Food contaminated with molds can be an inconvenience at best and life-threatening at worst. But new research shows that removing just one protein can leave some mold toxins high and dry, and that may be good news for food safety.
Some molds produce toxic chemicals called mycotoxins that not only spoil food, such as grains, but can also make us sick. Aflatoxins, one of the more dangerous types of mycotoxins, can cause liver cancer and other health problems in humans.
“It’s a silent enemy,” says fungal researcher Özgür Bayram of Maynooth University in Ireland, because most people don’t notice when foods like corn or wheat go bad.
For years, researchers knew that some fungi produce these toxins, but they didn’t know all the details. Now Bayram and colleagues have identified a group of proteins responsible for triggering the production of mycotoxins. Genetic engineering of the fungus Aspergillus nidulans removing even one of the proteins prevents the toxins from being made, the researchers report in the Sept. 23 issue of Nucleic Acid Research.
“There is a long line of genes involved in the production of proteins that, in a cascade effect, will result in the production of various mycotoxins,” said Felicia Wu, a food safety expert at Michigan State University in East Lansing, who was not involved in the investigation.
The newly identified proteins act like a key to start a car, Bayram says. The researchers wanted to figure out how to remove the key and prevent the start signal from going through, meaning no toxins would be created in the first place.
Bayram and his team identified the proteins in A. nidulans, showing that four proteins come together to make the key. The researchers genetically engineered the fungus to remove each protein in turn. When one of the four proteins is missing, the key doesn’t trigger mycotoxin inflammation, the team found.
In another study yet to be published, deactivating the same group of proteins in the closely related fungus A. flavus, which can make aflatoxins, prevents the production of those toxins, Bayram says. “So this is a great success, because we see the same, at least in two fungi [protein] complex does the same.”
The new work “builds on a body of research done for decades” to prevent mold contamination of food, Wu says. Several methods are already being used to control such contaminants. For example, because not all A. flavus strains produce aflatoxins, one method to prevent contamination is to spread nontoxic strains on fields of corn and peanuts, Wu explains. Those fungi multiply and can help prevent other poisonous strains from gaining a foothold.
This research is one of many ways that researchers are using genetic engineering to try to combat these toxins in food (SN: 3/10/17). A future application of the new research could be to genetically tweak a toxin-forming fungus and then potentially use it on crops and elsewhere. “In principle, we can prevent aflatoxin contamination in food, for example in the field, even in the warehouses, where a lot of contamination occurs,” says Bayram.
Fungi and fungus-like organisms known as water molds are estimated to wreak havoc one third of the world’s food crops per year. If that contamination can be prevented, Bayram estimates the food saved would be enough to feed 800 million people by 2022.
The new research is a good start, Wu says, but trying to understand how to operationalize this for agricultural purposes will still be challenging. It’s unclear how scalable the technique is, she says, and it could be difficult to get U.S. regulatory agencies to approve the use of a genetically modified fungus on key food crops.