Biodegradation of Aflatoxin B1 by Edible Mushroom Cultures and Their Cell-free Extracts

Introduction: Aflatoxins are highly toxic secondary metabolites predominantly produced by toxigenic Aspergillus flavus and Aspergillus parasiticus. Of these aflatoxins, aflatoxin B₁ (AFB₁) is the most potent carcinogen. It has been reported that edible mushrooms including Pleurotus ostreatus, have AFB₁ biodegradation activity.

Purpose: The purpose of this study was to investigate the AFB₁-degrading activity of edible mushroom cultures and their cell-free extracts.

Methods: Twenty edible mushrooms in Basidiomycota were obtained from mushroom farms in Gyung-gi province in Korea. AFB₁-degrading activity was screened using potato dextrose broth (PDB) containing 50 ng/mL of AFB₁. To find out AFB₁ degradation mechanism, cell-free extracts and cell-free culture broth were spiked with 0.1 – 1 μg/mL of AFB₁ and incubated at 25°C for 2 days. AFB₁ reduction in the samples was analyzed by HPLC-FLD.

Results: AFB₁ in PDB was reduced by 5 mushrooms; Auricularia auricular-judae, Bjerkandera adusta, Hericium erinaceus, Lentinula edodes, and Poria cocos. The cell-free extract of the mushrooms showed significant AFB₁-degrading activity; AFB₁ (initial concentration of 1 μg/mL) was reduced by more than 98% by A. auricular-judae, 70% by B. adusta, 37% by H. erinaceus, and 50% by L. edodes,  respectively, within 24 hr. The AFB₁ biodegradation was enhanced in the presence of NADPH and NaIO₄. No growth of the 5 AFB₁-degrading mushrooms was observed on cumarin agar plates and no decolorization of Remazol Brilliant Blue R agar plates was found from 4 mushrooms except B. adusta.

Significance: These results indicate that the extracts from the selected mushrooms, especially edible Auricularia auricular-judae and Lentinula edodes, which are major mushrooms produced commercially in Korea, have potentials for biodegradation of AFB₁in food and feed.