Japanese scientists engineer E. coli to mass-produce biodegradable plastic alternative to PET without byproducts

A Kobe University team of bioengineers has achieved a major milestone in the development of sustainable plastics. They successfully engineered Escherichia coli (E. coli) bacteria to produce PDCA (pyridinedicarboxylic acid), a biodegradable alternative to PET (polyethylene terephthalate), at unprecedented levels from glucose, and without generating unwanted byproducts.

PDCA is biodegradable, and materials made from it show physical properties comparable to, or even surpassing, those of PET, which is widely used in containers and textiles. The research, published in the journal Metabolic Engineering, reports bioreactor concentrations more than sevenfold higher than previously achieved.

What is PDCA, and why it matter in eliminating PET

Plastics (PET) are popular for their durability, but that same property makes them environmentally damaging. Extensive uses of plastic damage marine ecosystems and block rivers, just never to disappear.

According to the Switzerland-based Digital Publishing Institute (MDPI), to understand the severity, the global production of plastics in 2020 alone is estimated at 367 million metric tons. Adding on to that, a study published in the journal Plos One estimates humans can inhale as many as 68,000 tiny plastic particles daily.

Plastics are also primarily petroleum-derived, making them nonrenewable and vulnerable to global supply and political risks. Research groups worldwide are working on alternatives, but most biomass-based approaches face issues with yield, purity, and production costs.

Kobe University bioengineer TANAKA Tsutomu explained that most biomass-based plastic production focuses on simple molecules made of carbon, oxygen, and hydrogen. But some of the most promising high-performance plastics include nitrogen, and until now there were no efficient ways to make them biologically. Chemical methods also create unwanted byproducts.

PDCA, which contains nitrogen, is one such candidate. Tanaka said, “Our group took a new approach: we used cellular metabolism to absorb nitrogen and build the compound from start to finish.”

Technical Challenges

The team showed that metabolic reactions can successfully incorporate nitrogen without creating unwanted byproducts, allowing for a clean and efficient way to produce PDCA. Still, the process came with significant challenges.

One of the biggest obstacles arose when an introduced enzyme generated hydrogen peroxide (H₂O₂), a reactive compound that attacked and deactivated the very enzyme that produced it.
Tanaka explained, “Through refining the culture conditions, in particular by adding a compound that can scavenge H₂O₂, we could finally overcome the issue, although this addition may present new economic and logistical challenges for large-scale production.”

Path toward practical implementation

The research team sees this as a stepping stone toward large-scale industrial application.
Tanaka noted, “The ability to obtain sufficient quantities in bioreactors lays the groundwork for the next steps toward practical implementation. More generally, though, our achievement in incorporating enzymes from nitrogen metabolism broadens the spectrum of molecules accessible through microbial synthesis, thus enhancing the potential of bio-manufacturing even further.”