Avermectin Strain Screening And Optimization Of Fermentation Process

Avermectin is a sixteen membered macrolide compound,belonging to the macrolide antibiotic,which is mainly composed of Streptomyces avermitilis.With the application of Avermectin in depth,at present avermectin can be applied in crops,livestock and human medicine are involved.In this paper,the avermectin producing strain Streptomyces avermitilis as the research object,in order to improve the fermentation level of avermectin for the purpose of the study on mutation screening,control optimization of medium optimization and fermentation process of fermentation.Research results:1.Using UV,LiCl and NTG Mutagenesis method in combination with the breeding of avermectin producing strains,1 high yield strain were obtained,the experimental results show that the UV mutation in 60s with NTG induced concentration of 2.05 mg/ml,obtain high-yield mutant strain was 9.6%higher than the control strain yield.The mutation strain after 5 passages,its genetic stability,its genetic stability..2.The fermentation medium of high yield mutant UV-NTG-A7 was optimized.Through the substitution experiment of carbon source and nitrogen source and the price of material market,we chose cheap corn starch and high temperature soybean powder as the most suitable carbon and nitrogen sources.The results of microelement experiment showed that the potency of avermectin increased when the concentration of nickel sulfate,cobalt chloride,manganese sulfate,sodium molybdate and ammonium sulfate were 0.0003%,0.02%,0.0002%,0.0023%and 0.03%respectively.The addition of 0.6%concentration of calcium propionate to the fermented 24 h can increase the fermentation titer by 4.11%.3.The fermentation process was optimized,and the high yield strain UV-NTG-A7 was identified by seed bottle inspection.When seed was transferred to seed tank,25 h was suitable for seed selection.The best time to transfer seed was 42 h,and its fermentation potency reached 6346.0μg/ml,which was higher than that of other transgenic plants.It was determined that 8%of the transfer amount was the most appropriate.After 160 h fermentation,artificially increase the sugar point of control in advance of the fermentation tank to fill the operation and control of 4-5%sugar sugar,avermectin reached 6530.0μg/ml,fermentation control relatively high residual sugar than the original low sugar control process was increased by 19.8%.A set of fermentation techniques suitable for high yield strains was established.