Identification of bacillomycin D from Bacillus subtilis fmbJ and its inhibition effects against Aspergillus flavus

The study aimed to determine the structure and component of the antifungal substances against Aspergillus flavus produced by Bacillus subtilis fmbJ. With separation and purification, four of antifungal substances against A. flavus were obtained. By means of ESI-MS/CID analysis, their molecular weight was determined as being 1030D, 1044D, 1058D, 1072D, and the amino acid component of the antifungal substances were identified as being Asn-Tyr-Asn-Pro-Glu-Ser-Thr, which agreed with amino acid sequence of bacillomycin D. The mechanism of bacillomycin D against A. flavus was investigated. Bacillomycin D exhibited a high antifungal effect on the mycelium growth, sportulation and spore germination of A. flavus with the inhibition rate of 85.72%, 98.10% and 96.63% respectively under 200 μg/mL of purified bacillomycin D. It was found that bacillomycin D could injure the cell wall and cell membrane of the hypha and spore, then, cytoplasms and organelles inside the cell were exuded and form empty hole by observation of SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy). The growth of A. flavus on corns could be completely inhibited in the presence of bacillomycin D at the concentration of 200 μg/g to 400 μg/g.