Researchers find bacteria in the Arctic and Alps that can break down plastic at low temperatures.

Finding, developing, and bioengineering creatures that can process plastic guides in the evacuation of contamination is, however, presently a large business. A few microorganisms that can do this have proactively been found, yet when their proteins that make this conceivable are applied at a modern scale, they ordinarily just work at temperatures above 30°C.

The warming required implies that modern applications are expensive to date and aren’t carbon-neutral. In any case, there is a potential answer to this issue: locating specialized microbes that can survive in the cold and whose enzymes function at lower temperatures.

The Swiss Federal Institute WSL’s scientists were aware of where to look for such microorganisms: in the polar regions or at high altitudes in their country’s Alps. Frontiers in Microbiology has published its findings.

“In this study, we demonstrate that unique microbial species isolated from the ‘plastisphere’ of alpine and arctic soils were capable of degrading biodegradable plastics at a temperature of 15 °C. The cost and environmental impact of an enzymatic recycling process for plastic may be lessened with the aid of these microbes.

Author Dr. Joel Rüthi, currently a guest scientist at WSL.

First author Dr. Joel Rüthi, who is currently a guest scientist at WSL, stated, “Here we show that novel microbial taxa obtained from the ‘plastisphere’ of alpine and arctic soils were able to break down biodegradable plastics at 15°C.” An enzymatic plastic recycling procedure could benefit from the assistance of these organisms by lowering both costs and environmental impact.

In Greenland, Svalbard, and Switzerland, Rüthi and colleagues collected samples from 19 strains of bacteria and 15 strains of fungi that were living on plastic that had been intentionally buried and left there for a year. During the Swiss Arctic Project 2018, students conducted fieldwork to observe the effects of climate change firsthand and collected the majority of the plastic litter from Svalbard. The soil from Switzerland had been collected in the valley of Val Lavirun and on the summit of the Muot da Barba Peider (2,979 m), both in the canton of Graubünden.

The researchers used molecular methods to identify the isolated microbes after allowing them to grow as single-strain cultures in the laboratory at 15°C in darkness. The findings revealed that the fungi and bacterial strains belonged to 10 genera in the phyla Ascomycota and Mucoromycota, while the fungi belonged to 13 genera in the phyla Actinobacteria and Proteobacteria.

Surprising results They then tested each strain using a variety of tests to see if it could digest sterile samples of non-biodegradable polyethylene (PE), biodegradable polyester-polyurethane (PUR), and two biodegradable mixtures of polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) that are readily available on the market.

Even after incubation on these plastics for 126 days, none of the strains were able to digest PE. However, 19 strains, or 56%, including 11 fungi and 8 bacteria, were able to digest PUR at 15°C, while 14 fungi and 3 bacteria were able to digest the PBAT and PLA plastic mixtures. Both a fluorescence-based assay and nuclear magnetic resonance (NMR) analysis demonstrated that these strains were capable of breaking down the PLA and PBAT polymers into smaller molecules.

Rüthi stated, “We found that a large fraction of the tested strains were able to degrade at least one of the tested plastics.” “It was very surprising for us.”

The best entertainers were two uncharacterized contagious species in the genera Neodevriesia and Lachnellula, which were capable of digesting all tested plastics with the exception of PE. The majority of strains’ capacity to digest plastic was also determined to be dependent on the culture medium, with each strain reacting differently to each of the four media tested.

Effect of plant polymer digestibility How did plastic digestibility develop? Since plastics have only been around since the 1950s, it is almost certain that natural selection did not initially target the ability to degrade plastic.

“A wide range of polymer-degrading enzymes involved in the breakdown of plant cell walls have been demonstrated to be produced by microorganisms.” “Due to their ability to produce cutinases that target plastic polymers due to their similarity to the plant polymer cutin, plant-pathogenic fungi are frequently reported to biodegrade polyesters,” explained Dr. Beat Frey, the final author and group leader at WSL.

Since Rüthi et al., difficulties persist. They just tried for assimilation at 15°C; they don’t yet know the ideal temperature at which the proteins of the fruitful strains work.

Frey stated, “However, we know that the majority of the tested strains can grow well between 4°C and 20°C, with an optimum around 15°C.”

“Identifying the plastic-degrading enzymes produced by the microbial strains and optimizing the procedure to obtain large quantities of proteins will be the next major challenge.” “What’s more, further adjustment of the chemicals may be expected to upgrade properties like protein soundness.”

More information: Discovery of plastic-degrading microbial strains isolated from the alpine and Arctic terrestrial plastisphere, Frontiers in Microbiology (2023). DOI: 10.3389/fmicb.2023.1178474 , … il.2023.1161627/full

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