Purification and Characterization of Antifungal Lipopeptide From Bacillus amyloliquefaciens BI_2

摘要

Bacillus amyloliquefaciens BI_2 isolated from straw feed was shown to be antagonistic against Aspergillus flavus. Crude extract of antagonistic substance was obtained by ultrafiltration, nanofiltration, acid precipitation, and solvent extraction and it was stable to high temperature, different pH value, and several proteinases. Then the pure substance was isolated and purified by Sephadex G-15 column chromatography and prepared thin-layer chromatography. Oil-film collapsing, emulsification of toluene and on-plate hydrolysis experiments showed the compound was cyclic peptide, and its molecular structure was determined by UV absorption spectrum and infrared absorption spectrum following the amino acid analysis, ESI-MS and MS-MS. It showed that isolated compound consists of three homologues with molecular mass 1,008, 1,022 and 1,036 Da, and bearing a cyclic structure. Meanwhile, it also showed that antifungal substance had absorption peak at 206 nm. All of those indicated that the isolated substance belongs to the homologues of surfactin.