One answer to the plastic waste problem? Hungry, hungry enzymes

The world has a major problem when it comes to waste plastic. A reported 91% of plastic is not recycled, adding up to billions of tons over the past decades. Much of this winds up becoming trash. A hungry, plastic-munching “enzyme cocktail” could help.

Researchers at the U.K.’s University of Portsmouth and the National Renewable Energy Laboratory in Golden, Colorado, have developed an enzyme that’s capable of breaking down polyethylene terephthalate (PET) into its composite building blocks impressively quickly — like, days instead of hundreds of years. This means that plastics could be manufactured and reused endlessly. That, in turn, could have a significant impact on our reliance on fossil resources like oil and gas. In short, it could turn out to be a game-changer for recycling.

The international team of investigators behind the enzyme mix has been working on this problem for a while. They previously had some promising results with a plastic-consuming enzyme called PETase. But in their latest work, they have re-engineered it in a lab and combined it with a second enzyme called MHETase, for a proof-of-concept mixture able to digest plastic up to six times faster than their previous creation.

“This project essentially joins two natural enzymes that originated in the bacterium discovered in [a] Japanese PET recycling site,” John McGeehan, director of the Center for Enzyme Innovation at Portsmouth University, told Digital Trends.

Although this combination is undoubtedly impressive, however, McGeehan said there is still more fine-tuning to be done. “While we see a six times activity improvement in this chimeric enzyme compared to the PETase enzyme alone, there is large scope for further improvements using protein engineering,” he said. “In addition, we also have the potential to connect other enzymes together to tackle different plastics or mixed plastics. This current enzyme is too slow to be commercially viable at this point, but companies such as Carbios are already starting to build large-scale plants to do this.”

A study describing the work, titled “Characterization and engineering of a two-enzyme system for plastics depolymerization,” was recently published in the journal Proceedings of the National Academy of Sciences of the United States of America.

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