Scientists engineer bacteria to make 1st-ever ‘thermally-stable’ bioplastic

Researchers in Korea have made a significant breakthrough in developing plastic-producing microbes as an alternative to the petroleum-based plastics industry—they have engineered bacteria to produce polymers with ring-like structures, which enhance the rigidity and thermal stability of the plastics.

“I think biomanufacturing will be a key to the success of mitigating climate change and the global plastic crisis,” says senior author Sang Yup Lee.

“We need to collaborate internationally to promote bio-based manufacturing so that we can ensure a better environment for our future.”

Typically, these ring-containing molecules are toxic to microorganisms, so the researchers had to design a unique metabolic pathway. This pathway allows E. coli bacteria to not only synthesize the polymer but also tolerate the accumulation of both the polymer and its precursors.

The resulting polymer is biodegradable and possesses physical properties that could be useful in biomedical applications, such as drug delivery systems.

First-ever microbial production of aromatic and aliphatic polymers

Most plastics used in packaging and industrial applications, like PET and polystyrene, contain aromatic, ring-like structures.

While earlier studies successfully engineered microbes to produce polymers with a mix of aromatic and aliphatic (non-ring-like) monomers, this marks the first instance where microbes have been able to produce polymers entirely composed of monomers with aromatic sidechains.

To achieve this, the researchers first created a novel metabolic pathway by integrating enzymes from various microorganisms, enabling the bacteria to produce an aromatic monomer called phenyllactate.

They then used computer simulations to design a polymerase enzyme capable of efficiently assembling these phenyllactate monomers into a fully aromatic polymer.

“This enzyme can synthesize the polymer more efficiently than any of the enzymes available in nature,” said Lee in the press release .

Scaling up for industrial use

After refining the bacteria’s metabolic pathway and the polymerase enzyme, the researchers scaled up their experiments by cultivating the microbes in 6.6-liter (1.7-gallon) fermentation vats.

The optimized strain successfully produced 12.3 grams per liter of the polymer , poly(D-phenyllactate). However, to move toward commercialization, the team aims to boost this yield to at least 100 grams per liter.

Looking ahead, the researchers plan to develop additional aromatic monomers and polymers with diverse chemical and physical properties, such as those with higher molecular weights necessary for industrial use.

They are also working to further optimize their process to enable larger-scale production.

“If we put more effort into increasing the yield, then this method might be able to be commercialized at a larger scale,” says Lee. “We’re working to improve the efficiency of our production process as well as the recovery process, so that we can economically purify the polymers we produce.”

The study has been published in the journal Trends in Biotechnology .