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Plastic-munching moth could help ease pollution

A moth that prefers plastic to pullovers could help solve the problem of discarded shopping bags and packaging, researchers believe.

The larvae of the greater wax moth normally thrive on beeswax, making them a hated enemy of bee keepers across Europe.

But a chance discovery has shown that they will also happily munch on plastic.

Placed in a plastic bag the grubs quickly leave it riddled with holes, in much the same way that a woollen jumper is attacked by clothes moth caterpillars.

Understanding how the larvae eat plastic could provide a biotechnological method of disposing of bags and packaging, a major source of land and sea pollution, say scientists.

Dr Paolo Bombelli, a member of the international team from Cambridge University, said: "If a single enzyme is responsible for this chemical process, its reproduction on a large scale using biotechnological methods should be achievable.

"This discovery could be an important tool for helping to get rid of the polyethylene plastic waste accumulated in landfill sites and oceans."

The caterpillars, known as "wax worms", are commercially bred for fishing bait and in the wild live as parasites in bee colonies.

A member of the research team from Spain, who happens to keeps bees, spotted their penchant for plastic while removing the pests from her hives.

Dr Federica Bertocchini, from the Institute of Biomedicine and Biotechnology of Cantabria in Santander, placed the larvae in a plastic shopping bag and later found it was full of holes.

In a follow-up test conducted in Cambridge, 100 wax worms were let loose on a plastic bag from the British supermarket.

Holes began to appear after just 40 minutes, and over a period of 12 hours 92mg of plastic was consumed.

The caterpillars worked much faster than bacteria, which in previous experiments took a day to biodegrade just 0.13mg of plastic.

Polyethylene is largely used in packaging and accounts for 40% of the total demand for plastic products across Europe.

Up to 38% of discarded plastic in Europe is buried in landfill sites. In the oceans, plastic waste breaks down into small particles which pose a serious health risk to the fish that ingest them.

Each year, some eight million tonnes of waste plastic from around the world ends up in the sea .

Dr Bertocchini said: "Plastic is a global problem. Nowadays waste can be found everywhere, including in rivers and oceans.

"Polyethylene in particular is very resistant, and as such is very difficult to degrade naturally."

Beeswax consists of fatty compounds with a chain-like chemical structure similar to that of polyethylene, said the scientists.

The wax worm larvae are thought to digest beeswax and plastic in much the same way, by breaking down their chemical bonds.

Research published in the journal Current Biology showed that the grubs transformed polyethylene into unbonded molecules of ethylene glycol.

The holes in the plastic bags were not merely caused by chewing.

"The caterpillars are not just eating the plastic without modifying its chemical make-up," said Dr Bombelli.

"We showed that the polymer chains in polyethylene plastic are actually broken by the wax worms,.

"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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