Scientists of the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL), the University of Portsmouth and other partners have discovered further insights into the workings of plastic-eating enzymes.

Recent findings show, that two synergistic enzymes - PETase and MHETase - work effectively in tandem to break down polyethylene terephthalate (PET). This research follows an earlier collaboration between these partners focused on PETase, back in 2018.

A bacterium, Ideonella sakaiensis 201-F6, was discovered in the soil outside of a Japanese PET bottle recycling plant in 2016. It was shown that this bacterium secretes both PETase and MHETase. Researchers at NREL and Portsmouth were able to engineer PETase to increase the enzyme’s ability to digest PET. The team was co-led by Professor John McGeehan, Director of the Centre for Enzyme Innovation at the University of Portsmouth, and Dr Gregg Beckham, Senior Research Fellow at NREL.

According to Gregg Beckham, MHETase and PETase degrade PET faster than PETase alone. “They are better together than they are separate. PETase conducts the initial breakdown of the PET polymer, and MHETase further deconstructs the soluble products of PETase to produce the building blocks of PET,” he said. Mixing PETase with MHETase resulted in doubled speed of PET breakdown. Furthermore, engineering a connection between the two enzymes to create a ‘super-enzyme’, increased this activity by a further three times.

The study “Characterization and engineering of a two-enzyme system for plastics depolymerization,” was published in the journal Proceedings of the National Academy of Sciences of the United States of America.