US, British Researchers Develop Plastic-Eating Enzyme

Sean Reid
April 17, 2018

Our plastic pollution crisis is only getting worse, but scientists may soon have a valuable new tool to chip away at the problem.

Scientists have improved a naturally occurring enzyme which can digest some of our most commonly polluting plastics. The new enzyme indicates a way to recycle clear plastic bottles back into clear plastic bottles, which could slash the need to produce new plastic.

So they mutated the PETase active site to make it more like cutinase, and unexpectedly found that this mutant enzyme was even better than the natural PETase at breaking down PET.

Professor John McGeehan and his team from the University of Portsmouth along with Dr Gregg Beckham from the US Department of Energy's National Renewable lab had both been trying to find a way of combating this plastic pest when they stumbled on the solution.

As for when we can expect to see industrial degradation processes developed using this enzyme, in order to make plastics more recyclable, that depends on how well the researchers can improve its performance through engineering. "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".

Professor John McGeehan at work in his laboratory.

It has the capacity to digest PET plastic that was patented in the 1940s and now used in million tons, especially to manufacture bottles.

The findings of the team were published on Monday in the Proceedings of the National Academy of Sciences journal.

Working with United States colleagues, the Portsmouth scientists subjected PETase to intense X-ray beams at the Diamond Light Source synchrotron facility in Harwell, Oxfordshire.

PET now lasts for hundreds of years in the environment and this accidental discovery could provide a viable recycling solution for millions of tonnes of bottles and packaging.

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.

"I think [the new research] is very exciting work, showing there is strong potential to use enzyme technology to help with society's growing waste problem", said Oliver Jones, a chemist at RMIT University in Melbourne, Australia, and not part of the research team.

According to Innova Market Insights data, 58 percent of globally launched food and beverage products are packaged in plastic, a 5 percent increase from 2013, while 96 percent of all newly launched water products in 2017 are packaged in PET bottles.

PETase is secreted by a plastic-eating bacterium called Ideonella sakaiensis 201-F6. "Few could have predicted that in the space of 50 years, single-use plastics such as drink bottles would be found washed up on beaches across the globe", said McGeehan.

"After just 96 hours you can see clearly via electron microscopy that the PETase is degrading PET", says NREL structural biologist Bryon Donohoe.

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