Sources of aflatoxin-degrading enzymes for potential use in decontaminationof agricultural products

Abstract: To find microbial sources of enzymes which catabolaze aflatoxin we screened 41fungal strains, belonging to 18 genera, which co-colonize natural substrates with toxigenic A.flavus. Aflatoxin-catabolizing potential of each strain was assessed, in vitro, by cultivation for 7days in liquid media supplemented with aflatoxin B1. After incubation, the amount of B1remaining in the cultural filtrates was quantified by HPLC and compared to that of controls (nofungal inoculum). Among the tested strains, 28 were able to degrade B1 to varying degrees. Themost active B1 degradation was found in isolates of Phoma glomerata, Cladosporium sp.,Gliocladium roseum and Ulocladium sp., which catabolized 80-98% of the B1. One time-coursestudy on aflatoxin catabolism showed that G. roseum degraded almost 50% of the B1 within thefirst 3 days of culture. Interestingly, one biocontrol agent, Trichoderma viride, degraded B1 insubmerged, liquid cultures only if the fungus was cultured on solid agar containing B1 prior toinoculation into liquid media.