Plastic-Eating Caterpillar Could Halt PE Bag Waste

Wax worms can chemically digest polyethylene films.

Scientists claim that a caterpillar commercially bred for fishing bait has the ability to biodegrade polyethylene. Called wax worms, the larvae of the common insect Galleria mellonella, or greater wax moth, live as parasites in honeybee colonies. Wax moths lay their eggs inside beehives, where the worms hatch and grow on beeswax—whence they get their name.

A chance discovery occurred when one of the scientific team, Federica Bertocchini, an amateur beekeeper, was removing the parasitic pests from the honeycombs in her hives. The worms were temporarily kept in a typical plastic shopping bag that became riddled with holes. Bertocchini, from the Spanish National Research Council (CSIC), collaborated with colleagues Paolo Bombelli and Christopher Howe at the University of Cambridge’s Dept. of Biochemistry in the U.K. to conduct a timed experiment.

Around 100 wax worms were exposed to a plastic bag from a supermarket. Holes started to appear after just 40 min, and after 12 hr there was a reduction in plastic mass of 92 mg from the bag. Scientists say that the degradation rate is extremely fast compared with other recent discoveries, such as bacteria reported last year to biodegrade some plastics at a rate of just 0.13 mg a day.

“If a single enzyme is responsible for this chemical process, its reproduction on a large scale should be achievable,” stated Bombelli, co-author of the study published last month in the journal Current Biology. “This discovery could be an important tool for helping to get rid of the polyethylene plastic waste accumulated in landfill sites and oceans.”

The beeswax on which wax worms feed is composed of a diverse mixture of fats, oils and some hormones. The researchers say it is likely that digesting beeswax and polyethylene involve breaking similar types of chemical bonds. “Wax is a polymer, a sort of ‘natural plastic,’ and has a chemical structure not dissimilar to polyethylene,” said Bertocchini.

Spectroscopic analysis showed that the worms transform the polyethylene into ethylene glycol. “We showed that the polymer chains in polyethylene are actually broken by the wax worms,” said Bombelli. “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.”

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