Conversion of Aflatoxin B1 to Aflatoxicols by Various Fungi Isolated from Aflatoxicols Contaminating Corn (Feedstuff)

The conversion of aflatoxin (AF) B1 to aflatoxicols (AFL) by 10 fungi isolated from moldy corn (used for livestock feeds) which was naturally contaminated with both AF and AFL was investigated. After incubation of each strain at 25°C for 2 to 15 days in AF B1-containing medium, the amounts of AF B1 and AFL were measured. Added AF B1 was converted efficiently to AFL by Aspergillus niger (2 strains), Eurotium rubrum, Rhizopus sp. and Fusarium solani, while it was only slightly converted by a non-AF-producing strain of A. flavus. Four strains of Penicillium spp. failed to convert AF B1 to AFL, though they could degrade AF B1. In most cases, the accumulation of AFL was higher in the cultures after 6 days of incubation than in the cultures after 10 days.The effect of incubation period on the conversion of AF B1 to AFL by A. niger (one strain), E. rubrum and Rhizopus sp. was also examined. The accumulation of AFL in the cultures began on the 2nd day, rapidly increased between the 6th day and the 8th day, and then gradually decreased toward the 15th day, at the end of the incubation period.