Microbes have been biorecycling for millions of years by feeding on plant and animal waste. They use enzymes to break down complex molecules into simpler molecules, including water and carbon dioxide. The recipes to make these enzymes are in their genes.
Might some microbes that survive on fallen leaves or the bones of dead animals be able to recycle plastics instead?
Solving the riddle of waste
Dr Bronwyn Campbell is a postdoctoral fellow with our Environomics Future Science Platform (FSP). The FSP uses genetics to solve environmental problems like detecting species, determining the ages of fish and cleaning up waste.
"The amount of plastic waste that went to landfill in 2018 was more than the combined weight of everybody in Australia," Bronwyn said.
"It would be great if we could use plastic-munching microbes to degrade that plastic waste. And it would be even better if they degraded it into intermediate organic materials that we could turn back into plastics.
"Instead of sending plastic to landfill or letting it end up in the ocean, we could bring our plastic waste into a circular economy model," she said.
The first part of Bronwyn's project is to go bioprospecting (exploring biological resources) for wild microbial communities.
Finding new resources in nature
Bronwyn will start field work this year to collect wild microbes for biorecycling. She will be focussing on bacteria and fungi that can munch on plastic.
"I want to hunt for communities of microbes that can degrade plastic in environments where there is already a large amount of plastic. This includes landfills, plastic-polluted areas such as urban streams, and soils around plastic manufacturing and recycling facilities," Bronwyn said.
"I'll also collect microbes from environments where there are hydrocarbons, such as oil spills and petroleum wastewater facilities. This is because hydrocarbons are the parent material of traditional plastics and so have similar components to plastics," she said.
Back in the lab, Bronwyn will try to work out which of the microbial communities can degrade mixed plastics, and then optimise these processes.
Plastic munching for biorecycling
Most of the microbes known to degrade plastics are bacteria, but several fungal species can do it too. These microbes can generally degrade a few different types of plastic each. They come from environments like those where Bronwyn will be looking for microbial communities.
"One of the biggest challenges with plastic waste is how complicated it is. Different plastics, dyes, food scraps and other waste are all mixed in together," Bronwyn said.
"This is where a dream team of plastic-degrading microbes working together as a community has the potential to outshine individual microbial specialists. They can all work together to break down different bits of the waste," she said.
Bronwyn will first work out which types of plastics can be biorecycled by the microbial communities that she collects. Then she will try to increase the range of mixed plastics that the microbial community can degrade by adding plastic-munching microbes from international culture collections.
"This will be tricky because microbes have a terrible habit of murdering and consuming each other," she said.
"If they can get along, we’ll need to work out what they leave behind when they degrade the plastics."
A circular economy
Whether Bronwyn succeeds in breaking down mixed plastics using microbes from nature or microbes from international culture collections, the next step will be to work out how to feed the end products back into plastic production.
"In the future, I hope we can transform plastic waste into a circular resource. But the most important thing right now is to reduce the amount of waste we produce wherever we can," Bronwyn said.
Bronwyn's research is funded by CSIRO and Bioplatforms Australia and takes place at our site in Floreat, Perth, on Nyoongar country.