No more microbes that can degrade plastics in places heavily polluted by plastics – sciencedaily

The number of microbial enzymes capable of breaking down plastic is increasing, correlating with local levels of plastic pollution. That’s the conclusion of a new study from Chalmers University of Technology, Sweden, which measured environmental DNA samples from around the world. The results illustrate the impact of plastic pollution on the environment and suggest potential new solutions to deal with the problem.

Global plastic pollution problems are all too prevalent, as mass production of plastic has exploded over the past 70 years or so, from around 2 million tonnes per year to around 380 million. This gave sufficient evolution time for various microbes in the environment to react to these compounds, and many different enzymes have been discovered in previous studies with the ability to degrade different plastics.

The new study, recently published in the scientific journal mBIO, analyzed environmental DNA samples from hundreds of locations around the world. The researchers used computer modeling to look for microbial enzymes with potential for plastic degradation, which were then crossed with official figures for plastic waste pollution in countries and oceans.

“Using our models, we found several sources of evidence supporting that the potential for plastic degradation of the global microbiome is strongly correlated with measurements of environmental plastic pollution – a significant demonstration of how the environment reacts to the pressures we place on it, “says Aleksej Zelezniak, associate professor of systems biology at Chalmers University of Technology.

More enzymes in the most polluted areas

In other words, the quantity and diversity of plastic degrading enzymes is increasing, in direct response to local levels of plastic pollution. In total, over 30,000 enzyme “homologues” have been found with the potential to degrade 10 different types of commonly used plastics. Homologues are members of protein sequences sharing similar properties. Some of the places with the highest amounts were notoriously heavily polluted areas, for example samples from the Mediterranean Sea and the South Pacific Ocean.

“Currently, very little is known about these plastic-degrading enzymes, and we didn’t expect to find so many of them in so many different microbes and environmental habitats. It’s a surprising finding that really illustrates the point. ‘magnitude of the problem,’ explains Jan Zrimec, first author of the study and former post-doctoral fellow in the group of Aleksej Zelezniak, now a researcher at the National Institute of Biology of Slovenia.

Potential value in tackling the global plastic crisis

Every year, around 8 million tonnes of plastic leak into the world’s oceans. The natural progress of plastic degradation is very slow – the lifespan of a PET bottle, for example, can reach hundreds of years. The growth and accumulation of plastic waste in the oceans and on land is a truly global problem and there is a growing need for solutions to manage this waste. The researchers believe their results could potentially be used to discover and adapt enzymes to new recycling processes.

“The next step would be to test the most promising candidate enzymes in the lab to closely study their properties and the rate of plastic degradation they can achieve. From there, you could design microbial communities with targeted degradation functions for specific types of polymers, ”says Aleksej. Zelezniak.

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Material provided by Chalmers University of Technology. Original written by Susanne Nilsson Lindh and Joshua Worth. Note: Content can be changed for style and length.

Bryce K. Locke