Growth and current production of mixed culture anodic biofilms remain unaffected by sub-microscale surface roughness

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.

The Limits of Three‐Dimensionality: Systematic Assessment of Effective Anode Macrostructure Dimensions for Mixed‐Culture Electroactive Biofilms

“…However, recent studies have shown that although structurest hat are small compared to the biofilm thickness can influence biofilm attachment and initial growth,t hey do not significantly enhance long-term performance. [19][20][21] Macrostructures with ac omparatively larger size [22] can, however,d rastically increaset he current density,w hichh as been shown by several studies with specific 3D macrostructure designs. [15,17,23] Here, clogging of the 3D structures during the biofilm growth represents a major obstacle that needs to be overcome.…”

“…The introduction of small structures (i.e., nanometer or micrometer scale) can drastically increase the electrochemically active surface area of an electrode. However, recent studies have shown that although structures that are small compared to the biofilm thickness can influence biofilm attachment and initial growth, they do not significantly enhance long‐term performance . Macrostructures with a comparatively larger size can, however, drastically increase the current density, which has been shown by several studies with specific 3 D macrostructure designs .…”

Rational Selection of Carbon Fiber Properties for High-Performance Textile Electrodes in Bioelectrochemical Systems

“…Especially, the core element bioanode is in the focus of research and development. Independent from the electrode material, chemical and physical modifications have been applied successfully to increase electrode performances in BES (He et al, 2011;Guo et al, 2013;Kipf et al, 2013;Artyushkova et al, 2015;Baudler et al, 2015;Champigneux et al, 2018;Pierra et al, 2018;Moß et al, 2019).…”

Is there a Function for a Sex Pheromone Precursor?

“…According to our analysis the cAD1 precursor and its orthologs from other bacteria are encoded by genes adjacent to apbE homologs (Figure 2-Figure 5). A number of mentioned above Firmicutes genera [32], [33] and particularly Listeria [34], Catonella [35] representatives, as well as Bacteroidia (Bacteroides) [36], were considered as electrogenic and shown to populate MFCs [4] under different conditions. We show that cAD1 precursor has two sites specific for ApbE-dependent FMN insertion (TGAT) ( Figure 7), and its homologs have at least one FMN covalent binding insertion motif.…”