Study On The Agro-antibiotics A11 Against Pyricularia Grisea

A strain named A11 is isolated from the soil of farm fields in Sichuan Agricultural University. It is identified as Norcardia sp. strain characterized through colony analysis and biochemical determination. It produces an antibiotic substance which can obviously inhibit Pyricularia Grisea. To use strain A11 as starting strain, some high yield mutant strains are obtained after UV irradiation, DES treatment and Microwave irradiation. When UV irradiates it for 120s,the best forward-mutant strain than others is obtained. Through fermentation, the mutant strain which is irradiated by UV for 120s increases by 43.4% compared with the starting strain. And the mutant strain which is irradiated by MV for 20s increases by 32.8% compared with the starting strain; Moreover, the mutant strain of DES treated by 0.2% density increases by 32.8% compared with the starting strain. Afterconstant cultured 8 times, the strains' hereditary characters are stable.On shaking flask lever, we screened the optimum carbon and nitrogen sources by single-factor experiment in fermentation media. Then, we screened the optimum level of every component of the fermentation media by orthogonal experiment. We also investigated temperature, inorganic factor, volume and agitation. The optimum condition to higher chemical potency was obtained: fermentation media: starch soluble 5%, soybean powder 2%, KH₂PO₄ 0.1 %,NaCl 0.1%, CaCO₃ 0.4%. biomass 10%,temperature 28℃,speed of shaking incubator 160r/min,time of fermentation 4d.The routine to isolate and purify the antibiotics from A11 fermentation products was established on the basis of studies on biological activity, thin layer chromatography, high performance liquid chromatography and other purified method research. The mycelium cake was extracted by mixture solvent of chloroform and ethyl acetate(l:2,v/v), then the extraction solvent was concentrated to get concentration material. And the concentration material was dissolved by acetone. After centrifugation, the sedimentation was abandoned...