People around the world use more than a trillion plastic bags every year. They're made of a notoriously resilient kind of plastic called polyethylene that can take decades to break down.
But a humble worm may hold the key to biodegrading them.
It was an accidental discovery. Scientist and beekeeper Federica Bertocchini was frustrated to find that her beehives were infested with the larvae of Galleria mellonella, commonly known as a wax worm.
Bertocchini, who works at the Institute of Biomedicine and Biotechnology of Cantabria in Spain, tells NPR that she was cleaning out the hive and put the worm-infested parts in a plastic bag.
But shortly afterward, she noticed that "they were all crawling around my place and the plastic bag was riddled with holes."
This got her thinking about whether the creatures were simply chewing up the plastic or actually breaking it down chemically. Bertocchini and a team of researchers decided to test it, so they ground some wax worms into a pulp and spread it on the polyethylene plastic.
The plastic still degraded. "So it had to be something chemical that was going on and not a physical breakdown," one of the scientists, Christopher Howe of the University of Cambridge, tells NPR.
The scientists also found that what the worms did transformed the plastic into ethylene glycol, which is commonly used in antifreeze. "It's not itself a very exciting product, from our point of view, but what matters is that we're able to turn the plastic into something else," Howe says.
So why would the wax worm have this ability? Bertocchini says it might be because the critter commonly lives in beehives. "It eats wax and honey," she said. "So because of the similarities between wax and the polyethylene, to a certain extent clearly, maybe that's the reason why these insects developed this capability."
The process of biodegrading both beeswax and polyethylene involves breaking strong carbon bonds, the scientists wrote in their recent paper in Current Biology.
It's worth noting that the scientists haven't yet pinpointed how the worm chemically breaks down plastic. In fact, they said it may not be the worm itself doing the work, but a bacteria in its gut that starts the process.
Either way, identifying the enzyme responsible could have big ramifications for breaking down plastic waste.
The idea isn't to release millions of worms for a feeding frenzy at a dump. As Bertocchini explains, researchers are hoping to find biotechnological solutions to the problem of plastic waste. The best scenario, she says, would be to isolate the molecule responsible and "produce it in large scale in a lab in vitro, and then distribute the molecule in large scale."
The wax worm isn't the only organism that can break down plastics. For example, gut bacteria in the larvae of the Indian mealmoth Plodia interpunctella can break down polyethylene, but at a slower rate.
And the wax worm discovery is still far from a solution to the world's piles of waste, says Susan Selke, director of the Michigan State University School of Packaging. "It's a long way from discovering something that can biodegrade polyethylene to creating a system where that biodegradation serves a useful purpose," she says.