Could a mutant enzyme solve the planet's plastic problem?
Plastic pollution is reaching crisis level. Of the 1 million plastic bottles sold every minute across the globe, only 14% are recycled. The vast amount of unrecycled plastic that ends up in our oceans contaminates marine ecosystems and harms ocean life.
A huge part of the problem is the strong plastic used in drinks bottles: polyethylene terephthalate (PET). It currently takes hundreds of years for PET to break down naturally in the environment.
But now a team – led by our own Professor John McGeehan, Director of the Centre for Enzyme Innovation, and Dr Gregg Beckham of the US Department of Energy’s National Renewable Energy Laboratory (NREL) – has created a new mutant enzyme that breaks down plastic bottles faster.
Their modified version of the PETase enzyme – first discovered in a Japanese waste dump in 2016 – starts breaking down plastic in days. The discovery could revolutionise the recycling process and help solve one of the planet’s biggest environmental issues.
The breakthrough took place after the team examined PETase's structure at Diamond Light Source, near Oxford – where intense X-rays 10 billion times brighter than the sun revealed its individual atoms.
There's an urgent need to reduce the amount of plastic that ends up in landfill and the environment. I think if we can adopt these technologies we have a potential solution to doing that
The structure of the enzyme was similar to one evolved by many bacteria to break down cutin – a natural polymer used as a protective coating by plants. The team then manipulated the enzyme to explore this connection.
And when they did, they found they had improved its ability to eat PET in the process. Further tests also revealed the enzyme can degrade polyethylene furandicarboxylate (PEF), a bio-based PET alternative.
A patent for the enzyme has been filed, and now Professor McGeehan and team – which includes our PhD student, Harry Austin – are working on improving it for industrial use.
And in doing so, they're opening the door to a sustainable recycling solution to the world's plastic problem.
Professor McGeehan said: "(To improve the enzyme) was a bit of a shock and while it is a modest improvement – 20% better – that is not the point.
"It’s incredible because [the research] tells us that the enzyme is not yet optimised. It gives us scope to use all the technology used in other enzyme development and make a super-fast enzyme.
"(PET) is incredibly resistant to degradation. It's one of these wonder materials that's been made a little bit too well.
"There is an urgent need to reduce the amount of plastic that ends up in landfill and the environment. I think if we can adopt these technologies we actually have a potential solution in the future to doing that."
It’s incredible because [the research] tells us that the enzyme is not yet optimised. It gives us scope to use all the technology used in other enzyme development and make a super-fast enzyme.