• Journal of Microbiology and Biotechnology
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• v.14 no.3
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• pp.540-546
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• 2004

We deviced a new graphite-Mn(II) electrode and found that the modified electrode with Mn(II) can catalyze NADH oxidation and $NAD^+$ reduction coupled to electricity production and consumption as oxidizing agent and reducing power, respectively. In fuel cell with graphite-Mn(II) anode and graphite-Fe(III) cathode, the electricity of 1.5 coulomb (A x s) was produced from NADH which was electrochemically reduced by the graphite-Mn(II) electrode. When the initial concentrations of pyruvate and acetaldehyde were adjusted to 40 mM and 200 mM, respectively, about 25 mM lactate and 35 mM ethanol were produced from 40 mM pyruvate and 200 mM acetaldehyde, respectively, by catalysis of ADH and LDH in the electrochemical reactor with $NAD^+$ as cofactor and electricity as reducing power. By using this new electrode with catalytic function, the bioelectrocatalysts are engineered; namely, oxidoreductase (e.g., lactate dehydrogenase) and $NAD^+$ can function for biotransformation without electron mediator and second oxidoreductase for $NAD^+$/NADH recycling.

• Journal of Microbiology
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• v.43 no.5
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• pp.451-455
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• 2005

In this study, whole cells and a crude enzyme of Candida peltata were applied to an electrochemical bioreactor, in order to induce an increment of the reduction of xylose to xylitol. Neutral red was utilized as an electron mediator in the whole cell reactor, and a graphite-Mn(IV) electrode was used as a catalyst in the enzyme reactor in order to induce the electrochemical reduction of $NAD^+$ to NADH. The efficiency with which xylose was converted to xylitol in the electrochemical bioreactor was five times higher than that in the conventional bioreactor, when whole cells were employed as a biocatalyst. Meanwhile, the xylose to xylitol reduction efficiency in the enzyme reactor using the graphite-Mn (IV) electrode and $NAD^+$ was twice as high as that observed in the conventional bioreactor which utilized NADH as a reducing power. In order to use the graphite-Mn(IV) electrode as a catalyst for the reduction of $NAD^+$ to NADH, a bioelectrocatalyst was engineered, namely, oxidoreductase (e.g. xylose reductase). $NAD^+$ can function in this biotransformation procedure without any electron mediator or a second oxidoreductase for $NAD^+/NADH$ recycling

• Journal of the Korean Magnetic Resonance Society
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• v.21 no.4
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• pp.139-144
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• 2017

Ni(II) containing coenzyme F430 catalyzes the reduction of $CO_2$ in methanogen. Macrocyclic Ni(II) complexes with N,O shiff bases have been received a great attention since metal ions play an important role in the catalysis of reduction. The reducing power of metal complexes are supposed to be dependent on oxidoreduction state of metal ion and structural properties of macrocyclic ring moiety that can enhance electrochemical properties in catalytic process. Six different ${\alpha}$-oximinoketone compounds, precursor of macrocyclic ligands used in $CO_2$ reduction coenzyme F430 model complexes, were synthesized with yields over 90% and characterized by NMR. The molecular geometries of ${\alpha}$-oximinoketone analogues were fully optimized at Beck's-three-parameter hybrid (B3LYP) method in density functional theory (DFT) method with $6-31+G^*$ basis set using the ab initio program. In order to understand molecular planarity and substitutional effects that may enhance reducing power of metal ion are studied by computing the structure-dependent $^{13}C$-NMR chemical shift and comparing with experimental results.