Iturin produced by Bacillus pumilus HY1 from Korean soybean sauce (kanjang) inhibits growth of aflatoxin producing fungi

A new strain of Bacillus pumilus, designated HY1, was isolated from Korean soybean sauce (kanjang). This classification was based on morphological, physiological, and chemotaxonomic features of the organism that identified it as a Gram-positive bacillus, and confirmed by 16S rDNA based phylogenetic analysis. Strain HY1 showed strong antifungal activity against the aflatoxin-producing fungi Aspergillus flavus and Aspergillus parasiticus, two common contaminants of fermented soybean foods. MALDI-TOF mass analysis revealed that the antifungal compound was similar to the known lipopeptide iturin. Iturin purified from strain HY1 had three isoforms with protonated masses of m/z 1,043.4, 1,057.4, and 1,071.4, and different structures in combination with Na+ ion using MALDI-TOF MS. Purified iturin from HY1 also exhibited antifungal activity against A. flavus and A. parasiticus.