Researchers have found fungi that eat up widely used plastics and are now trying to scale up the process.
The fungi studied in the research are common in nature – Aspergillus terreus, a soil mould and Engyodontium album – and have special enzymes that aid the breakdown of plastic.
Both can break down polypropylene, a cheap and flexible plastic used to make packaging, car parts and batteries, and is widely used in other industrial manufacturing.
The use of plastics, especially industrially, is unlikely to conclude any time soon. But with increased public awareness of the role of plastics in ecosystem pollution and as an end-product of fossil oil use, demand for less environmentally impactful materials is increasing.
To test whether their fungi would chew through plastic, the researchers pre-treated polypropylene samples with heat, ultraviolet light or Fenton’s reagent (a solution of hydrogen peroxide and iron).
Samples were then added to a petri dish with a single culture of either of the two fungi and incubated for 30 and 90-day periods.
Within a month, a fifth of the plastic had been reduced. In three months, more than a quarter had disappeared.
Fungi don’t have mouths though, so what enables them to ‘eat’ their way through plastics? The process observed in the Sydney lab boils down to the unique enzymes produced by each fungi, which enables them to decompose the polypropylene into simpler molecules that can be taken up by the fungi.
It’s these enzymes that are being closely studied as part of the experiment.
“We want to see how effective these enzymes that actually help to degrade this plastic [are],” says Amira Farzana Samat, who conducted the experiments at the University of Sydney’s School of Chemical and Molecular Engineering under the supervision of Professor Ali Abbas.
“Basically, there are many types of enzyme that can be produced by the fungi, but we focus on this particular lactase enzyme, that are known to be produced by many other types of fungi.”
Initial indications suggest hydrogen, carbon dioxide and methane result from the fungal feasting, as well as microsized pieces of plastic.
The scale challenge
Samat and Abbas’s research is currently at lab scale, but their initial results have them hopeful of future upscaling of the process.
Working with the university’s mycology expert to identify natural-state, safe-to-use fungi for plastic degradation, there are likely to be other potential candidates that can work faster or more efficiently at chewing up undesirable materials.
“We are a few steps away from getting this into a commercial implementation,” Abbas says.
“That will require some chemical process engineering and we are doing that at the moment to ensure we can scale this process up to a pilot facility.”
One question that might also be answered through their experiments – and inform commercial outcomes – is whether the fungi are needed at all. If the specific enzymes produced by the fungi are responsible for deterioration, it might be possible to isolate these molecules.
But Samat cautions that such a move might have unindented drawbacks if other fungal properties aid the degradation process. It’s for this reason that her focus is on using the entire biological system.
“We’ve seen that the use of whole microbes are actually more effective, because we know that it is not that only particular enzyme that can help. Other types of enzyme can too,” Samat says.
“We haven’t had a whole experimental lineup to extract out whatever enzymes or secondary metabolites are able to be produced by these fungi.
“If, let’s say one day, we are able to determine everything – all of the metabolites or enzymes – and select one that particularly can degrade higher compared to the others, we might be able to do that.
“But for now, Ali and I are concerned with using the whole microorganism to scale up the process.”