Aflatoxin B1 Detoxification Activities Produced by Fungi Isolated from Meju, a Korean Traditional Fermented Soybean Product

Introduction: Aflatoxins (AFs) are toxic secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus on agricultural crops. Aflatoxin B₁ (AFB₁) is the most potent human carcinogen among major AFs. Since AFB₁ could pose a threat to human health, it is needed to find methods for controlling AFB₁ contamination in foods.

Purpose: The purpose of this study was to investigate AFB₁-biodegradation activities of fungal isolates from meju, a Korean traditional fermented soybean product for safe application to foods.

Methods: The AFB₁-biodegradation activities were investigated using cultures of Aspergillus oryze, Aspergillus tubingensis, and Rhizopus oryzae. The Ames test was used to confirm the AFB₁-biodegradation activities of the fungal isolates.

Results: All of the 3 fungal isolates showed significant AFB₁-biodegradation activities in liquid cultures; the amount of AFB₁ was reduced by more than 60% within 14 day cultures. Cell-free culture broth of the fungal isolates degraded more than 50% of AFB₁ within 7 day cultures. The Ames tests with Salmonella Typhimurium TA 98 mutants showed that the mutagenic effects of AFB₁ decreased to 5.6, 4.9, and 6.0% in frame-shift mutation when treated with the 3 fungal stains. The base-substituting mutagenicity of AFB₁ with the fungal isolates on Salmonella Typhimurium TA 100 also decreased to the same level as a control (52.3%).

Significance: The AFB₁-biodegradation activities produced by the 3 fungal isolates could be applied safely to foods.