The planet is facing a mounting challenge: plastic waste accumulating at an alarming rate. Solving this is tough because the plastic pollution problem continues to grow by tens of millions of tons each year. Finding a system to cut this waste, and the germs that might help do it, is the goal for many scientists. Promising steps are emerging, including a significant year from the Swiss Federal Institute WSL.
In recent years, several types of microorganisms capable of processing plastics have been identified. A major hurdle remains the high temperatures these organisms typically require to function—often above 30ºC—to carry out the process.
This constraint raises both economic costs and hurdles toward achieving a carbon-neutral solution.
Now, scientists have discovered that some cold-adapted microbes host enzymes that can operate at very low temperatures, potentially simplifying the approach.
Researchers from the Swiss Federal Institute WSL extended their trials into the Alps and into polar regions, where they found microorganisms able to break down plastics at cooler temperatures. An article published in Boundaries in Microbiology explains how cold-adapted microbes could transform the plastic recycling landscape.
Tests highlighted that these organisms thrive in cold environments.
Studies indicate these microbes are located in the Alps and the Arctic. They can decompose biodegradable plastics at 15ºC, reducing both the economic burden and environmental impact of enzymatic recycling, as described by the work’s principal investigator, Joel Rüthi.
Researchers found that the bacterial strains belonged to 13 genera within the bacterial species, cultivated as single strains using molecular techniques in a controlled lab setting, under dark conditions and at 15 °C. The groups included Actinobacteria and Proteobacteria, spanning 10 genera within these families.
They succeeded in breaking down biodegradable plastic
Through a series of tests, the team evaluated each strain’s ability to digest three materials: non-biodegradable polyethylene (PE), biodegradable polyester-polyurethane (PUR), and commercially available blends such as PBAT and polylactic acid (PLA).
While none of the strains could digest PE after 126 days, 56% of the strains, comprising 11 fungi and eight bacteria, managed to degrade PUR at 15°C. Additionally, 14 fungi and three bacteria could digest mixtures of PBAT and PLA.
Using nuclear magnetic resonance (NMR) and fluorescence-based assays, researchers confirmed that these strains could break PBAT and PLA polymers into smaller molecules.
Plastic pollution on the planet has drawn heightened attention from environmental groups, with calls for practical, science-based solutions.
“It was surprising to see. Most tested strains could degrade at least one of the plastics examined. The most effective organisms were two previously uncharacterized fungal species from the genera Neodevriesia and Lachnellula, capable of digesting all plastics tested except PE”, explained Rüthi.
“Interestingly, we observed that plastic-degrading ability depended on the culture medium for most strains, and each responded differently to the four environments tested”, added the scientist.
Beat Frey, a senior WSL scientist and group leader, noted: “Microbes produce a wide variety of enzymes that target polymer breakdown, including those involved in plant cell wall degradation.”
Although the study focused on digestion at 15 °C, the exact optimal temperature for the enzymes in the successful strains remains undetermined. Most strains grow well between 4°C and 20°C, with an apparent optimum near 15°C.
The next step is to identify the specific plastic-degrading enzymes produced by these microbial strains and to optimize the production process to yield larger amounts of the responsible proteins.
Experts suggest that further enzyme modification may be needed to improve properties such as stability, paving the way for environmentally friendly and cost-effective plastic recycling methods.
The referenced work is available in Frontiers in Microbiology at a dedicated study published in 2023. [1]
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Note: this summary reflects ongoing research in the field of microbial plastic degradation and is intended to convey current findings and potential implications for recycling technologies.
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