INNOVATIVE STRATEGIES FOR MITIGATING CONTAMINATIONS OF MYCOTOXINS IN GRAINS: BIOLOGICAL DETOXIFICATIONS OF DEOXYNIVALENOL

According to Food and Agriculture Organization (FAO) 780 million people in the world are till starving /undernourishment in 2016, however, tremendous amounts of harvested grains are rejected for human consumption because of mycotoxin contaminations. FAO has estimated that about 25% of the world’s agricultural produce is contaminated with various mycotoxins. Deoxynivalenol (DON) is one of the most prevalent mycotoxins commonly found in grains associated with fungal infections of Fusarium species, and it is a documented health hazard and a food safety risk for humans. The presence of this mycotoxin in grains accounts for a great portion of food and feed rejections and costs the global economy billions of dollars annually in trade losses. Recent data indicates that changes in the global climate have affected fungal pathogen populations resulting in increased severity of Fusarium diseases and therefore DON contamination in certain geographic regions. Above of all, new intervention strategies are much needed for controlling such mycotoxin as the current early detection and elimination technologies have proved inadequate. Innovative strategies and technologies, such as postharvest treatments with UV radiation, plasma-based technology, etc. are being explored for the mitigation of DON contamination in food/feed commodities. More significantly, due to its safety, specificity and other advantages, interests in developing microbial and enzymatic DON detoxifications are being increased notably. Several aerobic and anaerobic microorganisms selected from ruminants, swine, poultry, fish, and other agricultural commodities have been found to exhibit various DON transformation capabilities. The need for restrictive conditions during DON bio-transformation, such as an anaerobic atmosphere and/or the presence of DON as the sole carbon source, has limited the applications of these isolates. The most recent isolation and characterization of Devosia mutans 17-2-E-8, a novel gram-negative bacterium capable of transforming DON to a non-toxic epimer, 3-epi-DON, under aerobic conditions is opening doors for better management strategies of this mycotoxin. The enzymatic epimerization process proceeds through a two-step bio-catalysis. DON is initially oxidized to a short living intermediate, 3-keto-DON, that is specifically reduced in a later stage to 3-epi-DON. This proposes an irreversible bioconversion system of DON which particularly addresses many of the issues observed earlier in connection with the exploitation of enzymatic biotransformations for detoxification purposes. The enzymes responsible for the epimerization system have been identified and showed great effectiveness when tested in vitro. Further studies are underway to optimize the enzymes for more sustainable applications in mitigating Fusarium toxin contaminations. Considering the involvement of DON in the pathogenesis of different Fusarium species, it looks very plausible to develop plants that are resistant/tolerant Fusarium diseases by utilizing the epimerization process of DON. The enzymes would also have the capacity to minimize the possible passage of DON contamination to food/feed value chains when applied in post-harvest treatments such as the wet-milling of grains or semi-liquid feeding of animals.