Adaptively evolved Escherichia coli for improved ability of formate utilization as a carbon source in sugar???free conditions

Background: Formate converted from CO2 reduction has great potential as a sustainable feedstock for biological production of biofuels and biochemicals. Nevertheless, utilization of formate for growth and chemical production by microbial species is limited due to its toxicity or the lack of a metabolic pathway. Here, we constructed a formate assimilation pathway in Escherichia coli and applied adaptive laboratory evolution to improve formate utilization as a carbon source in sugar-free conditions. Results: The genes related to the tetrahydrofolate and serine cycles from Methylobacterium extorquens AM1 were overexpressed for formate assimilation, which was proved by the 13C-labeling experiments. The amino acids detected by GC/MS showed significant carbon labeling due to biomass production from formate. Then, 150 serial subcultures were performed to screen for evolved strains with improved ability to utilize formate. The genomes of evolved mutants were sequenced and the mutations were associated with formate dehydrogenation, folate metabolism, and biofilm formation. Last, 90 mg/L of ethanol production from formate was achieved using fed-batch cultivation without addition of sugars. Conclusion: This work demonstrates the effectiveness of the introduction of a formate assimilation pathway, combined with adaptive laboratory evolution, to achieve the utilization of formate as a carbon source. This study suggests that the constructed E. coli could serve as a strain to exploit formate and captured CO2

Metal-organic and covalent organic frameworks as single-site catalysts

[EN] Heterogeneous single-site catalysts consist of isolated, well-defined, active sites that are spatially separated in a given solid and, ideally, structurally identical. In this review, the potential of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) as platforms for the development of heterogeneous single-site catalysts is reviewed thoroughly. In the first part of this article, synthetic strategies and progress in the implementation of such sites in these two classes of materials are discussed. Because these solids are excellent playgrounds to allow a better understanding of catalytic functions, we highlight the most important recent advances in the modelling and spectroscopic characterization of single-site catalysts based on these materials. Finally, we discuss the potential of MOFs as materials in which several single-site catalytic functions can be combined within one framework along with their potential as powerful enzyme-mimicking materials. The review is wrapped up with our personal vision on future research directions.S. M. J. Rogge, J. Hajek, and V. Van Speybroeck acknowledge the Fund for Scientific Research - Flanders (FWO), the Research Board of Ghent University (BOF) and BELSPO in the frame of IAP/7/05 for financial support. V. Van Speybroeck acknowledges funding from the European Union's Horizon 2020 research and innovation programme (consolidator ERC grant agreement no. 647755 - DYNPOR (2015-2020)). This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 641887 (project acronym: DEFNET). W. Dewitte and C. Caratelli are acknowledged for technical support with the figures. J. Gascon acknowledges funding from the European Union's 2020 research and innovation programme (ERC grant agreement no. 335746 - CrystEng-MOF-MMM) and from the Dutch Organization for Scientific Research (NWO, VIDI grant agreement 723.012.107 - MetMOFCat).Rogge, SMJ.; Bavykina, A.; Hajek, J.; García Gómez, H.; Olivos-Suarez, AI.; Sepulveda-Escribano, A.; Vimont, A.... (2017). Metal-organic and covalent organic frameworks as single-site catalysts. Chemical Society Reviews. 46(11):3134-3184. https://doi.org/10.1039/c7cs00033bS31343184461