Mode of Action of Bacillus subtilis on Aflatoxin Control of Aspergillus flavus

Aflatoxin is one of the most hazardous mycotoxins injurious to both humans and animals. Aflatoxin contamination of crops is a serious economic loss inflicted upon agriculture, food and animal industry throughout the entire world. In nature, there are microorganisms able to alleviate aflatoxin contamination in crop products. In this work, the effects of four strains of Bacillus subtilis in reducing aflatoxin, induced by Aspregillus flavus, were investigated under in vitro conditions. The results indicated that strain BsP1 could completely inhibit the mycelial growth of A. flavus in PDB liquid medium. Strains BsP4, BsP5 and BsP38 caused a mass reduction of 58.88, 27.41 and 29.03% of fungal biomass, followed by 86.85, 21.80 and 26.16% reduction of aflatoxin B1 (AFB1), respectively. There also was a negative significant correlation observed between the decrease in fungal biomass and AFB1 production. Bioremediation studies revealed that the bacteria didn’t have the ability to remediate AFB1 after 3 days of incubation. However, the strain BsP1 could completely remediate AFB1 even after 5 days of incubation. Cell walls of these bacterial strains showed no sign of an ability for binding and removing of AFB1. The supernatant fluid of strain BsP1 was considerably able to degrade AFB1. The results finally suggest that the promising isolate of B. subtilis is of the potential to reduce aflatoxin in susceptible crops, possibly through antibiosis and degradation mechanisms.