Pac-Man-like enzyme that eats plastic could be gamechanger for waste disposal

By Tom Campbell via SWNS

A Pac-Man-like enzyme that eats harmful plastic by munching the building blocks of the single-use material could revolutionize how we dispose of our waste in a greenway.

The TPADO enzyme transforms plastic waste into valuable chemicals that can be used elsewhere, scientists discovered.

It could help combat plastic pollution clogging up the seas or being sent to landfills by putting old bottles and clothes to good use, according to a new study.

More than 300 million tonnes of plastic waste are produced every year, most of which goes to landfills where it takes hundreds of years to decompose.

An enzyme that breaks down PET plastics, commonly used for packaging and in clothes, was discovered by researchers in 2018.

But two chemical building blocks - ethylene glycol (EG) and terephthalate (TPA), remain once the plastic has been broken down.

While these could be recycled to make other products, TPA has proven challenging to work with until now.

Professor Jen DuBois, an author of the study at Montana State University in the United States, said: "While EG is a chemical with many uses - it’s part of the antifreeze you put into your car, for example - TPA does not have many uses outside of PET, nor is it something that most bacteria can even digest.

"However, the Portsmouth team revealed that an enzyme from PET-consuming bacteria recognizes TPA like a hand in a glove.

"Our group at MSU then demonstrated that this enzyme, called TPADO, breaks down TPA and pretty much only TPA, with amazing efficiency.”

Plastic pollution has become one of the most pressing environmental issues, killing millions of animals every year.

The new enzyme converts TPA into "simpler molecules" which can be used to make valuable chemical products.

Professor John McGeehan, a co-author of the study at the University of Portsmouth, said: "The last few years have seen incredible advances in the engineering of enzymes to break down PET plastic into its building blocks.

"This work goes a stage further and looks at the first enzyme in a cascade that can deconstruct those building blocks into simpler molecules.

"These can then be utilized by bacteria to generate sustainable chemicals and materials, essentially making valuable products out of plastic waste."

The researchers have also mapped out TPADO's structure so others can build on their discovery.

Professor McGeehan added: "Using powerful X-ray at the Diamond Light Source, we were able to generate a detailed 3D structure of the TPADO enzyme, revealing how it performs this crucial reaction.

"This provides researchers with a blueprint for engineering faster and more efficient versions of this complex enzyme.”

Putting TPA to good use will help tackle plastic pollution which has increased almost continuously since the 1950s.

The findings were published in the journal The Proceedings of the National Academy of Sciences (PNAS).