Assimilation of formic acid and CO

Area of Science:

• Synthetic biology
• Metabolic engineering
• Biotechnology

Background:

• Gaseous one-carbon (C1) compounds, such as formic acid derived from CO2, are promising feedstocks for bio-based chemical production.
• Efficient microbial assimilation of C1 compounds is crucial for sustainable biomanufacturing.

Purpose of the Study:

• To engineer Escherichia coli strains capable of assimilating carbon dioxide (CO2) and formic acid (FA).
• To reconstruct the tetrahydrofolate (THF) cycle and reverse the glycine cleavage (gcv) pathway for C1 assimilation.
• To enhance the conversion of C1 compounds into valuable metabolic intermediates like pyruvate.

Main Methods:

• Reconstruction of the THF cycle by expressing key enzymes from Methylobacterium extorquens.
• Reversal of the gcv pathway through gene knockout (gcvR) and overexpression (gcvTHP).
• Metabolic flux analysis to quantify the contribution of FA and CO2 to pyruvate formation.
• Expression of Candida boidinii formate dehydrogenase (Fdh) to reduce glucose dependency.

Main Results:

• Engineered E. coli synthesized 96% glycine and 86% serine from FA and CO2.
• Pyruvate-forming flux from FA and CO2 reached 14.9% after genetic modifications.
• The engineered strain exhibited high consumption rates for glucose, FA, and CO2.
• The C1 assimilation pathway consumed 21.3 wt% of FA, and cells showed limited growth on FA and CO2 post-glucose depletion.

Conclusions:

• The developed E. coli strains effectively assimilate FA and CO2 via a reconstructed THF cycle and reversed gcv pathway.
• Integration of C1 assimilation pathways and formate dehydrogenase offers a promising strategy for developing glucose-independent microbial cell factories.
• This work lays the foundation for sustainable production of bio-based chemicals using C1 feedstocks.