Abstract:

In order to improve the yield of antagonistic substance produced by B. velezensis 6-61 which has antagonistic activity against Verticillium dahliae Kleb, the analysis of the properties of antagonistic substance and fermentation conditions optimization of stain 6-61 were studied to provide a basis for further study of the antagonistic mechanism. First, the fermented broth of strain 6-61 was treated by two following methods: extraction with organic solvent and precipitation by ammonium sulfate respectively. The results indicated that the component of strain 6-61 responsible for antagonistic activity was considered as protein. Then, the optimum fermentation medium ingredients, such as carbon sources, nitrogen sources and inorganic salts, were determined by using the single-factor methods. And the optimal medium compositions and other fermentation conditions of antagonistic bacteria 6-61were optimized through 16(44) orthogonal experiment. The final optimization of the medium was obtained as follows: malt sugar 3%, soybean protein peptone 3%, NaCl 0.01%, KCl 0.01%, pH 7.0, inoculation volume 8%, seed culture time 16 h and bottle filling capacity 30 mL/250 mL. In the optimal medium compositions and culture conditions, the inhibition zone diameter of the fermentation liquid could reach 36mm. And the final fermentation medium has more fermentation productions compared with some other common media.