Plastic-eating enzyme could help fight pollution, scientists say


Originally discovered in 2016 in sediments at a bottle recycling site in the port city of Sakai, Japan, the team has successfully modified the enzyme - known as Ideonella Sakaiensis - to break-down PET bottles at an accelerated rate of just three days.

One man's trash is this enzyme's lunch.

Two scientists have accidentally stumbled upon an organic enzyme that can eat some of our worst polluting plastics, providing a possible solution to what is arguably one of the world's biggest environmental problems.

Scientists have created a mutant enzyme that breaks down plastic drinks bottles made from polyethylene terephthalate (PET), and they did it completely by accident.

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.

"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".

United Kingdom consumers use around 13 billion plastic drinks bottles a year but more than three billion are not recycled.

The researchers, who published their findings in the journal Proceedings of the National Academy of Sciences on Monday, are now working to further improve the enzyme so it can be used on an industrial scale.

The research team used the Diamond Light Source, near Oxford, UK - a highly-sophisticated X-ray machine which creates light 10 times brighter than the sun - to view the precise structure of the enzyme.

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Using the PETase blueprint provided by the Diamond Light Sources, the scientists re-engineered an active region of the molecule.

"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", McGeehan told The Guardian. And according to the Earth Institute at Columbia University, only 9.5 percent of plastic is recycled and there are already 165 million tons of plastic debris in our oceans.

Lead scientist prof John McGeehan, from Portsmouth university, said: 'Serendipity often plays a significant role in fundamental scientific research, and our discovery is no exception.

"These enzymes are not abundantly present in nature, so you would need to produce the enzyme first, then add it to the PET plastic to degrade it", Wim Soetaert, head of the Industrial Biotechnology Centre at the University of Ghent, pointed out. The structure of PET is too crystalline to be easily broken down and while PET can be recycled, most of it is not.

PETase was also tested on PEF plastic, a proposed plant-based alternative to PET that is similarly slow to degrade in nature.

And that was when the unexpected happened - the researchers found that the PETase mutant was better than the natural PETase in degrading PET.

The research was funded by the University of Portsmouth, NREL and the Biotechnology and Biological Sciences Research Council (BBSRC).

The paper's lead author is postgraduate student jointly funded by the University of Portsmouth and NREL, Harry Austin.