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Can bacteria and larvae break down plastic? The research is now facing scathing criticism
Many mistakes are being made in studies of bacteria and larvae that break down plastic.
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You may have heard of studies in which researchers found bacteria or insects that eat plastic.
Plastic accumulates in the environment and does not break down naturally. Researchers are searching for bacteria, fungi, or insects capable of attacking plastic. This could provide the basis for an environmentally friendly method of recycling these materials.
In recent years, several studies have emerged concerning organisms that can break down plastic, but the research often has weaknesses, according to a new article in the journal Nature.
This is particularly true for research on the most common types of plastic.
Many researchers make these mistakes
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"There are many people publishing articles in this field, but the problem so far has been that it's very easy to make mistakes in research on plastic degradation. And many researchers do make these mistakes," says Gustav Vaaje-Kolstad, a professor at the Norwegian University of Life Sciences (NMBU).
For several years, he has worked on a major project at NMBU investigating the biological degradation of plastic.
"We hoped to find new enzymes that could break down plastic, but we ended up publishing almost nothing but articles correcting study practices in the field," the researcher says.
Enzymes are proteins that facilitate chemical reactions within an organism. Discovering such enzymes could lead to methods for breaking down plastic.
Following a lecture in the United States, Vaaje-Kolstad was approached by the journal Nature and asked to assemble a group of experts and write an article offering guidelines and advice to help prevent common errors in the field.
Remarkable larvae
What kinds of mistakes are being made? Vaaje-Kolstad provides several examples.
A particular larva has attracted a great deal of attention. Researchers discovered that wax moth larvae could eat plastic. However, whether they can actually digest it has been a matter of controversy, according to Vaaje-Kolstad.
"It would have been fantastic, because then we could simply feed the plastic to the larvae," he says.
An article in Nature Communications that attempted to explain the mechanism behind this caused quite a stir.
"But the research team didn't know the plastic they were using well enough, and they had misinterpreted contamination in the samples as degradation," says Vaaje-Kolstad.
It turned out that while the larvae did indeed munch on the plastic, they were merely breaking it down into smaller pieces.
Another error in the field involves the use of a substrate– a material for bacteria to grow on– that is not pure plastic.
One commercially available product is polyethylene, the most widely used type of plastic.
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"But polyethylene also contains a kind of paraffin wax, which bacteria can grow on quite easily. It’s more like a candle. When microorganisms start growing on it, people assume they are growing on the plastic itself,” says Vaaje-Kolstad.
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They only eat the additives
Another error concerns additives. Some types of plastic are mixed with plasticisers, substances that make the plastic softer. These are often used in PVC, for instance. These additives contain substances that bacteria can break down.
"If you conduct experiments on standard PVC, you may well see bacterial growth. But the bacteria are actually growing on the additives, not the PVC itself," the researcher says.
In such an experiment, it's easy to believe that you have discovered a plastic-eating bacterium, but that is not actually the case.
Vaaje-Kolstad explains that plastic also undergoes some degradation when it is heated during the manufacturing of plastic products.
"It's rarely possible to obtain completely pure plastic," he says.
Bacteria can make use of plastic fragments that have already undergone some degradation, according to Vaaje-Kolstad.
"This is something that contaminates the plastic and can mislead you into thinking it was caused by enzymes if you have not carried out the proper control reactions," he says.
Some plastics can be broken down biologically
There are major differences between different types of plastic, according to Vaaje-Kolstad.
The most widely produced types of plastic have carbon-carbon bonds. These are known as non-hydrolysable plastics. They cannot be broken down by any enzymes currently known to us.
This applies to the plastics produced in the largest quantities worldwide, such as polypropylene, polyethylene, and PVC.
"Finding something that can break down these plastics – that’s the holy grail," says Vaaje-Kolstad.
He notes that the PET plastic used in bottles can be broken down.
"PET is a fantastic example of a plastic that can be recycled biologically," he says.
A French company called Carbios is currently building an industrial-scale recycling plant to do just that.
Nylon should also be possible to break down biologically. The material contains oxygen and nitrogen in its molecular backbone.
"This means that nature has enzymes available that can actually break down nylon," says Vaaje-Kolstad.
Completely agrees
Gaston Courtade is an associate professor at NTNU’s Department of Biotechnology and Food Science. He studies biopolymers and has also investigated the degradation of plastic using enzymes.
Courtade was not involved in the new article, but he has read it and says he completely agrees that research in the field contains weaknesses and that experimental designs need to be improved. He believes the studies are often too imprecise and that researchers do not always sufficiently verify whether degradation actually took place.
“You can find a lot of claims in the research literature that appear to confirm the hype surrounding the biodegradation of these types of plastic. These claims are based on low-resolutuion data and methods with a high risk of false positives, and they lack proper control experiments," he says.
Courtade says the Nature article provides a good, comprehensive overview of existing research on the biodegradation of non-hydrolysable plastics.
“Secondly, it proposes a concrete roadmap with recommendations regarding analytical methods, control experiments, and what to look for, ensuring that future studies are of high scientific quality,” he says, adding:
“In short, the recommendations make claims about plastic degradation falsifiable – meaning other researchers can test them and, in principle, disprove them. Those are the kinds of results you can trust.”
Not giving up on plastic biodegradation
So far, only one study from 2025 is convincing when it comes to the degradation of non-hydrolysable polymers, according to Vaaje-Kolstad.
That study concerns a particular method for breaking down polystyrene, a material similar to Styrofoam.
Vaaje-Kolstad does not rule out the possibility that there might be organisms or enzymes in nature that could be capable of breaking down these types of plastics.
“I am a biotechnologist, and I tell my students that we’re like the explorers of the 15th century who sailed the seas and discovered new lands. Biology offers an endless landscape of genes and possibilities. The diversity in nature is immense,” he says.
Vaaje-Kolstad also highlights the 2024 Nobel Prize in Chemistry, which focused in part on predicting protein structures using artificial intelligence.
"I can envision designing entirely new proteins and enzymes capable of oxidising plastics that are otherwise difficult to break down," he says. "For that to happen, we need to know how to analyse the process. That's one reason why our new article is important. We hope it will make the field stronger."
Offers advice
"How can other researchers avoid the kinds of mistakes you have identified in the future?"
"Our recommendations are to become thoroughly familiar with the method you intend to use, and preferably to collaborate with chemists, for example. Polymer chemists have extensive knowledge of plastics. That's a major asset," says Vaaje-Kolstad.
The researchers also provide recommendations on analytical methods, what kinds of control experiments should be conducted, and what researchers should look for.
References:
Bombelli et al. Polyethylene bio-degradation by caterpillars of the wax moth Galleria mellonella, Current Biology, 2017. DOI: 10.1016/j.cub.2017.02.060
Pujol et al. Harnessing Colloidal Dispersion for Laccase-Driven Enzymatic Depolymerization of Polystyrene, Angewandte Chemie International Edition, 2025. DOI: 10.1002/anie.202513937
Sanluis-Verdes et al. Wax worm saliva and the enzymes therein are the key to polyethylene degradation by Galleria mellonella, Nature Communications, 2022. DOI: 10.1038/s41467-022-33127-w
Stepnov et al. Assessing biological degradation of non-hydrolysable synthetic polymers, Nature, 2026. DOI: 10.1038/s41586-026-10918-5
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Translated by Ingrid P. Nuse
Read the Norwegian version of this article on forskning.no
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