Superworms, a hope for recycling styrofoam?

Scientists could use the worms to devise a better way to recycle this substance, which may otherwise persist in the environment for centuries

The larvae of the darkling beetle, nicknamed “superworms” perhaps because of their size, are usually content to munch on wheat bran. But a number of the 2-inch-long creatures recently found themselves dining on polystyrene, the long-lived plastic packing material known sometimes by the brand name Styrofoam.

The larvae that managed to choke down this peculiar feedstock did not die. As scientists noted in a new paper published in the journal Microbial Genomics, they even gained a bit of weight, prompting the researchers to check their digestive systems for microbes that could break down the polystyrene. If scientists can understand such microbes’ tool kits, they can devise a better way to recycle this substance, which, if left on its own, may persist in the environment for hundreds of years.

Other insects have been fed polystyrene. Mealworms can eat the substance that makes up packing peanuts, among other plastics, said Christian Rinke, a microbiologist at the University of Queensland in Australia and an author of the new paper. Mealworms and superworms alike have been observed consuming polystyrene, and they lose this ability when they’re fed antibiotics. So researchers concluded their gut microbiomes are likely to be behind this odd talent.

To find out what was in those microbiomes, Rinke and his colleagues grew three groups of superworms. One group ate bran, one ate blocks of polystyrene and the third ate nothing.

While bran was more enticing, the larvae were willing to give polystyrene a go. Within 48 hours, the polystyrene group’s faeces turned from light brown to white, and their weight crept up slowly.

“Polystyrene is definitely a poor diet,” Rinke said. But “the worms can survive it — they don’t look sick or anything.”

The researchers sequenced all the DNA they could extract from the guts of the larvae. They were less interested in which specific microbes were present than in what enzymes were being made as the microbes worked to break down polystyrene. They pinpointed a handful of likely candidates — all types of enzymes known for their slicing-and-dicing abilities — that were possibly shearing polystyrene down into smaller pieces.