Enzymatic Electrosynthesis of Glycine from CO₂ and NH₃

Abstract

Enzymatic electrosynthesis has gained more and more interest as an emerging green synthesis platform, particularly for the fixation of CO 2 . However, the simultaneous utilization of CO 2 and a nitrogenous molecule for the enzymatic electrosynthesis of value-added products has never been reported. In this study, we constructed an in vitro multienzymatic cascade based on the reductive glycine pathway and demonstrated an enzymatic electrocatalytic system that allowed the simultaneous conversion of CO 2 and NH 3 as the sole carbon and nitrogen sources to synthesize glycine. Through effective coupling and the optimization of electrochemical cofactor regeneration and the multienzymatic cascade reaction, 0.81 mM glycine was yielded with a highest reaction rate of 8.69 mg L À 1 h À 1 and faradaic efficiency of 96.8 %. These results imply a promising alternative for enzymatic CO 2 electroreduction and expand its products to nitrogenous chemicals.

Electrocatalytic synthesis of C–N coupling compounds from CO2 and nitrogenous species

“…Moreover, enzymatic electrosynthesis has successfully produced glycine from CO 2 and NH 3 through an in vitro multienzymatic cascade. 138 Optimizing individual modules in the enzymatic electrocatalytic system has resulted in the production of glycine (0.81 mM) with a remarkable FE of 96.8%. The electrocatalytic synthesis of C-N coupling compounds beyond urea is summarized in Table 3, highlighting diverse examples that illustrate the electrochemical synthesis of various organic com-pounds containing C-N bonds from CO 2 and nitrogen sources.…”

“…Chiral kink sites on chiral Cu films restrict the configuration of the stereoselective intermediates, favoring enantiomeric serine synthesis in both thermodynamical and kinetical aspects. Moreover, enzymatic electrosynthesis has successfully produced glycine from CO 2 and NH 3 through an in vitro multienzymatic cascade 138 . Optimizing individual modules in the enzymatic electrocatalytic system has resulted in the production of glycine (0.81 mM) with a remarkable FE of 96.8%.…”

Bioelectrocatalytic Synthesis: Concepts and Applications

“…The Zhu group developed a multienzyme cascade for the production of glycine, the simplest amino acid, with only CO 2 and NH 3 as feedstocks. [103] The impressive cascade is broken down into four modules: (i) CO 2 reduction to formic acid by NADH-dependent formate dehydrogenase (FDH); (ii) conversion of formic acid to 5,10-methylene-THF by an ATP-dependent formate-tetrahydrofolate ligase (FtfL), a methenyltetrahydrofolate cyclohydrolase (FchA) and an NADPH-dependent methylenetetrahydrofolate dehydrogenase (MtdA); (iii) fixation of CO 2 and NH 3 and cleavage of THF by a glycine cleavage system (GcvT, GcvH, GcvP, and GcvL) to afford glycine; (iv) regeneration of the NADH and NADPH through a Cu foam electrode. Additionally, ATP was regenerated through a polyphosphate kinase (PPK) with stoichiometric polyphosphate.…”

Exploring the Feasibility of Cell-Free Synthesis as a Platform for Polyhydroxyalkanoate (PHA) Production: Opportunities and Challenges

“…For instance, the cost of NADH is approximately $260 g −1 [ 111 ]. To enhance economic feasibility, researchers are striving to regenerate and reuse cofactors [ 112 , 113 ] or reduce the use of expensive ones [ 114 , 115 , 116 , 117 ]. Artificial analogs can substitute for expensive cofactors [ 118 ] and can be designed to be more stable than their natural counterparts while still being recognized by enzymes.…”