No abstract

In this study the characterization of Geoalkalibacter subterraneus is presented, a novel 11 halophilic anode respiring bacteria (ARB) previously selected and identified in a 12 potentiostically controlled bioelectrochemical system (BES) inoculated with sediments from a 13 salt plant. Pure culture electroactive biofilms of Glk. subterraneus were grown during 14 chronoamperometric batch experiments at a graphite electrode poised at +200 mV (vs. SCE) 15 with 10 mM acetate as electron donor. These biofilms exhibited the highest current density 16 (4.68 ± 0.54 A/m 2 ) reported on a planar material with a pure culture under saline conditions 17 (3.5% NaCl). To investigate possible anodic electron transfer (ET) mechanisms, cyclic 18 voltammetry (CV) of mature visible apparent reddish biofilms was performed under 19 bioelectrocatalytic substrate consumption (turnover) and in absence of substrate (non-20 turnover). CV evidenced a well defined typical sigmoidal shape and a pair of clear redox 21 couples under turnover and non-turnover conditions, respectively. Moreover, the calculation 22 of their formal potentials indicated the presence of a common ET mechanism present in both 23

No abstract

Bioelectrochemical systems couple electricity demand/supply to the metabolic redox reactions of microorganisms. Generally, electrodes act not only as electron acceptors/donors, but also as physical support for an electroactive biofilm. The microorganism-electrode interface can be modified by changing the chemical and/or topographical features of the electrode surface. Thus far, studies have reported conflicting results on the impact of the electrode surface roughness on the growth and current production of biofilms. Here, the surface roughness of the glassy carbon electrodes was successfully modified at the sub-microscale using micro electrodischarge machining, while preserving the surface chemistry of the parent glassy carbon. All microbial electrodes showed similar startup time, maximum current density, charge transport ability across the biofilm and biomass production. Interestingly, an increase in the average surface cavity depth was observed for the biofilm top layer as a function of the electrode surface roughness (from 7 μm to 16 μm for a surface roughness of 5 nm to 682 nm, respectively). These results indicated that the surface roughness at a sub-microscale does not significantly impact the attachment or current production of mixed culture anodic biofilms on glassy carbon. Likely earlier observations were associated with changes in surface chemistry, rather than surface topography.

No abstract