An enzyme ‘cocktail’ has been discovered that could contribute to the breaking down and reuse of plastics in the future. This could have a significant positive impact on tackling one aspect of the current environmental crisis.

Plastic pollution is a global environmental crisis. A paper published in Current Opinion in Biotechnology in 2011 describes plastic as one of the most non-biodegradable synthetic materials. Plastics can be cheaply produced, and their strength, flexibility and durability mean they can be used for a lot of different purposes, but their durability has caused them to be described as a ‘major environmental threat’.  

But there is new evidence that plastic might have met a natural enemy. A study published in the journal Proceedings of the National Academy of Sciences in October 2020 wrote that there are microbes evolving in response to this plastic crisis. A microbe is a very small living thing that can cause things to break down, including fungi and bacteria. Some microbes have been found to have developed the ability to use synthetic materials such as plastic as sources of carbon and energy.

One of these bacteria makes a natural enzyme called PETase. It was identified in 2016, and the University of Portsmouth reports that PETase reduces the time it takes to break down PET, the most common thermoplastic, from hundreds of years to only days. PET plastic is used to produce many common use products such as single-use plastic bottles.

On 28 September, the University of Portsmouth reported that the same team who originally found that PETase could break down PET plastic has since found another way to break it down even more effectively. By combining a second enzyme called MHETase with PETase, the PET is broken down twice as fast as it would with PETase alone. These two enzymes working together could allow for plastic to be made and reused endlessly. This has the potential to decrease the build-up of plastic waste in the environment as well as reducing our dependence on fossil fuels. 

The team who created this ‘cocktail’ of PETase and MHETase enzymes was co-led by the scientists who originally engineered the PETase enzyme – Professor John McGeehan, Director of the Centre for Enzyme Innovation at the University of Portsmouth and Dr Gregg Beckham, Senior Research Fellow at the National Renewable Energy Laboratory in the US.

Julia Brick – Science reporter