Gothenburg, Sweden – A team of scientists led by Aleksej Zelezniak at Chalmers University of Technology has found that the plastic-degrading potential of the global microbiome correlates with recent pollution trends.
As plastic production and usage have ballooned over the past 70 years, they said, there has been plenty of time for microbes to respond to the increasing prevalence of plastic waste in the environment. Many plastic-degrading enzymes have already been identified, including those that break down polyurethane.
In the study, the team analysed samples of environmental DNA from hundreds of locations around the world, and used computer modelling to look for microbial enzymes with the potential to degrade plastic. This was cross-referenced with plastic waste pollution statistics across different countries and oceans.
They found more than 30,000 enzyme homologues with the potential to degrade 10 different types of commonly used plastic, including polyurethane. Highly polluted areas such as the Mediterranean Sea and the south Pacific were among the places with the largest numbers of enzymes. Nearly 60% of the enzymes identified plastic-degrading enzymes did not map to any known classes.
Notably, enzymes acting on PU were only found in the ocean, and not in the soil microbiome. The ocean samples also showed how the quantity of plastic-degrading enzymes increased with depth, indicating a connection to the higher levels of microplastics that have repeatedly been found at deeper levels in the ocean.
‘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,’ Zelezniak said. ‘[This is] a significant demonstration of how the environment is responding to the pressures we are placing on it.’
The team believes that there is potential in 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,’ he said. ‘From there you could engineer microbial communities with targeted degrading functions for specific polymer types.’
The study was published as an open-access paper in the journal mBio.