Caterpillars eat plastic shopping bags

A TYPE of caterpillar known as a waxworm has been found to be able to eat and digest polyethylene (PE) plastic, in a chance discovery by a biochemist at the University of Cambridge, UK.

In the wild the waxworm, the caterpillar of the greater wax moth Galleria mellonella, lives in bee colonies, feeding off the beeswax. Cambridge researcher Federica Bertocchini, who keeps bees in her spare time, removed an infestation of waxworms from her hives and temporarily put the creatures in a plastic carrier bag. After a relatively short amount of time, the bag was full of holes.

Bertocchini teamed up with Cambridge’s Paolo Bombelli and Christopher Howe to investigate the phenomenon in the laboratory. They set around 100 waxworms to work on a standard supermarket carrier bag. After just 40 minutes, holes began to appear, and in 12 hours, the bag was 92 mg lighter.

It is not the first time that waxworms have been found to be useful in the fight against plastic pollution. For example in 2014, a team of researchers from the US and China identified strains of bacteria in the gut of a different species, Plodia interpunctella, which could break down PE. However, the rate was much slower, with just 100 mg of plastic degraded over 100 days, which is significantly slower.

To show that the PE was degrading, and not just being broken up, the team used spectroscopic analysis, which identified ethylene glycol, proving that the polymer bonds were breaking. In addition, they mashed up some of the waxworms and spread that on the carrier bags. Again, the bags broke down.

The Cambridge researchers believe that breaking down beeswax, the waxworm’s natural food, and PE, involves breaking similar chemical bonds, but this will require further investigation.

Around 40% of plastic products in Europe are made of PE, and as much of this is packaging, the polymer accounts for a large proportion of plastic waste. It is resistant to degradation will cause pollution problems for centuries. The waxworm, or at least the contents of its digestive system, could provide a solution to the problem.

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

Current Biology doi.org/b6d8