A startling discovery shows the scale of plastic pollution and reveals enzymes that can boost recycling. Microbes in the world’s oceans and soils are evolving to eat plastic, according to one study.
The research scanned more than 200 million genes found in DNA samples taken from the environment and found 30,000 different enzymes that can degrade 10 different types of plastic.
The study is the first large-scale global assessment of the bacteria’s potential for plastic degradation and found that one in four of the organisms tested carried an adequate enzyme. The researchers found that the amount and type of enzymes they discovered matched the amount and type of plastic pollution in different locations.
The results “provide evidence of a measurable effect of plastic pollution on global microbial ecology,” the scientists said.
Plastic in every corner of the planet
Millions of tons of plastic are dumped into the environment each year, and pollution is now encroaching on the planet from the very top of the Mount Everest to the deepest oceans. Reducing the amount of plastic used is vital, as is the collection and proper treatment of waste.
But many plastics are currently difficult to degrade and recycle. Using enzymes to quickly break them down into their basic components would allow new products to be made from old ones, reducing the need to produce virgin plastic. The new research provides many new enzymes to be investigated and adapted for industrial use.
“We found several lines of evidence to support the fact that the global microbiome’s potential for plastic degradation is strongly correlated with measurements of plastic environmental pollution, a significant demonstration of how the environment is responding to the pressures we are exerting. Him,” said Professor Aleksej Zelezniak. , at Chalmers University of Technology in Sweden.
Unexpected result
Jan Zrimec, also of Chalmers University, said: “We didn’t expect to find such a large number of enzymes in so many different microbes and environmental habitats. This is a startling finding that really illustrates the magnitude of the problem. “
The explosion in plastic production over the past 70 years, from 2 million tons to 380 million tons a year, has given microbes time to evolve and deal with plastic, the researchers said. The study, published in the journal Microbial Ecology , began by compiling a dataset of 95 microbial enzymes already known to degrade plastic, often found in bacteria in dumps and similar places filled with plastic.
The team then looked for similar enzymes in environmental DNA samples collected by other researchers from 236 different locations around the world. Importantly, the researchers ruled out potential false positives by comparing the enzymes initially identified with human gut enzymes, which are not known to have enzymes that degrade plastic.
Plastic-degrading microbes multiply
About 12,000 of the new enzymes were found in ocean samples, collected from 67 locations and at three different depths. The results showed consistently higher levels of enzyme degradation at deeper levels, coinciding with the highest levels of plastic pollution known to exist at lower depths.
Soil samples were taken from 169 sites in 38 countries and 11 different habitats and contained 18,000 plastic-degrading enzymes. Soils are known to contain more plastics with phthalate additives than oceans, and researchers have found more enzymes that attack these chemicals in terrestrial samples.
Nearly 60% of new enzymes do not fit into any known enzyme class, the scientists said, suggesting that these molecules break down plastics in ways previously unknown.
“The next step would be to test the most promising enzyme candidates in the laboratory to closely investigate their properties and the rate of plastic degradation they can achieve,” Zelezniak said. “From there, he could design microbial communities with specific degradation functions for specific types of polymer.”
Mutant enzymes created in laboratories
The first plastic-eating insect was discovered in a Japanese garbage can in 2016. Scientists then tweaked it in 2018 to try to learn more about how it evolved, but inadvertently created an enzyme that was even better at breaking plastic bottles. Additional adjustments in 2020 increased the degradation rate by six.
Another mutant enzyme was created in 2020 by the company Carbios, which breaks down plastic bottles for recycling within hours. German scientists have also discovered a bacterium that feeds on toxic polyurethane plastic, which is often dumped in landfills.
Last week, scientists revealed that the levels of microplastics people ingest through their food caused damage to human cells in the laboratory.
By Damian Carrington. Article in English