Conversion of Aflatoxin B1 by Humicola fuscoatra.

Abstract

The conversion of aflatoxin B1 by six kinds of fungi, previously reported to assimilate aflatoxin B1, was investigated. The tested fungi were Aspergillus fumigatus, Paecilomyces lilacinus, P. inflatus, Humicola fuscoatra, Penicillium spinulosum, and Trichoderma aureoviride.After incubation at 25°C for 4 weeks, most of the tested fungi lowered the aflatoxin B1 level in the broth to less than 10% of the starting level. Penicillium spinulosum contained 80% of aflatoxin B1 in the mycelia, but the other fungi contained less than 30% of aflatoxin B1 in the mycelia. This fact suggests that aflatoxin B1 was converted by these 5 kinds of fungi.Only Humicola fuscoatra showed a marked difference in the aflatoxin conversion rate between intact and sterilized mycelia. Intact mycelia of the fungus degraded 90% of aflatoxin B1 but sterilized mycelia had no effect on aflatoxin B1. Aflatoxin B1 was converted in the mycelia of the fungus but not in the broth filtrate. These findings indicate that the conversion by Humicola fuscoatra was a biological reaction.The conversion products of aflatoxin B1 by Humicola fuscoatra were identified to be aflatoxicols A and B by TLC and HPLC, and all the reduced aflatoxin B1 was converted to aflatoxicols A and B.