Superworms can eat and recycle polystyrene plastic

Two-inch-long insect larvae called superworms can digest polystyrene: one of the most irritating plastics.

The ability, according to new research, lies in your gut bacteria: there are microbes in your intestines that have plastic digestion enzymes. These microbes could be used in plastic processing and recycling.

“Insect larvae have a history of being able to damage or even poke holes in plastic,” says Chris Rinke, a researcher at the University of Queensland’s School of Chemistry and Molecular Biosciences and lead author of a paper describing the superworm microbiome. . genomics, published in microbial genomics.

Rinke and the rest of his team at UQ wanted to understand the dark beetle’s plastic-eating ability (zophobas morio) larvae. The larvae of this beetle are called “superworms”.

“There were some reports out there – there was one about the wax worm, or common mealworm. And they are about 1-2 cm. But the superworm is longer than 5 cm. It’s much bigger. So that’s what we thought: maybe this guy can do it too. And maybe even better, because it’s one size larger. That’s how we started.”

The researchers created three groups of superworms, with bran, polystyrene or nothing, over a three-week period.

“We found that superworms fed a polystyrene-only diet not only survived, but even had marginal weight gains,” says Rinke.

“This suggests that the worms can get energy from polystyrene, likely with the help of their gut microbes.”

Superworms chewing polystyrene. Credit: University of Queensland.

The researchers then investigated the superworms’ gut microbiomes, using a technique called metagenomics.

“This allows us to recover all the DNA of these microbes in the gut. So we can sequence that and we can actually see what enzymes are encoded in there,” says Rinke.

“It’s a very powerful technique that allows us to explore the entire system.”

They detected several enzymes that could break down polystyrene in the superworms’ gut microbes.

More on plastic digestion enzymes: Another round of microbes versus plastic

On its own, the bacteria are unlikely to degrade the plastic – it needs some processing by the superworm first.

“Superworms are like mini recycling plants, crushing polystyrene in their mouths and then feeding the bacteria in your gut,” says Rinke.

“The decomposition products of this reaction can be used by other microbes to create high-value compounds such as bioplastics.”

The researchers are now investigating ways to grow the gut bacteria separately and test their ability to further break down polystyrene.

“We can then look at how we can improve this process to a level necessary for an entire recycling plant,” says co-author Jiarui Sun, a doctoral candidate at UQ.

Close-up of superworm intestine showing small white polystyrene bubbles
Polystyrene in a superworm intestine. Credit: University of Queensland

“It’s really an early stage,” says Rinke. “But what we want to do next is get these enzymes and express them in the lab and characterize them in more detail so we know exactly under what conditions they work, at what temperature, how efficient they are and whether one is more efficient than the other. .”

What would a recycling plant based on these superworms look like?

“You can grow a large number of superworms, it’s possible,” says Rinke.

“But it’s much more viable to mimic what the worm does. Then you would have a mechanical milling of the polystyrene. And then you would basically have big Pyrexes, where you add the enzyme or various enzymes to break it down. That’s how I imagine it.”

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