E. coli engineered to grow on CO2 and formic acid as sole carbon sources

Now, a metabolic engineering research group at KAIST has developed a strategy to grow anE. colistrain to higher cell density solely on CO₂and formic acid. Formic acid is a one carbon carboxylic acid, and can be easily produced from CO₂using a variety of methods. Since it is easier to store and transport than CO₂, formic acid can be considered a good liquid-form alternative of CO₂.

With support from the C1 Gas Refinery R&D Center and the Ministry of Science and ICT, a research team led by Distinguished Professor Sang Yup Lee stepped up their work to develop an engineeredE. colistrain capable of growing up to 11-fold higher cell density than those previously reported, using CO₂and formic acid as sole carbon sources. This work was published in Nature Microbiology on Sept. 28.

Despite the recent reports by several research groups on the development ofE. colistrains capable of growing on CO₂and formic acid, the maximum cell growth remained too low (optical density of around 1) and thus the production of chemicals from CO₂and formic acid has been far from realized.

The team previously reported the reconstruction of the tetrahydrofolate cycle and reverse glycine cleavage pathway to construct an engineeredE. colistrain that can sustain growth on CO₂and formic acid. To further enhance the growth, the research team introduced the previously designed synthetic CO₂and formic acid assimilation pathway, and two formate dehydrogenases.

Metabolic fluxes were also fine-tuned, the gluconeogenic flux enhanced, and the levels of cytochrome bo3 and bd-I ubiquinol oxidase for ATP generation were optimized. This engineeredE. colistrain was able to grow to a relatively high OD600 of 7~11, showing promise as a platform strain growing solely on CO₂and formic acid.

Professor Lee said, "We engineeredE. colithat can grow to a higher cell density only using CO₂and formic acid. We think that this is an important step forward, but this is not the end. The engineered strain we developed still needs further engineering so that it can grow faster to a much higher density."

Professor Lee's team is continuing to develop such a strain. "In the future, we would be delighted to see the production of chemicals from an engineeredE. colistrain using CO₂and formic acid as sole carbon sources," he added.