A novel enzyme engineering platform to facilitate enzymatic plastic recycling

Researchers from Manchester Institute of Biotechnology (MIB).

They developed a novel enzyme engineering platform to improve plastic-degrading enzymes through directed evolution.

The platform can successfully degrade polyethylene terephthalate (PET), a plastic commonly used in plastic bottles.

Enzymatic processing

Researchers say that in recent years, enzymatic recycling of plastics has become an attractive and environmentally friendly strategy to help alleviate the problems associated with plastic waste.

They said that despite existing methods of recycling plastics, enzymes could potentially offer a more cost-effective and energy-efficient alternative. Additionally, they can be used to selectively break down certain components of mixed plastic waste streams that are currently difficult to recycle with existing technologies.

While the technology is promising, researchers say there are significant hurdles to overcome before enzymatic plastic recycling can be widely used on a commercial scale. One problem they highlighted is that natural enzymes capable of breaking down plastics are usually less efficient and less stable under the conditions required for an industrial process.

To address these limitations, in an article published today in Catalysis of natureresearchers from University of Manchester reported a novel enzyme engineering platform that can rapidly improve the properties of plastic-degrading enzymes to make them more suitable for plastic recycling on a large scale. Their integrated and automated platform can successfully evaluate the plastic degradation capacity of about 1000 enzyme variants per day.

Plastic is destroyed

Dr Elizabeth Bell, who led the experimental work at MIB, says of the platform; “The accumulation of plastic in the environment is a serious global problem. For this reason, we sought to use our enzyme evolution capabilities to improve the properties of plastic-degrading enzymes to help alleviate some of these problems.

“In the future, we hope that our scalable platform will allow us to rapidly develop new and specific enzymes suitable for use in large-scale plastic recycling processes.”

To test their platform, they set out to develop a new enzyme, HotPETase, by directed evolution of IsPETase. IsPETase is a newly discovered enzyme produced by the bacterium Ideonella sakaiensis that can use PET as a carbon and energy source.


While IsPETase has a natural ability to degrade some semi-crystalline forms of PET, the enzyme is unstable at temperatures above 40°C, well below the desired process conditions. This low stability means that the reactions must take place at temperatures below the glass transition temperature of PET (~65°C), resulting in low depolymerization rates.

To address this limitation, the team developed a thermostable enzyme, HotPETase, which is active at 70°C, which is above the glass transition temperature of PET. This enzyme can depolymerize semi-crystalline PET faster than previously reported enzymes and can selectively deconstruct the PET component of the laminated packaging material, highlighting the selectivity that can be achieved by enzymatic processing.

Professor Anthony Green, lecturer in organic chemistry, said: “The development of HotPETase is a good illustration of the capabilities of our enzyme engineering platform. We are now excited to collaborate with process engineers and polymer scientists to test our enzyme in the real world.


“Moving forward, we hope that our platform will prove useful for the development of more efficient, stable and selective enzymes for the processing of a wide range of plastics.”

A university spokesman added: “The development of robust plastic-degrading enzymes such as HotPETase, together with the availability of a versatile enzyme engineering platform, are making an important contribution to the development of a biotechnological solution to the problem of plastic waste.

“Advancement of this promising technology will now require a collaborative and interdisciplinary effort involving biotechnologists, process engineers, and polymer scientists from various academic and industrial communities. As the world faces an ever-increasing waste problem, biotechnology can provide an environmentally sustainable solution.”

Manchester Institute Biotechnology is one of the university’s research beacons – a model of interdisciplinary collaboration and cross-sector partnerships that lead to groundbreaking discoveries and improve people’s lives around the world. A novel enzyme engineering platform to facilitate enzymatic plastic recycling

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