Scientists accidentally engineer an enzyme that eats plastic

Scientists from the UK and US have accidentally engineered an enzyme that can digest some of world’s most commonly polluting plastics.

The discovery could result in a recycling solution for millions of tonnes of plastic bottles made from PET, which currently persists for hundreds of years in the environment.

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

Professor John McGeehan at the University of Portsmouth and Dr Gregg Beckham at NREL solved the crystal structure of PETase—a recently discovered enzyme that digests PET— and used this 3D information to understand how it works. During this study, they inadvertently engineered an enzyme that is even better at degrading the plastic than the one that evolved in nature.

The researchers are now working on improving the enzyme further to allow it to be used industrially to break down plastics in a fraction of the time.

Professor McGeehan said: “Few could have predicted that since plastics became popular in the 1960s huge plastic waste patches would be found floating in oceans, or washed up on once pristine beaches all over the world.

“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.”

The researchers made the breakthrough when they were examining the structure of a natural enzyme which is thought to have evolved in a waste recycling centre in Japan, allowing a bacterium to degrade plastic as a food source.

PET, patented as a plastic in the 1940s, has not existed in nature for very long, so the team set out to determine how the enzyme evolved and if it might be possible to improve it.

The goal was to determine its structure, but they ended up going a step further and accidentally engineered an enzyme which was even better at breaking down PET plastics.

“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.”

The research team aims to now apply the tools of protein engineering and evolution to continue to improve it.

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

Dr Colin Miles, head of strategy for industrial biotechnology at BBSRC, said: “This is a highly novel piece of science based on a detailed molecular-level understanding of an enzyme able to depolymerise a common type of plastic, whose persistence in the environment has become a global issue. 

“It will be interesting to see whether, based on this study, the performance of the enzyme can be improved and made suitable for industrial-scale application in the recycling and the future circular economy of plastic.”