Thanks to a honeycomb, we know the secret of the waxworm’s ability to destroy plastic: ScienceAlert
Researchers have identified a pair of enzymes in waxworm saliva that naturally break down a common form of plastic within hours at room temperature.
Polyethylene is one of the most widely used plastics in the world, having uses in everything from food containers to shopping bags. Unfortunately, its robustness also makes it a stubbornly persistent pollutant – the polymer must be treated at high temperatures to trigger the degradation process.
Waxworm saliva contains the only enzymes we know of that can work on untreated polyethylene, making these natural proteins potentially quite useful for recycling.
Federica Bertocchini, molecular biologist and amateur beekeeper, discovered by chance, a few years ago, that waxworms have a talent for degrading plastic.
“At the end of the season, beekeepers usually put empty hives in a storage room, to put them back in the field in the spring,” Bertocchini recently told AFP.
“One year I did this, and found my stored honeycombs infested with waxworms.”
She cleaned the honeycomb and put all the waxworms in a plastic bag. When she returned soon after, she found the bag “riddled with holes”.
Wax worms (Galleria mellonella) are larvae that eventually turn into short-lived wax moths. In the larval stage, the worms settle in the hives where they feed on wax and pollen.
After this chance discovery, Bertocchini and his team at the Margarita Salas Center for Biological Studies in Madrid set to work analyzing the waxworm’s saliva and publishing their findings in Nature Communication.
The researchers used two methods: gel permeation chromatography, which separates molecules based on their size, and gas chromatography-mass spectrometry, which identifies fragments of molecules based on their mass-to-charge ratio.
They confirmed that saliva actually breaks the long chains of hydrocarbons found in polyethylene into small oxidized chains.
They then used proteomic analyzes to identify “a handful of enzymes” in saliva, two of which were found to oxidize polyethylene, the researchers write.
The researchers named these enzymes “Demetra” and “Ceres”, after the ancient Greek and Roman goddesses of agriculture, respectively.
“To our knowledge, these polyethyleneases are the first enzymes capable of producing such modifications on a polyethylene film working at room temperature and in a very short time”, write the researchers.
As these two enzymes overcome “the first and most difficult step in the degradation process”, they add, the process could represent an “alternative paradigm” for waste management.
Although still in its infancy in investigations, these enzymes could potentially be mixed with water and poured onto plastic at a waste management facility, Bertocchini told AFP. They could be used in remote locations where waste facilities are not available, or even in individual homes.
As promising as their saliva is, waxworms aren’t the only organisms known to degrade plastic.
A 2021 study showed that ocean and soil microbes and bacteria evolved to eat plastic.
In 2016, researchers reported a bacterium in a Japanese landfill that could break down polyethylene terephthalate, also known as PET or polyester. This then inspired scientists to create an enzyme that could quickly break down plastic drink bottles.
Around 400 million metric tons plastic waste is generated each year in the world, of which around 30% is in the form of polyethylene. Of the 7 billion tons generated by the world to date, only 10 percent has been recycled, leaving the world with a considerable legacy of waste.
Reducing consumption and reusing materials will undoubtedly limit the impact of plastic waste on the environment, but having a toolkit to clean up our messes could help us get our plastic waste problem under control.
The new study was published in Nature Communication.