Efficient CO2-Reducing Activity of NAD-Dependent Formate Dehydrogenase from Thiobacillus sp. KNK65MA for Formate Production from CO2 Gas

Hyunjun Choe,Yong Hwan Kim,Min Hoo Kim,Dae Haeng Cho,Sang Hyun Lee,Jeong Chan Joo,Kwang Deog Jung,Joel H Weiner

doi:10.1371/journal.pone.0103111

Hyunjun Choe, Yong Hwan Kim + Show 6 more

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https://doi.org/10.1371/journal.pone.0103111

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Abstract

NAD-dependent formate dehydrogenase (FDH) from Candida boidinii (CbFDH) has been widely used in various CO2-reduction systems but its practical applications are often impeded due to low CO2-reducing activity. In this study, we demonstrated superior CO2-reducing properties of FDH from Thiobacillus sp. KNK65MA (TsFDH) for production of formate from CO2 gas. To discover more efficient CO2-reducing FDHs than a reference enzyme, i.e. CbFDH, five FDHs were selected with biochemical properties and then, their CO2-reducing activities were evaluated. All FDHs including CbFDH showed better CO2-reducing activities at acidic pHs than at neutral pHs and four FDHs were more active than CbFDH in the CO2 reduction reaction. In particular, the FDH from Thiobacillus sp. KNK65MA (TsFDH) exhibited the highest CO2-reducing activity and had a dramatic preference for the reduction reaction, i.e., a 84.2-fold higher ratio of CO2 reduction to formate oxidation in catalytic efficiency (k cat/K B) compared to CbFDH. Formate was produced from CO2 gas using TsFDH and CbFDH, and TsFDH showed a 5.8-fold higher formate production rate than CbFDH. A sequence and structural comparison showed that FDHs with relatively high CO2-reducing activities had elongated N- and C-terminal loops. The experimental results demonstrate that TsFDH can be an alternative to CbFDH as a biocatalyst in CO2 reduction systems.

Highlights

Reducing the atmospheric CO2 level has received a great deal of attention recently as an approach to combat global warming and fossil-fuel shortages, but this process remains challenging
Formic acid has been produced by the hydrolysis of methyl formate, which is synthesized via methanol carbonylation in commercial processes
KNK 65MA (TsFDH, BAC92737.1) [32] as well as the gene for CbFDH (CAA09466.2) were synthesized, and all recombinant formate dehydrogenase (FDH) were successfully expressed with a Cterminal hexa-histidine tag in E. coli

Summary

Introduction

Reducing the atmospheric CO2 level has received a great deal of attention recently as an approach to combat global warming and fossil-fuel shortages, but this process remains challenging. Biological CO2 fixation is one of the most important approaches to solving these problems. Enzymatic CO2 reduction has been examined extensively as a promising approach to greenhouse gas fixation and the production of renewable fuels and chemicals [1,2,3]. The enzymatic reduction of CO2 using FDHs has been widely studied for the production of valuable chemicals, such as formic acid and methanol [4,5]. Formic acid is considered to be a promising replacement for methanol in miniature fuel cells [6]. Formic acid has been produced by the hydrolysis of methyl formate, which is synthesized via methanol carbonylation in commercial processes. It would be environmentally attractive to prepare formic acid from CO2 gas by enzymatic biotransformation

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