A potential solution to one of the world’s biggest environmental problems: plastic. A team of scientists led by the University of Portsmouth and the US Department of Energy’s National Renewable Energy Laboratory have designed an enzyme that can digest some of our most polluting plastics.
The discovery, published in the journal PNAS , could emerge as a curious but fantastic recycling remedy for millions of tons of plastic bottles , made of polyethylene terephthalate, or PET, that currently persist for hundreds of years in the environment.
The experts studied the crystal structure of PET, 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 plastic than the one that evolved in nature, the enzyme produced by the bacterium Ideonella sakaiensis .
The researchers are now working on improving the enzyme to allow its industrial use to break down plastics in a short time.
“Few could have predicted that since plastics became popular in the 1960s, huge patches of plastic would end up floating in the oceans or being stored on beaches around the world that were once pristine,” explains John McGeehan, co-author of the work.
“We can all play an important role in addressing the plastic problem, but the scientific community that ultimately created these ‘wonderful materials’ must now use all the technology at their disposal to develop real solutions .”
The researchers made this breakthrough when they were examining the structure of a natural enzyme believed to have evolved at a waste recycling center in Japan, allowing a bacterium to break down plastic as a food source.
The goal was to determine its structure, but they ended up going one step further and accidentally designed an enzyme that was even better at breaking down PET plastics.
“Chance often plays an important role in fundamental scientific research, and our discovery here is no exception,” said McGeehan.
The research team intends to apply the tools of protein engineering and evolution to continue improving this enzyme.
Interestingly, the enzyme can also degrade polyethylene furandicarboxylate, or PEF, a bio-based substitute for PET plastics that comes as a replacement for glass beer bottles.
“The engineering process is very similar to that of the enzymes currently used in detergents for biowashing and in the manufacture of biofuels; the technology exists and it is within the possibility that in the coming years we will see an industrial viability in the process to convert PET and potentially other substrates like PEF, PLA and PBS in their original building blocks so they can be recycled sustainably, “says McGeehan.
It is clear that we are only at the beginning of this research and there is much to do in this field. We will all be on the lookout for solutions to address one of the biggest problems facing our planet.
Reference: Harry P. Austin el al., “Characterization and engineering of a plastic-degrading aromatic polyesterase,” PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1718804115
