Scientists may have just discovered a solution to one of the world’s largest environmental problems – plastic waste. Researchers accidentally engineered an enzyme capable of digesting common plastic pollutants, which they say could help recycle millions of tonnes of plastics that often end up in the Earth’s oceans.
Led by teams at the University of Portsmouth in the United Kingdom and the United States Department of Energy’s National Renewable Energy Laboratory, researchers made the discovery while studying a “plastic-eating bacteria” that evolved in a Japanese waste collection facility and was discovered in 2016.
The teams were studying a natural enzyme the bacteria possessed to determine its structure and how it evolved. In the process, they engineered a new enzyme that breaks down plastics made of polyethylene terephthalate (PET) better than the original enzyme they were studying. Their findings were published on Tuesday in the Proceedings of the National Academy of Sciences.
“Serendipity often plays a significant role in fundamental scientific research and our discovery here is no exception,” said Professor John McGeehan, director of the Institute of Biological and Biomedical Sciences at the University of Portsmouth.
“Although the improvement is modest, this unanticipated discovery suggests that there is room to further improve these enzymes, moving us closer to a recycling solution for the ever-growing mountain of discarded plastics.”
While some countries in Europe have implemented measures to reduce single-use plastics and subsequent waste, plastic pollution remains a global problem. PET plastics, commonly used in plastic bottles, remain in the environment for hundreds of years before breaking down, which pollutes natural areas and harms wildlife around the globe.
“Few could have predicted that since plastics became popular in the 1960s huge plastic waste patches would be found floating in oceans, or washed up on once pristine beaches all over the world,” said Prof McGeehan.
Prof McGeehan said the enzyme, known as PETase, was unique because “it digests something man-made. Most enzymes are digesting maybe grass stains or things like that in your clothing. But this material has only existed for the last 50 years, so to have an enzyme involved that actually eats this man-made material is really stunning.”
While the discovery offers hope for reducing plastic pollution, environmentalists have pointed out that there is still a long way to go. Currently, the enzyme only works on PET and PEF, a plant-based plastic alternative, and takes several days to break the substances down.
The researchers are currently looking at ways to improve the enzyme using protein engineering and evolution so that it could be used on an industrial scale.
Prof McGeehan was optimistic about the potential of the discovery: “It’s well within the possibility that in the coming years we will see an industrially viable process to turn PET and potentially other substrates like PEF, PLA, and PBS, back into their original building blocks so that they can be sustainably recycled.”