Plastic-eating caterpillars could help get rid of the world’s waste

Plastic is fantastic. It’s cheap, durable, and doesn’t react to the usual organisms that break down organic matter. This has made it incredibly useful for the packaging industry, but has also led to mountains of waste, like the trillion plastic bags dumped in landfills annually. Now, though, the fight against plastic might have an unexpected ally: a type caterpillar called the wax worm that loves to chow down on plastic bags.

The discovery of the wax worm’s previously unknown diet was made accidentally by Spanish researcher, Federica Bertocchini. Bertocchini is a part-time beekeeper, and is used to removing wax worms from her hives, where the caterpillars like to munch on the beeswax inside. After leaving a recently evicted troupe of wax worms in a plastic bag one day, Bertocchini found that the critters had munched their way to freedom.

THE CATERPILLARS CAN CHEW HOLES IN A PLASTIC BAG IN LESS THAN AN HOUR

Bertocchini was curious as to whether the centimeter-long wax worms were actively digesting the bag’s plastic, or just chewing through it. She confirmed that they were, by mashing the creatures into a paste and applying it to a plastic film, which slowly degraded. She then teamed up with researchers from the University of Cambridge to analyze the worm paste and was able to confirm her findings. The resulting study was published inCurrent Biology.

Bertocchini thinks that the caterpillar’s digestive feat might be because of structural similarities between plastic and the wax that constitutes part of their usual diet. The next step is to find out whether this discovery can be put to any use. It’s not the first time we’ve found organisms capable of breaking down plastic (although the wax worms work faster than most), and some scientists have their doubts.

Ramani Narayan, a researcher from Michigan State University who studies how to degrade various plastics, told The Atlantic that using wax worms to recycle on an industrial scale might just create new problems. Chewing up plastics could create small fragments that “pick up toxins like a sponge, transport these toxins up the food chain, and can cause harm to the environment and human health,” said Naryan.

But Bertocchini says the next step isn’t to use the wax worms themselves, but to find the enzyme in their digestive systems that’s being used to break up the plastic in the first place. If scientist could isolate that, it could be used as a treatment in landfills. That would certainly be easier than dealing with millions of wriggly caterpillars.

Discovery of plastic-eating caterpillar could prove a boon in waste disposal

An accidental discovery of a caterpillar that eats plastic could one day lead to the elimination of plastic waste, researchers hope.

The fast-eating caterpillar known as Galleria mellonella, a wax worm, is sometimes used as fish bait. But the caterpillars are also known to beekeepers as parasitic pests that lay eggs in hives where the offspring grow and feed on beeswax.

Paolo Bombelli, lead author on the paper published in Current Biology, said the discovery occurred purely by accident. His colleague Frederica Bertocchini, an amateur beekeeper (and a co-author of the paper), was puzzled after finding holes in the plastic bags in which she'd deposited wax worms removed from her beehives. She asked him what he thought about it.

for video

http://www.cbc.ca/news/technology/caterpillar-eat-plastic-1.4084672

Breaking the bonds

The process by which the caterpillars consume the plastic isn't entirely understood. It could be an enzyme associated with the wax worm.

Wax worms are known to feed on the wax in beehives. Wax has a similar chemical composition to plastic. (Cesar Hernandez/CSIC)

But it's known the caterpillars are able to break the extremely stable molecular chain in the polyethylene plastic, transforming the polyethylene to ethylene glycol, essentially breaking the bonded molecules. It's the chain's stability that makes plastic so difficult to break down in nature.

The wax in beehives has a chemical composition similar to that of plastic bags.

"I was surprised about the similarity of the chemical structure between wax and the plastic," Bombelli said. "The caterpillar is able to munch through the wax the same way they are able to munch through the polyethylene.… The caterpillar probably doesn't really notice that there is a difference between the wax and the polyethylene."

The researchers are quick to note that another species of wax worm was known to be able to biodegrade plastic as well. In 2014, scientists discovered the Plodia interpunctella could chew through polyethylene. They isolated the bacterial strain responsible for the biodegradation, though it acted significantly slower than in the recent discovery. As well, the biodegradation in that case didn't transform the polyethylene to ethylene glycol.

Promise for plastic waste

A 2015 study estimated that about 275 million tonnes of plastics was generated in 2010, with approximately eight million tonnes entering our oceans. A subsequent study estimated that the number of microplastic particles — those measuring five millimetres or less — ranged from about 93,000 to 236,000 tonnes. This new discovery could pave the way to the creation of a biodegradable solution, Bombelli said.

A wax worm chews a hole through plastic. Polyethylene debris can be seen attached to the caterpillar. (Federica Bertocchini, Paolo Bombelli and Chris Howe)

"You look around you, you can easily spot many, many objects that are made of plastics. So we really depend on plastics," he said. "However, what we need to fight is plastic waste. We would like to provide new tools for helping battling against plastic waste. In the meantime, we should learn how to minimize the plastic waste."