PETpla.net Insider 09 / 2018

MATERIALS / RECYCLING PET planet Insider Vol. 19 No. 09/18 www.petpla.net 11 this 3D information to understand how it works. During this study, they inadvertently engineered an enzyme that is a step better at degrading the plastic than the one that evolved in nature. “Although the improvement is modest, this unanticipated discovery suggests that there is room to further improve these enzymes, moving us closer to a recycling solution for the ever-growing mountain of discarded plastics,” Professor McGehhan said. The University of Portsmouth and NREL collaborated with scien- tists at the Diamond Light Source in the UK, a synchrotron that uses intense beams of X-rays, 10 billion times brighter than the sun, to act as a microscope powerful enough to see individual atoms. With help from computational modelling scientists at the University of South Florida and the University of Campinas in Brazil, the team discov- ered that PETase looks very similar to a cutinase (an enzyme that catalyses the chemical reac- tion), but it has some un usual features including a more open active site, making it able to accommodate man-made, rather than natural polymers, which suggested that PETase may have evolved in a PET-con- taining environment. To test that hypoth- esis, the researchers mutated the PETase active site to make it more like a cutinase; it was then that they found the mutated PETase was better than the natural PETase in degrading PET. The enzyme can also degrade poly- ethylene furandicarboxylate (PEF), a bio-based alternative to PET. The research team now intends to apply the tools of protein engineering and evolution to continue to improve it. The engineering process is reported to be very similar to that used in the production of enzymes currently found in bio-washing deter- gents, and in the manufacture of biofuels. As the technology already exists, the teams are optimistic that an industrially viable process could be developed to turn PET and other sub- strates back into their original building blocks for sustainable recycling. The research was funded by the University of Portsmouth, NREL and the UK’s Biotechnology and Biological Sciences Research Council. www.port.ac.uk www.nrel.gov PETase converts PET to MHET, with trace amounts of TPA and bis-TPA (BHET) as secondary products. The bacteria produces a second enzyme, MHETase (MHET- digesting enzyme), which further converts MHET into the two monomers, TPA and ethylene glycol (EG).