Isolation And Identification Of Bacillicus Subtilis KC-5 And Its Fermentation Optimization

The microbial resources in soil are very rich. Bacillus subtilis is one of the microbial groups with important research and application value. Because of its high ability of stress resistance and antifungal activities, Bacillus subtilis has shown great application and development value in the field of biocontrol.With Crossed the plate method and Tablet confrontation France, this study isolated an antagonistic strain from the rape rhizosphere soil samples collected in Jiaonan Langyatai, which could inhibit the activity of Fusarium oxysporum, Fusarium moniliforme, layers of Fusarium and Fusarium solani. By analyzing morphological, physiological and biochemical, and phylogenetic of 16S rRNA sequences, the strain was identified as Bacillus subtilis and named KC-5.In order to improve fermentation efficiency of this strain, the study of its fermentation medium and fermentation conditions was conducted to determine optimum fermentation medium components and optimum conditions, the former contained corn starch 5g/L, soybean meal 12.5 g/L, NaCl 12.18 g/L, KH2PO40.5 g/L, CaCO31.25 g/L, MgSO4 0.2 g/L and MnSO4 0.25 g/L, and the latter included 2% inoculum concentration, initial pH 7.0 and a rotation speed of 200 rpm at 30℃. Under these conditions, the cell number reached 47×108cfu/ml. In order to be applied in production, KC-5 cells were expansively cultured in fermentation tank and maximum number of spores reached to 30.3 X 108 cfu/ml.To verify the potential biocontrol application of Bacillus subtilis KC-5 in the field, its control effect on cucumber plants was measured. The results showed that Bacillus subtilis KC-5 had some potential biocontrol on Cucumber stem blight.