Study On Fermentation Of Strain NRRL8165 And The Synergism Between Avermectin And Bacillus Thuringiensis

The solvent system of thin-layer chromatography was screened. Avermectins can be isolated in the developing solvent chloroform: ethylacetate: methanol (30:3:1). By orthogonal test, the fermentation media of Streptomyces avermitilis NRRL8165 were screened, and the yield of Avermectin Bl component of improved media was 1.87 times as high as that of the control medium. Furthermore, we studied the metabolism of NRRL8165 during the fermentation.The method of isolation and determination of Avermectins by High Performance Liquid Chromatography with Photodiode Array Detector was examined. The Relative Standard Deviation values were 0.2percent and 0.5percent; the rates of recovery were 98.8% and 100.0%. These showed that the method was precise and reliable.The synergism of Avermectins and Bacillus thuringiensis to Plutella xylostella and Heliothis armigera in 1:500~1:1500(w/w) were tested. When the proportions were 1:10000~ 1:20000, the mixtures were synergism to Spodoptera exigua.The mixtures of Avermectins and Bacillus thuringiensis were dried by Spray-Dryer. The powder was available. The results of bioassay showed that the toxicity of this powder remained. Furthermore, effects of five kinds of anti-ultraviolet material (AU-a, AU-b, AU-c, AU-d, and AU-e) on protecting Avermectin Bl components were tested. We found that the material AU-b was superior to the others. We added the material AU-b to the powder in the proportion of 1:50(material AU-b: Avermectin, w/w). After 2 hours' exposure under the ultraviolet lamp, the loss of Avermectins in the powder with material AU-b reduced 13.9% compared with that in the powder without anti-ultraviolet material. In addition, the loss of toxicity in the powder with material AU-b reduced 12.6% in bioassay.