SOLVE magazine Issue 01 2020 - Page 11

SUSTAINABILITY AND THE ENVIRONMENT: BIOTECHNOLOGY WASTE FIND BRINGS PET TO HEEL Plastic pollution is now widely recognised as one of the worst environmental calamities of our time. Over the past 70 years more than 8.3 billion metric tonnes of plastic has been produced globally, and almost all of it remains in the environment – particularly in the ocean because of the ‘scouring’ effect of river catchments that collect discarded rubbish in towns and cities and disgorge it, eventually, into the sea. For marine scientists, plastic pollution has surpassed crisis level and is now an existential threat to ocean life – at a time when the ocean is going to be more vital than ever for human food security as terrestrial agriculture strains under the pressure of climate change. This grim scenario brings into sharp relief the importance of groundbreaking research by the University of Portsmouth in engineering a naturally occurring enzyme that can break down one of the most abundant plastics, polyethylene terephthalate or PET, used in single-use drink bottles, clothing and carpets. It has been estimated that it will take 450 years for a PET drink bottle to break down naturally in the ocean, and the EU alone consumes 46 billion PET drink bottles every year. Not surprisingly, the University’s enzyme research – now housed within the newly established Centre for Enzyme Innovation (CEI) – has attracted worldwide attention and acclaim among scientists, governments and also the plastics industry itself. The team was recently awarded the Times Higher Education STEM Research Project of the Year. Like many scientific breakthroughs, the discovery was partly serendipitous. Researchers at the University led by Professor John McGeehan – and in partnership with the US Department of Energy’s National Renewable Energy Laboratory (NREL) – were investigating the inner workings of PETase, an enzyme discovered in a Japanese bottle-recycling facility in 2016. This PETase enzyme appeared to be breaking down plastic and the team was trying to understand how it had evolved to digest artificial plastics, given PET has only been around since the 1940s – a very short period for an evolutionary adjustment. The researchers could see that the structure of the enzyme was similar to one evolved by bacteria to break down cutin, a natural polymer used by plants as a protective coating. The team was manipulating the enzyme to explore this connection when they unintentionally improved its PET-digesting ability. Collaborating NREL scientists Dr Bryon Donohoe and Dr Nic Rorrer subsequently tested PETase on PET samples from drink bottles. Observing with an electron microscope, they saw the PETase enzyme begin degrading the pieces of PET plastic after just four days. The researchers knew they were only at an early stage and that further engineering could potentially make the enzyme work much faster and be a genuine tool for revolutionising plastics recycling. Professor McGeehan and his team are now working on improving this enzyme for industrial-scale use, while continuing the search for new enzymes that can break down other highly-polluting plastics. The research is being facilitated by the Portsmouth researchers’ access to the UK’s national synchrotron in Oxfordshire, called the Diamond Light Source. The synchrotron’s I23 beamline uses intense beams of X-rays 10 billion times brighter than the sun to act as a microscope powerful enough to make individual atoms visible. It reveals the 3D structures of nature’s molecules of life, allowing researchers to apply the tools of protein engineering and directed evolution to continue to improve the PETase enzyme. It is of the utmost importance that the UK Government has recognised the need to fund research and innovation to take our fundamental science through to real-world industrial and environmental applications. – John McGeehan ISSUE 1 / 2020 11