A so-called “superworm” is gifted with its new scientific superpower: consuming and breaking down plastic products such as polystyrene.
Zofoba the dying is a species of dark beetle in larval form native to numerous North American habitats, from deserts to forests and everything in between. According to a study published in June 2022, the insect has a special bacterial enzyme in the gut and a unique appetite for polystyrene, a type of plastic most commonly found in polystyrene and other plastic foams.
Dark beetles survive in a wide range of habitats, as do plastics. Because they are inexpensive and durable, plastics, made from organic polymers, can take decades to degrade. Polystyrene, a common ingredient in polystyrene, is one of the most produced plastics in the world and can persist in the environment for decades. In 2018 alone, which is the latest data available, at the time of this writing, plastic production reached 396 million tons (360 million tons), European trade association Plastics Europe reported, and demand it should only grow while recycling rates remain low. That’s why scientists are exploring various ways to break down plastic.
Report the superworm.
Over the course of several weeks, researchers from the University of Queensland in Brisbane, Australia divided a total of 171 worms into three groups: one that ate only organic wheat bran, one that was fed a diet based on of polystyrene and a third group that has not been fed at all. Scientists monitored the worms, their eating habits, and their potential weight gain.
Superworms from each diet completed their life cycle and, surprisingly, of the worms treated with only a plastic diet, more than 95% survived the course of the study, a survival rate on par with the other groups.
“We found that superworms fed a polystyrene-only diet not only survived, but also had marginal weight gain,” study author Chris Rinke said in a news release. “This suggests that worms can derive energy from polystyrene, most likely with the help of their gut microbes.”
But how could an organic organism survive on a purely plastic diet? To find out, the researchers conducted a type of DNA analysis known as metagenomics. This area of study identifies the genomes of microorganisms, such as those that live in the guts of superworms, to identify certain enzymes, which are proteins used to speed up the chemical reaction in a cell.
In short, insects offer a two-way physical and biochemical approach to breaking down plastic. First, they use their mouths to chew the material into smaller pieces. Second, superworms ingest plastic particles which are then further broken down by the microbial community in the digestive tract.
These plastic-degrading enzymes, described in the peer-reviewed journal Microbial Genomics, are also found in other species associated with polystyrene degradation. These species include a type of human bacterium and pathogen called Pseudomonas that often causes pneumonia in foals, a disease known as Rhodococcus, and dozens of Corynebacterium, a bacterium known to infect humans.
The ability to break down plastic is seen in other species. For example, wax worms, known as the Indian flour moth, (Plodia interpunctella) are able to degrade polyethylene, as well as the Mellonella gallery, a honeycomb moth found all over the world. Mealworms are also able to survive solely on a polystyrene-based diet and have been shown to break down plastic molecules in their digestive systems, converting about half of the plastic to carbon dioxide and the other half to feces.
However, the researchers in the worm study noted that their results raised many new questions: The results opened up a new can of worms, so to speak.
“Which members of the microbial community are active and which genes are transcribed during a [polystyrene] diet versus regular feed? What are the complete pathways of polystyrene and styrene degradation used by gut microbes? Can some bacteria save energy by using polystyrene components other than polystyrene? “They wrote, adding that all of those questions could one day be areas of future study.
One goal, for example, would be to someday design intestinal enzymes in superworms to degrade plastic waste in large-scale recycling plants, a process known as enzymatic biodegradation. As part of this goal, the research team plans to grow the gut bacteria of the superworm study independently of the worms to test their ability to degrade polystyrene.
“Superworms are like mini recycling plants, which destroy polystyrene with their mouth and then feed it to the bacteria in their gut,” Rinke said. “The breakdown products of this reaction can then be used by other microbes to create high-value compounds such as bioplastics.”
The idea plays with the idea of a circular waste economy, which recycles materials rather than disposing of them. Such “bio-recycling” of plastic waste could help reduce landfills and increase plastics degradation and recycling capacities.
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