Wax Moth Caterpillars Found to Eat Polyethylene
An international team of researchers from Spain and the United Kingdom has found that a caterpillar of the greater wax moth ( Galleria mellonella ) — commonly known as a wax worm — has the ability to biodegrade polyethylene.
Polyethylene degradation by wax worms. Left: plastic bag after exposure to about 100 wax worms for 12 hours; Right: magnification of the area indicated in the image at left. Image credit: Bombelli et al , doi: 10.1016/j.cub.2017.02.060.
Polyethylene is the most commonly used plastic in the world: about 80 million tons are made annually.
It is largely utilized in packaging: nearly 50% of polyethylene is used to produce plastic films for food storage as well as agricultural and environmental use; the remainder is used to produce plastic bottles and injection-molded products.
Polyethylene is highly resistant to breaking down, and even when it does the smaller pieces choke up ecosystems without degrading.
The environmental toll is a heavy one. Yet nature may provide an answer.
“We have found that the larva of a common insect is able to biodegrade one of the toughest, most resilient, and most used plastics,” said Dr. Federica Bertocchini, a researcher at the Institute of Biomedicine and Biotechnology of Cantabria in Spain.
A chance discovery occurred when Dr. Bertocchini, who is also an amateur beekeeper, was removing the parasitic pests from the honeycombs in her hives.
The worms were temporarily kept in a typical plastic shopping bag that became riddled with holes.
Further study showed that the worms can do damage to a plastic bag in less than an hour. After 12 hours, there was a reduction in plastic mass of 92 mg from the bag.
“The degradation rate is extremely fast compared to other recent discoveries, such as bacteria reported last year to biodegrade some plastics at a rate of just 0.13 mg a day,” the researchers said.
Dr. Bertocchini and co-authors showed that the wax worms were not only ingesting the plastic, they were also chemically transforming the polyethylene into ethylene glycol.
Although wax worms wouldn’t normally eat plastic, the researchers suspect that their ability is a byproduct of their natural habits.
In the wild, wax worms live as parasites in bee colonies. Wax moths lay their eggs inside hives where the worms hatch and grow on beeswax — hence the name.
The molecular details of wax biodegradation require further investigation, but it’s likely that digesting beeswax and polyethylene involves breaking down similar types of chemical bonds.
“Wax is a polymer, a sort of ‘natural plastic,’ and has a chemical structure not dissimilar to polyethylene,” explained Dr. Bertocchini, who is the lead co-author of a paper published in the journal Current Biology .
“If a single enzyme is responsible for this chemical process, its reproduction on a large scale using biotechnological methods should be achievable,” added first author Dr. Paolo Bombelli, a postdoctoral researcher in the Department of Biochemistry at the University of Cambridge.
“We are planning to implement this finding into a viable way to get rid of plastic waste, working towards a solution to save our oceans, rivers, and all the environment from the unavoidable consequences of plastic accumulation,” Dr. Bertocchini said.
“However, we should not feel justified to dump polyethylene deliberately in our environment just because we now know how to biodegrade it.”