Plastic-destroying enzyme could eliminate billions of tonnes of waste

A ‘pac-man’ protein that gobbles up plastic, breaking it down, could open the door to eliminating billions of tonnes of landfill waste.

The enzyme destroys PET (polyethylene terephthalate) – used in food and drink packaging, textiles and fibres.

It offers hope of helping solve global pollution by enabling full recycling.

Major industries would be able to recover and reuse products at the molecular level.

Professor Hal Alper, of The University of Texas at Austin, said: ‘The possibilities are endless across industries to leverage this leading-edge recycling process.

‘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 envision a true circular plastics economy.’

PET makes up 12 percent of all global waste. Like all plastics, it’s made up of long string-like molecules.

The enzyme reduces them into smaller parts – before chemical reassembly.

In some cases, the plastics can be fully broken down in as little as 24 hours. In the oceans, they survive for centuries.

AI (artificial intelligence), or machine learning, generated novel mutations to a natural enzyme called PETase that allows bacteria to degrade PET.

The computer neural network identified those that would be most effective at less than 50C – making it both portable and affordable.

Prof Alper and colleagues analysed dozens of discarded plastic items including containers, water bottles and polyester fibres and fabrics – all made from PET.

Experiments proved the effectiveness of the enzyme named FAST-PETase (functional, active, stable and tolerant PETase).

Co-author Prof Andrew Ellington, also from Texas, said: ‘This work really demonstrates the power of bringing together different disciplines, from synthetic biology to chemical engineering to artificial intelligence.’

In 2020, 367m tonnes of plastic were produced globally. Less than ten percent is recycled.

Beaches are littered with plastic bottles and wrappers. The stomachs of marine turtles, are filled with fragments of plastic.

Plastic fishing nets dumped at sea can throttle unsuspecting animals. An expanse of water in the Pacific twice the size of France contains at least 79,000 tonnes of plastic.

After landfill, burning is the second most common method of disposal. It’s costly – and spews noxious gas into the air.

Other alternative industrial processes are as energy-intensive. Biological solutions require much less.

The enzyme is described in Nature – the world’s most prestigious science journal.

Production is being scaled up to prepare for industrial and environmental applications.

The US team have filed a patent and are eying several different uses. Cleaning up landfills and greening high waste-producing industries are the most obvious.

But another key potential use is environmental remediation. The researchers are looking at a number of ways to clean up polluted sites.

Prof Alper said: ‘When considering environmental clean-up applications, you need an enzyme that can work in the environment at ambient temperature. This requirement is where our tech has a huge advantage in the future.’

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