'Superworm' That Eats Plastic Newly Discovered

In an earlier post, we discussed the major threats that microplastics may pose to the environment. While human bodies cannot break down plastic debris of such minute size, the newly discovered plastic-eating ‘Superworms’ may provide clues for better recycling.

According to the American Chemistry Council, in 2018 in the United States, 27.0 million tons of plastic ended up in landfills compared to just 3.1 million tons that were recycled. Worldwide the numbers are similarly worrisome, with just 9% of plastic being recycled according to a recent OECD report.

The statistics are even worse for certain types of plastic. For example, out of 80,000 tons of styrofoam (polystyrene) containers generated in the United States, a negligible amount (less than 5,000 tons) was recycled.

Now, researchers at the University of Queensland in Australia have found a species of worm—Zophobas morio ‘superworms’—with an appetite for polystyrene could be the key to plastic recycling on a mass scale.

These superworms are beetle larvae that look like giant mealworms and are usually sold in pet shops as food source for fish, birds, and reptiles. However, these worms are far more significant than just ordinary pet food, as they can consume and break down polystyrene plastic.

While plastic takes several hundred years to decompose, superworms and mealworms have been found to consume and break down polystyrene within a matter of just a few weeks. After analyzing the worms, scientists Jiaojie Li and Dae-Hwan Kim have linked their ability to eat polystyrene to a bacteria strain and enzymes that live within the larvae’s gut.

For the study, the scientists team put fifty superworms in a chamber with plastic as their only source of carbon over a three-week period. After twenty-one days, the worms had ingested roughly 70% of the polystyrene. Then, the researchers isolated a strain of Pseudomonas aeruginosa bacteria from the worm’s gut and proved that it could grow on the surface of the plastic and break it down.

The researchers used a technique called metagenomics to have 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. Accordingly, the long-term goal is to engineer enzymes to degrade plastic waste in recycling plants through mechanical shredding, followed by enzymatic biodegradation.

Scientists have in fact formerly discovered larvae eating plastic. 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 similar compounds to plastic. But this recent study takes it a step further in that in increases an understanding of how bacteria in gut do this at the molecular level.

“We found the superworms fed a diet of just polystyrene not only survived, but even had marginal weight gains,” Dr. Rinke from University of Queensland’s School of Chemistry and Molecular Biosciences said. “This suggests the worms can derive energy from the polystyrene, most likely with the help of their gut microbes.”

“The breakdown products from this reaction can then be used by other microbes to create high-value compounds such as bioplastics.” Dr. Rinke further said.

It’s hoped this bio-upcycling will incentivize plastic waste recycling and reduce landfill, but some question whether such techniques will ever be commercially viable. “The scale-up and translation of research like this is always a challenge, which is magnified in the area of plastics by the incredible scale of the problem and the economics in terms of how cheap new plastic is to produce,” Professor Colin Jackson, Australian National University researcher, said.

This research has been published in Microbial Genomics, at https://doi.org/10.1099/mgen.0.000842