Environment

Can this plastic-eating enzyme devour our PET pollution problem?

Can this plastic-eating enzyme...
A close-up electron microscope image of the newly engineered enzyme degrading PET plastic
A close-up electron microscope image of the newly engineered enzyme degrading PET plastic
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A close-up electron microscope image of the newly engineered enzyme degrading PET plastic
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A close-up electron microscope image of the newly engineered enzyme degrading PET plastic
Professor John McGeehan from the University of Portsmouth and his team inadvertently engineered an enzyme that is better at degrading plastic than another naturally occuring enzyme
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Professor John McGeehan from the University of Portsmouth and his team inadvertently engineered an enzyme that is better at degrading plastic than another naturally occuring enzyme

Our plastic pollution crisis is only getting worse, but scientists may soon have a valuable new tool to chip away at the problem. With a little luck, researchers have happened upon an engineered enzyme with an appetite for some of the most commonly disposed of types of plastic, meaning this waste could conceivably be broken down relatively quickly rather than contaminating the environment for hundreds of years.

We produce hundreds of millions of tons of polyethylene terephthalate (PET) plastic each year for use in things like soda and shampoo bottles. Little of this is recycled, which means we are polluting our environment with materials that take centuries to degrade, much of which washes out into the ocean where it breaks into tiny pieces that are nearly impossible to track, let alone clean up.

Scientists have made some promising discoveries when it comes to putting living organisms to work on this dilemma, with wax worms and bacteria a couple of recent examples. Another is the recently discovered enzyme that consumes PET plastics called PETase, which scientists at the University of Portsmouth and the US Department of Energy's National Renewable Energy Laboratory (NREL) used as a starting point for their groundbreaking research.

The researchers set out to better understand the crystalline structure of PETase, which is believed to have come of age in a Japanese recycling center. What interested the scientists was the evolution of the enzyme, given that PET plastics have only existed in the environment since the 1940s. Their thinking was that if they could understand how it came about in a relatively short space of time, perhaps they could understand how to make it more effective at eating plastic.

They began by using a synchrotron at the Diamond Light Source facility in the UK, which allows them to see individual atoms inside the structure of the enzyme by blasting them with beams of X-ray light 10 billion times brighter than the sun. Through this method they wound up with a ultra-high resolution 3D model of PETase.

"The Diamond Light Source recently created one of the most advanced X-ray beamlines in the world and having access to this facility allowed us to see the 3D atomic structure of PETase in incredible detail," says Professor John McGeehan from the University of Portsmouth. "Being able to see the inner workings of this biological catalyst provided us with the blueprints to engineer a faster and more efficient enzyme."

Key to the breakthrough were observations that, at this high resolution, PETase appears very similar to the enzyme cutinase, but with a few notable differences. One of these was a more open active site that better allowed it to accommodate manmade polymers instead of natural variants.

This suggested that PETase had evolved in an environment with PET present, so the researchers mutated the PETase active site to behave more like cutinase, in search of more evidence of this theory. But instead of the mutated PETase proving more ineffective at degrading PET, the team found the opposite, that it actually performed better.

"Serendipity often plays a significant role in fundamental scientific research and our discovery here is no exception," said McGeehan. "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."

The engineered enzyme has the added benefit of being able to degrade polyethylene furandicarboxylate (PEF), a PET alternative that has been floated as a replacement for glass beer bottles. The team is now working to continue refining the engineered enzyme to make it even more effective.

"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 and 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," says McGeehan.

The research will be published in the journal Proceedings of the National Academy of Sciences.

Source: University of Portsmouth

8 comments
Booleanboy
Hmmm.... Brits of a certain age will recall how this could end up: https://www.imdb.com/title/tt0564476/
Bricorn
What if it "learns" to eat plastic BEFORE it becomes waste?
Vinny
It looks like the Science Fiction is becomming Science facts
Observer101
When something "eats" something else, usually there is a by-product....What is that in this case? And, what does it "eat" when plastic is not available? One must also wonder, how much is enough to "solve" the problem?
notarichman
this could help get rid of the pacific ocean waste, but i agree with others --- how do we know it won't cause massive damage to others; fish, mammals, ships, shore line facilities?
Trylon
A lot of alarmists in these comments. The enzyme doesn't "learn" to eat anything. It's an enzyme. It must be applied. You might as well be worrying that your laundry detergent will learn to clean your clothes while you're wearing them. It doesn't "eat" anything. Again, it's an enzyme, not an organism like a bacterium or a virus. If it has nothing to consume, it just sits there. It's not alive so it won't die. As for what it produces, read the linked article: "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."
ljaques
Great idea. Instead of collecting the plastics in the existing ocean garbage dump, they want to dump "enzymes they discovered by accident" into the ocean to disperse the PET into what? And what will that do to the ecosystem? Why, INSTEAD, isn't every country mandating that they collect their own sources of this trash before it ends up in the rivers and oceans? Why -aren't- we recycling all of it now? Don't add to humans' droppings, CLEAN UP YOUR OWN ROOMS, KIDS!
Craig Jennings
So what generated the enzyme in the first place? Assume a bacteria. So there you go people above, they'll have to engineer the bacteria to produce the re-engineered enzyme probably, and they don't usually like salt water. If they can just generate lots of enzyme instead, then they break down just like everything else in the world after X amount of "uses". The "replace glass beer bottles" was a bit OT, the FET it would replace PET bottles first and foremost and would have a place for "beer bottles" in places like football matches so they don't become weapons, otherwise, why would you replace 100% recyclable glass (the context of the article seems environmental pollution) except for the energy consumed perhaps but once again CONTEXT of the article.