Kenyan lesser mealworm larvae can consume polystyrene

An encouraging development in efforts to combat plastic pollution has emerged: mealworm larvae can consume polystyrene.

They are now among the small number of insects shown to break down this polluting plastic. Crucially, this is the first African-native insect species found to have this capability.

Polystyrene, often called styrofoam, is widely used for packaging food, electronics and industrial products. Because it is highly durable and difficult to degrade, it persists for a long time. Conventional recycling approaches, including chemical and thermal treatments, are costly and may generate pollutants. These limitations prompted us to investigate biological ways of dealing with this stubborn waste.

I am a member of a scientific team at the International Centre of Insect Physiology and Ecology that discovered that larvae of the Kenyan lesser mealworm can chew polystyrene. They also carry gut bacteria that contribute to breaking the material down.

The lesser mealworm is the larval stage of the Alphitobius darkling beetle, lasting from 8 to 10 weeks. These mealworms are most commonly found in warm poultry-rearing houses, where a reliable supply of food creates favourable conditions for growth and reproduction.

Although lesser mealworms are believed to originate in Africa, they occur in many countries worldwide. However, the species identified in our study may be a subspecies within the Alphitobius genus. Further research is under way to establish whether this is the case.

We also studied the bacteria in the insects' guts, aiming to identify the bacterial communities that might assist the plastic-degradation process.

Plastic pollution has reached critically high levels in some African countries. While plastic waste is a serious environmental problem across the world, Africa faces an especially difficult situation because of substantial imports of plastic products, limited reuse and insufficient recycling.

By examining these natural "plastic-eaters", we aim to develop tools that can remove plastic waste more rapidly and effectively. Releasing vast numbers of insects at waste sites would not be practical. Instead, the microbes and enzymes they produce could be used in factories, landfill sites and clean-up locations. This could make tackling plastic waste at scale more manageable.

Key findings

We conducted a trial lasting more than a month. The larvae received either polystyrene only, bran only - a nutrient-rich food - or a mixture of polystyrene and bran.

Mealworms given the polystyrene-and-bran diet had higher survival rates than those fed polystyrene alone. They also consumed polystyrene more efficiently than the larvae on a polystyrene-only diet. This demonstrates the value of maintaining a nutrient-rich diet for the insects.

Although a diet consisting only of polystyrene allowed the mealworms to survive, it did not provide sufficient nutrition for them to break down polystyrene efficiently. The result underlined the need for a balanced diet if the insects are to consume and degrade plastic optimally. They may eat polystyrene because it consists mainly of carbon and hydrogen, which could act as an energy source.

Over the course of the trial, mealworms fed polystyrene and bran broke down approximately 11.7 percent of the total polystyrene.

Gut bacteria in Kenyan lesser mealworms

Analysis of the mealworm gut showed substantial diet-related changes in bacterial composition. Understanding these changes is vital because they indicate which microbes are actively involved in plastic breakdown. It will enable us to isolate the individual bacteria and enzymes that could be used in plastic-degradation work.

The guts of larvae fed polystyrene contained greater levels of Proteobacteria and Firmicutes. These bacteria can adapt to a variety of environments and degrade a broad range of complex substances.

Bacteria including Kluyvera, Lactococcus, Citrobacter and Klebsiella were also especially abundant. They are known to produce enzymes capable of digesting synthetic plastics. When used at scale, the bacteria would not harm either the insect or the environment.

Their abundance suggests that the bacteria have an essential role in degrading the plastic. This could indicate that mealworms do not inherently possess the ability to consume plastic.

Rather, once the insects begin eating plastic, their gut bacteria may alter in ways that help to degrade it. In other words, microbes in mealworms' stomachs can adapt to unusual food sources such as plastic.

These results support our hypothesis that the guts of certain insects can facilitate plastic degradation. This is probably because their gut bacteria can generate enzymes that break down plastic polymers.

They also suggest the potential to isolate these bacteria and the enzymes they produce, creating microbial solutions to address plastic waste on a larger scale.

What's next

Some insect species - including yellow mealworms (Tenebrio molitor) and superworms (Zophobas morio) - have already been shown to consume plastics. With the support of gut bacteria, they can degrade materials such as polystyrene.

Our research is distinctive because it examines insect species native to Africa, which have received limited study in relation to plastic degradation.

This regional emphasis matters because African insects and environmental conditions may differ from those elsewhere in the world. They could therefore provide fresh insights and workable responses to plastic pollution in African contexts.

The Kenyan lesser mealworm's capacity to consume polystyrene indicates that it may contribute to natural waste reduction, particularly for plastics that resist standard recycling techniques.

Future research could concentrate on isolating and identifying the particular bacterial strains responsible for polystyrene degradation, as well as investigating their enzymes.

We hope to determine whether these enzymes can be manufactured at scale for waste recycling.

We may also investigate other forms of plastic to assess this insect's potential for wider waste-management uses.

Expanding the use of lesser mealworms for plastic degradation would also require approaches to protect insect health during prolonged consumption of plastic. It would additionally be necessary to assess whether the resulting insect biomass is safe for animal feed.

Fathiya Khamis, Senior Scientist, International Centre of Insect Physiology and Ecology

This article is republished from The Conversation under a Creative Commons licence. Read the original article.