| Biocontrol strains Bacillus subtilis S-16. which has distinct control effects for sunflower disease caused by Sclerotinia sclerotiorum(Lib.) deBary, is isolated from the rhizosphere of Sunflower, The test was conducted by the agronomy laboratory in Inner Mongolia Agricultural University. Previous studies have found that B. subtilis S-16 has obvious control effect on sunflower sclerotinia. In order to develop and utilize the strains to make biological control agents, it is used in agricultural production. Spore content in the preparation i:the main factor which influences the biological control effect of the preparation. This experiment on B. subtilis S-16 used for fermentation medium and fermentation conditions, through the method of combining liquid to increase the amount of spores in the fermented liquid. This reduces the cost of production and simplifies the production process, preparing the ground for large-scale industrial production.The study firstly uses a one factor-at-a-time experiment to select notable factors-wheat bran, sweet potato vinasse. CaCl2 that affect the bacteria amount of strain S-16, using response surface analysis method to optimize, it identifies the best fermentation groups:wheat bran 3.42%. sweet potato feed are 2.29%, CaCl2 0.5%, K2HPO40.03%,KH2PO40.01%, MgSO4·7H2O 0.02%. MnSO4 H2O 0.01%, Fe2(SO4)3 0.01%, NaCl 0.2%, ZnSO40.03%.Fermentation medium components are determined, in the liquid fermentation conditions of initial pH, temperature. rotating speed of the shake-flask, bottled fluid volume and quantity ultimately determine the best fermentation condition:the initial pH of 7.2-7.4, culture temperature 32 ℃, rotation speed of 190 r/min, bottled fluid volume is 500 mL triangle into 200 mL medium, and 3% inoculated quantity. After optimizing the fermentation of the strain S-16 liquid, the bacteria amount of the fermentation liquid increases from 14.83×108cfu/mL up to 72.125×108 cfu/mL, nearly 4.87 times. |
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