Post-harvest biodegradation of aflatoxin B1 in rice grain and peanut seeds infected with Aspergillius flavus using a recombinant oxidase from Armillaria tabescens

Abstract

Post-harvest contamination of agroproducts including rice and peanut with aflatoxin B1 (AFB1) produced by Aspergillus flavus is a global problem in conventional and sustainable agriculture. AFB1 degradation by microbial enzymes, which convert this dangerous compound to non-toxic or less toxic derivatives, is considered as a promising detoxification approach that meets the main principles of organic farming. Advanced technologies of protein heterologous expression open wide avenues for large-scale production of such enzymes. In this study, we used a recombinant extracellular AFB1 oxidase (rAFO) from Armillaria tabescens expressed in Pichia pastoris yeast cells to degrade AFB1 in rice grain and peanut seeds artificially inoculated with a toxigenic A. flavus strain. The homogenous enzyme was purified from cell-free culture liquid using immobilized metal affinity chromatography. Treatments of the infected samples with an aqueous solution of freeze-dried rAFO preparation for 72 h at 30 or 20–22°C resulted in a significant (2.5- and 3-fold) reduction in the mycotoxin contamination of peanut and rise, respectively. The obtained results showed rAFO may be promising as an environment-friendly tool for providing the safety of organic agricultural production. The possibilities to improve same rAFO characteristics to promote the practical application of the enzyme are discussed.