A team of researchers that previously re-engineered a plastic-eating enzyme named PETase have now combined it with a second enzyme to speed up the process, according to a press release from the University of Portsmouth.
The super enzyme could have major implications for recycling polyethylene terephthalate (PET), which is the most common thermoplastic used in single-use drinks bottles, carpets, and clothing.
PET takes hundreds of years to degrade in the environment. PETase can break it down into its building blocks in a few days.
John McGeehan, lead co-author and director of the Centre for Enzyme Innovation at the University of Portsmouth, told CNN that this latest development represents a huge stop towards using enzymes to recycle plastic and reduce plastic pollution.
“We were actually quite surprised it worked so well,” said McGeehan, although he underlined that the process is “still way too slow” to be commercially viable.
He told CNN that researchers have received funding to carry out further experiments, and successful developments could mean existing PET could be recycled instead of using fossil fuels to create new plastic.
“We’re looking at huge energy savings,” said McGeehan.
How does it work?
The super enzyme combines PETase and MHETase. A mixture of the two breaks down PET twice as fast as PETase on its own, while connecting the two enzymes increased the speed by a further three times.
McGeehan used the Diamond Light Source, a device that uses X-rays 10 billion times brighter than the Sun to be able to see individual atoms, to map the molecular structure of MHETase.
Researchers were then able to engineer the new super enzyme by connecting MHETase and PETase, effectively stitching the enzymes DNA together to create one long chain, McGeehan told CNN.
The technique is commonly used in the biofuels industry, which uses enzymes to break down cellulases, but McGeehan said this is the first he is aware of enzymes being combined to break down plastic.
The full study was published Monday in the journal Proceedings of the National Academy of Sciences of the United States of America.
How else can plastic be broken down?
Plastic pollution is one of the most pressing environmental issues. A recent report from The Pew Charitable Trusts projected the volume of plastic entering the ocean could nearly triple to 29 million metric tons per year by 2040 — the equivalent of 50 kilograms for every meter of the planet’s coastline.
It also said there was “no single solution,” but that “an ambitious recycling strategy” could slash 31-45% of plastic pollution.
In April, French firm Carbios announced the publication of a study into its own PET-eating enzyme, which will be tested at a demonstration plant near the city of Lyon in 2021, according to a press release from the company.
Other possible solutions include the tiny waxworm, which can chomp through plastic, even polyethylene, a common and non-biodegradable plastic currently clogging up landfills and seas, thanks to its gut bacteria.
Mealworms, the larval stage of the mealworm beetle, could also contribute. Around 3,000-4,000 mealworms can break down one Styrofoam coffee cup in about a week thanks to the bacteria living in their gut.