Scissors cut paper. Paper wraps rock. Lab-made enzyme eats plastic

Brit boffins save planet

Plastic waste bottles polyethylene recycling

A new enzyme developed at the University of Portsmouth will enable the recycling of plastic used for disposable drinks containers.

A commercial infrastructure based around the enzyme would have two benefits: disposing of the original container, and creating new clear plastic for reuse.

Professor John McGeehan said the research came from studying a bacterium – Ideonella sakaiensis 201-F6 – discovered in a Japanese waste recycling centre that was capable of breaking down plastic.

McGeehan, from the University of Portsmouth, Gregg Beckham from the US Department of Energy’s National Renewable Energy Laboratory (NREL) and Lee Woodcock from the University of South Florida led the research team.

As they were attempting to replicate I sakaiensis 201-F6's properties, they "accidentally engineered" an enzyme that was even better at breaking down polyethylene terephthalate (PET). It can also chew through polyethylene furanoate (PEF), the bio-substitute for PET, more rapidly. Scientists used crystallography and 3D computational modelling at the Diamond Light Source facility in Oxfordshire to identify the enzyme and explore how it worked. Five research centres contributed.

David Attenborough drew the nation's attention to the problem of plastics pollution with his nature documentary Blue Planet 2 where he called on people to reduce their use of plastic.

However, the impetus to act on the information is not universal.

Britain banned the sale of products containing plastic microbeads in January. Environment secretary Michael Gove announced a deposit return scheme (DRS) for single-use plastic, aluminium and glass bottles, although not everyone is happy with it. The scheme is estimated to cost around £1bn to set up and £1bn a year to run.

It's the durable quality of plastic so desired by consumers that causes the pollution problem. As NREL put it: "The structure of PET is too crystalline to be easily broken down and while PET can be recycled, most of it is not. PET that is recycled often exhibits inferior material properties as well. In addition, PEF plastics, although bio-based, are not biodegradable, and would still end up as waste in landfills and in the seas."

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While the production of new plastic product is often cheaper than using recycled, McGeehan said: "It's well within the possibility that in the coming years we will see an industrially viable process to turn PET and potentially other substrates like PEF, PLA [polylactic acid], and PBS [polybutylene succinate], back into their original building blocks so that they can be sustainably recycled."

The Portsmouth boffins' paper, "Characterization and engineering of a plastic-degrading aromatic polyesterase", will be published this week in the Proceedings of the National Academy of Sciences.

McGeehan said: "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." ®

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