Scientists invent enzyme that can break down plastic waste in ‘hours instead of centuries’

Recycling process could revolutionise how big industry reuses materials, reports Jane Dalton

Around 10 billion tonnes of plastic have been produced in the world (AFP via Getty Images)

Scientists have invented an enzyme variant they say can break down plastic waste in just hours or days instead of centuries.

They say the discovery could supercharge recycling on such a scale that it would revolutionise how big industry reuses plastics that currently pollute the environment, destroying wildlife and marine life, and ending up in human bodies.

Earlier this year, experts reported that the threat from plastic pollution is almost equivalent to climate change, saying the overproduction of plastics threatens the planet’s basic ability to maintain a habitable environment.

Engineers and researchers at the University of Texas at Austin, US, looked at polyethylene terephthalate (PET), a polymer found in most consumer packaging, including food packaging, drinks bottles and fibres and textiles. It accounts for 12 per cent of all global waste.

The new enzyme broke down the plastic into smaller parts, then chemically put it back together, according to the research, published in Nature.

In some cases, these plastics can be fully broken in as little as 24 hours, the experts found.

Campaign group Plastic Oceans says humans produce at least 380 million tons of plastic every year, more than 10million of which are dumped into the sea. Half of it is used just once before being thrown away.

And more than five trillion pieces of plastic – largely derived from food and drink packaging as well as clothing – are floating in the world’s oceans, damaging every part of the food chain, according to international research published in journal PLOS One in 2014.

The Environmental Investigation Agency says there is a 10 billion tonne plastic pollution time bomb “ticking away in every corner of the planet”.

Other research has found that  people eating seafood in the UK commonly consume plastic.

The most common method of disposing of plastic, besides throwing into landfill, is burning it, which is costly and energy-intensive, and spews noxious gas into the air.

“The possibilities are endless across industries to leverage this leading-edge recycling process,” said Hal Alper, professor in the McKetta Department of Chemical Engineering at the university.

“Beyond the obvious waste-management industry, this also provides corporations from every sector the opportunity to take a lead in recycling their products. Through these more sustainable enzyme approaches, we can begin to envisage a true circular plastics economy.”

Researchers used a machine learning model to generate novel mutations to a natural enzyme called PETase that allows bacteria to degrade PET plastics.

The model predicted which mutations in the enzymes would quickly “depolymerise” post-consumer waste plastic at low temperatures.

The study looked at 51 plastic containers, five polyester fibres and fabrics, and water bottles all made from PET. They are calling the new enzyme FAST-PETase (functional, active, stable and tolerant PETase).

Until now, no one had been able to make enzymes that work at low temperatures to make them affordable at large industrial scale, but the scientists say FAST-PETase can do so at less than 50C.

They also hope their discovery will be used to clean up landfill and other polluted sites.