Effects of constant or dynamic low anode potentials on microbial community development in bioelectrochemical systems.
In bioelectrochemical systems, exoelectrogenic bacteria respire with anode electrodes as their extracellular electron acceptor; therefore, lower anode potentials can reduce the energy gain to each microbe and select against ones that are not able to respire at a lower potential range. Often fully developed anode communities are compared across bioelectrochemical systems with set anode potentials or fixed external resistances as different operational conditions. However, the comparative effect of the resulting constantly low versus dynamically low anode potentials on the development of anode microbial communities as well as the final cathode microbial communities has not been directly demonstrated. In this study, we used a low fixed anode potential of -250 mV and a higher-current control potential of -119 mV vs. Standard Hydrogen Electrode to approximately correspond with the negative peak anode potential values obtained from microbial fuel cells operated with fixed external resistances of 1 kΩ and 47 Ω, respectively. Pyrosequencing data from a 2-month time series show that a lower set anode potential resulted in a more diverse community than the higher- and variable-potential systems, likely due to the hindered enrichment of a Geobacter-dominated community with limited energy gain at this set potential. In this case, it appears that the selective pressure caused by the low set potential was counteracted by the low energy gain over a 2-month time scale. The air cathode microbial community with constant low anode potentials showed delayed enrichment of denitrifiers or perchlorate-reducing bacteria compared to the fixed external resistance condition.
Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett, University Park, PA, 16802, USA.|Physical Sciences Building North, University of California, Santa Barbara, CA, 2520C, USA.
Hengjing
H
Yan
Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett, University Park, PA, 16802, USA.
Matthew D
MD
Yates
Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett, University Park, PA, 16802, USA. JRegan@engr.psu.edu.
John M
JM
Regan
D001419:Bacteria / Q000145:classification / Q000254:growth & development; D001674:Bioelectric Energy Sources; D058448:Biota; D004560:Electricity; D004566:Electrodes / Q000382:microbiology*
Anode potentials; Geobacter; Microbial community; Microbial fuel cells; Potentiostatic control; Pyrosequencing