Screening, Identification and Fermentation Conditions Optimization of Antagonistic Bacteria LBC-2 against Alternaria brassicae and Biocontrol Efficiency

Strain LBC-2 with strong antagonistic activity to cabbage spots pathogens was screened by confrontation method. Twenty strains with antagonistic activities against Alternaria brassicae had been screened on plate in preliminary screening, and a strain named LBC-2 with a relatively higher antagonistic activity was obtained in secondary screening. The mycelium shape, colony characteristic observation, a series of physiological and biochemistry experiments and determination of the sequence of 16 SrRNA of the LBC-2 had been done. LBC-2 was identified as Bacillus methylotrophicus. The concentration of fermentation conditions were optimized through orthogonal design and the final fermentation medium had more fermentation productions. The optimum medium and culture condition of strain were all studied with single factor test. The strain was easy to cultivate, and the optimal antibiotic production condition was in a medium(20 g/L sucrose, 30 g/L soybean meal, 0.5 g/L CaCl2, 0.1 g/L ZnCl2, pH 7.5) at 37 ℃200 r/min for 40 h. The control efficacy was 79.08%, and the result of the plot trials showed that LBC-2 had a visible preventive effect on cabbage black spot disease.