Mealworm beetles offer 'green' plastic disposal

In a bid to mitigate the harmful effects of conventional plastic disposal, scientists in Kenya said they have found a promising solution: mealworm beetles.

Fathiya Khamis, a molecular biologist at the International Centre of Insect Physiology and Ecology, or ICIPE, said that while previous studies have identified a few insect species capable of degrading plastic, the discovery involved a native African insect with the ability.

Khamis leads a team that found the larvae of Kenyan mealworm beetles eating through polystyrene, a common type of plastic, with the bacteria in their guts breaking down the material through digestion.

"Mealworm beetles are storage pests that attack stored grain, but we noticed their presence at a chicken coop where plastic insulation had degraded," Khamis said.

"To further our inquiry, we examined the mealworm larvae's gut and noticed bacterial communities that may support the plastic degradation process."

She described the finding as significant because Kenya and Africa as a whole face high levels of plastic production and importation, combined with inadequate recycling and unsustainable disposal practices.

After carrying out laboratory tests for more than a month, Khamis and her team found heightened levels of bacteria adapting to various environments and breaking down a wide range of complex substances. They also discovered bacteria known to produce enzymes capable of digesting synthetic plastics.

As naturally occurring organisms, the bacteria and their enzymes are harmless to both the mealworm beetle and the environment when applied at scale — bolstering Khamis' optimism with the method for degrading plastics.

"The abundance of bacteria indicates that they play a crucial role in breaking down the plastic," Khamis said.

"Even though the mealworms may not naturally have the ability to digest plastic, when they start eating it, the bacteria in their guts change to help break plastic down. We therefore realized the microbes in mealworms' stomachs can adjust to unusual diets like plastic."

Duncan Chacha, an entomologist at the Centre for Agriculture and Biosciences International in Kenya, said biocontrol measures offer a sustainable approach to tackling problems such as pests, invasive plant species or plastics, but only if properly applied.

He mentioned the risk of interfering with the ecological balance of biocontrol agents such as the mealworm beetle. Scaling up production of these insects for their plastic-degrading properties could lead to population explosions, which might be devastating in other areas such as grain storage where these beetles are known pests, he said.

Applying the solution could also face social resistance as communities and individuals often have different attitudes toward handling items such as insects, he added.

Future studies

Khamis explained that the next stage of their research entails isolating the bacteria and enzymes produced by mealworm larvae after they consumed plastics, to develop microbial solutions for large-scale plastic waste management.

"Our future studies will focus on isolating and identifying the specific bacterial strains involved in polystyrene and plastic degradation and examining their enzymes," Khamis said.

"We hope to figure out if the enzymes can be produced at scale for recycling waste, because producing millions of mealworms and releasing them at a dumpsite to physically eat through the plastic is not sustainable."

She added that their research is unique because it focuses on native African insect species that remain underexplored in the context of plastic degradation. The regional focus is considered important because Africa's unique insects and environmental conditions may offer new insights and solutions for plastic pollution in African settings.

Komivi Senyo Akutse, head of the arthropod pathology unit at ICIPE, said using biocontrol agents to fight challenges such as plastic waste should be encouraged because they do not leave toxic residues that could contaminate the environment.

These agents also reduce reliance on chemical treatments while posing fewer health risks to humans, animals and the environment, Akutse added.