Researchers have found that dozens of animal species carry enzymes capable of breaking down a family of microbial bioplastics called PHAs — an ability previously thought to belong only to bacteria and fungi. Nature, it turns out, invented biodegradable plastic long before we did, and animals may have been feeding on it for hundreds of millions of years.

What a PHA is

Polyhydroxyalkanoates are polymers that bacteria produce and store internally as an energy reserve — roughly the microbial equivalent of body fat. They are genuine plastics in the chemical sense: long chains of repeating units, mouldable, water-resistant.

Crucially, they are also genuinely biodegradable, including in seawater and soil, because organisms evolved to eat them long before anyone manufactured anything. That sets them apart from conventional plastics, whose backbones no organism had any reason to develop enzymes against.

PHAs are already produced commercially for packaging and medical uses. They remain expensive relative to petroleum plastics, which is the main reason they are not everywhere.

Why finding the enzymes in animals matters

The assumption underpinning claims that a material is biodegradable is that microbes will do the work. If animals across many groups also carry the necessary enzymes, the picture of how these materials break down in a real environment changes.

It suggests degradation may be faster and more widespread than models based on microbial action alone would predict. It implies an ancient evolutionary relationship, since the ability is spread across species that diverged very long ago. And it raises a question worth asking rather than assuming: if animals can digest a material, they may also gain something from eating it — or be affected by consuming it in quantities nothing evolved to encounter.

The caution that belongs with any “biodegradable” claim

This is where findings like this get over-read, so it is worth stating the limits plainly.

Biodegradability is conditional, not a property a material simply has. It depends on temperature, oxygen, moisture and the organisms present. A material that degrades in weeks in warm shallow water may persist for years in cold deep sediment or in a landfill with no oxygen. Certification standards generally specify laboratory conditions that bear little resemblance to a river or a seabed.

There is also a well-documented behavioural effect: labelling a product biodegradable increases how readily people discard it. A material that breaks down over months still causes harm if the response to the label is to drop more of it outdoors.

And none of this touches conventional plastics, which are the overwhelming majority of what is in the environment. PHAs are a small fraction of global plastic production.

Why it is still worth knowing

The practical value of a finding like this is not that it solves plastic pollution. It is that it improves the models used to decide which materials are actually better, and it identifies enzymes that could be studied or engineered for waste processing.

It also carries a useful corrective. The framing of biodegradable plastics as a human invention is backwards. The chemistry is ancient, the organisms that break it down are ancient, and what is new is only the scale at which we are producing the material — and the far larger quantity of the other kind, which nothing eats at all.

Sources

• ScienceDaily — animal species found to possess enzymes that break down PHA bioplastics, 17 August 2026