High Biofilm Conductivity Maintained Despite Anode Potential Changes in a Geobacter‐Enriched Biofilm

Abstract

This study systematically assessed intracellular electron transfer (IET) and extracellular electron transfer (EET) kinetics with respect to anode potential (E ) in a mixed-culture biofilm anode enriched with Geobacter spp. High biofilm conductivity (0.96-1.24 mS cm ) was maintained during E changes from -0.2 to +0.2 V versus the standard hydrogen electrode (SHE), although the steady-state current density significantly decreased from 2.05 to 0.35 A m in a microbial electrochemical cell. Substantial increase of the Treponema population was observed in the biofilm anode at E =+0.2 V, which reduced intracellular electron-transfer kinetics associated with the maximum specific substrate-utilization rate by a factor of ten. This result suggests that fast EET kinetics can be maintained under dynamic E conditions in a highly conductive biofilm anode as a result of shift of main EET players in the biofilm anode, although E changes can influence IET kinetics.

Spatially Resolved Electron Transport through Anode‐Respiring Geobacter sulfurreducens Biofilms: Controls and Constraints

“…Dcyt m 2 s -1 10 -5 -10 -10 (7×10 -7 ) Effective diffusion coefficient Estimated from [116][117][118] kD m 4 mol s -1 10 -5 -10 5 (100) Electron transfer rate constant Estimated from Dcyt = kD[Cyttot]δ δ nm 0.7 Spatial distance between adjacent redox-active molecules [119] σ S m -1 10 -4 -10 -2 (1.5×10 -3 ) Biofilm conductivity [12,21,35,120] Anw m 2 1.26×10 -17 Cross-section area of a single pilus Calculated from dnw dnw nm 4 Diameter of a single pilus [31,32] Aact m 2 10 -14 -10 -13 Redox active surface area Estimated from [108] β -0.5 Charge transfer coefficient [108] ϕanode V -0.1, +0.24 Poised low, high anode potential [58] ϕox/red 0' V -0.07, -0.15 Redox-active center mid-potential [44,56] Nnw,cell -1-200 (49) Number of connections per cell Estimated from [32,[108][109][110][111] Fixed concentration were imposed for all chemical species at the outer domain boundary except for CO2, CO3 2-, Cytred, R-COOH, R-NH2, R-PO4H2. No flux conditions were imposed at the bulk-biofilm interface and anode surface for CO2, CO3 2-, Cytred.…”

Characterization and significance of extracellular polymeric substances, reactive oxygen species, and extracellular electron transfer in methanogenic biocathode

“…During experiments, the anode potential was fixed at − 0.4 versus Ag/AgCl with a potentiostat (Squidstat Prime, Admiral Instruments, Arizona, USA). This anode potential was selected to enrich and maintain kinetically efficient EAB as suggested in the literature 40 – 42 . The reactors were operated at room temperature (21 ± 1 °C) with continuous mixing (130 ± 5 rpm) of the liquid medium with magnetic stirrers.…”

Hydrogen peroxide production in a pilot-scale microbial electrolysis cell

“…The anode modules and the cathode were connected to a data logging system (Keithly 2700, Keithley Instruments, Inc. USA) with copper wires [ 18 ]. The power supply (Array 3654A, Array Electronic co., LTD, China) was utilized as an external voltage supplier, and applied voltage was adjusted manually daily to maintain anode potential between −0.3 and −0.5 V vs SCE in which kinetically efficient ARB can be enriched well [ 15 , 19 , 20 ]. A pH probe (RK-27003-12, Cole-Parmer, USA) was installed in the anode chamber and connected to a meter (ECPHCP0550, Eutech Instruments, USA) to continuously monitor anolyte pH.…”