Scientists have discovered a new tool in recycling that could help to reduce the environmental burden and costs associated with enzymatic recycling processes for plastic. In the latest discovery, researchers have found microbes that can break down and digest plastics at low temperatures.
While several microorganisms that can perform this have already been found, they usually only work at temperatures above 30 degrees Celsius, making them expensive to use in the industrial sector due to additional heating costs.
Scientists from the Swiss Federal Institute WSL have found microbes that can digest plastics at 15 degrees Celsius, which could be a scientific breakthrough in microbial recycling. The researchers sampled 19 strains of bacteria and 15 varieties of fungi growing on free-lying or intentionally buried plastic kept in the ground for one year in Greenland, Svalbard and Switzerland.
They then tested these strains to determine if they could digest different types of plastic.
The results of the study showed that while none of the strains were able to digest non-biodegradable polyethylene (PE), 19 strains (56%), including 11 fungi and eight bacteria, were able to digest biodegradable polyester-polyurethane (PUR) at 15 degrees Celsius. Additionally, 14 fungi and three bacteria were able to digest the plastic blends of polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA). The plastics tested are widely used in industry, so these findings could have a significant impact on reducing plastic waste.
Dr Joel Rüthi from WSL and colleagues allowed the microbes to grow as single-strain cultures in the laboratory in the dark at 15 degrees Celsius. The bacterial strains belonged to 13 genera in the phylum actinobacteria and proteobacteria, and the fungi to 10 genera in the phylum ascomycota and mucoromycota. Their findings have been published in the journal Frontiers in Microbiology.
Dr Rüthi told the Guardian, “Here we show that novel microbial taxa obtained from the ‘plastisphere’ of alpine and arctic soils were able to break down biodegradable plastics at 15C. These organisms could help to reduce the costs and environmental burden of an enzymatic recycling process for plastic.”
He added that it was astonishing that a large fraction of the tested strains were able to degrade at least one of the tested plastics.
Dr Beat Frey, one of the study authors, explained that microbes have been shown to produce a wide variety of polymer-degrading enzymes involved in the breakdown of plant cell walls. In particular, plant-pathogenic fungi are often reported to biodegrade polyesters, because of their ability to produce cutinases, which target plastic polymers due to their resemblance to the plant polymer cutin.
These new findings are a significant development in the ongoing efforts to find solutions to the global plastic waste problem.
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