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This Caterpillar Can Eat Plastic

The find could lead to new techniques for breaking down our ever-growing plastic waste

A piece of plastic after 10 worms nibbled it for 30 minutes (CSIC Communications Department)
smithsonian.com

Wax worms, which are the larval stage of the wax moth Galleria mellonella, are commonly used in the United States as fishing bait or birdfeeder snacks. But in Europe, the worms are considered a beehive pest where they chew through the beeswax, disrupting the hive. But researchers have found another use as plastic recyclers.

Federica Bertocchini, an amateur beekeeper and scientist at the Spanish National Research Council, picked some wax worms out of one of her beehives and put them in a plastic shopping bag. She left to clean the honeycomb panels. When she returned, the worms were all over the place.

"When I checked, I saw that the bag was full of holes. There was only one explanation: The worms had made the holes and had escaped. This project began there and then," she says in a press release.

Bertocchini and colleagues from Cambridge University began studying the creatures and found that the common wax worm can not only munch but also metabolize polyethylene, the plastic in shopping bags which makes up about 40 percent of the plastics used in Europe. They published their results this week in the journal Current Biology.

In order to study the worms’ munching ability, the researchers put 100 wax worms in a plastic shopping bag from a U.K. supermarket. Within 40 minutes, holes began to appear. Within 12 hours, they had eaten about 92 milligrams of plastic, which Bertocchini says is pretty fast, especially compared to bacteria discovered last year which dissolves polyethylene at a rate of about 0.13 milligrams per day.

Credit: César Hernández/Ainhoa Goñi

As Ian Sample at The Guardian reports, the researchers wanted to make sure the worms weren’t just chewing the plastic into microscopic particles. So they smooshed up some of the worms and applied the paste to the plastic, which also caused holes to appear.

“The caterpillars are not just eating the plastic without modifying its chemical make-up. We showed that the polymer chains in polyethylene plastic are actually broken by the wax worms,” co-author Paolo Bombelli says in a press release. “The caterpillar produces something that breaks the chemical bond, perhaps in its salivary glands or a symbiotic bacteria in its gut. The next steps for us will be to try and identify the molecular processes in this reaction and see if we can isolate the enzyme responsible.”

The hope is that the discovery could lead to a method for breaking down polyethylene that is currently filling in landfills and clogging waterways. But just how that will work is speculative.

The enzyme could be produced by modified E. coli bacteria or plankton that would attack plastic in the wild, writes Sample. Bombelli also suggests it may be possible to breed and release an army of wax worms. But that means learning more about the worm’s motivation.

“We want to know if they’re munching the plastic to use as a food, or just because they want to escape,” Bombelli tells Sample. “If they just want to escape, they are going to get fed up very soon. But if they’re munching it to use as an energy source it’s a completely different ball game.”

But getting worms or plastic-gobbling E. coli to focus on plastic and not something tastier may prove difficult. “When it comes to microbial breakdown, it’s like asking teenagers to clean their rooms on the weekend,” Christopher Reddy, marine chemist at Woods Hole Oceanographic Institute who was not involved in the study, tells Charlie Wood at the Christian Science Monitor. “They may do it, they may not do it. They may do a little. They may do the easiest way first.”

But the problem is growing bigger every day. According to the press release, 80 million tons of polyethylene is produced each year, taking between 100 and 400 years to break down. So any little bit helps.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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