Researchers in Australia have identified enzymes in the gut of certain beetle larvae that can degrade plastic. In a study published in Microbial Genomics, they write that these “superworms,” of the species Zophobas morio, could help reduce plastic waste in the future.
“Superworms are like mini recycling plants, shredding the polystyrene with their mouths and then feeding it to the bacteria in their gut,” Chris Rinke from the University of Queensland in Australia said in a statement. “The breakdown products from this reaction can then be used by other microbes to create high-value compounds such as bioplastics.”
In the study, scientists split beetle larvae into three groups, feeding one group wheat bran, one polystyrene and one nothing. Over three weeks, they monitored their growth.
“We found the superworms fed a diet of just polystyrene not only survived, but even had marginal weight gains,” Rinke said in the statement. “This suggests the worms can derive energy from the polystyrene, most likely with the help of their gut microbes.”
On the other hand, the plastic-fed worms gained much less weight and were overall much less healthy than the bran-fed ones, though better off than the starvation group. After three weeks, some larvae were also set aside to grow into beetles, per the study. About 93 percent of the bran-fed larvae formed pupae, while about 67 percent of the polystyrene-fed larvae and 10 percent of the starved larvae pupated.
The researchers sequenced the organisms in the superworm’s gut microbiome to find the specific enzymes linked to plastic degradation, writes Fionna M. D. Samuels for Scientific American. The enzyme that degrades the polystyrene appears to reside with the gut bacteria, namely the Pseudomonas, Rhodococcus and Corynebacterium species, not the worm itself.
“We are the first ones to use a high-resolution method [to identify] potential polystyrene-degrading enzymes in the microbes of the superworm guts,” Rinke tells New Scientist’s Carissa Wong. “We could also identify the bacterial lineages that possess these polystyrene-degrading capabilities.”
Polystyrene is one of the most common plastics used today, appearing as packing peanuts, packaging, as CDs and DVDs, among a multitude of other applications. It’s made up of up a series of linked, repeating chemical units called styrenes. Polystyrene is not very chemically reactive, and breaking it down with industrial recycling methods that break polystyrene down to its styrene components takes high heat (upwards of 400 degrees Fahrenheit). So, researchers have been looking for plastic-degrading enzymes and organisms for years.
Further research will still need to be done to figure out how to optimize these worms, bacteria and enzymes to use in recycling facilities.
“It is still too early to make any predictions about when a bioprocess for polystyrene recycling will be available,” Ren Wei at the University of Greifswald, Germany, tells New Scientist. “It will take time to isolate and characterize these enzymes… and then engineer them to meet the stringent requirements for developing a bio-based recycling process.”
But some scientists say banning polystyrene altogether is a better solution.
“I don’t want to give the impression that there’s a solution [to styrofoam pollution] when there’s not,” Muxina Konarova from the University of Queensland, who wasn’t involved in the study, tells the Australian Broadcasting Corporation’s Nick Kilvert. “Why not just ban this polystyrene? It’s a horrible plastic.”