Plastic-Eating Mealworms Can Safely Digest Styrofoam
More than 1 million tons of plastic cups and plates—most made of polystyrene resin—were discarded in the U.S. in 2013, according to the Environmental Protection Agency. “The plastic pollution issue is a serious environmental problem,” says Wei-Min Wu, a senior research engineer in the Department of Civil and Environmental Engineering at Stanford University. But there may be a simple solution: mealworms.
Two papers published in the journal Environmental Science & Technology in September by Wu and his colleagues at Stanford and Beihang University in Beijing found that mealworms, the larvae form of the beetle Tenebrio molitor, can eat and rapidly break down Styrofoam and other forms of polystyrene generally thought to be nonbiodegradable. Though for many years we’ve known that insects, birds and other animals occasionally eat plastic, Wu’s team was able to show for the first time that in some cases, the polystyrene is not only consumed, but also is broken down into small, harmless components that can be absorbed back into the environment.
The researchers found that each mealworm consumed from 12 to 100 milligrams of Styrofoam per day, depending on their larval stage and size. After roughly 10 days adapting to the new diet, the mealworms could degrade the plastic in their guts in less than 24 hours, turning 47.7 percent of what they ingested into carbon dioxide and most of the rest into fecal matter.
Several forms of analysis showed that the mealworms’ guts had depolymerized the polystyrene molecules—in other words, they could break apart the links among the molecule’s components. The Styrofoam-eating mealworms completed their life cycles—from larva to pupa and finally adult beetle—just as those subsisting on a normal diet of bran do, though their weight did not increase as much as that of a bran-fed mealworm control group.
The researchers’ second paper looked more closely at the microbial environment of the mealworm gut and the essential role it plays in the plastic degradation process. After giving their insect subjects antibiotics for 10 days to suppress the activity of gut bacteria, the scientists found that the creatures could no longer degrade the plastic. They also isolated one bacterial strain and demonstrated its degrading effect on polystyrene even when outside the gut—albeit at a much slower pace.
“I am always cautious to accept these results immediately unless more verification is done but I am also quite optimistic,” Amarjeet Bassi, a professor of chemical and biochemical engineering at Western University in London, Ontario, tells Newsweek in an email. “If proven possible by other groups, these studies should have a major impact on the large problem of plastic wastes in the environment.” Bassi says he would be interested in studies focus on the intermediaries—the enzymes involved in degradation, for example—to try to explain the biochemistry and metabolism at work here.
Wu agrees: He and his colleagues will next research in detail the mechanism at work in the mealworms’ guts as well as testing other plastics and isolating other bacterial strains. Other potential lines of investigation could focus on plastic pollution in oceans, where it poses a hazard to habitats and marine life. The ultimate goal, Wu says, would be to figure out “what technology we could develop to accelerate remediation of plastic contaminated sites.”