Purification and structural identifications of the antifungal lipopeptides produced by marine bacterium Bacillus subtilis 3512A.

Bacillus subtilis 3512A,a marine bacterium,was isolated from Pacifigorgia sp. in South China Sea. The strain showed significant antagonistic activities against many pathogens. The crude antifungal extract was stable against high temperature and acid,whereas the antifungal activity reduced notably when pH value is higher than 10. Bioassay-directed fractionation using acid precipitation,flash chromatography and HPLC led to the isolation and purification of two pure metabolites. Oil-film collapsing,emulsification of toluene and on-plate hydrolysis experiments showed the two compounds are cyclic peptides. 1H-NMR experiment confirmed both of them were lipopeptide derivatives.