Almost a third of the world’s plastic waste is polypropylene, a tough plastic used to make bottle caps and food containers that can take hundreds of years to degrade. But now scientists have used two strains of fungi found in soil to break down lab samples of polypropylene in just 140 days.
the two mushrooms, Aspergillus terreus And Engyodontium Albumgave the plastic a meal in the laboratory experiments: between 25 and 27 percent of the samples were devoured after 90 days, and the plastic was completely degraded after 140 days. the researchers report.
The team of Australian scientists behind the study, led by PhD student Amira Farzana Samat, has described their work as an “important stepping stone” in developing practical biological routes to treat plastic waste.
“This is the highest degradation rate known to us in the literature [of] the world,” said chemical engineer Ali Abbas of the University of Sydney told Australian Broadcasting Corporation technology reporter Danny Tran.
While it could be a speed record for fungi, plastic-eating bacteria recently discovered in a compost heap could break down 90 percent of PET, or polyethylene terephthalate. in just 16 hours. But a bit of healthy competition is good; this is how evolution works.
More than 400 microorganisms They have previously been found to naturally degrade plastics, with fungi attracting quite a bit of attention due to their versatility and ability to degrade all types of synthetic substrates with a powerful mixture of enzymes.
“Recent studies suggest that some fungi even break down some of the “Eternal Chemicals”. like PFAS, but the process is slow and not well understood,” explained Microbiologist Dee Carter from the University of Sydney.
At a basic chemical level, plastics are a chain of carbon atoms adorned with various side chains that give each type of plastic its specific properties. In theory, recycling plastic should be as easy as Breaking apart the repeating subunits assemble the plastics and put them together into something new.
But there are so many different types of plastic that it’s virtually impossible to separate and recycle them when they’re all spilled together and mixed with other materials as waste. Most plastic waste is either incinerated or disposed of in landfills.
“We must support the development of disruptive recycling technologies that improve the circularity of plastics, particularly those technologies powered by biological processes.” says Abbas.
Laboratory experiments showed that the two fungi together could decompose granules and thin polypropylene films, as well as aluminum-coated polypropylene films.
While the researchers don’t yet know exactly how the fungi digested the plastic — that could be the focus of future research — researchers hypothesize that fungi break down materials like plastic into simpler molecules that they can then ingest or excrete.
As you can see in the image below, the normally smooth plastic became pockmarked as the fungi did their dirty work.
The process requires a pre-treatment step using either UV light, heat, or a chemical reagent to weaken the waste material for the fungi to attack. This step mimics the environmental conditions fungi need to attach to and pry up plastics and is thought to make the degradation process more efficient.
Abbas says Their method could be scaled up like any fermentation process, but adds that his team has not yet optimized the experimental conditions for working on an industrial scale. The method is also not a substitute for efforts to reduce plastic waste, he says.
One predictable limitation common to plastic-crunching microbes is that they Struggle to break down higher crystalline forms of plastic used in commercial products as well as in other types of plastic waste.
The next steps for the researchers include building a benchtop prototype, testing modifications to speed up the process, and evaluating the economic feasibility and environmental impact of applying their method on a commercial scale.
However, it is often a bumpy road from experimenting on the lab bench to developing a market-ready product.
Last we heard in 2015, researchers behind a sphere-like Prototype device called Fungi Mutarium — which turn plastic waste into a safe, edible product using two species of fungi — continued their work to speed up the decomposition process.
More recently, scientists have been busy finding ways to manufacture it useful bioplastics from the airCreate recyclable plastics made from superglue instead of crude oil, and Conversion of plastic polymers back into liquid fuel.
These exciting discoveries will require a lot more work if they are to make a real dent in the vast amounts of plastic waste that is quickly piling up.
The research was published in npj: material degradation.
