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 the humble wax 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 caterpillar 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.
AUDIE CORNISH, HOST:
Wax worms can make a mess of things, especially in beehives where they eat the wax. Two years ago, a Spanish scientists and beekeeper made the connection between this type of caterpillar and another substance - plastic.
CHRISTOPHER HOWE: She'd got some beehive material that she'd stored in plastic bags, and she discovered that actually the wax worms had managed to break out of the plastic bag.
ARI SHAPIRO, HOST:
That's Christopher Howe of the University of Cambridge. He was part of a team that tested the caterpillar's ability to take on plastic. They published the results yesterday in the journal Current Biology. The scientists exposed hundreds of wax worms to a plastic bag, and in less than an hour, holes appeared.
HOWE: Then of course could just be that they're physically chewing the bags to pieces. And what we needed to do was to see if some kind of extract from the wax worms would work as well.
CORNISH: That extract was a very unpleasant sounding mush.
HOWE: A puree of wax worm.
CORNISH: This soup of dead caterpillars also ate through plastic.
HOWE: It had to be something chemical that was going on and not a physical breakdown.
SHAPIRO: So it would be wrong to say that these caterpillars are eating plastic. But after contact with wax worms, some of the plastic was converted into ethylene glycol, a sign that it had been degraded. Another study will examine more closely what's going on.
CORNISH: But don't count on these little creatures to solve the worldwide glut of plastic waste. In fact, when wax worms interact with plastic, they may release nasty byproducts, toxins released into the atmosphere. Some scientists are skeptical about how this study might be used. Michigan State University Professor Susan Selke has doubts about its application to the plastic problem.
SUSAN SELKE: It's a long way from discovering something that can biodegrade to polyethylene to creating a system where that biodegradation serves a useful purpose.
SHAPIRO: Selke says if you bother to collect a massive pile of plastic bags, don't wait for science to figure out anytime soon whether wax worms can make that pile disappear. Go ahead and recycle.
(SOUNDBITE OF OSCAR PETERSON TRIO'S "EVERY TIME WE SAY GOODBYE")
SHAPIRO: And now we have some news about this program that we want to share with you. Our friend and colleague Robert Siegel, host of ALL THINGS CONSIDERED for more than 30 years, announced his retirement plans today.
CORNISH: But don't worry. You have some time to say goodbye. Robert will continue to be in the host rotation through the end of this year.
SHAPIRO: Congratulations, Robert. We have both learned so much from you. And while I know you're looking forward to the next phase, we are all glad that you're not leaving right away.
CORNISH: In fact, don't get too comfortable because we look forward to having you back here on air on Monday.
(SOUNDBITE OF OSCAR PETERSON TRIO'S "EVERY TIME WE SAY GOODBYE") Transcript provided by NPR, Copyright NPR.