Plastic-eating bacteria could revolutionize recycling

In France, biotech startup Carbios recycles polyethylene terephthalate (PET), a strong and lightweight plastic that’s used to make drinks bottles, food trays, and textiles. But instead of grinding it down or using chemicals, it mixes the PET with a bacterial enzyme that chews it up. It’s a pioneering process—and it might just offer a glimpse of the future. 

Carbios is commercializing an idea that has steadily been gaining traction in biochemistry research: Enlisting microbes to eat plastic, breaking it down for reuse. And as we look to minimize global carbon emissions, this experimental approach could prove invaluable. 

“This offers a way to remake new plastics without having to go back and dig out more fossil fuels to make fresh ones,” says Dr. Elizabeth Bell, who works on the discovery and optimization of enzymes for the recycling of plastics at the US government’s National Renewable Energy Laboratory. 

Plastic is a popular material because it is cheap and versatile. We produce around 450 million tonnes of it each year, but this has a deleterious impact on the environment because it’s mostly made from petrochemicals. It is often thrown away after a single use, so we also produce around 400 million tonnes of plastic waste each year. 

Huge quantities of this waste are incinerated, releasing the carbon into the atmosphere, and what escapes the incinerators accumulates in landfills and the natural environment. At least 14 million tons of plastic end up in the ocean every year, according to a report by the International Union for Conservation of Nature. Another influential report anticipates that, by weight, there will be more plastic than fish in the sea by 2050.

Scientists, then, must improve them by tinkering with bacterial DNA. Bell has used genetic engineering to optimize IsPETase to work faster, but believes we will inevitably discover new enzymes altogether. “Enzymatic recycling is still in its infancy for many other types of plastic,” she says. 

Within a decade, enzymatic recycling of PET is likely to become more commonplace, she predicts, and other plastics will follow. The technique uses equipment that has already been proven for large operations, which means it has the capacity to scale up. In 2025, Carbios plans to open its first commercial plant, which it claims will recycle 50,000 tonnes of PET waste per year. 

This potential shift in recycling technology could open up a variety of new possibilities.

In theory, if this new technology becomes mainstream, each city could have its own semi-automated recycling plant. The monomers would feed directly into a nearby processing facility and the plastics would be passed on to local industries. 

What’s more, enzymatic recycling may eventually help clear up our oceans. In 2019, scientists genetically engineered marine algae to produce and secrete IsPETase, enabling it to break down plastic in saltwater. Bell explains that this could possibly be industrialized via a sewage plant-like system; ocean plastic would be collected and put into a controlled reactor with the engineered algae. She notes that one wouldn’t want to release genetically modified organisms into the oceans without knowing exactly what they might do. 

And, if we wanted to eliminate certain plastics altogether, we may be able to engineer microorganisms that consume the products of enzymatic recycling. “So you can break down the plastic into monomers, then another organism can come along and basically eat those monomers as food,” says Bell.

However, it’s unlikely that all kinds of plastic can be efficiently digested. In some cases, such as polyethylene, their chemical bonds will be too strong for the enzymes to overcome. It’s also expensive, though Bell is confident that costs will come down as the technology matures. 

And then there are the possible legal hurdles because of the risks of genetically modified plastic-eating bacteria escaping into the environment. In Bell’s view, however, the risk is minimal because large-scale reactions such as Carbios’ are being done using the enzyme alone, and the engineered microbes from which the enzyme is harvested wouldn’t work outside of a controlled laboratory environment. 

“The risks of industrial plastic-degrading bacteria escaping into the environment are very low,” says Bell. “Scientists work hard to develop fail-safe mechanisms to ensure these bacteria can’t survive on their own in the wild.”

Ultimately, it is likely that the global plastic problem will call for a diverse mix of technological solutions—as well as ratcheting up the drive to simply use less of it. “But enzymatic recycling is filling an important gap.”