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Biodetoxification to mitigate mycotoxin DON in grains

Principal Investigator: Ting Zhou

Research Institution: Agriculture and Agri-Food Canada (AAFC)

Timeline: November 2019 – March 2023  

Objectives:

  • To develop a green technology to mitigate DON (mycotoxin) contamination in grains based on the microbial epimerization system recently discovered by AAFC which is able to detoxify DON into less / non-toxic compounds by microbial and enzymatic conversions.

Impacts:

  • Assure grain farmers sustainable profits with possibilities of valorization of contaminated grains.
  • Provide multiple grain industries with innovative, highly-specific​, environmentally​ green, yet safe and effective mycotoxin mitigation tools to proactively mitigate the risks of DON.
  • Ensure consumer confidence in Canadian grains by reducing food-safety risks associated with DON.   

Scientific Summary:

Contamination of grains, such as corn and wheat, with the mycotoxin deoxynivalenol (DON) has long been a serious problem in Canada and many other countries around the world. While there are yearly variations, the prevalence and severity of DON contamination in Ontario corn has been higher in the past five years with 2018 as the worst year. In the survey by the Ontario Ministry of Agriculture and Food, 40% of the corn samples showed 2 ppm DON or higher, and 25% of the total samples had 5 ppm or more DON; much higher than previous years. Calculated using acreage and yield, Ontario produced more that 360 million bushels corn in 2018, resulting in an estimated 90 million bushels of corn highly (5 ppm or higher) contaminated with DON. Grain Farmers of Ontario estimated a $200 million revenue loss to farmer-members in 2018 alone due to significant reduction or complete loss of market value. The severe contaminations of Ontario corn crops in 2018 undoubtedly signified that new strategies are much needed for mitigating this unavoidable mycotoxin.

The contamination of animal feed with DON costs millions of dollars of loss to Canadian producers annually due to reduced weight gain and/or higher prices for feed with lower DON levels (Pestka, 2007). These losses can be especially high during years of heavy Fusarium infection (such as feed produced from the 2016 and 2018 harvest). Currently there is no satisfactory way of mitigating the effects of DON in feed; no chemical means of destroying mycotoxins has been approved in any jurisdiction and mycotoxin binders have not been approved by either the CFIA or the FDA. There have been no binders shown to be effective for DON (Danicke and Doll, 2010), and in one study binders were shown to increase DON concentration in plasma (Osselaere et al., 2012). Even in feed that is below the threshold for DON contamination, it is believed that interactions between multiple toxins may lead to deleterious effects on animals (Wielogórska et al., 2016). Bioconversions / biodetoxifications with microorganisms and their enzymes offer an effective and environment-friendly green technology for mitigating the serious DON contamination problem; DON can be detoxified, not just bound to be later released after feeding as is potentially the case with binders. Enzymes are currently used in food and feed production processes, demonstrating that adding enzymes is safe and does not disrupt the process.

Recently Dr. Ting Zhou’s research group at AAFC-Guelph Research and Development Center has developed an effective biological detoxification system, known as the DON epimerization (Dep) system. A bacterial strain, Devosia mutans 17-2-E-8, originating from an Ontario agricultural soil sample, was discovered to have the capability to convert the DON molecule at its C3 position, hence detoxifying the mycotoxin under more practical feed processing conditions before the toxin enters the animal alimentary canal. This system detoxifies DON to 3-keto-DON, a molecule with approximately 5-fold less toxicity than DON and converts 3-keto-DON to 3-epi-DON a compound shown to be at least 50-fold less toxic than DON. The two enzymes, designated as DepA and DepB, responsible for the DON detoxification have been identified. It was shown that DepA can convert 100% of DON to 3-keto-DON and 3-keto-DON completely disappears from solution when treated with DepB. These enzymes have been optimized, expressed and purified in the lab and an initial characterization has shown these enzymes function over a wide pH range and are stable at 60°C. Under lab conditions these enzymes can easily be produced, purified and used to rapidly detoxify DON.

This project will further develop the system with the ultimate goal of applying the system to detoxify DON in contaminated grains and animal feeds. A list of mycotoxins that the Dep system is able to detoxify and how efficiently it detoxifies the other mycotoxins compared to DON will be determined; the possibility to use the Dep system in liquid feeding system and methodologies for using the Dep enzymes at different feed production systems will be determined and developed. The project will also develop methodologies for applications of the detoxification microorganisms at different feed production stages. The results obtained from the project will be comprehensively​ analysed and the various methods (enzymes or microorganisms)​ developed for detoxifying DON in different points of feed production will be thoroughly compared,  which should pave the way for future industrial commercialization.

External Funding Partners:

Agriculture and Agri-Food Canada (AAFC)

Funding for this project has been provided by Agriculture and Agri-Food Canada.

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