Functional characterization and substrate interactions of spore coat protein A laccase from Bacillus velezensis ST15 for broad-spectrum mycotoxin transformation
This study demonstrates that a recombinant CotA laccase from *Bacillus velezensis* ST15 effectively transforms multiple mycotoxins, including the novel substrate alternariol monomethyl ether, into less toxic derivatives under optimized conditions, highlighting its potential as a versatile biocatalyst for detoxifying food and feed matrices.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Mold is a constant companion in the world of agriculture, growing on crops from the field to the storage bin. While some molds are harmless, others produce invisible chemical poisons called mycotoxins. These substances can survive cooking and processing, lingering in the food we eat and the feed we give to livestock. Among the most dangerous are toxins like aflatoxin, which can damage the liver, and zearalenone, which disrupts the body's hormonal balance. Because these poisons are so stable, removing them is difficult. Traditional methods often rely on harsh chemicals or high heat, which can ruin the food's quality or leave behind unwanted residues. Scientists have long looked for a gentler solution, hoping to find a biological tool that could break these toxins down safely, much like a specialized key fitting into a lock to disable a mechanism.
In this search, researchers turned their attention to a specific bacterium found in a traditional fermented food from China. They isolated a strain called Bacillus velezensis ST15, which showed a natural ability to reduce the levels of certain toxins in a test tube. To understand how this worked, the team looked inside the bacterium's genetic code and identified a specific gene responsible for producing an enzyme called CotA laccase. This enzyme acts as a molecular machine capable of altering the structure of chemical compounds. The researchers then took the instructions for this enzyme, copied them into a different, well-understood bacterium, and produced a large supply of the pure protein. They named this purified version rCotA.
The team put this enzyme to the test against a lineup of four different mycotoxins: zearalenone, aflatoxin B1, alternariol, and alternariol monomethyl ether. These toxins vary widely in their chemical shapes and origins, representing a broad spectrum of the threats found in food. When the researchers mixed the pure enzyme with these poisons, they observed a dramatic change. The enzyme successfully broke down all four toxins without needing any extra chemical helpers, a feat that many other enzymes struggle to achieve. The process worked best when the mixture was kept at a warm temperature between 60 and 70 degrees Celsius and in a slightly alkaline environment, conditions that are relatively easy to maintain in an industrial setting.
As the enzyme worked, it did not simply destroy the toxins; it transformed them into new, simpler molecules. Using advanced mass spectrometry, which measures the weight of molecules to identify them, the researchers tracked the changes. They found that the original poisons were converted into hydroxylated versions, meaning the enzyme added oxygen and hydrogen groups to the toxin structures. For example, zearalenone became a form with an added hydroxyl group, and aflatoxin B1 turned into a derivative known as aflatoxin Q1. Previous studies on similar enzymes suggest that these new forms are significantly less toxic than the originals, losing much of their ability to harm cells or disrupt hormones. This transformation suggests the enzyme acts as a detoxifier, turning dangerous compounds into safer ones.
To understand how the enzyme grabbed onto such different toxins, the researchers used computer simulations to model the interaction. They built a digital representation of the enzyme's active site, the pocket where the chemical reaction happens, and placed models of the four toxins inside it. The simulations showed that the pocket was flexible enough to accommodate all four shapes. The toxins held on through a combination of weak chemical attractions, such as hydrogen bonds and hydrophobic contacts, which are forces that allow molecules to stick together without forming permanent bonds. This structural flexibility explains why a single enzyme could handle such a diverse group of poisons, a trait that is rare among biological catalysts.
The researchers also tested the enzyme in a more realistic setting, using actual plant materials that had naturally become contaminated with these toxins. They treated samples of mulberry fruit and ziziphus seeds, which are common in food and medicine, with the enzyme. Even in these complex mixtures, where other plant chemicals are present, the enzyme successfully reduced the levels of the toxins. This result is significant because it shows the enzyme can function outside of a clean laboratory environment, suggesting it could be useful for treating real-world food products.
While the study confirms that this enzyme can break down these specific toxins and points toward a safer outcome, the researchers note that the safety of the new breakdown products has not been fully tested in living organisms. The work provides strong evidence that this bacterial enzyme is a versatile candidate for cleaning up food supplies. By identifying a single biological tool that can target multiple threats under practical conditions, the study offers a promising step toward safer food systems, moving away from harsh chemical treatments and toward precise, natural solutions.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.