Antifungal compounds from Bacillus subtilis B-FS06 inhibiting the growth of Aspergillus flavus
The cell-free culture filtrate (CCF) was prepared from a culture of an Aspergillus flavus antagonist, Bacillus subtilis B-FS06. The CCF inhibited the growth and spore germination of A. flavus at a series of concentrations (10, 25, 50%) (v/v). It still retained the activity after treatment at pH values ranging from 2 to 12 for 24 h or at 100 °C for 30 min. The antifungal activity, however, was reduced by 30% after treatment at 121 °C for 20 min. After purification by anion exchange chromatography, gel filtration chromatography and HPLC, the active compounds revealed six ion peaks: [M–H] m/z = 1006.78, 1020.71, 1034.74, 1049.54, 1056.78, and 1071.64 by using electrospray ionization mass spectrometry (ESI-MS) analysis. In the presence of the active compounds at 200 μg/g, the growth of A. flavus on peanuts was completely inhibited.