Effects of Surface Charge and Hydrophobicity on Anodic Biofilm Formation, Community Composition, and Current Generation in Bioelectrochemical Systems

Abstract

The focus of this study was to investigate the effects of surface charge and surface hydrophobicity on anodic biofilm formation, biofilm community composition, and current generation in bioelectrochemical systems (BESs). Glassy carbon surfaces were modified with -OH, -CH3, -SO3(-), or -N(+)(CH3)3 functional groups by electrochemical reduction of aryl diazonium salts and then used as anodes with poised potential of -0.2 V (vs Ag/AgCl). The average startup times and final current densities for the -N(+)(CH3)3, -OH, -SO3(-), and -CH3, electrodes were (23 d, 0.204 mA/cm(2)), (25.4 d, 0.149 mA/cm(2)), (25.9 d, 0.114 mA/cm(2)), and (37.2 d, 0.048 mA/cm(2)), respectively. Biofilms on different surfaces were analyzed by nonturnover cyclic voltammetry (CV), fluorescence in situ hybridization (FISH), and 16S rRNA gene amplicon pyrosequencing. The results demonstrated that 1) differences in the maximum current output between surface modifications was correlated with biomass quantity, and 2) all biofilms were dominated by Geobacter populations, but the composition of -CH3-associated biofilms differed from those formed on surfaces with different chemical modification. This study shows that anode surface charge and hydrophobicity influences biofilm development and can lead to significant differences in BESs performance. Positively charged and hydrophilic surfaces were more selective to electroactive microbes (e.g. Geobacter) and more conducive for electroactive biofilm formation.

Surface Modification for Enhanced Biofilm Formation and Electron Transport in Shewanella Anodes

“…The order in which the current densities generated by the electrodes increase follows the order in which the bacterial coverage changes, demonstrating an expected correlation between MFC performance and biofilm formation on the surface of the anode. 5,10,16 Detection of metabolites implicated in extracellular electron transfer.-Cyclic voltammograms of the tested S. oneidensis anodes ( Figure 5) demonstrate increasing capacitance with the increasing time of UV/O 3 exposure, which can be explained by the increasing ECSA of the treated electrode materials. One can also identify peaks that can be attributed to both MET and DET as it has been observed before.…”

“…2 Therefore, electrode design is one of the greatest challenges in making MFCs a cost-effective and scalable technology. [3][4][5][6][7][8] Among the general requirements, such as good conductivity, chemical stability, mechanical strength, high surface area and low cost, anode materials should posses several key characteristics that will determine the rate of bacteria-electrode interactions. These are, but not limited to: i) high surface roughness; ii) biocompatibility; and iii) surface chemistry that enhances bacterial attachment and electron transfer.…”

Increasing the temperature is a relevant strategy to form microbial anodes intended to work at room temperature

“…The effect of the anode surface topography (roughness, porosity, etc.) has been checked [20] and surface chemistry has been widely investigated with different kinds of surface modification, including electrochemical treatments [21,22], self-assembled monolayers [23], chemical modification [24,25], surfactant treatments [24,26], and functionalized coatings [25], which pointed out the importance of the hydrophilic/hydrophobic property of the surface [27]. From a biological standpoint, reducing the start-up time of MFCs has been attempted by changing the nature of the inoculum [28] and with various treatments of the inlet, e.g.…”

Relationship between surface chemistry, biofilm structure, and electron transfer in Shewanella anodes

“…1,[4][5][6][7][8] Attachment surface charge and wettability (hydrophilicity/ hydrophobicity) may be particularly important to the growth, development, and properties of bacterial biofilm and optimization of BES performance. 9 Positively charged and hydrophilic surfaces were shown to improve attachment of the electrogen Geobacter, and therefore improved electroactive biofilm growth and development. 9 We previously reported the importance of hydrophilic moieties and surface morphology on bacterial attachment, dynamics of biofilm formation, and MFC performance.…”