In a moment of accidental genius, scientists have created a mutant enzyme that breaks down plastic drinks bottles. The international team, led by the University of Portsmouth’s own Professor John McGeehan, embarked on their research following the discovery of a bacterium at a waste dump in Japan in 2016 that had naturally evolved to eat plastic.
Following research that outlined the structure of the enzyme, the bacterium produced the international team sought to manipulate and alter the enzyme to see how this evolution had occurred. In doing so, the team accidentally enhanced the enzyme’s ability to break down polyethylene terephthalate (PET) – the plastic used to make soft drinks bottles. “What actually turned out was we improved the enzyme, which was a bit of a shock,” said McGeehan. “It’s great and a real finding.”
Ocean plastic pollution has become a serious environmental issue in recent decades, with most plastics expected to take centuries to break down completely in the ocean. The permeation of plastic into our oceans harms marine life and therefore the ecological pyramid as well as potentially harming people that eat seafood. Currently the enzyme takes a few days to start breaking down plastic but with further manipulation, scientists are confident that the process can be significantly sped up to help combat the plastic pollution crisis worldwide.
Currently, just 14% of plastic bottles are recycled and even those can only be turned into opaque fibres which are most commonly used for clothing or carpets. But with this new enzyme, we can potentially gain the ability to recycle plastic bottles into new plastic bottles which would significantly decrease the need to produce new plastic.
One possible model being looked at in helping to improve the enzyme’s ability to break down plastic is the structure of industrial enzymes, such as the ones used in washing powders and biofuel production. These enzymes have been engineered to work up to a 1,000 times faster than the original form – a benchmark that scientists hope to emulate and exceed. Another option being explored is to transform the enzyme into an ‘extremophile bacteria’ that can survive temperatures above 70c – the melting point of PET. This would increase the speed at which the plastic degrades.
“Enzymes are non-toxic, biodegradable and can be produced in large amounts by microorganisms,” said Oliver Jones, a chemist at RMIT University in Melbourne, Australia. “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.”