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April 25, 2017

This caterpillar could be the key to biodegradable plastic

A species of caterpillar that typically consumes honey and the wax from beehives may be the answer to the growing problem of plastic waste, as new research has revealed that it can easily devour a commonly used type of the material and cause it to return to a useful compound.

As Spanish National Research Council (CSIC) scientist Federica Bertocchini and her colleagues reported Monday in the journal Current Biology, the larvae of the greater wax moth (or Galleria mellonella) is capable of causing polyethylene, a type of plastic used in shopping bags and food packaging, to biodegrade into a substance that can be used in various consumer products.

Bertocchini discovered that the caterpillars, which are also known as wax worms, had a taste for plastic while removing them from beehives, Sky News and the Los Angeles Times explained. As she extracted them, she placed them in plastic bags, and later found those bags full of holes.

Following that discovery, she and her colleagues observed wax worms placed on a polyethylene film and found that in as little as 40 minutes, the insects had already started boring holes through the plastic material. In fact, each worm was consuming it at a rate of roughly 2.2 holes/hour, and a team of 100 caterpillars consumed 92 milligrams of a plastic shopping bag in 12 hours.

To further test the wax moth larvae, they created a slurry of worms and placed it on polyethylene films, the Times said. Fourteen hours later, 13 percent of the plastic’s mass had degraded, and the research team discovered that the worms had left behind ethylene glycol – a compound used as a coolant, a heat transfer agent, and in the manufacturing of polyester fibers and plastic bottles.

Researchers hope to discover, replicate substance responsible

The discovery, which has been patented by the researchers, could prove to be an unexpected help in the battle against plastic refuse. Approximately 80 million metric tons of polyethylene is made globally every year, the CSIC said in a statement, and plastic bags made out of the substance can take up more than a century to decompose.

Each year, the average person uses well over 200 plastic bags, resulting in the creation of at least 100,000 tons of polyethylene waste annually, the research council explained. “New solutions for plastic degradation are urgently needed,” they wrote, according to the Times. With the new study, it appears as though they may have serendipitously discovered one in nature.

How does the wax moth larvae cause the plastic to biodegrade at such a rapid rate? As the scientists told the Times, the most likely explanation is because of the chemical similarity between plastics and the beeswax contained in the hives that the creatures normally consume. As study co-author Chris Howe from the University of Cambridge said, “the larvae have evolved to be able to break down the beeswax, and can break down plastic as well, given the chemical similarity.”

Howe’s Cambridge colleague and co-author Paolo Bombelli explained to Sky News that the wax worms were not just devouring the plastic, but were actually producing a substance which caused the chemical bonds to break. The next step, he said, is to discover what that substance is and find a way to reproduce it so that it could be used to degrade existing polyethylene waste.

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Image credit: Wayne Boo/USGS Bee Inventory and Monitoring Lab