Researchers have created a ‘super-enzyme’ to break down plastic bottles

A plastic bottle waste container in Moscow.

Good news on the plastic pollution front: a ‘super-enzyme’ capable of ‘digesting’ plastic in a few hours has been developed by two teams of English and American researchers. Their discovery was published in late September in the American scientific journal Proceedings of the National Academy of Sciences (PNAS). 

Back in 2018, the French firm Carbios had observed that an enzyme, PETase, was capable of attacking the crystalline surface of polyethylene terephthalate (PET) bottles and breaking it down into its component parts in a few days but at a temperature of 70°C. 

The researchers from the University of Portsmouth’s Centre for Enzyme Innovation in the United Kingdom and the National Renewable Energy Laboratory in the United States combined PETase with another enzyme, MHETase. This enzyme cocktail produced a truly ‘gluttonous enzyme’ able to degrade plastic six times faster than PETase alone and at a temperature of 20°C. 

PETase and MHETase had been identified in the bacterium Ideonella sakaiensis, discovered in 2016 in a landfill in Japan, but their combination is too complex to be naturally synthesized by a bacterium.

A powerful enzyme cocktail 

“This discovery is a first step toward the industrial production of fast enzymes. It makes it possible to endlessly recycle PET and it is also a solution for reducing marine plastic pollution and the associated greenhouse gas emissions,” remarks John McGeehan, a researcher at the University of Portsmouth and coauthor of the article, who hopes to commercially launch the super-enzyme in two years’ time. 

Other combinations are conceivable, such as a mix of enzymes that ‘digest’ plastic and others that break down natural fibers. This kind of combination would deal with garments made of cotton and polyester, which are a real headache for the textile industry, as they are extremely difficult to recycle. 

In the meantime, the scientists are continuing their research to accelerate the enzymes’ ‘digestion,’ as the commercial potential is enormous. A one-million-pound testing center is already under construction in Portsmouth, while Carbios is currently building a plant in Lyon.

SOURCE :

« Characterization and engineering of a two-enzyme system for plastics depolymerization », Proceedings of the National Academy of Sciences, 28 septembre 2020- www.pnas.org/cgi/doi/10.1073/pnas.2006753117

« New super-enzyme eats plastic bottles six times faster », The Guardian, 28 septembre 2020 - www.theguardian.com/environment/2020/sep/28/new-super-enzyme-eats-plastic-bottles-six-times-faster

« Scientists create mutant enzyme that recycles plastic bottles in hours », The Guardian, 8 avril 2020 - www.theguardian.com/environment/2020/apr/08/scientists-create-mutant-enzyme-that-recycles-plastic-bottles-in-hours