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A race against climate change spurs discovery of enzyme that transforms toxin threatening corn

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Producers in Canada are all too familiar with fungi and the problems they can cause in the field, during processing or in storage. Fungi often secrete small toxic molecules called mycotoxins that help them survive on the host crops. Mycotoxin contamination can have huge economic impact for farmers, and ingestion by humans or livestock can cause significant negative health consequences, including death.

While some fungi prefer dry conditions, others thrive in moist climates. With climate change and warmer temperatures, the fungi that create fumonisin mycotoxins will reproduce even more. It’s the perfect environment for increased threats to our food system.

Almost every food source can be a host for fungi that make toxic chemicals. Grains like corn and wheat are particularly susceptible, and it’s concerning because we produce so much of these crops for food, feed and bioethanol. There are hundreds of these fungal compounds that threaten to end up in our food systems. In developing countries, the mycotoxin threat can often mean loss of human and animal life. In Canada, fungi threaten economic losses caused by destroyed crops rather than health consequences, mainly due to the vigorous testing procedures we have in place.

“Ways to improve food and feed safety through reducing the toxicity of mycotoxins are needed. Total losses to mycotoxins in Canada can be as high as $1 billion in a very bad year and global loss estimates are in the billions of dollars each and every year.”

- Dr. Mark Sumarah, a mycotoxin and fungal expert at the London Research and Development Centre in London, Ontario

It was while analyzing one kind of mycotoxin in his lab — fumonisin — that Mark began to ask an important question: “I wondered how the fungus could produce so much toxin but not have that toxin kill itself,” he says.

“Although fumonisins are currently not a big problem in Canada, they are very likely to be a threat to Canadian crops as the climate warms up. I began to ask what do we need to do to meet this challenge head on.”

Mark’s colleague, Dr. Justin Renaud, a chemist specializing in metabolomics and analytical chemistry, suggested they analyze the fumonisin mycotoxin using the Centre’s high resolution mass spectrometer.

“This piece of equipment is so powerful, it allows us to identify things that are present before we even know what we’re looking for,” he explains. “It allowed us to see everything that was being made by the fungi that makes the fumonisin mycotoxin.”

In fact, the spectrometer helped them discover two new types of non-toxic fumonisin mycotoxins. They could actually see how the fungus had figured out how to remove a single atom in order to ensure it didn’t harm itself. “It’s making the toxic fumonisins into a non-toxic form after the concentration gets to a certain level,” says Justin.

Fascinated by these new toxins, Mark and Justin shared their discovery with a third London colleague, Dr. Chris Garnham, a biochemist and structural biologist who had just started up his own lab at the Centre.

“They told me that these newly discovered toxins were likely generated by an unknown enzyme and asked if I could help them find the enzyme responsible,” says Chris. “The research sounded interesting and challenging, and I thought it would be a good way for me to apply my protein biochemistry skills into a brand-new research area and collaborate with my colleagues.”

Chris isolated and analyzed protein from the fungus and, after some trial and error, successfully identified the enzyme responsible for decreasing the toxicity of the molecule. The real test, however, would be when he cloned this enzyme to test how it reacted in yeast systems similar to those used in bioethanol production — would it remove the toxin in this real world scenario and not just in its native host?

“This enzyme fully converted the fumonisin toxin into a non-toxic form,” says Chris. “Needless to say, we were very excited when we saw the data indicating the enzyme was active and capable of targeting fumonisins.”

The enzyme, which is now pending a patent, shows great promise to be used as a tool to remediate fumonisin-contaminated food and feed. The researchers are working with their Canadian industrial partner Lallemand Inc. to further develop this enzyme into a safe and effective tool to improve the quality of food and feed for Canadian producers and consumers.

“The collaboration between Mark, Justin, and I worked well because we each brought unique skill sets that complement each other's research programs very well,” says Chris. “This really will be a win for farmers, a win for animals and a win for bioethanol processors.”

What’s next for this research trio? They’re working on finding an enzyme that will attack vomitoxin in corn and wheat — another threat to Canadian farmers. Given their success, the future looks promising.

Key Discoveries (Benefits)

Photo gallery

Headshot photos of three scientists who worked on this research – Dr. Chris Garnham, Dr. Mark Sumarah, Dr. Justin Renaud
Dr. Chris Garnham, Dr. Mark Sumarah, Dr. Justin Renaud
Yellow microscopic crystals of the discovered enzyme that removes the harmful effects of the toxin.
Crystallized enzyme
Glass beaker containing blackened corn kernels covered with white fuzzy fungus.
Fusarium verticillioides (fungus that produces fumonisin mycotoxins) growing on corn
The corn kernels have turned black while the fungus (white) grows.

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