Arctic microbes can degrade bio-plastics | Polarjournal
Plastic persists for a very long time, especially in cold habitats, like here on Svalbard. Now it has been discovered that cold-adapted microorganisms also produce enzymes that can break down plastic. In large parts of the Arctic, however, it would still be too cold. (Photo: Julia Hager)

Swiss researchers discovered microorganisms in Greenland, Svalbard and the Alps that produce enzymes that can break down plastic even at relatively cool temperatures. These could contribute significantly to the recycling of plastics.

Each year the global plastics problem grows by several hundred million tons. Following stagnation at the beginning of the pandemic, plastics production rose to 391 million tons worldwide in 2021, according to PlasticsEurope, a 16-million-ton increase over 2019. With a substantial portion of this ending up in the environment, there is now an increased focus on avoidance and recycling, in other words, sustainability instead of new production.

However, the current mechanical and chemical recycling methods have various disadvantages. In the case of mechanical recycling, large quantities of microplastics are lost during the necessary washing processes and are released into the environment with the wastewater, as a recent study from Great Britain showed. In addition, the recycled plastic polymers lose quality and cannot be recycled an unlimited number of times. Chemical recycling is also not sustainable, as it requires high temperatures and toxic solvents.

Researchers call the ecosystems that develop on plastic the plastisphere, with organisms ranging from microbes to larger animals such as barnacles (pictured here). Photo: (Julia Hager)

It is therefore all the more important to continue the search for microorganisms that produce plastic-degrading enzymes, especially at temperatures that do not require additional energy input in industrial applications.

A Swiss research team from the Swiss Federal Institute for Forest, Snow and Landscape Research and ETH Zurich has succeeded for the first time in isolating several cold-adapted bacterial strains and fungal species from plastic pieces that produce plastic degrading enzymes. The researchers specifically searched for the microbes on plastic pieces that they had previously buried in Greenland and in alpine soils in Switzerland and left there for one year. They also examined plastic from beaches of the Svalbard archipelago.

The team then let the isolated bacterial strains and fungi grow in the laboratory at a temperature of 15°C. Until now, plastic-degrading microbes had mainly been studied in environments with higher temperatures of 20°C and more. However, the average temperature of terrestrial ecosystems is significantly lower, making the researchers’ discovery very important.

The plastics used in the study were polyethylene (PE) and the biodegradable plastics polyester polyurethane (PUR), two commercial films made from polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) from compostable waste bags and mulch films respectively, as well as pure PBAT and PLA in the form of industrial pellets.

Of the total of 34 isolated bacterial strains and fungal species, 14 fungal and 3 bacterial strains were able to digest the films made of PBAT and PLA. The dispersed PUR, which is used for example for prints on T-shirts, could be processed by 11 fungal and 8 bacterial strains. Polyethylene, on the other hand, as one of the most commonly used conventional types of plastic, could not be decomposed by any of the strains. The researchers published their results in the journal Frontiers in Microbiology.

The new study showed that bio-plastics buried in the soil of Greenland were degraded by the microbes settling on them, but whether this also applies to this candy wrapper is open to question. (Photo: Julia Hager)

The researchers also report that the two fungal strains Thelebolus and Lachnellula of the genus Neodevriesia were also able to degrade plastic, which was previously unknown. The former comes from a beach on Svalbard, the other from the Swiss Alps. Of the 17 microbial strains isolated in the Arctic, 12 were able to decompose plastic, but not to the same extent as those from Switzerland.

However, the time needed by the different bacterial and fungal strains to digest the plastic polymers was quite long, more than 120 days. The two films degraded the fastest: within 60 days, their weight was reduced by 46 % and 39 %, respectively.

Nevertheless, the researchers’ discovery is promising. On one hand, the microorganisms could contribute to the degradation of plastic in nature. On the other hand, they could be of great use in industrial recycling. However, the next step would be to first identify the enzymes and optimise them for industrial application, says Beat Frey, a researcher at the Swiss Federal Institute for Forest, Snow and Landscape Research and co-author of the study.

The extent to which the microorganisms investigated in the study can break down not only biodegradable but also conventional plastics is also likely to be the subject of further research.

But until then, it remains up to us to stem the tide of plastic and ensure that the environment is as free from plastics as possible… not just in the Arctic and Antarctica, but everywhere.

Julia Hager, PolarJournal

Link to the study: Rüthi Joel, Cerri Mattia, Brunner Ivano, et al. Discovery of plastic-degrading microbial strains isolated from the alpine and Arctic terrestrial plastisphere. Frontiers in Microbiology, 14, 2023. https://www.frontiersin.org/articles/10.3389/fmicb.2023.1178474

More about this topic

error: Content is protected !!
Share This