Recycling polyethylene terephthalate (PET) plastics is difficult as the hard material is tough to breakdown. For years there’s been research into using bacteria to eat the plastic to help with getting the plastic to reusable state. This year a bacterial enzyme called “PETase” has been found to be highly effective at breaking down this hardened plastic. The enzyme itself comes from a bacteria that was found within a plastic recycling plant (nature always finds a way) which was subsequently modified to be more efficient. This discovery may lead to a healthier use of plastic, but for now the best thing you can do is buy less plastic objects.
They compared the DNA sequence of the PETase gene with that of cutinases from thousands of bacterial species, looking for differences. They then created new versions of PETase, each with one or more of its amino-acid building blocks changed to resemble those of ancestral cutinases.
As many of the differences between PETase and cutinases were, presumably, what allowed PETase to do its job, they expected these new enzymes to digest the plastic less efficiently. To their surprise, however, one of the engineered enzymes (with two amino acids mutated to be more cutinase-like) was able to digest PET about 20% faster than the natural one. That is a modest increase, but one that came about by accident rather than design. This, Dr McGeehan argues, shows there is plenty of scope for further improvement.