Assimilation of formic acid and CO2 by engineered Escherichia coli equipped with reconstructed one-carbon assimilation pathways

Junho Bang, Sang Yup Lee
2018 Proceedings of the National Academy of Sciences of the United States of America  
Gaseous one-carbon (C1) compounds or formic acid (FA) converted from CO 2 can be an attractive raw material for bio-based chemicals. Here, we report the development of Escherichia coli strains assimilating FA and CO 2 through the reconstructed tetrahydrofolate (THF) cycle and reverse glycine cleavage (gcv) pathway. The Methylobacterium extorquens formate-THF ligase, methenyl-THF cyclohydrolase, and methylene-THF dehydrogenase genes were expressed to allow FA assimilation. The gcv reaction was
more » ... gcv reaction was reversed by knocking out the repressor gene (gcvR) and overexpressing the gcvTHP genes. This engineered strain synthesized 96% and 86% of proteinogenic glycine and serine, respectively, from FA and CO 2 in a glucose-containing medium. Native serine deaminase converted serine to pyruvate, showing 4.5% of pyruvate-forming flux comes from FA and CO 2 . The pyruvate-forming flux from FA and CO 2 could be increased to 14.9% by knocking out gcvR, pflB, and serA, chromosomally expressing gcvTHP under trc, and overexpressing the reconstructed THF cycle, gcvTHP, and lpd genes in one vector. To reduce glucose usage required for energy and redox generation, the Candida boidinii formate dehydrogenase (Fdh) gene was expressed. The resulting strain showed specific glucose, FA, and CO 2 consumption rates of 370.2, 145.6, and 14.9 mg·g dry cell weight (DCW) −1 ·h −1 , respectively. The C1 assimilation pathway consumed 21.3 wt% of FA. Furthermore, cells sustained slight growth using only FA and CO 2 after glucose depletion, suggesting that combined use of the C1 assimilation pathway and C. boidinii Fdh will be useful for eventually developing a strain capable of utilizing FA and CO 2 without an additional carbon source such as glucose. tetrahydrofolate cycle | glycine cleavage pathway | formate dehydrogenase | formic acid | CO 2
doi:10.1073/pnas.1810386115 fatcat:7luejzzk6fev7cyfibyflvqgce