Scientists Accidentally Create A Plastic-Eating Enzyme

The discovery may be a breakthrough in tackling the plastic pollution crisis.

A Japanese waste dump is an unlikely location for what may be a huge breakthrough in the plastics pollution crisis.

But back in 2016, a team of Japanese scientists sifting through plastic waste found bacteria capable of breaking down and “eating” one of the world’s most popular plastics ― polyethylene terephthalate, or PET. It was hailed as a potential breakthrough at the time. But in a new twist, British and American scientists have announced that while studying this bacteria, they accidentally created a mutant enzyme that’s even more efficient at breaking down plastic bottles.

The discovery came as a team of scientists from the University of Portsmouth in the U.K. and the National Renewable Energy Laboratory in the U.S. examined an enzyme produced by the Japanese bacteria to find out more about its structure. By shining intense beams of X-rays on it, 10 billion times brighter than the sun, they were able to see individual atoms. Manipulating the structure to better understand how it worked, they accidentally engineered the mutant enzyme.

“Serendipity often plays a significant role in fundamental scientific research and our discovery here is no exception,” said John McGeehan, a biology professor at the University of Portsmouth and one of the lead scientists on the research. “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.”

A worker sorts plastic bottles at a recycling workshop in Islamabad, Pakistan.
A worker sorts plastic bottles at a recycling workshop in Islamabad, Pakistan.
Caren Firouz / Reuters

The researchers, who published their findings in the journal Proceedings of the National Academy of Sciences on Monday, are now working to further improve the enzyme so it can be used on an industrial scale.

“The engineering process is much the same as for enzymes currently being used in bio-washing detergents and in the manufacture of biofuels ― the technology exists,” said McGeehan. It’s possible that within the next few years there could be an industrially viable process for turning PET into other substances or back into its “original building blocks” so it can be sustainably recycled, he added.

The ability to scale up the process will be crucial. Plastic pollution is fast becoming one of the biggest environmental issues of our time. The mass-produced material is ubiquitous: More than 1 million plastic bottles are bought around the world every minute. That’s more than 16,000 every second. Most of these bottles are made from PET, which can take up to 400 years to biodegrade, and many are littering the oceans. Around 8 million tons of plastics enter the oceans each year.

PET is relatively easy to recycle, but over half of global PET waste is not collected for recycling, according to research from the Ellen MacArthur Foundation, and only 7 percent of bottles are recycled into new bottles (most go into lower-value products).

Some companies that rely on PET have committed to do more. Coca-Cola, for example, which produces more than 100 billion plastic bottles a year, according to Greenpeace, has promised to increase the recycled content of its bottles 50 percent by 2020.

But progress is slow, partly because big businesses have aesthetic concerns about bottles made from 100-percent recycled plastic. The newly discovered enzyme promises to recycle plastic bottles back into new clear plastic bottles, which would require much less virgin plastic.

More than 8 million tons of plastic enters the oceans each year. By 2050 it is predicted there will be more plastic than fish in the ocean.
More than 8 million tons of plastic enters the oceans each year. By 2050 it is predicted there will be more plastic than fish in the ocean.
Gary Bell via Getty Images

Some environmentalists and scientists say the breakthrough, though promising, is nowhere near enough to solve our pollution crisis.

“These enzymes are not abundantly present in nature, so you would need to produce the enzyme first, then add it to the PET plastic to degrade it,” Wim Soetaert, head of the Industrial Biotechnology Centre at the University of Ghent, pointed out. “This is likely to be a slow process. If you have gone through the trouble of collecting the PET waste, then there are clearly far better ways to recycle it or burn it for energy.” He suggested the use of commercially available biodegradable bioplastics would be a better bet.

Greenpeace’s senior oceans campaigner Louise Edge pointed to a desperate need to change recycling and consumption systems on a much wider scale.

“What we really need are system changes to reduce the volume of throwaway plastic packaging and make sure plastic drinks bottles are collected and separated effectively,” said Edge. “An enzyme alone can’t clean up the complex and widespread legacy of plastic pollution that we have already created.”

CORRECTION: A previous version of this story indicated 20,000 plastic bottles are bought worldwide every second. In fact, the number is more than 16,000.

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