Beetles with larvae that can digest polystyrene may help to solve the world鈥檚 mounting plastic waste crisis. Expanded polystyrene, which is聽used to make cups and boxes, is increasingly clogging up landfill and polluting oceans because it doesn鈥檛 biodegrade.
Until recently, no organisms were known to be able to break down polystyrene. But Hyung Joon Cha at Pohang University of Science and Technology in South Korea and his colleagues have discovered that the larvae of a north-east Asian beetle called Plesiophthalmus davidis can do the job.
When the researchers gave the larvae nothing but expanded polystyrene boxes to eat for two weeks, they consumed about 34 milligrams of the plastic each. The bacteria in their guts converted the long polystyrene molecules into carbon dioxide gas and small chemical fragments that were excreted as droppings.
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The larvae are probably able to degrade the plastic because they normally feed on rotten wood, which contains cellulose and lignin molecules that have similar structures to polystyrene, says Cha.
P. davidis is related to three other wood-eating beetles whose larvae have also recently been shown to degrade polystyrene: Tenebrio molitor, Tenebrio obscurus听补苍诲 Zophobas atratus.
The four types of larvae could potentially be used to break down some of the millions of tonnes of polystyrene waste that are produced each year, says Wei-Min Wu at Stanford University in California, who led the work studying the other larvae. However, they probably couldn鈥檛 chew through the whole lot, since each larva only decomposes a few milligrams per day, he says.
Wu and his team are now studying whether gut bacteria or digestive enzymes extracted from the larvae can break down polystyrene more efficiently than the insects themselves.
They are also trying to find applications for the chemical fragments that are excreted by the larvae when they digest polystyrene. For example, they are investigating whether the droppings could be聽processed into valuable chemicals or聽used as soil conditioners or fertilisers.
Applied and Environmental Microbiology
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