Kinetics based reaction optimization of enzyme catalyzed reduction of formaldehyde to methanol with synchronous cofactor regeneration

Abstract

Enzymatic reduction of carbon dioxide (CO ) to methanol (CH OH) can be accomplished using a designed set-up of three oxidoreductases utilizing reduced pyridine nucleotide (NADH) as cofactor for the reducing equivalents electron supply. For this enzyme system to function efficiently a balanced regeneration of the reducing equivalents during reaction is required. Herein, we report the optimization of the enzymatic conversion of formaldehyde (CHOH) to CH OH by alcohol dehydrogenase, the final step of the enzymatic redox reaction of CO to CH OH, with kinetically synchronous enzymatic cofactor regeneration using either glucose dehydrogenase (System I) or xylose dehydrogenase (System II). A mathematical model of the enzyme kinetics was employed to identify the best reaction set-up for attaining optimal cofactor recycling rate and enzyme utilization efficiency. Targeted process optimization experiments were conducted to verify the kinetically modeled results. Repetitive reaction cycles were shown to enhance the yield of CH OH, increase the total turnover number (TTN) and the biocatalytic productivity rate (BPR) value for both system I and II whilst minimizing the exposure of the enzymes to high concentrations of CHOH. System II was found to be superior to System I with a yield of 8 mM CH OH, a TTN of 160 and BPR of 24 μmol CH OH/U · h during 6 hr of reaction. The study demonstrates that an optimal reaction set-up could be designed from rational kinetics modeling to maximize the yield of CH OH, whilst simultaneously optimizing cofactor recycling and enzyme utilization efficiency.

Sequential Co-immobilization of Enzymes in Metal-Organic Frameworks for Efficient Biocatalytic Conversion of Adsorbed CO2 to Formate

“…As the presence of NAD + suppresses the reduction of CO 2 to formic acid and accelerates its reverse oxidation reaction, the efficient regeneration of NADH is highly desirable. Enzymes such as glucose dehydrogenase (Obón et al, 1998; Marpani et al, 2017; Zhang Z. et al, 2018), xylose dehydrogenase (Marpani et al, 2017) and GDH (Ji et al, 2015) have been successfully used for the regeneration of NADH. In our work, GDH was adopted to attain the continuous conversion of NAD + to NADH.…”

Construction of an Artificial In Vitro Synthetic Enzymatic Platform for Upgrading Low-Cost Starch to Value-Added Disaccharides

“…For example, Marpani et al modeled the reduction of formaldehyde to methanol by alcohol dehydrogenase and surmised that metabolite formaldehyde is toxic, which might cause irreversible inhibition of the enzymes. To avoid a detrimental effect of formaldehyde on the enzymes and to increase the yield of methanol, repetitive batch setups were designed instead of introducing an inhibition constant into the model . However, from a kinetic point of view, it is clear that such an approach only provides accurate predictions at low substrate concentrations.…”

A Review on the Design and Performance of Enzyme-Aided Catalysis of Carbon Dioxide in Membrane, Electrochemical Cell and Photocatalytic Reactors

“…There are other enzymes, also, that could be utilized for NADH regeneration, such as glucose dehydrogenase (GDH), xylose dehydrogenase (XDH), lactate dehydrogenase (LDH), among others. Marpani et al [85] reported that the reduction rate (V max ) of NAD + to NADH via GDH is faster than the rate of NADH oxidation to NAD + by ADH, the values for which are 6.3 µmol/mg.min and 4.7 µmol/mg.min, respectively. This is a good sign, as the NADH would be readily available to catalyze the CHOH to CH 3 OH during the third step of the multi-enzymatic cascade CO 2 conversion.…”