Microbes are evolving to eat plastics, study finds

By Julia Wray 15-Dec-2021

Plastics-degrading microbial enzymes could be the key to novel recycling processes

The number of microbial enzymes with the ability to degrade plastic is growing as the world gets more polluted, raising interesting possibilities for plastics recycling.

A new study from Chalmers University of Technology in Sweden, published in Microbial Ecology, measured samples of environmental DNA from hundreds of locations around the globe, and discovered that the quantity and diversity of plastic-degrading enzymes is increasing in direct response to local levels of plastic pollution.

The researchers used computer modelling to search for microbial enzymes with plastic-degrading potential, which was then cross-referenced with the official numbers for plastic waste pollution across countries and oceans.

“Using our models, we found multiple lines of evidence supporting the fact that the global microbiome's plastic-degrading potential correlates strongly with measurements of environmental plastic pollution – a significant demonstration of how the environment is responding to the pressures we are placing on it,” said Aleksej Zelezniak, Associate Professor in Systems Biology at Chalmers.

In total, over 30,000 enzyme ‘homologues’ were found with the potential to degrade ten different types of commonly used plastics. Homologues are members of protein sequences sharing similar properties.

According to the Chalmers team, some of the locations that contained the highest amounts were notoriously highly polluted areas, for example samples from the Mediterranean Sea and South Pacific Ocean.

The mass production of plastic has grown from around 2 million tonnes per year 70 years ago to around 380 million tonnes today, and each year, around 8 million tonnes of plastic escapes into the world’s oceans.

The natural timeline for the degradation of a PET bottle can take hundreds of years, but the researchers are hoping that the results of their study could be a springboard for discovering and adapting enzymes for novel recycling processes.

“The next step would be to test the most promising enzyme candidates in the lab to closely investigate their properties and the rate of plastic degradation they can achieve,” added Zelezniak.

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“From there you could engineer microbial communities with targeted degrading functions for specific polymer types.”

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