Fig 1.
Schematic illustration of the experimental setup.
A three-electrode setup and sampling port were incorporated in four-neck round-bottom flasks. In one-chamber reactors, working and counter electrode are located in one compartment. Therefore, Geobacter spp. enrichment biofilms can consume cathodically produced hydrogen. In two-chamber reactors, a counter electrode chamber with a fixed cation exchange membrane is introduced minimizing crossover of cathodically produced hydrogen. All reactors were sampled at the beginning as well as at the end of a batch cycle and every 6 h during a batch cycle for obtaining total (CEt) and incremental coulombic efficiencies (CEi), respectively.
Table 1.
List of total coulombic efficiencies derived from studies cultivating Geobacter sulfurreducens and Geobacter spp. enrichment biofilms in one- and two-chamber reactors.
Table 2.
List of studies that applied Michaelis-Menten kinetics to Geobacter sulfurreducens and Geobacter spp. enrichment biofilms and determined KM and vmax values.
Fig 2.
Temporal progressions of current density (j), acetate concentration (CAc), and incremental coulombic efficiency (CEi) of two-chamber reactors.
R1-3 represent experimental replicates. Open circles indicate sampling events. Vertical dashed line indicates beginning of 2nd batch cycle after medium exchange.
Fig 3.
Temporal progressions of current density (j), acetate concentration (CAc), and incremental coulombic efficiency (CEi) of one-chamber reactors.
R4-6 represent experimental replicates. Open circles indicate sampling events. Vertical dashed line indicates beginning of 2nd batch cycle after medium exchange.
Table 3.
List of total coulombic efficiencies (CEt) determined in this study.
Fig 4.
Dot plots of (A) maximum substrate uptake rate (vmax,i) and (B) half-saturation concentration (KM,i) based on either acetate uptake (closed circles) or current production (open circles) derived from Michaelis-Menten kinetics regression analysis of two- and one-chamber reactors. As the prolonged current decrease and slower acetate uptake of R3 impaired application of Michaelis-Menten kinetics, respective results were omitted from this data comparison. bc: batch cycle.