title: Escherichia coli-catalyzed bioelectrochemical oxidation of acetate in the presence of mediators.
abstract: Bioelectrocatalytic oxidation of acetate was investigated under anaerobic conditions by using Escherichia coli K-12 (IFO 3301) cells cultured on aerobic media containing poly-peptone, glucose or acetate as the sole carbon source. It was found that all E. coli cells cultured on the three media work as good catalysts of the electrochemical oxidation of acetate as well as glucose with Fe(CN)6(3-), 2,3-dimethoxy-5-methyl-1,4-benzo-quinone (Q0), 2,6-dichloro-indophenol, or 2-methyl-1,4-naphthoquinone as artificial electron acceptors (mediators). Acetate-grown E. coli cells exhibited the highest relative activity of the acetate oxidation against the glucose oxidation. On the other hand, all the artificial electron acceptors used work as inhibitors for the catalytic oxidation of acetate at increased concentrations. The inhibition phenomenon can be interpreted in terms of competitive substrate inhibition as a whole. Apparent values of Michaelis constant, catalytic constant, and inhibition constant were evaluated by amperometric methods. Q0 is an effective artificial mediator as evidenced by a large reaction rate constant between the cell and Q0 at least at low concentrations (<50 microM). However, Fe(CN)6(3-) is a promising mediator in biosensor applications because the inhibition constant is very large and it works as an electron acceptor even under aerobic conditions.
authors.affiliation: Department of Environmental Engineering, National Cheng Kung University, No. 1. University Road, Tainan City, Taiwan, ROC.
authors.forename: Yung-Fu
authors.initials: YF
authors.lastname: Wang
authors.forename: Sheng-Shung
authors.initials: SS
authors.lastname: Cheng
authors.forename: Seiya
authors.initials: S
authors.lastname: Tsujimura
authors.forename: Tokuji
authors.initials: T
authors.lastname: Ikeda
authors.forename: Kenji
authors.initials: K
authors.lastname: Kano
mesh_terms: D015086:2,6-Dichloroindophenol / Q000737:chemistry*; D000085:Acetates / Q000737:chemistry* / Q000378:metabolism*; D016227:Benzoquinones / Q000737:chemistry*; D002384:Catalysis; D004563:Electrochemistry; D004926:Escherichia coli / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D005295:Ferrocyanides / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry; D007700:Kinetics; D010084:Oxidation-Reduction; D010461:Peptones / Q000737:chemistry; D024483:Vitamin K 3 / Q000737:chemistry*
chemical_list: D000085:Acetates; D016227:Benzoquinones; D005295:Ferrocyanides; D010461:Peptones; C109863:ubiquinone-O; D024483:Vitamin K 3; D015086:2,6-Dichloroindophenol; D005947:Glucose