A so-called super-enzyme that eats plastic could be a leap forward in finding ways to tackle the pollution crisis, scientists have said.
The enhanced protein comprises two enzymes produced by a type of bacterium that feeds on plastic bottles, known as Ideonella sakaiensis.
Prof John McGeehan, the director of the Centre for Enzyme Innovation at Portsmouth university, said that unlike natural degradation, which can take hundreds of years, the super-enzyme can convert plastic back to its original materials, or building blocks, in just a few days.
He told the PA news agency: “Currently, we get those building blocks from fossil resources such as oil and gas, which is really unsustainable. But if we can add enzymes to the waste plastic, we can start to break it down in a matter of days.”
The process would allow plastics to be “made and reused endlessly, reducing our reliance on fossil resources”, he added.
In 2018, Prof McGeehan and his team accidentally discovered an engineered version of one enzyme, PETase, was able to break down plastic in days.
For their study, published in the journal Proceedings of the National Academy of Sciences, the professor and his team mixed PETase with the second enzyme, MHETase, and found “the digestion of the plastic bottles literally doubled”.
Prof McGeehan, one of the study authors, said: “This allowed us to create a super-enzyme six times faster than the original PETase enzyme alone.
“This is quite a significant leap forwards because the plastic that ends up in our oceans today is going to take hundreds of years to break down naturally. Eventually, through sunlight and wave action, it will start to break down into smaller and smaller pieces – and we will end up with microplastics – a serious problem for the organisms that live in the environment.”
Tests showed that this super-enzyme was able to break down a type of plastic used in soft drinks and fruit juice packaging, known as PET (polyethylene terephthalate).
Although it is said to be highly recyclable, discarded PET persists for hundreds of years in the environment before it degrades. Aside from PET, the super-enzyme also works on PEF (polyethylene furanoate), a sugar-based bioplastic used in the manufacture of beer bottles. Prof McGeehan added, however, that the super-enzyme was not able to break down other types of plastic.
For the next part of their studies, the researchers will look at ways to further accelerate the breaking-down process, so that the technology can be adapted for commercial purposes.
Prof McGeehan said: “The faster we can make the enzymes, the quicker we can break down the plastic, and the more commercially viable it will be.”