Abstract:Bacillus subtilis strain BAB-1 exhibited an effective inhibitory activity against Botrytis cinerea which caused tomato gray mold.To clarify the chemical nature of the antagonistic compounds,lipopeptides were isolated from the cultural supernatant of strain BAB-1 by the methods of hydrochloric acid precipitation and methanol extraction.The lipopeptide compound showed a similar retention time to the standard sample of surfactin in HPLC and TLC analyses.Furthermore,ESI/MS analysis of the purified surfactant revealed 3 + ion peaks at m/z 1 009.3,m/z 1 023.4 and m/z 1 037.4 respectively,which were in agreement with the 3 homologous compounds of standard surfactin.Specific PCR amplification of the sfp gene fragment confirmed the existence of the surfactin biosynthetic genes in strain BAB-1.In addition,the purified surfactin had hemolytic and oil expansion activities,and its crystals appeared a cruciate structure under light microscope.