Microbes around the world are evolving to eat plastic (and it could help deal with plastic pollution)

Dhaka, Bangladesh- November 12, 2018: Plastic bags are seen in Buringanga River in Dhaka, Bangladesh on November 12, 2018.
Plastic bags are seen in Buringanga River in Dhaka, Bangladesh.

Across the world, microbes are evolving to eat plastic and the finding could have important implications for the battle against plastic pollution.

Microbes in the ground and in seawater have evolved to have enzymes which can break down different plastics, researchers at Sweden’s Chalmers University have found.

The global plastic problem has exploded in the past 70 years — from around two million tonnes per year to around 380 million — which has given microbes time to evolve.

The researchers analysed samples of environmental DNA from around the world, looking for microbial enzymes which could break down plastic.

They found that levels of such enzymes were highest in the areas with most plastic pollution.

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Aleksej Zelezniak, associate professor in systems biology at Chalmers, said: “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.”

In total, more than 30,000 enzyme ‘homologues’ were found with the potential to degrade 10 different types of commonly used plastic.

Homologues are members of protein sequences sharing similar properties.

Some of the locations that contained the highest amounts were highly polluted areas, for example samples from the Mediterranean Sea and South Pacific Ocean.

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Jan Zrimec, lead author of the study and former postdoctorate student in Zelezniak’s group, now a researcher at the National Institute of Biology in Slovenia, said: “Currently, very little is known about these plastic-degrading enzymes, and we did not expect to find such a large number of them across so many different microbes and environmental habitats. This is a surprising discovery that really illustrates the scale of the issue.”

Every year around eight million tonnes of plastic escapes into the world’s oceans, but the natural progresses for plastic degradation are very slow – the lifetime of a PET bottle, for example, can be up to hundreds of years.

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The researchers believe that their results could potentially be used to discover and adapt enzymes for novel recycling processes.

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

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