Scientists accidentally create mutant enzyme that eats plastic waste

Scientists accidentally create mutant enzyme that eats plastic waste

Originally discovered in 2016 in sediments at a bottle recycling site in the port city of Sakai, Japan, the team has successfully modified the enzyme - known as Ideonella Sakaiensis - to break-down PET bottles at an accelerated rate of just three days. During this study, they inadvertently engineered an enzyme that is better still at degrading the plastic than the one that evolved in nature.

The researchers, from the United Kingdom and the USA, made the discovery as they examined a naturally-occurring enzyme that evolved in a plastic disposal centre in Japan. This is the first time an organism has been able to break down plastic, which it does using two specialised enzymes.

Finding that this enzyme was helping a bacteria to break down, or digest, PET plastic, the researchers chose to "tweak" its structure by adding some amino acids, said John McGeehan, a professor at Portsmouth who co-led the work.

But progress is slow, partly because big businesses have aesthetic concerns about bottles made from 100-percent recycled plastic.

The new research, published in the journal Proceedings of the National Academy of Sciences, began by determining the precise structure of the enzyme produced by the Japanese bug.

"We can all play a significant part in dealing with the plastic problem, but the scientific community who ultimately created these "wonder materials" must now use all the technology at their disposal to develop real solutions".

A high definition 3D model of the enzyme was created, using the powerful x-ray beamline at Diamond Light Source in Oxfordshire.

Portsmouth University and NREL collaborated with scientists at the Diamond Light Source.

"What we are hoping to do is use this enzyme to turn this plastic back into its original components, so we can literally recycle it back to plastic", McGeehan said. Although it is said to be recyclable, discarded PET can last for centuries before it degrades.

"Serendipity often plays a significant role in fundamental scientific research and our discovery here is no exception", said John McGeehan, a biology professor at the University of Portsmouth and one of the lead scientists on the research.

PET, patented as a plastic in the 1940s, has not existed in nature for long, so the team set out to determine how an enzyme called PETase evolved and if it might be possible to improve it by determining its structure. "It is so easy for manufacturers to generate more of that stuff, rather than even try to recycle". The impact of such an innovative solution to plastic waste would be global. But instead of the mutated PETase proving more ineffective at degrading PET, the team found the opposite, that it actually performed better.

The work reported in PNAS was enabled by funding from NREL's Laboratory Directed Research and Development (LDRD) program, the University of Portsmouth, and the UK's Biotechnology and Biological Sciences Research Council. The bad news: it doesn't work fast enough to solve plastic recycling at the industrial scale.

PETase was also tested on PEF plastic, a proposed plant-based alternative to PET that is similarly slow to degrade in nature.

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