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Scientists are engineering an enzyme that eats plastic waste

By Colleen de Bellefonds ; Updated April 23, 2018

News flash: We’ve got a plastic problem. If current plastics production trends continue, we’ll have produced 34 billion tons of plastic trash by 2050. That’s four times the amount we’ve produced since plastic debuted in 1907 — and nearly half of it will end up in landfills, according to recent research.

But there’s hope. Scientists have engineered a bacteria-derived enzyme that completely breaks down one type of plastic, and they plan to develop a new chemical process that can quickly and safely eliminate a huge portion of plastic waste, finds a new study published in the journal Proceedings of the National Academy of Sciences.

Researchers from the University of Portsmouth and the U.S. Department of Energy’s National Renewable Energy Laboratory set out to study PETase, a recently discovered natural enzyme (or chemical produced by bacteria) that eats polyethylene terephthalate (PET).

PET is a flexible plastic made by processing petroleum that accounts for about 10 percent of all plastics produced worldwide. What’s more, about 70 percent of soft drinks are packaged in plastic PET bottles, according to the British Plastics Federation. It’s only been around since the 1940s, and it doesn’t break down on its own for hundreds of years. That means we only have four ways right now to deal with plastic waste: It can be recycled, converted to fuel or energy, disposed of in managed waste systems or discarded, according to the Ocean Conservancy.

Current PET recycling processes, however, are relatively inefficient, explains Lee Woodcock, Ph.D., study author and associate professor at the University of South Florida’s department of chemistry — which limits the amount of PET that actually is recycled. “Ultimately, this means way more of this ends up in landfills and the environment, like the ocean, than should,” he says. In fact, an estimated 79 percent of all plastic ever produced has been discarded to date, as evidenced by a pile of floating plastic trash discovered in the Pacific Ocean that’s three times the size of France.

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Woodcock’s team wanted to understand how the PETase enzyme developed and whether they could improve upon it. Using a powerful new microscope called a synchrotron, they accidentally engineered an enzyme that’s even better at digesting plastic than the one found in nature. The newly discovered enzyme works by combining an enzyme pair (PETase and MHETase), allowing for the complete degradation of PET into its original building blocks.

“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,” said study author John McGeehan, Ph.D., a professor of structural biology and the director of the Institute of Biological and Biomedical Sciences in the School of Biological Sciences at Portsmouth.

Researchers are now working to figure out how to improve the enzyme so it can break down industrial plastic faster, which they think can be accomplished with relatively minor changes. “This is a very strong indication that further enzyme engineering can be done to greatly enhance its activity. This, no doubt, is going to be a major worldwide effort in the coming years,” Woodcock says.

Woodcock expects that it will take about a decade, give or take, before scientists improve PETase enough to start solving our plastics problem. “As these improvements occur, the ability to build pilot-scale applications to test engineered enzymes on plastic recycling will become far more practical, ultimately leading to industrial application,” says Woodcock.

PET is only one of the many types of plastics out there, but scientists are actively looking for similar solutions for other plastics. Woodcock says his team also tested their engineered PETase on another potential next-generation replacement for PET, polyethylene furandicarboxylate (or PEF). “We have plans to extend the testing of PETase to other problematic plastics and to conduct enzyme engineering on a per-plastic basis,” he says.

In the meantime, Greenpeace recommends taking the following steps to reduce your plastic use and cut down on waste:

  • Use reusable water bottles and coffee cups.
  • Skip plastic straws and disposable cutlery.
  • Bring your own cloth bags to shop at the supermarket.
  • Choose fresh foods (like fresh produce and grains from the bulk bins) over prepackaged foods whenever possible — they’re better for your body anyway!

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