Caterpillars that eat plastic bags discovered, could lead to pollution solution

Wax worms
© Plastic biodegraded by 10 worms in 30 minutes. (César Hernández/CSIC)

The greater wax moth caterpillar can biodegrade polyethylene, one of the most widely used and indestructible plastics vexing the planet.

Caterpillars. They're cute, they star in children's books, they turn into pretty moths and butterflies. And now it turns out they may hold the solution to the planet's plastic predicament.

Like many great findings and inventions, the discovery of a caterpillar that eats plastic was made accidentally. Biologist Federica Bertocchini, a biologist at Spain's Institute of Biomedicine and Biotechnology of Cantabria, was tending to her hobby beehives and used a polyethylene shopping bag to collect pests known as wax worms – AKA our superhero caterpillars, the larvae of the moth Galleria mellonella. Known for infesting hives and eating honey and wax, Bertocchini was surprised to see the shopping bag riddled with holes before long. She got in touch with colleagues from the University of Cambridge, Paolo Bombelli and Christopher Howe, reports the Washington Post. “Once we saw the holes the reaction was immediate: that is it, we need to investigate this.”

While there have been other creatures that biodegrade plastics – recently a bacteria and mealworm were found to have an appetite for such – none of them have been able to do so with such rapacity as the wax worm. Given the completely insane rate at which we produce, use (one time), and toss plastic bags, the idea of something that devours them is pretty intriguing. In America alone we use some 102 billion plastic bags per year; globally, we use a trillion plastic bags annually. Some 38 percent of plastic is discarded in landfills, where it can survive for 1,000 years or more.

With this in mind, the team began investigating the plastic-eating wonders of the wax worm. They offered a plastic bag from a UK supermarket to a group of 100 wax worms. They began creating holes after 40 minutes; 12 hours later, they had reduced the mass of the bag by 92mg. The plastic-eating bacteria mentioned above biodegrades plastics at a scant rate of 0.13mg a day.

Wax worms© Wax worm and biodegraded holes in a polyethylene plastic shopping bag from a UK supermarket. (Paolo Bombelli)

"If a single enzyme is responsible for this chemical process, its reproduction on a large scale using biotechnological methods should be achievable," says Bombelli. "This discovery could be an important tool for helping to get rid of the polyethylene plastic waste accumulated in landfill sites and oceans."

The key to the caterpillar’s talents could lie in its taste for honeycomb, say the scientists.

"Wax is a polymer, a sort of 'natural plastic,' and has a chemical structure not dissimilar to polyethylene," says Bertocchini. The researchers considered that perhaps the plastic was being broken down by the mechanical action of chewing, but proved otherwise.

"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," says Bombelli. The worms transformed the polyethylene into ethylene glycol. "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."

Which is to say that the solution isn’t in unleashing hordes of caterpillars upon the world’s landfills, but rather to work on a large-scale biotechnological solution, inspired by the wax worm, for managing polyethylene pollution.

“We are planning to implement this finding into a viable way to get rid of plastic waste,” says Bertocchini, “working towards a solution to save our oceans, rivers, and all the environment from the unavoidable consequences of plastic accumulation."

The study was published in Current Biology

Tags: Insects | Plastic Bags | Plastics

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