Researchers ‘accidentally improve’ a plastic-munching enzyme

Researchers have created an enzyme that can break down the pervasive kind of plastic which takes hundreds of years to degrade; they did it by accident.


Electron microscope image of enzyme degrading PET plastic.
Image credits Dennis Schroeder / NREL.

The team initially started their research intending to take a better look at the crystal structure of a recently-discovered enzyme, PETase. This substance has evolved naturally and is known to break down and digest polyethylene terephthalate (PET) plastics. However, sometime during our intrepid band’s quest for knowledge, ‘disaster’ struck — the team introduced an unwanted mutation to PETase, making it more efficient at munching plastics than the original.

‘I totally wanted to do that, haha!’

“Serendipity often plays a significant role in fundamental scientific research, and our discovery here is no exception,” says co-author John McGeehan, a professor of structural biology at the University of Portsmouth in the U.K.

PETase was first detected in the bacterium Ideonella sakaiensis. The critter made a home in the soil under a PET-recycling facility in Japan and employed this enzyme to dine on bits of plastic waste that got lodged in the ground. Researchers think PETase is a redesigned version of an ancient enzyme aimed at breaking down waxy coatings, which plants sometimes employ to defend their tissues. This made PETase doubly attractive as a research subject: first, to help us understand its evolutionary path, and secondly because it could help us fight our ever-growing problem of plastic waste.

During their research, the team inadvertently changed the enzyme’s structure — this, however, had the fortunate effect of making it more effective, the team notes.

PETase doesn’t work very fast, and definitely isn’t up to the task of munching our plastic waste. The accidentally-improved version is a tad more efficient, but it’s main advantage isn’t speed: it’s scope. Its tweaked structure allows it to attack and consume another type of plastic called polyethylene furandicarboxylate (PEF), “literally drilling holes through the […] sample, according to co-author Gregg Beckham, a senior engineer at the National Renewable Energy Laboratory (NREL).

Still, despite its bigger teeth and expanded menu, this PETase 2.0 is still facing a mammoth challenge. Estimates place the global amount of plastic waste at around 9 billion tons (8.3 billion metric tons) — half of which has been produced since 2004. The findings, however, suggest that we may be able to solve the global plastic problem by improving enzymes such as PETase in the lab. Further research on this particular enzyme and its lab-derived cousins could lead to even more efficient plastic munchers, the authors report.

“Given these results, it’s clear that significant potential remains for improving its activity further,” said study co-author Nicholas Rorrer, a postdoctoral researcher at NREL.

The paper “Characterization and engineering of a plastic-degrading aromatic polyesterase” has been published in the journal Proceedings of the National Academy of Sciences.

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