Scientists in South Korea have engineered tiny bacterial cells that are churning out plastic. The plastics produced by the modified Escherichia coli (E. coli) bacteria are known as polyester amides (PEAs). Unlike the petroleum-derived plastics that litter oceans and landfills, PEAs are biodegradable.
And now, for the first time, they can be biosynthesized by living organisms.
Plastic from Bacteria
Plastics are everywhere. In 2022, global plastic production reached 400.3 million metric tons, most of it made from petroleum. The problem is that the same qualities that make plastic so appealing (durability and low cost), make it a bane for the environment. Many of these polymers take centuries to break down, polluting ecosystems and food chains.
Scientists have long been searching for biodegradable alternatives. Microbial production of biopolymers—plastics made by living organisms—has emerged as a promising solution. Some bacteria naturally turn excess carbon into polyhydroxyalkanoates (PHAs), a type of polyester that decomposes in the environment. But PEAs, which combine the strength of polyamides (like nylon) with the biodegradability of polyesters, had never been synthesized biologically. Until now.
In nature, PHAs serve as energy reserves—bacteria build them up when times are good and break them down when food becomes scarce. But what if this biological trick could be harnessed for industrial production?
To achieve this, the team focused on two key enzymes: one from Clostridium, known for its ability to link molecules to Coenzyme A, and another from Pseudomonas, which had been previously modified to expand its range of accepted molecules. When introduced into E. coli, these enzymes enabled the bacteria to stitch together amino acids into polymers, potentially forming biodegradable plastics.
By tweaking the amino acid content in the feedstock, the team could control the properties of the resulting polymer. Some versions of the plastic stretched further before breaking, while others melted at lower temperatures—useful traits for industrial applications.
The challenge, however, was efficiency. Initial yields were low, and one of the enzymes even slowed bacterial growth. To work around this, the researchers bred a strain of E. coli that tolerated the enzyme better. They also boosted the bacteria’s production of lysine, one of the amino acids incorporated into the polymer. By tweaking the system further—knocking out genes related to lactic acid production and adding extra enzymes—the team increased polymer yield to over 50% of the bacteria’s weight.
A Step Toward Sustainable Plastics
The result is an impressively flexible system. The bacteria can incorporate a wide range of chemicals into their polymers, potentially allowing researchers to fine-tune plastic properties for different applications. “It was reasoned that these [amino acids] might be more efficiently incorporated into the polymer if generated within the cells from a suitable carbon source,” the researchers write. In other words, by feeding the bacteria simple sugars, scientists may be able to produce biodegradable plastics tailored to specific needs.
But hurdles remain. The process does not yet allow complete control over the polymer’s composition—some random chemicals from the cell’s metabolism still find their way in. Extraction and purification present additional challenges, and production rate cannot yet compete with traditional fossil fuel-based plastics.
Still, the implications are promising. Unlike conventional plastics, which require petroleum and contribute to pollution, these bioengineered polymers could be produced sustainably and degrade naturally.
For now, plastic-producing bacteria won’t be churning out the next generation of biodegradable water bottles. But as research progresses, nature’s own engineers may provide the key to solving one of humanity’s most persistent pollution problems.
The findings appeared in the journal Nature Chemical Biology.
