The Screening Of High Yield Strain And The Study On The Fed-batch Fermentation Process Of Avermectins

Avermectin is a good antibiotic insecticide,miticide,which shows high biological activity on harmful mites of variety crops and other pest.Because of its unique mechanism of action,Abamectin can effectively prevent the pests and mites which generate resistance and patience on the general insecticide,miticide.Nowadays,Avermectin is one of the ideal agricultural pesticide varieties on Agricultural integrated pest control.Avermectin, as a pesticide,was put into the market in 1985.A huge market potential make it as a hot topics.Avermectin preparation has the largest production value among varity microbial pesticides in China, its annual output has reached million tons.With the development of domestic agriculture and animal husbandry and the spread of biological pesticides,the demand of avermectin will certainly grow steadily,with a vast development prospects.The most important factors to determine Avermectin fermentation producing level include three aspects:Strain,Fermentation craft and Extraction Process.Currently,the pervasive problem in Avermectin fermentation is the low output and high production costs.In most domestic pharmaceutical companies, the avermectin fermentation level only get to 3000μg/mL,seriously restricting the competitiveness of avermectin pharmaceutical manufacturers,which restricts the further development of enterprises.The urgent problem need to be solved at present,that is how to improve the fermentation unit of avermectin,and how to reduce its production costs.Therefore,it’s extremely important to Selectively breed avermectin high yield strain,to optimize the fermentation craft,and to improve the Avermectin fermentation unit.This study carries out two aspects:the screening of Avermectin high yield strain and the establishment of the fed-batch fermentation process of Avermectin.Firstly,in the screening of avermectin producing strain,choose mutagen:5-FU and Avermectin,combines them with UV mutagenesis,and do the mutation breeding on the original strains of abamectin.Under study, with comprehensive survey the factors of selected strains’s morphology,biomass,sugar consumption rate and the fermentation unit and other factors,screening the avermectin high yield strain X-28-68.Secondly,determination of the fed-batch fermentation process of avermectin.Taking screening test method for single factor,select the optimum carbon source,the optimum nitrogen and phosphate that new fermentation required,and get the optimum fermentation medium:Monose B,soybean meal,yeast powder,nitrogenB,dipotassium hydrogen phosphate,calcium carbonate, ammonium sulfate and related various trace elements.This medium is conducive to rapid growth of mycelium,early synthesis of product,and development of feeding process. Subsequently,determination of the optimal concentration on carbon source,nitrogen source and phosphate,and study of the continuous fed-batch fermentation process,ensure the appropriate concentration of each component in medium, the optimum pH of bacteria growth and continuous feeding fermentation process of glucose. Small fermentor test shows that the fermentation index of new strain, new craft can reach 1.6221,is 46.70%higher than the original batch fermentation average index of 1.1057,avermectin production get increased greatly.Finally,pilot plant test of fermenter on new strains,new craft 2m3.The test result is: fermentation unit get to 4680mg/L, increased by 15.6%,the loading coefficient get increased by 15%, the fermentation cycle get shorten for 40 hours or so,the average fermentation index is 1.6486,it get increased by 41.12%,compared with the original process index of 1.1857.But large-scale fermentation production needs further experiments.