Aflatoxin B1 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 B₁ (AFB₁)-biodetoxification fungi. These fungi were identified as <i>Aspergillus oryzae</i> MAO103 and <i>A. oryzae</i> MAO104 by sequencing the beta-tubulin gene. The two <i>A. oryzae</i> strains were able to degrade more than 90% of AFB₁ (initial concentration: 40 μg/l) in a culture broth in 14 days. The mutagenic effects of AFB₁ treated with <i>A. oryzae</i> MAO103 and MAO104 significantly decreased to 5.7% and 6.4%, respectively, in the frame-shift mutation of Ames tests using <i>Salmonella typhimurium</i> TA98. The base-substituting mutagenicity of AFB₁ was also decreased by the two fungi. Moreover, AFB₁ production by <i>Aspergillus flavus</i> was significantly decreased by the two <i>A. oryzae</i> strains on soybean-based agar plates. Our data suggest that the two AFB₁-detoxifying <i>A. oryzae</i> strains have potential application to control AFB₁ in foods and feeds.