title: Micro-coulometric study of bioelectrochemical reaction coupled with TCA cycle.
abstract: The mediated electro-enzymatic electrolysis systems based on the tricarboxylic acid (TCA) cycle reaction were examined on a micro-bulk electrolytic system. A series of the enzyme-catalyzed reactions in the TCA cycle was coupled with electrode reaction. Electrochemical oxidation of NADH was catalyzed by diaphorase with an aid of a redox mediator with a formal potential of -0.15 V vs. Ag|AgCl. The mediator was also able to shuttle electrons between succinate dehydrogenase and electrode. The charge during the electrolysis increased on each addition of dehydrogenase reaction in a cascade of the TCA cycle. However, the electrolysis efficiencies were close to or less than 90% because of the product inhibition. Lactate oxidation to acetyl-CoA catalyzed by two NAD-dependent dehydrogenases was coupled with the bioelectrochemical TCA cycle reaction to achieve the 12-electron oxidation of lactate to CO(2). The charge passed in the bioelectrocatalytic oxidation of 5 nmol of lactate was 4 mC, which corresponds to 70% of the electrolysis efficiency.
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan. seiya@ims.tsukuba.ac.jp
authors.forename: Seiya
authors.initials: S
authors.lastname: Tsujimura
authors.forename: Jun
authors.initials: J
authors.lastname: Fukuda
authors.forename: Osamu
authors.initials: O
authors.lastname: Shirai
authors.forename: Kenji
authors.initials: K
authors.lastname: Kano
authors.forename: Hideki
authors.initials: H
authors.lastname: Sakai
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Tokita
authors.forename: Tsuyonobu
authors.initials: T
authors.lastname: Hatazawa
mesh_terms: D000105:Acetyl Coenzyme A / Q000737:chemistry; D015374:Biosensing Techniques / Q000379:methods*; D002384:Catalysis; D002952:Citric Acid Cycle; D055664:Electrochemical Techniques; D004566:Electrodes; D004572:Electrolysis; D019344:Lactic Acid / Q000737:chemistry*; D009243:NAD / Q000737:chemistry; D009245:NADH Dehydrogenase / Q000737:chemistry; D010084:Oxidation-Reduction; D013385:Succinate Dehydrogenase / Q000737:chemistry
chemical_list: D009243:NAD; D019344:Lactic Acid; D000105:Acetyl Coenzyme A; D013385:Succinate Dehydrogenase; D009245:NADH Dehydrogenase