Mealworms Have a Healthy Appetite for Styrofoam, Scientists Learn

October 2, 2015 | Sarah Tse

squirrel eating a styrofoam cup
Photo credit: marc falardeau/Flickr/CC BY 2.0

As it turns out, the solution to our mounting trash problems may have been at the pet store all along.

Styrofoam and other plastics made of polystyrene have earned a reputation as the worst kind of garbage. The material biodegrades so slowly that it sits in landfills for hundreds of years, and can infiltrate water supplies and poison animals. Yet its flimsy, disposable nature makes people less likely to recycle it than other plastic containers. Despite its notoriety, we continue to use styrofoam for cheap food and drink containers and insulation — Americans throw away a whopping 2.5 billion plastic foam cups each year.

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But we finally have a way to get rid of this particularly pesky plastic, and it comes from the lowly mealworm. Pet-owners might recognize them as a tasty treat for reptiles, fish, and birds, and some cultures even incorporate these worms into their cuisine. Now these tiny larvae of the darkling beetle can fulfill a more glorious purpose, thanks to their appetite for styrofoam.

A group of engineers, including Jun Yang from China’s Beihang University and Wei-Min Wu from Stanford University, had been looking for invertebrates that might help us with our growing problem of plastic pollution. In the same way that cows possess gut bacteria that allow them to digest cellulose from tough plant matter, many species carry even more hardcore microbial passengers that can break down manmade materials like plastic. Earlier research found that waxworms, the larvae of Indian mealmoths, contain microbes that can biodegrade polyethylene, a filmy plastic used in trash bags and wrappings.

Styrofoam was proving to be a more stubborn adversary — until Yang tried using it to tempt mealworms. Surprisingly, the worms ate it up. A group of 100 ate about a small pill’s worth of Styrofoam per day, and they converted more and more of the foam into carbon dioxide as the experiment continued. At 16 days, they were converting half of the carbon they consumed into CO2. Within 24 hours of ingestion, the rest of the Styrofoam would come out as biodegraded fragments, and this waste is perfectly safe to use as soil for growing crops. And despite what seems like a pretty poor diet, the mealworms didn’t seem any worse for wear.

To confirm that microbes were responsible for this magical transformation, Yang and his team administered the antibiotic gentamicin to the mealworms. As expected, the worms could no longer digest the Styrofoam and it exited their systems in exactly the same form as it entered. The researchers then isolated these gut bacteria to test their performance. When grown on polystyrene film, the bacterial cultures did make some holes and dents, but they appeared to perform much more efficiently inside the cozier environment of the mealworms’ guts.

This discovery will have a huge impact on the future of plastic pollution. Once they pin down the most favorable conditions to encourage the mealworms and their microbial assistants, scientists can engineer powerful techniques to degrade other plastics, and even design new polymers that will go down a bit easier. Biology continues to provide elegant and simple solutions to man-made problems, reminding us to never underestimate nature.

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