Environment and sustainability – University of Portsmouth: Portsmouth news and information (Portsmouth)

Discovery of a new enzyme is another step towards the fight against plastic waste

Posted: Mar 23, 2022 9:26 a.m.

The scientists who helped pioneer the use of enzymes to eat plastic have taken an important step in developing nature-based solutions to the global plastics crisis.

They characterized an enzyme that has the remarkable ability to help break down terephthalate (TPA), one of the chemical building blocks of polyethylene terephthalate (PET) plastic, which is used to make single-use beverage bottles, clothes and rugs.

The research, which is published in The Proceedings of the National Academy of Sciences (PNAS), was co-led by Professor Jen DuBois, of Montana State University, and Professor John McGeehan of the University of Portsmouth, who in 2018 led the international team that designed a natural enzyme that could break down PET plastic. Enzymes (PETase and MHETase) break down the PET polymer into the chemical building blocks ethylene glycol (EG) and TPA. This new research outlines the next steps, particularly for the management of TPA.

Professor DuBois said: “Although EG is a chemical with many uses – it’s part of the antifreeze you put in your car, for example – TPA doesn’t have many uses outside of PET, or even something that most bacteria can digest. However, the Portsmouth team revealed that an enzyme from PET-eating 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.

With more than 400 million tons of plastic waste produced each year, the overwhelming majority of which ends up in landfills, it is hoped that this work will open the door to improving bacterial enzymes, such as TPADO. This will help address the challenge of plastic pollution and develop biological systems capable of converting plastic waste into valuable products.

Professor McGeehan, director of the university’s Center for Enzyme Innovation, said: “Recent years have seen incredible advances in the engineering of enzymes to break down PET plastic into its building blocks. This work goes further and examines the first enzyme in a cascade that can deconstruct these building blocks into simpler molecules. These can then be used by bacteria to generate chemicals and durable materials, essential for making valuable products from plastic waste.

Using powerful X-rays 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 designing faster, more efficient versions of this complex enzyme.

The study was undertaken as part of the BOTTLE Consortium, an international US-UK collaboration bringing together researchers from a wide range of scientific fields to tackle plastic recycling and upcycling.

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