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 persistently persistent pollutant – the polymer must be treated at high temperatures to initiate the degradation process.
Waxworm saliva contains the only enzymes we know of that can work on virgin polyethylene, making these natural proteins potentially rather useful for recycling.
Federica Bertocchini, a molecular biologist and amateur beekeeper, accidentally discovered that wax worms have a talent for degrading plastic a few years ago.
“At the end of the season, usually beekeepers put some empty hives in a warehouse, to put them back in the field in the spring,” Bertocchini told AFP recently.
“One year I did this and found my stored combs infested with wax worms.”
He cleaned the honeycomb and put all the wax worms in a plastic bag. When he returned a short time later, he found the bag “full of holes”.
wax worms (Galleria mellonella) they are larvae that eventually metamorphose into a rock-living wax moth. In the larval stage, the worms make their home in beehives where they feed on wax and pollen.
Following this serendipitous discovery, Bertocchini and her team at the Margarita Salas Center for Biological Studies in Madrid set to work analyzing waxworm saliva, publishing their findings in Nature communications.
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 broke the long hydrocarbon chains found in polyethylene into short, oxidized chains.
They then used proteomic analyzes to identify “a handful of enzymes” in saliva, two of which were shown 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 in a polyethylene film operating at room temperature and in a very short time,” the researchers write.
As these two enzymes bypass “the first and most difficult step in the degradation process,” they add, the process could represent an “alternative paradigm” for waste management.
Although it is early days in the research, these enzymes could potentially be mixed with water and poured over 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, wax worms aren’t the only organisms known to degrade plastic.
A 2021 study showed that microbes and bacteria in the oceans and soil evolved to eat plastic.
In 2016, researchers reported a bacterium at a Japanese waste site that could break down polyethylene terephthalate, also known as PET or polyester. This later inspired scientists to create an enzyme that could quickly break down plastic drink bottles.
About 400 million metric tons of plastic waste are produced each year worldwide, of which approximately 30% is in the form of polyethylene. Only of the 7 billion tons produced by the world to date 10 percent has been recycled, leaving the world with a significant legacy of waste.
Reducing consumption and reusing materials will undoubtedly reduce the impact that plastic waste has on the environment, but having a toolbox to clean up our mess could help us tackle the problem of plastic waste.
The new study was published in Nature communications.