-component and new structural antibiotic. All these indicate that antibiotic LA5 has wide potential application in control of plant diseases. But the potency of LA5 strain is rather low and its capability of producing antibiotic is not stable, and can't meet the requirement of industrious manufacture. So, it is necessary to carry out mutation breeding of LA5 strain and screen high yield strains for large-scale production of antibiotic in the future.In my study, to explore the biological character of LA5 strain fermentation in Erlenmeyer flask, the mutation breeding of LA5 strain was carried out through exposing the LA5 spores to UV light, microwave and NTQ respectively, and screened out the antibiotic high yield strains. The main experimental results are stated below:1. The results of experimenting on biological characters of LA5 strain showed thatPDA is the optimum culture medium for stain LA5 growth and producing spores. The maximum amount of LA5 mycelia appeared at fermenting for 72h. The pH value initially tended to decrease, then rise, and then decrease again. The maximum antibiotic productivity appeared at 108h and pH is 7.11 here. The optimum liquid culture volume was 50ml in 250ml Erlenmeyer flask, and the optimum inoculum amount was 1% of the liquid...