Identification of Antifungal Peptides from Bacillus subtilis BS-918

Bacillus subtilis BS-918 shows strong activity against a broad spectrum of plant and postharvest pathogenic fungi. Antifungal compounds produced by BS-918 were isolated by extraction and gel chromatography, and structural identification was performed by electrospray ionization coupled with collision induced dissociation mass spectrometry. Two kinds of precursor ions belonging to iturin and fengycin were revealed. The first precursor ion at m/z 1071.7 was analyzed by collision induced dissociation mass spectrometry and was identified to be iturin A with a C₁₆ β-amino fatty acid chain. Collision induced dissociation mass spectrometry of the second precursor showed the presence of two fengycins. Ions at m/z 1449.5 and m/z 1463.9 were identified to homologs of fengycin A with C₁₅ and C₁₆ β-hydroxy fatty acid chains, whereas ions at m/z 1477.8 and m/z 1491.9 were homologs of fengycin B with C₁₅ and C₁₆ fatty acid chains.