Biological detoxification of the mycotoxin deoxynivalenol and its use in genetically engineered crops and feed additives

Abstract

Deoxynivalenol (DON) is the major mycotoxin produced by Fusarium fungi in grains. Food and feed contaminated with DON pose a health risk to humans and livestock. The risk can be reduced by enzymatic detoxification. Complete mineralization of DON by microbial cultures has rarely been observed and the activities turned out to be unstable. The detoxification of DON by reactions targeting its epoxide group or hydroxyl on carbon 3 is more feasible. Microbial strains that de-epoxidize DON under anaerobic conditions have been isolated from animal digestive system. Feed additives claimed to de-epoxidize trichothecenes enzymatically are on the market but their efficacy has been disputed. A new detoxification pathway leading to 3-oxo-DON and 3-epi-DON was discovered in taxonomically unrelated soil bacteria from three continents; the enzymes involved remain to be identified. Arabidopsis, tobacco, wheat, barley, and rice were engineered to acetylate DON on carbon 3. In wheat expressing DON acetylation activity, the increase in resistance against Fusarium head blight was only moderate. The Tri101 gene from Fusarium sporotrichioides was used; Fusarium graminearum enzyme which possesses higher activity towards DON would presumably be a better choice. Glycosylation of trichothecenes occurs in plants, contributing to the resistance of wheat to F. graminearum infection. Marker-assisted selection based on the trichothecene-3-O-glucosyltransferase gene can be used in breeding for resistance. Fungal acetyltransferases and plant glucosyltransferases targeting carbon 3 of trichothecenes remain promising candidates for engineering resistance against Fusarium head blight. Bacterial enzymes catalyzing oxidation, epimerization, and less likely de-epoxidation of DON may extend this list in future.

The enzymatic detoxification of the mycotoxin deoxynivalenol: identification of DepA from the DON epimerization pathway

“…Several attempts to reduce DON levels through chemical means have been deemed impractical due to the associated costs or their detrimental effect on the final grain quality (Karlovsky et al ., 2016). The microbial detoxification of DON by various species has been demonstrated using a wide variety of microorganisms and been extensively reviewed (Karlovsky, 2011; Zhu et al ., 2016). Earlier reported mechanisms of DON microbial detoxification have focused on de‐epoxidation, transformation of the C3 carbon (or attached groups), or the complete mineralization of DON (Karlovsky, 2011; Zhu et al ., 2016).…”

“…The microbial detoxification of DON by various species has been demonstrated using a wide variety of microorganisms and been extensively reviewed (Karlovsky, 2011; Zhu et al ., 2016). Earlier reported mechanisms of DON microbial detoxification have focused on de‐epoxidation, transformation of the C3 carbon (or attached groups), or the complete mineralization of DON (Karlovsky, 2011; Zhu et al ., 2016). Reported modifications of C3 include oxidation and epimerization of the attached hydroxyl group, which was demonstrated to reduce toxicity (He et al ., 2015a,b).…”

“…The reduced toxicity of both reported enzymatic products (3 ‐ keto‐DON intermediate and the final 3‐ epi‐ DON stereoisomer), demonstrated in in vitro and in vivo experimental models, opens up the potential of finding an enzymatic solution to address DON contamination. Enzymes that play a role in DON detoxification through epimerization have been under intense investigation by the mycotoxin community, but their identities still remain elusive (Karlovsky, 2011). Identifying the enzymes responsible will enable the development of multiple technologies that could prove immediately useful.…”

Mycotoxins in Wheat and Mitigation Measures

“…This approach includes fungal, microbial, and enzymatic degradation of mycotoxins. Several very recent reviews on this topic can be found in the literature to which the reader is directed for specific insights [84,118,119,127,128]. Despite the many publications on this topic, this promising approach is still at a research level and far from an immediate outcome and application in practice for mycotoxin detoxification of food at industrial level.…”

Short Communication: Antioxidant capacity in the intestinal mucosa of weanling piglets fed diets containingFusariummycotoxins and the efficacy of commercial supplements sold as detoxifiers

“…While researchers have studied numerous feed additives for this purpose, few have proven effective in reducing the negative effects of DON in pigs (Do¨ll and Da¨nicke 2004;Karlovsky 2011). The blend of yeast cells, bacteria and plant extracts would be efficient to mitigate the negative effect of Fusarium toxins on growth performance in poultry (Da¨nicke et al 2002;Ghareeb et al 2012) but not in pigs (Barnes et al 2010), whereas aluminosilicates were not able to mitigate adverse effects of trichothecenes in pigs (Do¨ll et al 2005).…”