Researchers make DON breakthrough

Agriculture Canada scientists close in on a way to detoxify vomitoxin in wheat, barley and corn crops

Researchers at Agriculture Canada have discovered a naturally occurring soil-borne bacteria that has the potential to detoxify deoxynivalenol or DON, a mycotoxin that affects important Canadian crops such as wheat, barley and corn.

The discovery has potential to greatly reduce economic losses related to DON, a pathogen that can render infected cereal grains unfit for consumption by humans or livestock.

“Vomitoxin, or DON, has been a serious issue for corn and other cereal crops for a long time,” said Agriculture Canada scientist Ting Zhou.

“The discovery of this bacteria definitely opens a very big door for solving this problem….”

Ting, based at Guelph, Ont., is a leading expert in development of biological strategies aimed at controlling mycotoxin contaminations in food and animal feed.

DON is caused by a number of fungal pathogens, most notably fusarium graminearum, that reside in the soil. The fungi thrive in wet conditions, reducing yields and producing toxins that infect the grains of harvested cereal crops.

Once contaminated with DON, infected grains are difficult to detoxify because the toxins are resistant to heat treatment and other processing methods.

Harvested crops that contain small amounts of DON can be used as feed for some types of livestock, but higher levels make the grain unusable as animal feed.

Consumption of contaminated grains by livestock can result in illness and weight loss.

Infected grains can be used in ethanol production but the co-products, including distillers dried grains (DDGs), cannot be used in livestock rations.

Ting’s research identified a naturally occurring but previously unreported bacterial species — Devosia mutans — that has the potential to detoxify DON and inhibit the pathogen’s growth.

The bacteria produces two enzymes, DepA and DepB, which alter the molecular structure of deoxynivalenol and convert DON to a non-toxic or much less toxic form.

The detoxifying effects of the enzymes have been confirmed in experiments involving laboratory mice, Ting said.

In addition to inhibiting the pathogen in the field, the enzymes may also be able to detoxify infected harvested grain.

High DON levels can greatly reduce the economic value of harvested grain and in severe cases, can make grain crops unmarketable.

Estimates vary but economic losses associated with the disease have been valued at hundreds of millions of dollars annually, particularly when growing conditions are conducive to fusarium graminearum.

Ting said commercialization of the bacteria or the enzymes it produces may be years away.

Commercial products that stem from the research could come in many forms, he added.

“The technology … can work in both pre-harvest and post-harvest (situations),” Ting said.

“For example, maybe the bacteria can be used in the field as a soil amendment….”

“Another possibility is that maybe it can be applied as a biological agent … on the plant.”

Other possible applications include seed treatments or additives that could be mixed with infected feed grains.

“In the long run … because we already have the enzymes identified (that are responsible for altering the molecular structure of DON) we also have access to genes … that can possibly be used to make the plants themselves more resistant to the disease.”

This is not the first time that scientists have looked for bacterial solutions to address toxicity in harvested grain.

But according to Agriculture Canada, it is the most promising for reducing economic losses associated with DON.

Unlike previous discoveries of bacteria that can detoxify DON contaminated grain, Devosia mutans doesn’t need DON as a food source to grow and it can grow at lower temperatures, in the presence of oxygen.

In a recent news release, Agriculture Canada said the bacteria discovered and named by Ting is “well suited to industrial applications as there is potential to add the bacteria, or just the two purified enzymes, to harvested grain in storage to reduce contamination to levels acceptable for animal feed.”

The research serves as a foundation for the development of a feed treatment to detoxify DON, particularly in liquid-feeding systems, Ag Canada added.

Cereals Canada president Cam Dahl said Ting’s findings demonstrate the value of research and innovation to the Canadian ag industry.

“If we could … resolve the issue of DON, that would be a significant benefit to farmers across the country…,” Dahl said.

“Fusarium and DON has been a huge issue and resolving it is very much at the top end of the list of research objectives.”

Ag Canada said it will now look to partner with industry groups to develop commercial products, such as microbes and enzymes.

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