UK scientists engineer an enzyme that eats plastic

An accidental discovery by scientists from the University of Portsmouth have raised hopes that an enzyme can digest polluting plastics on an industrial scale.

By Kieren Puffett
Published 9 Apr 2019, 00:39 BST
Photograph by David Jones

It’s one of the most promising breakthroughs in the fight against plastic pollution – an enzyme that can digest plastic that is commonly found polluting our environment.

The discovery could result in a recycling solution that can process millions of tonnes of plastic, made from polyethylene terephthalate (also known as PET), which currently persists in the environment for hundreds of years.

The research was led by teams at the University of Portsmouth and the US Department of Energy’s National Renewable Energy Laboratory (NREL), with the results being published in the National Academy of Sciences (PNAS).

The findings follow the discovery of an enzyme that had evolved to digest PET plastic, which is often used in the production of plastic bottles, food containers and even fibres in clothes. Professor John McGeehan from the University of Portsmouth and Dr Gregg Beckham at the NREL, studied the crystal structure of this enzyme to understand how it works.

Serendipity Strikes

Electron microscope image of enzyme degrading PET plastic
Photograph by Dennis Schroeder, Nrel

During the study, the team accidently engineered a mutant version that is even better at degrading the plastic than the one that has evolved in nature.

The researchers are now working on further improving the effectiveness of the enzyme so it can be applied to industrial uses where it can break down plastic in a fraction of the time.

Professor McGeehan, Director of the Institute of Biological and Biomedical Sciences in the School of Biological Sciences at Portsmouth, 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.”

Enzyme Evolution

During the study of the enzyme and its plastic digesting abilities, Professor John McGeehan and colleagues inadvertently engineered a quicker acting version than the one which had evolved in nature.
Photograph by Stefan Venter, Upix Photography

The breakthrough came through the examination of the structure of the enzyme that had evolved in nature and thought to have been discovered in a recycling site in Japan. The aim was to understand how the enzyme had evolved and to see if it might be possible to improve it. During the study, however, the team accidently engineered an enzyme that was even better at breaking down PET plastic.

“Serendipity often plays a significant role in fundamental scientific research and our discovery here is no exception,” Professor McGeehan said.

“Although the improvement is modest, 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.”

Discarded Plastics

The challenge of removing plastic that is polluting the world's oceans is a major one, and the ability of this enzyme to digest plastic could provide one of the solutions.
Photograph by David Jones

The research team can now apply the tools of protein engineering and evolution to continue to improve the enzyme. The research also revealed that the enzyme can also degrade olyethylene furandicarboxylate, or PEF, a bio-based substitute for PET plastics that is being hailed as a replacement for glass beer bottles.

Professor McGeehan said: “The engineering process is much the same as for enzymes currently being used in bio-washing detergents and in the manufacture of biofuels –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, and PBS, back into their original building blocks so that they can be sustainably recycled.”

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