Plastics
Superworms to the rescue
By Michael Tracey Last Updated Jun 15, 2022
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We all know that plastics take a long time to decompose. Beetles and their larvae are such pests for gardeners. But remember the proverb, one man’s trash (pest) is another man’s treasure.
Beetle larvae aka superworms have been found to ingest and break down polystyrene within a few weeks. In 2019 a team of 4 students from Ellensburg High school won the first-place prize in the Itron Food, Energy and Water Challenge for their experiment with Styrofoam-eating larvae.
South Korean scientists are researching their use in reducing plastic pollution. After analyzing the worms, scientists Jiaojie Li and Dae-Hwan Kim have linked this ability to a bacteria strain in the larvae’s gut.
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For the study, the team put 50 superworms in a chamber with plastic as their only source of food. After twenty-one days, the worms had consumed roughly 70% of the polystyrene. Then, the researchers isolated a strain of Pseudomonas aeruginosa bacteria from the worm’s gut and demonstrated that it could grow on the surface of the plastic and break it down.
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They found that an enzyme from the bacteria, known as serine hydrolase, was responsible for most of the biodegradation. The team believes that either this enzyme or the bacteria that produce it could eventually be used to help break down plastic waste.
Scientists have discovered plastic-eating larvae in the past. In 2017, researchers found that honeycomb moth larvae also consume polyethylene. This is something natural to the species as they usually eat honeycomb wax, which has compounds similar to plastic.
In 2015, Stanford University scientists discovered that mealworms could be employed to break down Styrofoam (polystyrene) waste. The insects eat the material and break it down through digestion. Since then, the team has found that the worms do not absorb the toxic substance in the foam (hexabromocyclododecane, aka HBCD) into their bodies. This means the bugs are safe to eat! They can be used to help with the problem of Styrofoam waste and then used as livestock feed.
Researchers at the University of Queensland have found that the common Zophobas morio 'superworm' can eat through polystyrene, thanks to a bacterial enzyme in their gut.
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Dr Chris Rinke and his team from UQ's School of Chemistry and Molecular Biosciences fed superworms different diets over a three-week period, with some given polystyrene foam, some bran and others put on a fasting diet.
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"We found the superworms fed a diet of just polystyrene not only survived but even had marginal weight gains," Dr. Rinke said.
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"This suggests the worms can derive energy from the polystyrene, most likely with the help of their gut microbes."
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The researchers used a technique called metagenomics to find several encoded enzymes with the ability to degrade polystyrene and styrene.
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We can now look forward to a future where plastic waste will be a thing of the past.
