- author, Francis Augustine
- scroll, BBC Future
At first glance, there is nothing particularly special about these worms.
The larval form of the moth mellonella gallery, Also known as the honeycomb moth or wax moth, it feeds on the wax that bees use to make honeycombs. For beekeepers, they are pests that they try to get rid of quickly, without thinking twice.
But in 2017, molecular biologist Federica Bertuccini, who at the time was researching vertebrate embryonic development at Spain's National Research Council, found herself faced with an environmentally revolutionary discovery involving these creatures.
Bertuccini, an amateur beekeeper, came across these larvae by chance while cleaning her hive.
“I put the worms in a plastic bag and quickly noticed that they were making holes (in the plastic),” she says in an interview with BBC Earth.
There was something that caused the plastic to decompose when it came into contact with their mouths.
“It was a real eureka moment, it was amazing,” Bertuccini recalls, referring to the initial discovery and the concept of what it meant.
“It was the beginning of the story. The beginning of the whole research project.
The larvae were doing something that is extremely difficult for us humans to do: breaking down plastic, which takes decades to centuries to completely decompose.
Bertuccini and his fellow researchers began by collecting the secreted fluid from the caterpillars' mouths. They discovered that this “saliva” contains two important enzymes, called Ceres and Demeter — named after the Roman and Greek gods of agriculture, respectively — that are able to oxidize the polyethylene found in the plastic, essentially breaking down the material on contact. .
“It takes a few hours, at room temperature, in an aqueous solution,” she explains.
Furthermore, the larvae appear to digest plastic as if it were food.
“When the worm eats the plastic and starts breaking it down, its gut practically reacts as if it were eating regular food. This means that there is something going on in the animal's physiology that extracts something from this biodegradation of plastic,” says Christophe Lemoine, professor of comparative physiology at Brandon University. In Canada, “it continues as if it were a normal diet,” he told BBC Earth.
Inspired by Bertuccini's discoveries, he also began studying these larvae.
“We discovered that the plastic allows them to retain all the fat, and they should continue their life cycle,” he adds.
Basically, these caterpillars eat whatever they see in front of them, before turning into butterflies, at which point they no longer eat, they just reproduce.
“I always call them flying gonads, because that's all they do,” LeMoine jokes.
Leaving these worms loose in a plastic-polluted environment could pose a risk to ecosystems, especially given their ability to destroy beehives, Bertuccini points out. But she hopes that in the future, the enzymes produced by these larvae will help fight plastic pollution around the world.
Therefore, there is a race underway to discover how this mechanism works.
“This is the million-dollar or trillion-dollar question, because once we figure that out, we'll be able to dismantle a trillion dollars of plastic,” LeMoyne says.
Now chief technology officer at bioresearch startup Plasticentropy France, Bertuccini is working with a team to study the feasibility of applying these enzymes for widespread use in breaking down plastics.
“The main goal is to be able to apply these enzymes to plastic waste,” explains Bertuccini.
“I really want this discovery and this technology to be developed and turned into a solution that we can use globally.”
But why is plastic so difficult to decompose?
In nature, most things decompose because decomposing organisms break the chemical bonds that hold matter together.
They have evolved over thousands of years to analyze everything they encounter. Until along came plastic, which conquered the world, despite its current bad reputation.
Plastic is made of long chains of polymers with very strong bonds. One of the secrets to breaking these bonds is oxidation.
This appears to be what the larvae do with their saliva, as they introduce oxygen molecules into the plastic.
“This is sometimes achieved in the environment through light, for example, high temperature. This is the bottleneck. It takes time because the environment has its own time,” explains Bertuccini.
“So what the larvae do is simply introduce an oxygen molecule. And within a few hours, rather than months or years, or however long it may be. It's a way to solve the bottleneck in this reaction.”
Promising enzymes for this purpose can be found in many different organisms. In fact, more than 30,000 enzymes capable of digesting 10 different types of plastic have already been identified.
Some fungi and bacteria are known to digest plastics, but this is very rare in complex animals. And in 2022, it was discovered that another invertebrate animal also loves plastic – the 'superworm'. Zophobas MorioWho can gain weight on a polystyrene diet.
Bacteria in cows' stomachs can be used to digest polyester.
But the thing that is arousing a lot of interest from researchers is a bacteria called Ideonella sacaiensisAnd above all the enzyme PETase.
PET plastic, most commonly found in plastic bottles, takes hundreds of years to decompose in the environment. But PETase is able to break it down within days.
Currently, 400 million tons of plastic waste are produced globally every year.
Of this total, between 19 and 23 million tons (the equivalent of about 2,000 truckloads of garbage) seep into aquatic ecosystems, much of which is colonized by microorganisms or eaten by animals.
A series of global measures will be needed to reduce our dependence on and consumption of plastic. To this end, many countries have committed to help reduce the production and use of single-use plastics, and a global plastics treaty is expected to be concluded by the end of 2024.
But if such enzymes can one day be mass-produced to break down plastic, perhaps the little critters chewing on a bag of Bertuccini will play an important role in that, too.
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