Global team engineers plastic digesting enzyme

Global team engineers plastic digesting enzyme

Scientists have engineered a biological enzyme which can rapidly digest some of the most common forms of polluting plastics that persist for hundreds of years in the environment.

As the researchers were using the 3D information of this stucture to understand how it works, they inadvertently engineered an enzyme that is better still at degrading the plastic than the one that evolved in nature.

Scientists have created a mutant enzyme that is able to recycle plastic bottles.

"Other types of plastic could be broken down by bacteria currently evolving in the environment, McGeehan said: "People are now searching vigorously for those".

Ever hopeful: Prof John McGeehan at work in his laboratory.

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The new research was spurred by the discovery in 2016 of the first bacterium that had naturally evolved to eat plastic, at a waste dump in Japan.

NREL and the University of Portsmouth collaborated closely with a multidisciplinary research team at the Diamond Light Source in the United Kingdom, a large synchrotron that uses intense beams of X-rays 10 billion times brighter than the sun to act as a microscope powerful enough to see individual atoms. They and Gregg Beckham are among the worldwide team of researchers who are working to further improve the enzyme to allow it to be used industrially to break down plastics in a fraction of the time.

"What we are hoping to do is use this enzyme to turn this plastic back into its original components, so we can literally recycle it back to plastic", said Prof John McGeehan. "There is strong potential to use enzyme technology to help with society's growing waste problem by breaking down some of the most commonly used plastics". The structure was found to be very similar to that of the bacteria capable of breaking-down cutin, a natural polymer used as a protective coating by plants.

"What we've learned is that PETase is not yet fully optimised to degrade PET", biotechnologist Gregg Beckham from NREL explains.

Once they understood its structure, the team noted that they could improve the performance of PETase by adjusting a few residues on its surface.

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"It is a modest improvement - 20% better - but that is not the point", said McGeehan. The team is now working to continue refining the engineered enzyme to make it even more effective.

PET is relatively easy to recycle, but over half of global PET waste is not collected for recycling, according to research from the Ellen MacArthur Foundation, and only 7 percent of bottles are recycled into new bottles (most go into lower-value products).

He also added, "We can all play a significant part in dealing with the plastic problem, but the scientific community who ultimately created these "wonder-materials", must now use all the technology at their disposal to develop real solutions".

To examine PETase's efficiency at the molecular level, the team used X-rays to generate an ultra-high-resolution 3D model of the enzyme, revealing an unprecedented glimpse of PETase's active site that enables it to grip and break down its PET target - and also, by chance, how that mechanism can be improved.

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