The Study On The Antifungal Substance Produced By A Strain Of Bacillus Amyloliquefaciens

HN-06, a strain of antagonistic to plant pathogenic, was isolated from soil. HN-06 strain shows a strong inhibitory effect on some plant pathogenic fungi. It has a applicable prospect. This strain was identified. Its medium components and fermentation condition were optimized. The antifungal substance produced by HN-06 was purified preliminaryly and its physicochemical properties were studied. The results were as follows:HN-06 was identified as Bacillus amyloliquefaciens by study on phenotypic characteristics, physicochemical properties and phylogenetic analysis of 16Sr DNA sequences. HN-06 shows inhibitory effect on many pathogens such as Aspergillus niger, Magnaporthe oryzae, Rhizoctonia solani, Fusarium oxysporum and et al.Medium components and fermentation conditions of HN-06 were studied by single factor experiments, and then further optimized by L₁₆(4⁵) orthogonal experiment. The results showed the optimal condition was glucose 0.15%, soybean peptone 0.5%, KCl 0.05%, MgSO4 0.07%, Initial pH 7.5, inoculum2%, fermentation temperature 30℃, seed age 20h .The antifungal substance produced by HN-06 was separated by using ammonium sulfate salt-out. The result showed that it was salted out by 50% saturation of (NH4)2SO4. The precipitation was dissolved with ultrapure water, then the antifungal substance was purified by sephadex G-75 column chromatography and CM-cellulose iron exchange column chromatography. The antifungal substance was sensitive to high temperature, it lost completely its antifungal activities by 60℃heating treatment over 30min, while it maintained its activity well under lower temperatures. The antifungal substance had higher activity at the pH6.0 - 10.0, and highest activity at the pH7.0 - 8.0.