Environment

Newly discovered enzyme helps reduce plastic waste to a simple molecule

Newly discovered enzyme helps ...
Scientists have discovered a new enzyme that helps break down PET plastics
Scientists have discovered a new enzyme that helps break down PET plastics
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A newly discovered enzyme called TPADO can break down one of the key building blocks for PET plastics
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A newly discovered enzyme called TPADO can break down one of the key building blocks for PET plastics
Scientists have discovered a new enzyme that helps break down PET plastics
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Scientists have discovered a new enzyme that helps break down PET plastics

Over the past five years or so we've seen some important breakthroughs demonstrating how enzymes can be used to break down common plastics, such as the PET used for everything from drink bottles to shampoo containers. In pursuit of a circular economy for plastic waste, scientists have now discovered a new enzyme that further breaks down one of the key plastic building blocks left behind by this process, leaving simple molecules that can be repurposed for use in new products.

In 2016 scientists in Japan discovered a bacterium with a natural appetite for PET plastics, using enzymes to break it down in a matter of weeks. Researchers at the University of Portsmouth then succeeded in engineering a better-performing version of this enzyme, called PETase, and in 2020 combined it with another called MHETase to form a super enzyme that digests PET plastics at six times the speed.

What's left through the process is the two chemical building blocks of PET, ethlyene glycol (EG) and terephthalate (TPA), and one is more problematic than the other.

"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," explains study author Professor Jen DuBois. "However, the Portsmouth team revealed that an enzyme from PET-consuming bacteria recognizes TPA like a hand in a glove. Our group then demonstrated that this enzyme, called TPADO, breaks down TPA and pretty much only TPA, with amazing efficiency.”

A newly discovered enzyme called TPADO can break down one of the key building blocks for PET plastics
A newly discovered enzyme called TPADO can break down one of the key building blocks for PET plastics

The team's previous discoveries have come about by studying these enzymes at the Diamond Light Source Facility in the UK, which blasts them with beams of powerful X-rays. The result is an ultra-high resolution model of the enzyme that reveals the individual atoms inside it, showing how TPADO carries out its TPA-consuming duties. As in their previous work, this incredible detail offers a blueprint for the scientists to engineer even more efficient versions of the enzyme.

“The last few years have seen incredible advances in the engineering of enzymes to break down PET plastic into its building blocks," said study author Professor John McGeehan. "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, essential making valuable products out of plastic waste."

The research was published in the journal The Proceedings of the National Academy of Sciences.

Source: University of Portsmouth

8 comments
8 comments
Brian Beban
Like many advances, the details are scant. How expensive is the enzyme to produce? Is it more expensive than the plastic waste it reduces? Is it scaleable and efficient enough to use on an industrial scale. Is the end product more expensive than current raw materials and by how much ? All questions raised by the article but not addressed.
Aross
What if these bacteria that produce the enzymes escape into the wild? Shades of Andromeda?
Ornery Johnson
Brian: The article notes that both the enzyme PETase and TPADO are made by the same PET digesting bacteria. It would be a relatively simple matter to enhance the expression of each of these enzymes in this bacteria (or a completely different species of bacteria better-suited to an industrial environment). These articles aren't intended to be a complete "white paper" on the subject, but simply light reading. If you want more details, I'm sure Google would direct you to the original publication.
notarichman
How do these chemicals affect fiberglass?
Boats?, rope?, crab traps?, metal covered with plastic?, net floats?
DaveWesely
This is good and all, but the real problem isn't that plastic doesn't break down easily. The real problem is that it doesn't all end up in a landfill. Plastic, like most oil derived products, has a significant amount of carbon in it. If you burn it, it turns into CO2 and a lot of other nasty stuff. If you bury it, it is called carbon sequestration.
There is nothing wrong with putting plastic in landfills. It is inert. It doesn't leach into groundwater. It doesn't break down into methane or CO2.
There is nothing wrong with recycling. Just recycle stuff that makes sense to recycle. Do not put metal in a landfill. Even though it is relatively inert, it makes far more sense to melt it down and recycle it.
We stopped recycling plastic. Now we only recycle metal and glass. So much simpler.
re: Aross, if these bacteria escaped into the wild, they would probably die due to lack of plastic to eat.
dugnology
The reason we have bituminous coal is that plants that evolved lignite could not be ingested by bacteria. All of this dead wood would pile up and be anaerobically compacted for millions of years. Today, fallen trees pretty much decompose in a few years and that's the end of that. No more coal formation. What happens when bacteria suddenly evolve into something that eats plastic. In real time.
Username
There are a lot of waste management solutions floating around but they never see actual implementation because there is no infrastructure to support them.
ShahbazParsipour
cool ... but wait to see this enzyme's side effects too!