Insect Larvae Capable of Digesting Plastic Discovered in Kenya

Plastics, ubiquitous in modern society, have become a toxic menace all over the world, leaching PFAS “forever chemicals,” breaking down into microplastics and choking the world’s seas and landfills. 

In a promising study, scientists have discovered that mealworm larvae are capable of consuming polystyrene. They are one of few insects — and the first native African insect species — that has been found to be able to break down the polluting plastic.

Styrofoam, as polystyrene is commonly called, is a plastic material used in food, industrial and electronic packaging. It is strong and hard to break down in the environment. Traditional recycling methods, such as thermal and chemical processing, are costly and produce pollutants.

“Plastic pollution levels are at critically high levels in some African countries. Though plastic waste is a major environmental issue globally, Africa faces a particular challenge due to high importation of plastic products, low re-use and a lack of recycling of these products,” Fathiya Khamis, senior scientist with the International Centre of Insect Physiology and Ecology, wrote in The Conversation.

The center’s research team found that Kenyan lesser mealworm larvae could not only chew through polystyrene, but host gut bacteria who help them break down the material.

The lesser mealworm is primarily found in the warm environment of chicken raising operations, which also provide them with a consistent supply of food.

The team looked at the larvae’s gut bacteria to identify which bacterial communities might support the process of degrading plastic.

“By studying these natural ‘plastic-eaters,’ we hope to create new tools that help get rid of plastic waste faster and more efficiently. Instead of releasing a huge number of these insects into trash sites (which isn’t practical), we can use the microbes and enzymes they produce in factories, landfills and cleanup sites. This means plastic waste can be tackled in a way that’s easier to manage at a large scale,” Khamis explained.

The team’s study trial lasted more than a month, during which time the mealworm larvae were fed either bran — which is dense in nutrients — polystyrene by itself, or a combination of bran and the plastic material.

The scientists found that mealworms who consumed the diet of polystyrene and bran together had higher survival rates than those who were fed just polystyrene. They also discovered that the larvae on the combination diet ate polystyrene more efficiently than the worms on a diet of polystyrene alone. The findings highlight the benefits of making sure the insects had a nutrient-dense diet.

“While the polystyrene-only diet did support the mealworms’ survival, they didn’t have enough nutrition to make them efficient in breaking down polystyrene. This finding reinforced the importance of a balanced diet for the insects to optimally consume and degrade plastic. The insects could be eating the polystyrene because it’s mostly made up of carbon and hydrogen, which may provide them an energy source,” Khamis wrote in The Conversation.

On the polystyrene-bran diet, the mealworms could break down roughly 11.7 percent of all the polystyrene they were given during the trial period.

The mealworm gut analysis showed major shifts in gut bacterial composition depending upon their diet. Gaining an understanding of these changes is essential, since it reveals the particular microbes that are actively involved in the plastic decomposition process.

When used at scale, the bacteria will not harm the environment or the insect, Khamis said.

“The abundance of bacteria indicates that they play a crucial role in breaking down the plastic. This may mean that mealworms may not naturally have the ability to eat plastic. Instead, when they start eating plastic, the bacteria in their guts might change to help break it down. Thus, the microbes in the mealworms’ stomachs can adjust to unusual diets, like plastic,” Khamis wrote. “These findings support our hypothesis that the gut of certain insects can enable plastic degradation. This is likely because the bacteria in their gut can produce enzymes that break down plastic polymers.”

Other insect species have previously shown that they are able to consume plastics by breaking down polystyrene-like materials with their gut bacteria.

This study was different because it focused on native African insect species breaking down plastic, which had not yet been extensively studied.

“This regional focus is important because the insects and environmental conditions in Africa may differ from those in other parts of the world, potentially offering new insights and practical solutions for plastic pollution in African settings,” Khamis explained. “The Kenyan lesser mealworm’s ability to consume polystyrene suggests that it could play a role in natural waste reduction, especially for types of plastic that are resistant to conventional recycling methods.”

Khamis added that future research could focus on identifying specific bacterial strains that are involved in the degradation of polystyrene and looking at their enzymes.

“Additionally, we may explore other types of plastics to test the versatility of this insect for broader waste management applications,” Khamis said in The Conversation. “Scaling up the use of the lesser mealworms for plastic degradation would also require strategies for ensuring insect health over prolonged plastic consumption, as well as evaluating the safety of resulting insect biomass for animal feeds.”