PET, patented as a plastic in the 1940s, has not existed in nature for very long. So the team, headed by Professor John McGeehan at the University of Portsmouth and Dr Gregg Beckham at the US Department of Energy’s National Renewable Energy Laboratory (NREL), set out to determine how the enzyme evolved and if it might be possible to improve it.
Their goal was to determine its structure, but they ended up going a step further and accidentally engineered an enzyme which was even better at breaking down PET plastics.
The team solved the crystal structure of PETase—a recently discovered enzyme that digests PET— and used this 3D information to understand how it works. During this study, they inadvertently engineered an enzyme that is even better at degrading the plastic than the one that evolved in nature.
The researchers are now working on improving the enzyme further to allow it to be used industrially to break down plastics in a fraction of the time.
Professor McGeehan, Director of the Institute of Biological and Biomedical Sciences in the School of Biological Sciences at Portsmouth, said: ‘Few could have predicted that since plastics became popular in the 1960s huge plastic waste patches would be found floating in oceans or washed up on once pristine beaches all over the world.
‘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.’
The researchers made the breakthrough when they were examining the structure of a natural enzyme which is thought to have evolved in a waste recycling centre in Japan, allowing a bacterium to degrade plastic as a food source.
The research team can now apply the tools of protein engineering and evolution to continue to improve it.
The enzyme can also degrade polyethylene furandicarboxylate, or PEF, a bio-based substitute for PET plastics that is being hailed as a replacement for glass beer bottles.
Professor McGeehan said: ‘The engineering process is much the same as for enzymes currently being used in bio-washing detergents and in the manufacture of biofuels – the technology exists and it’s well within the possibility that in the coming years we will see an industrially viable process to turn PET and potentially other substrates like PEF, PLA, and PBS, back into their original building blocks so that they can be sustainably recycled.’
The paper’s lead author is postgraduate student jointly funded by the University of Portsmouth and NREL, Harry Austin.
He said: ‘This research is just the beginning and there is much more to be done in this area. I am delighted to be part of an international team that is tackling one of the biggest problems facing our planet.’