Multienzymatic cascade reactions have garnered the attention of many researchers as an approach for converting CO2 into methanol. The cascade reaction used in this study includes the following enzymes: a formate dehydrogenase (ClFDH), a formaldehyde dehydrogenase (BmFaldDH), and an alcohol dehydrogenase (YADH) from Clostridium ljungdahlii, Burkholderia multivorans, and Saccharomyces cerevisiae, respectively. Because this cascade reaction requires NADH as a cofactor, phosphite dehydrogenase (PTDH) was employed to regenerate the cofactor. The multienzymatic cascade reaction, along with PTDH, yielded 3.28 mM methanol. The key to the success of this cascade reaction was a novel formaldehyde dehydrogenase, BmFaldDH, the enzyme catalyzing the reduction of formate to formaldehyde. The methanol yield was further improved by incorporation of 1-ethyl-3-methylimidazolium acetate (EMIM-Ac), resulting in 7.86 mM of methanol. A 500-fold increase in total turnover number was observed for the ClFDH-BmFaldDH-YADH cascade system compared to the Candida boidinii FDH-Pseudomonas putida FaldDH-YADH system. We provided detailed insights into the enzymatic reduction of CO2 by determining the thermodynamic parameters (Kd and ΔG) using isothermal titration calorimetry. Furthermore, we demonstrated a novel time-dependent formaldehyde production from CO2. Our results will aid in the understanding and development of a robust multienzyme catalyzed cascade reaction for the reduction of CO2 to value-added chemicals.
- cascade reaction
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