Plastic is becoming a plague on the planet. Not only are landfills flooded with microplastics, but the oceans are also polluted to the point that tiny creatures who apparently ate microplastics were named. Eurythenes Plastics. Can we stop the diffusion of material that deposits faster than it decays?
There may be an answer, and the answer is fungi. Researchers at the Universities of Kelaniya and Peradeniya in Sri Lanka have discovered a species of fungus that can break down polyethylene, the same type of plastic used in bags, bottles, wraps and take-out containers. These fungi have one thing in common. These fungi usually decompose hardwoods, otherwise they won’t rot quickly. Hundreds of fungi and other microbes are known to degrade a variety of plastics, but it was previously unknown that these particular hardwood-eating species could degrade polyethylene. .
“Microbial biodegradation of plastics is a promising strategy for depolymerizing petroleum-based plastics into monomers or mineralizing them into carbon dioxide and water,” the researchers said in a recently published study. ing. pro swan.
breakdown
How difficult is it to break down hardwoods such as ironwood and ebony? Wood is hard because it is held together by lignin, a polymer in the cell walls of wood, which gives it strength. Masu. Lignin is rigid but can be broken down and depolymerized by suitable enzymes.
The research team found decaying broadleaf trees in forest reserves and was intrigued by the fact that these trees do not break easily. They collected fungal samples from the trees and brought them back to the lab. The fungi were then separated by species, placed in separate containers for each species, and fed with hardwood strips and polyethylene sheets.
The research team wanted to compare the plastic-eating abilities of fungal species and identify the different production levels of enzymes that break down lignin. The degree of degradation of plastic and hardwood was determined by comparing the weight of those materials before and after exposure to fungi. In 45 days, the wood weight decreased from just over 1 percent to nearly 36 percent. This weight loss occurred because fungi degraded lignin and cellulose into products containing carbon dioxide.
During the same time, the plastic also loses weight by being converted to simpler molecules by fungal enzymes, losing almost half of its mass. Polyethylene is typically a hydrophobic or water-resistant material, but it gradually loses its properties as it ages. Also, it breaks easily. As the fungi became more active, polyethylene became more brittle and lost its ability to repel water.
supper plastic
The researchers also wanted to see how the fungi would react if they were given only plastic, not wood. Perhaps something in the wood activates digestive enzymes, so if you can’t see your favorite food, you may consume less plastic. But what happened was rather surprising. “The most striking feature of the experiment was that all isolates showed enhanced degradation. [polyethylene] It’s more pronounced in the absence of wood than in the presence of wood,” the researchers said in the same study.
These fungi need carbon to survive. Wood was their preferred carbon source, but when it was not available, polyethylene was an alternative. The fact that more plastic was broken down when given plastic showed that even when there was no wood around, they could easily adapt metabolically and change their diet.
Lignin and polyethylene have common chemical properties. There did not appear to be any problems switching to plastic when ligninolytic enzymes were used without actual lignin.
In the future, fungi could be used to break down plastic waste on a larger scale, but developing large-scale operations that use fungi to remove plastic-filled waste will take time. . Until then, we must use biodegradable materials wherever possible and recycle all plastic.
PLOS One, 2023. DOIs: 10.1371/journal.pone.0288133