The Mutation Screening And The Production Optimization Of Avermectin Producing Strain

Avermectin (Avermectins, AVMs), also known as A Foman streptozotocin, is a kind of sixteen yuan macrolide compounds which could be used as insecticide, acaricidal, nematicidal.This paper uses ultraviolet light and nitrosoguanidine mutagenesis approaches towards Avermectin. The producing mutation strain was screened as SDSLAV-02-01,fermentation titer 5095μg/ml and 47% better than starting strain.According to the characteristics of secondary metabolites of Avermectin, Avermectin fermentation medium was optimized. Single factor method was applied to study the impact of a variety of different carbon sources and nitrogen sources on Avermectin fermentation. According to the results of shake flask, corn starch was selected as the main carbon source, and the soybean meal was selected as the main nitrogen source. Using a single factor, multi-level experimental to study the impact of the inorganic salts and trace elements in the culture medium towards Avermectin fermentation. At last, the optimized medium formula of fermentation tank is as following: corn starch 14.0%, high soybean meal 2.5%, yeast extract 1.0%, cobalt chloride 0.002%, manganese sulfate 0.00024%, molybdate Sodium 0.0023%, amylase 0.004%, calcium carbonate 0.03%, ammonium sulfate 0.03%, GPE defoamer 0.1%, Xpj680 defoamer 0.017%. It maintained the average level of the fermentation on about 5000μg/ml which is 8.4% better than the original process. The fermentation process was optimized through pilot fermentor. It was determined that the best inoculum was 8%. The fermentation dissolved oxygen was controlled by sub-controlling ventilation and stirring speed. through the study of the carbohydrate supplement process, it was determined that the fermentation unit reached 5137μg/ml which was 4.1% better than normal when the high-temperature sterilized corn starch was added in running after 200 hoursFinally, through the study on the common crystallization solvent of Avermectin, the effects of clearing impurity in different solvents were compared. As a result, the ethanol was selected as solvent. At the same time, optimizing the ratio of crystal liquor: solvent volume ratio of crystalline 1:6, the heating temperature is 60 ℃, holding time of 60 minutes, then cooling to get the crystallization, the crystallization of Avermectin process get a yield of 75.25%. The yield increased by 2.7%.