Aflatoxin B-1 Detoxification by Aspergillus oryzae from Meju, a Traditional Korean Fermented Soybean Starter

Abstract

Aflatoxins are classified as Group 1 (carcinogenic to humans) by the International Agency for Research on Cancer. In this study, a total of 134 fungal strains were isolated from 65 meju samples, and two fungal isolates were selected as potential aflatoxin B-1 (AFB(1))biodetoxification fungi. These fungi were identified as Aspergillus oryzae MAO103 and A. oryzae MAO104 by sequencing the beta-tubulin gene. The two A. oryzae strains were able to degrade more than 90% of AFB(1) (initial concentration: 40 mu g/l) in a culture broth in 14 days. The mutagenic effects of AFB(1) treated with A. oryzae MAO103 and MAO104 significantly decreased to 5.7% and 6.4%, respectively, in the frame-shift mutation of Ames tests using Salmonella typhimurium TA98. The base-substituting mutagenicity of AFB(1) was also decreased by the two fungi. Moreover, AFB(1) production by Aspergillus flavus was significantly decreased by the two A. oryzae strains on soybean-based agar plates. Our data suggest that the two AFB-dteoxifying A. oryzae strains have potential application to control AFB(1) in foods and feeds.