The redox biosynthesis system has important applications in green biomanufacturing of chiral compounds. Formate dehydrogenase (FDH) catalyzes the oxidation of formate into carbon dioxide, which is associated with the reduction of NAD(P)⁺ into NAD(P)H. Due to this property, FDH is used as a crucial enzyme in the redox biosynthesis system for cofactor regeneration. Nevertheless, the application of natural FDH in industrial production is hampered by low catalytic efficiency, poor stability, and inefficient coenzyme utilization. This review summarized the structural characteristics and catalytic mechanism of FDH, as well as the advances in protein engineering of FDHs toward improved enzyme activity, catalytic efficiency, stability and coenzyme preference. The applications of using FDH as a coenzyme regeneration system for green biomanufacturing of chiral compounds were summarized.
Catalysis ; Coenzymes/metabolism* ; Formate Dehydrogenases/metabolism* ; NAD/metabolism* ; Protein Engineering

In this study, Escherichia coli BL21 (DE3) was used as the host to construct 2 recombinant E. coli strains that co-expressed leucine dehydrogenase (LDH, Bacillus cereus)/formate dehydrogenase (FDH, Ancylobacter aquaticus), or leucine dehydrogenase (LDH, Bacillus cereus)/alcohol dehydrogenase (ADH, Rhodococcus), respectively. L-2-aminobutyric acid was then synthesized by L-threonine deaminase (L-TD) with LDH-FDH or LDH-ADH by coupling with two different NADH regeneration systems. LDH-FDH process and LDH-ADH process were optimized and compared with each other. The optimum reaction pH of LDH-FDH process was 7.5, and the optimum reaction temperature was 35 °C. After 28 h, the concentration of L-2-aminobutyric acid was 161.8 g/L with a yield of 97%, when adding L-threonine in batches for controlling 2-ketobutyric acid concentration less than 15 g/L and using 50 g/L ammonium formate, 0.3 g/L NAD+, 10% LDH-FDH crude enzyme solution (V/V) and 7 500 U/L L-TD. The optimum reaction pH of LDH-ADH process was 8.0, and the optimum reaction temperature was 35 °C. After 24 h, the concentration of L-2-aminobutyric acid was 119.6 g/L with a yield of 98%, when adding L-threonine and isopropanol (1.2 times of L-threonine) in batches for controlling 2-ketobutyric acid concentration less than 15 g/L, removing acetone in time and using 0.3 g/L NAD⁺, 10% LDH-ADH crude enzyme solution (V/V) and 7 500 U/L L-TD. The process and results used in this paper provide a reference for the industrialization of L-2-aminobutyric acid.
Aminobutyrates ; metabolism ; Escherichia coli ; genetics ; Formate Dehydrogenases ; metabolism ; Leucine Dehydrogenase ; metabolism ; NAD ; metabolism

L-2-aminobutyric acid (L-ABA) is an important chemical raw material and chiral pharmaceutical intermediate. The aim of this study was to develop an efficient method for L-ABA production from L-threonine using a trienzyme cascade route with Threonine deaminase (TD) from Escherichia. coli, Leucine dehydrogenase (LDH) from Bacillus thuringiensis and Formate dehydrogenase (FDH) from Candida boidinii. In order to simplify the production process, the activity ratio of TD, LDH and FDH was 1:1:0.2 after combining different activity ratios in the system in vitro. The above ratio was achieved in the recombinant strain E. coli 3FT+L. Moreover, the transformation conditions were optimized. Finally, we achieved L-ABA production of 68.5 g/L with a conversion rate of 99.0% for 12 h in a 30-L bioreactor by whole-cell catalyst. The environmentally safe and efficient process route represents a promising strategy for large-scale L-ABA production in the future.
Aminobutyrates ; chemical synthesis ; Bacillus thuringiensis ; enzymology ; Candida ; enzymology ; Escherichia coli ; enzymology ; Formate Dehydrogenases ; metabolism ; Leucine Dehydrogenase ; metabolism ; Threonine ; metabolism ; Threonine Dehydratase ; metabolism

To enhance biohydrogen production of Klebsiella sp. HQ-3, the global transcriptional factor (Fnr), formate dehydrogenase H (FDH1) and the pncB gene encoding the nicotinic acid phosphoribosyltransferase (NAPRTase) were for the first time over-expressed in Klebsiella sp. HQ-3. The fnr, fdhF, pncB genes were cloned from the genomic DNA of Klebsiella sp. HQ-3 by 3 pairs of universal primers, and introduced into the corresponding sites of the modified pET28a-Pkan, resulting in the plasmids pET28a-Pkan-fnr, pET28a-Pkan-fdhF and pET28a-Pkan-pncB. The 4 plasmids were then electroported into wild Klebsiella sp. HQ-3 to create HQ-3-fnr, HQ-3-fdhF, HQ-3-pncB and HQ-3-C, respectively. Hydrogen production was measured using a gas chromatograph and the metabolites were analyzed with a high-performance liquid chromatograph (HPLC). The results indicate that over-expression of fnr, fdhF and pncB significantly enhanced hydrogen production in the three recombinant strains. Hydrogen production per mol glucose for HQ-3 fnr, HQ-3 pncB, HQ-3 fdhF was 1.113, 1.106 and 1.063 mol of hydrogen/mol glucose, which was respectively increased by 12.26%, 11.62% and 7.28% compared with that of the control strain HQ-3-C (0.991 mol of hydrogen/mol glucose). Moreover, the analysis of HPLC showed that the concentrations of formate and lactate were markedly decreased, but succinate remained unchanged in culture media compared with those of the control strain HQ-3-C.
Fermentation ; Formate Dehydrogenases ; biosynthesis ; genetics ; Hydrogen ; metabolism ; Iron-Sulfur Proteins ; biosynthesis ; genetics ; Klebsiella ; genetics ; metabolism ; Metabolic Engineering ; methods ; Metabolic Networks and Pathways ; Pentosyltransferases ; biosynthesis ; genetics