title: The Roles of Biofilm Conductivity and Donor Substrate Kinetics in a Mixed-Culture Biofilm Anode.
abstract: We experimentally assessed the kinetics and thermodynamics of electron transfer (ET) from the donor substrate (acetate) to the anode for a mixed-culture biofilm anode. We interpreted the results with a modified biofilm-conduction model consisting of three ET steps in series: (1) intracellular ET, (2) non-Ohmic extracellular ET (EET) from an outer membrane protein to an extracellular cofactor (EC), and (3) ET from the EC to the anode by Ohmic-conduction in the biofilm matrix. The steady-state current density was 0.82 ± 0.03 A/m2in a miniature microbial electrochemical cell operated at fixed anode potential of -0.15 V versus the standard hydrogen electrode. Illumina 16S-rDNA and -rRNA sequences showed that the Geobacter genus was less than 30% of the community of the biofilm anode. Biofilm conductivity was high at 2.44 ± 0.42 mS/cm, indicating that the maximum current density could be as high as 270 A/m2if only Ohmic-conduction EET was limiting. Due to the high biofilm conductivity, the maximum energy loss for Ohmic-conduction EET was negligible, 0.085 mV. The energy loss in the second ET step also was small, only 20 mV, and the potential for the EC involved in the second ET was -0.15 V, a value documenting that >99% of the EC was in the oxidized state. Monod kinetics for utilization of acetate were relatively slow, and at least 87% of the energy loss was in the intracellular step. Thus, intracellular ET was the main kinetic and thermodynamic bottleneck to ET from donor substrate to the anode for a highly conductive biofilm.
authors: Department of Civil and Environmental Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario N2L3G1, Canada.
authors: Hyung-Sool
authors: HS
authors: Lee
authors: Department of Civil and Environmental Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario N2L3G1, Canada.
authors: Bipro Ranjan
authors: BR
authors: Dhar
authors: Department of Civil and Environmental Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario N2L3G1, Canada.
authors: Junyeong
authors: J
authors: An
authors: Swette Center for Environmental Biotechnology, The Biodesign Institute at Arizona State University , P.O. Box 875701, Tempe, Arizona 85287-5701, United States.
authors: Bruce E
authors: BE
authors: Rittmann
authors: National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 W. Martin Luther King Drive, Cincinnati, Ohio 45268, United States.
authors: Hodon
authors: H
authors: Ryu
authors: National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 W. Martin Luther King Drive, Cincinnati, Ohio 45268, United States.
authors: Jorge W
authors: JW
authors: Santo Domingo
authors: School of Electrical, Computer and Energy Engineering, Arizona State University , Tempe, Arizona 85287, United States.
authors: Hao
authors: H
authors: Ren
authors: School of Electrical, Computer and Energy Engineering, Arizona State University , Tempe, Arizona 85287, United States.
authors: Junseok
authors: J
authors: Chae
mesh_terms: D001674:Bioelectric Energy Sources; D018441:Biofilms; D004566:Electrodes; D045302:Geobacter; D007700:Kinetics