AUSTRALIA – Researchers from The University of Sydney, Australia, have harnessed two strains of fungi found in soils to break down lab samples of polypropylene (PP) in just 140 days.
The two fungi, Aspergillus terreus and Engyodontium album, made a meal of the plastic in the lab experiments: Between 25 and 27 percent of samples were devoured after 90 days, and the plastic was completely broken down after 140 days, the researchers report.
The team of Australian scientists behind the study, led by graduate student Amira Farzana Samat, have described their work as an “important stepping stone” in designing practical biological ways to treat plastic waste.
“Plastic pollution is by far one of the biggest waste issues of our time. The vast majority of it isn’t adequately recycled,” says Samat.
The researchers measured the weight loss of PP granule (GPP), film (FPP) and metalized film (MFPP) after 30, 60 and 90 days of incubation.
The gravimetric weight loss of pre-treated PP samples was higher than the control for both A. terreus and E. album.
The fungi were pre-treated with UV, heat or Fenton’s reagent, which is a common preliminary step before contemplating the biological approach in research.
UV-treated MFPP, FPP and GPP incubated with A. terreus and heat-treated GPP and FPP incubated with E. album demonstrated increasing gravimetric weight loss percentage trend to incubation days.
“It’s the highest degradation rate reported in the literature that we know [of] in the world,” said University of Sydney chemical engineer Ali Abbas.
While it might be a speed record for fungi, plastic-munching bacteria recently discovered in a compost heap have been able to break down 90 percent of PET, or polyethylene terephthalate, in just 16 hours.
More than 400 microorganisms have so far been found to degrade plastic naturally, with fungi attracting a fair bit of attention for their versatility and ability to degrade all sorts of synthetic substrates with a powerful concoction of enzymes.
“Recent studies suggest some fungi may even degrade some of the ‘forever chemicals’ like PFAS, but the process is slow and not yet well understood,” explains microbiologist Dee Carter of the University of Sydney.
On a basic chemical level, plastics are a string of carbon atoms adorned with different side chains that give each type of plastic its specific properties.
Recycling plastics, in theory, should be as easy as picking apart the repeating subunits that makeup plastics and reassembling them into something new.
But there are so many different types of plastics that when all sloshed together and mixed with other materials as waste, they are practically impossible to separate and recycle. Most plastic waste is either incinerated or dumped into landfill.
The researchers hope their method could one day reduce the vast amount of plastic polluting the environment and lead to a greater understanding of how plastic pollution might biodegrade naturally under certain conditions.
“We need to support the development of disruptive recycling technologies that improve the circularity of plastics, especially those technologies that are driven by biological processes like in our study,” concluded Abbas.
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