Screening Of High Producing Strain Of Avermectin B1a Component

In this paper,Streptomyces avermitilis strain 1-17 producing avermectin was mutated with UV and NTG on spores, then induced and selected by L-Ile, an avermectin B1a high-yielding strain 3-6 was selected, which produced 12.86% more avermectin Bla than the parent strain. Subculture test indicated that the heredity character of strain 3-6 was stable.The influences of different culture conditions were investigated. The result showed: The place of yeast extract production in slant medium, the cultural period of slant seed and the weight of tampon could influence the quantity of the slant seed and fermentation.Through analysis, it has been determined that the most suitable yeast extract production place is Hubei, the best cultural period of slant seed is 8 days, the most suitable weight of tampon is 7 g. The fermentation medium was optimized through orthogonal design, the yield was increased by 7.35 %. In addition, the effect of the addition of sodium proplonate precursor on fermentation was studied. The result showed that adding the certain density of sodium proplonate in fermentation medium could obviously increase the yield of fermentation. Adding 2.5 mmol/L sodium proplonate into the medium at 24 h, the yield of fermentation was increased by 9.89 %.The metabolism characteristic of the strain 3-6 in 3 ton seed tank and 100 ton fermentation tank were researched. The result showed: The proceed of the seed culture was optimized through the judgement of inoculation and adjusting the culture tempreture to 30℃; The fermentation proceed was optimized through adjusting the ratio of starch, the feeding time of glucose and the aeration rate. The avermectin yield of fermentation was increased. The fermentation unit, the total fermentation measurement of a batch and the index figure were increased each from difference by 14.81%,7.77%,6.92%.