Each minute around the world about 1 million plastic bottles are sold. Only 14% are recycled, the rest ends up in the environment, landfills or oceans, polluting even the remotest and wildest parts of our planet, harming marine life and eventually people who eat seafood.
“It is incredibly resistant to degradation. Some of those images are horrific,” said Prof John McGeehan, at the University of Portsmouth, UK, who led the research.“It is one of these wonder materials that has been made a little bit too well.”
Last April, in a Japanese dump, scientists discovered, quite by accident or chance, a bug eating plastic which could help solve the global plastic pollution crisis. This accident could be one of the biggest discoveries of our century. Scientists have created a mutant enzyme able to break down plastic bottles, a breakthrough enabling for the first time the full recycling process of bottles.
Back in 2016, scientists already found the first bacterium that had naturally evolved to eat plastic. Spurred by this discovery, they have today revealed the detailed structure of the crucial enzyme produced by the bug. The international team had inadvertently made the molecule even better at breaking down the PET plastic – mostly used for plastic bottles. “What actually turned out was we improved the enzyme, which was a bit of a shock,” said John McGeehan. “It’s great and a real finding.”
Far faster than the centuries it takes in the oceans to break down the plastic, the enzyme only takes a few days to start the process. However, researchers think that it can be speeded up to become a viable largescale process: “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,”said McGeehan. “It means we won’t need to dig up any more oil and, fundamentally, it should reduce the amount of plastic in the environment.”
However, currently even those bottles that are recycled can only be turned into opaque fibres for clothing or carpets. The new enzyme allows to recycle clear plastic bottles back into clear plastic bottles, which could stop the need to produce new plastic.
“You are always up against the fact that oil is cheap, so virgin PET is cheap,”said McGeehan. “It is so easy for manufacturers to generate more of that stuff, rather than even try to recycle. But I believe there is a public driver here: perception is changing so much that companies are starting to look at how they can properly recycle these.”
The structure of the enzyme looked very similar to one evolved by many bacteria to break down cutin, a natural polymer used as a protective coating by plants. But when the team manipulated the enzyme to explore this connection, they accidentally improved its ability to eat PET.
“It is a modest improvement – 20% better – but that is not the point,” said McGeehan. “It’s incredible because it tells us that the enzyme is not yet optimised. It gives us scope to use all the technology used in other enzyme development for years and years and make a super-fast enzyme.”
Other types of plastic could be broken down by bacteria currently evolving in the environment, McGeehan said: “People are now searching vigorously for those.”PET sinks in seawater but some scientists have conjectured that plastic-eating bugs might one day be sprayed on the huge plastic garbage patches in the oceans to clean them up.
“I think [the new research] is very exciting work, showing there is strong potential to use enzyme technology to help with society’s growing waste problem,”said Oliver Jones, a chemist at RMIT University in Melbourne, Australia, and not part of the research team.
“Enzymes are non-toxic, biodegradable and can be produced in large amounts by microorganisms,”he said. “There is still a way to go before you could recycle large amounts of plastic with enzymes and reducing the amount of plastic produced in the first place might, perhaps, be preferable. [But] this is certainly a step in a positive direction.”