Microbes in the Alps, Arctic can digest plastic at low temperatures

Harnessing nature to combat the planet’s plastic problem isn’t just an environmental win – it’s also becoming a lucrative venture.

We’ve already discovered a host of tiny life forms capable of devouring plastic, but their ability is often hampered by the need for high temperatures, typically over 30°C. This requirement for heat demands significant energy and isn’t exactly friendly to our planet. However, an innovative solution may lie with a different set of microbes, ones that prefer a chillier climate.

A team of Swiss scientists believed they had a good idea where to seek out these unique cold-loving microbes – in the lofty peaks of their home country or the icy extremes of the North and South Poles. Their intriguing discoveries were published in Frontiers in Microbiology.

We’ve identified new microbial species from plastic-laden soils in mountain and polar regions that can decompose eco-friendly plastics at a cool 15°C, explained the study’s lead scientist, Dr. Joel Rüthi. These life forms have the potential to reduce the cost and environmental impact of enzyme-based plastic recycling processes, he said.

The research team discovered 19 bacterial and 15 fungal species living on plastic waste in Greenland, Svalbard, and Switzerland. The plastic from Svalbard was collected during a 2018 Swiss Arctic Project, with students contributing to the effort as part of their climate change fieldwork. The soil samples from Switzerland were sourced from both a high peak and a valley in the Graubünden region.

Back in the lab, these microbes were cultivated in the dark at 15°C. Advanced techniques were employed to classify them, with the bacteria spanning 13 groups in two large families, while the fungi spread across 10 groups in two large families.

The researchers then assessed each species for its ability to break down various plastic types. None of them managed to break down PE, a non-biodegradable plastic, even after 126 days. However, over half were successful in decomposing PUR, a biodegradable plastic, at 15°C. Certain fungi and bacteria also managed to degrade two types of commercially available biodegradable plastics, PBAT and PLA.

It was quite a surprise to find such a significant number of species capable of decomposing at least one of the plastic types, Rüthi admitted.

Two new fungal species emerged as the most proficient plastic decomposers, managing to break down all tested plastics with the exception of PE. Interestingly, the study found that the plastic-degradation ability of these microbes was influenced by their growth conditions, with each species reacting differently to each of four different conditions.

So, how did these microbes acquire the ability to decompose plastic? After all, plastics only entered the scene in the 1950s.

Many microbes, particularly plant-disease-causing fungi, can produce a variety of enzymes capable of breaking down plant cell walls. These enzymes can target plastic polymers because they bear a resemblance to a type of plant polymer, clarified Dr. Beat Frey, a senior scientist and group leader.

Still, there’s work to be done. The team only tested at 15°C, so the optimal temperature for these plastic-eating microbes remains unknown.

Most of the species we tested appear to grow well between 4°C and 20°C, with the ideal temperature likely being around 15°C, noted Frey.

The next step is to identify the specific enzymes these microbes use to decompose plastic, and refine the process to generate large quantities of these proteins. We may also need to modify the enzymes to increase their stability, he added.

In essence, these scientists have unearthed microbes in cold regions with the ability to break down certain types of plastic. This is an exciting prospect as it could make plastic recycling more efficient and cost-effective.

The material in this press release comes from the originating research organization. Content may be edited for style and length. Want more? Sign up for our daily email.