University of Manchester researchers improve the ability of enzyme to break down plastic

17 August 2022 | Muriel Cozier

‘We are now excited to work with process engineers and polymer scientists to test our enzyme in real world applications.’

Researchers from the Manchester Institute of Biotechnology (MIB), at the University of Manchester, have developed an enzyme engineering platform which they say improves plastic degrading enzymes through ‘directed evolution’.

The researchers explain that while enzymes are a promising technology, there are still a number of hurdles to overcome before enzymatic plastic recycling can be used widely on a commercial scale. One of these challenges is that natural enzymes with the ability to break down plastics are typically less effective and are unstable under the conditions needed for industrial-scale processing of plastic.

Publishing their work in Nature Catalysis, the researchers say that they have developed an enzyme engineering platform that can quickly improve the properties of plastic degrading enzymes, making them more suitable for plastic recycling at large scales.

Using their platform the researchers created an enzyme called HotPETase, through the direct evolution of a recently discovered enzyme IsPETase. This enzyme is produced by the bacterium Ideonella sakaiensis, which can use PET as a carbon and energy source. IsPETase is unstable above 40°C. This low temperature stability means that reactions must be run at temperatures below the glass transition temperature of PET, around 65°C, leading to low depolymerisation rates.

Professor Anthony Green, University of Manchester
Professor Anthony Green believes the platform can help to develop ‘more efficient, stable and selective enzymes for recycling’. Image: University of Manchester

Addressing the limitation, researchers were able to develop the thermostable enzyme HotPETase, which is active at 70°C. This enzyme can depolymerise semi-crystalline PET more rapidly than previously reported enzymes and can selectively deconstruct the PET component of laminated packaging material.

Dr Elizabeth Bell, who led the experimental work at MIB said; ‘We are hopeful that in the future our scalable platform will allow us to quickly develop new and specific enzymes suitable for use in large-scale plastic recycling processes.’

Professor Anthony Green, Lecturer in Organic Chemistry added; ‘The development of HotPETase nicely illustrates the capabilities of our enzyme engineering platform. We are now excited to work with process engineers and polymer scientists to test our enzyme in real world applications. Moving forward we are hopeful that our platform will prove useful for developing more efficient, stable and selective enzymes for recycling a wide range of plastic materials.’

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