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Extremely hungry superworms had plastic for dinner. Now they'll help recycle it

A bacterial enzyme in their gut gives them superpowers.

Extremely hungry superworms had plastic for dinner. Now they'll help recycle it
The common Zophobas morio ‘superworm’ can eat through polystyrene. The University of Queensland

In a lab at the University of Queensland, plastic is a delicacy.

You heard it right. A species of worms known as the common Zophobas morio 'superworm' fancy polystyrene so much that they could have it three times a day. 

Or more. Without any ill effects.

Scientists from the UQ discovered that superworms can eat through polystyrene, thanks to a bacterial enzyme in their gut. Their findings have been published in Microbial Genomics.

We know what you're thinking. These 'plastivores' could aid in the biodegradation of plastic waste, playing a significant role in plastic recycling on a mass scale. How exciting!

Runs in the family

Dr. Chris Rinke and his team from UQ’s School of Chemistry and Molecular Biosciences fed the superworms different diets over three weeks, with some given polystyrene foam and some bran. Others were put on a fasting diet.

Why the bizarre study, though, you might ask.

"Insect larvae have actually a good track record when it comes to damaging and eating plastic. Previous reports have shown that waxworms and common mealworms were able to eat polystyrene. These are rather small insect larvae (1 to 2.5cm) and so we hypothesized that the much larger superworms can eat even more polystyrene compared to their smaller cousins," Rinke tells IE.

Why are these worms called 'superworms', though?

It turns out it's all about the brawn.

"Superworms are not actual worms, but rather the larvae of the darkling beetle Zophobas morio. These beetles lay eggs, and after a week, the larvae hatch, and these superworms live for five-plus months before they undergo pupation to finally emerge as beetles," explains Rinke.

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They are much larger than other insect larvae in the same insect family, which grants them the title of a 'superworm'.

Heroes of Might and Plastic

But do they really relish eating plastic?

We'll let you in on a secret. 

Rinke told us that a likely reason was a "lack of choice". "We compared several feeding trials, and one group of superworms was given only polystyrene to eat – no other food source. After 24 hours, they started eating their way into the polystyrene blocks, likely because there was nothing else to eat," he says.

These superworms not only survived but even had "marginal weight gains. This suggests the worms can derive energy from the polystyrene, most likely with the help of their gut microbes," says Rinke. 

The team didn't know if the superworms would actually eat the polystyrene, "but we had high hopes given the reports from other insect larvae," he adds.

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Primary focus on the enzymes

Though there have been other studies on superworms, theirs is the first to employ a metagenomics technique. It is the study of the structure and function of entire nucleotide sequences isolated and analyzed from all the organisms in a bulk sample.

The technique allowed the researchers to "recover all the enzymes encoded by the microbes in the superworm gut".

Now, this is far-reaching.

In a press release, co-author of the research, Ph.D. candidate Jiarui Sun, says that they aim to grow the gut bacteria in the lab and further test its ability to degrade polystyrene. 

"The actual chemical break-down of the polystyrene is performed by the microbes in the worms' guts, so we will focus on these. We plan to investigate the enzymes with polystyrene degrading capabilities further," Rinke tells us.

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Over the next few years, the enzymes will be characterized in more detail in a mission to find the most efficient ones, which can be further improved with enzyme engineering.

"Ultimately, we want to take the superworms out of the equation and mechanically shred the plastic waste, followed by microbial degradation in bioreactors, and subsequent microbial production of higher value compounds such as bioplastic. We envision that this upcycling approach will make plastic recycling more economically feasible and should incentivize plastic recycling," explains Rinke.

All in good time

Here's where the question of a potential time frame arises. 

Hint: It's not that far.

The researchers have already applied for funding for a four-year project, starting next year.

"We propose to functionally verify, express, and characterize these enzymes. If that all works as planned, it might take another two to three years to further optimize these proteins via enzyme engineering. And then we can incorporate them into the recycling process." So we are probably looking at a 10-year timeframe," says Rinke.

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Zoom out, and you'll realize how consequential this discovery this. Superworms or 'mini-recycling plants' can 'incentivize plastic waste recycling and reduce landfill'.

"Our team is very excited to push the science to make it happen," he adds.

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