The effect of additional salinity on performance of a phosphate buffer saline buffered three-electrode bioelectrochemical system inoculated with wastewater.

In bioelectrochemical system (BES), phosphate buffer saline (PBS) is usually used to achieve a suitable pH condition, which also increases electrolyte salinity. A series of factors that change with salinity will affect BES performance. To simplify the scenario, a three-electrode BES is used to investigate how additional salinity affects the performance of a 50 mM PBS-buffered BES.

Microbiosensor for the detection of acetate in electrode-respiring biofilms.

The goal of this work was to develop a microbiosensor to measure acetate concentration profiles inside biofilms in situ. The working principle of the microbiosensor was based on the correlation between the acetate concentration and the current generated during acetate oxidation by Geobacter sulfurreducens. The microbiosensor consisted of a 30-µm carbon microelectrode with an open tip as a working electrode, with G.

Electrochemical biofilm control: a review.

One of the methods of controlling biofilms that has widely been discussed in the literature is to apply a potential or electrical current to a metal surface on which the biofilm is growing. Although electrochemical biofilm control has been studied for decades, the literature is often conflicting, as is detailed in this review. The goals of this review are: (1) to present the current status of knowledge regarding electrochemical biofilm control; (2) to establish a basis for a fundamental definition of electrochemical biofilm control and requirements for studying it; (3) to discuss current proposed mechanisms; and (4) to introduce future directions in the field.

Electrochemical scaffold generates localized, low concentration of hydrogen peroxide that inhibits bacterial pathogens and biofilms.

We hypothesized that low concentrations of H2O2 could be generated through the electrochemical conversion of oxygen by applying an electric potential to a conductive scaffold and produce a low, but constant, concentration of H2O2 that would be sufficient to destroy biofilms. To test our hypothesis we used a multidrug-resistant Acinetobacter baumannii strain, because this species is often implicated in difficult-to-treat biofilm infections. We used conductive carbon fabric as the scaffold material ("e-scaffold").

Excess surface area in bioelectrochemical systems causes ion transport limitations.

We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: (i) showing that serially increasing NaCl concentration up to 200 mM increased current linearly up to a total of +273% vs. 0 mM NaCl under advective conditions; (ii) growing the biofilm with a starting concentration of 200 mM NaCl, which led to a maximum current increase of 400% vs.

Investigation of Electron Transfer by Biofilms by using an Electrochemical Quartz Crystal Microbalance.

Both the short- and long-term electron-transfer processes of electrode-respiring biofilms are demonstrated by using an electrochemical quartz crystal microbalance (QCM). The QCM monitors the frequency shift from the initial resonant frequency (background) in real time, while the current increases, because of biofilm growth. In the short term, the frequency shift is linear with respect to current for the biofilm.

Multiple cathodic reaction mechanisms in seawater cathodic biofilms operating in sediment microbial fuel cells.

In this study, multiple reaction mechanisms in cathodes of sediment microbial fuel cells (SMFCs) were characterized by using cyclic voltammetry and microelectrode measurements of dissolved oxygen and pH. The cathodes were acclimated in SMFCs with sediment and seawater from San Diego Bay. Two limiting current regions were observed with onset potentials of approximately +400 mVAg/AgCl for limiting current I and -120 mVAg/AgCl for limiting current II.

A trans-outer membrane porin-cytochrome protein complex for extracellular electron transfer by Geobacter sulfurreducens PCA.

The multi-heme, outer membrane c-type cytochrome (c-Cyt) OmcB of Geobacter sulfurreducens was previously proposed to mediate electron transfer across the outer membrane. However, the underlying mechanism has remained uncharacterized. In G.

Localized electron transfer rates and microelectrode-based enrichment of microbial communities within a phototrophic microbial mat.

Phototrophic microbial mats frequently exhibit sharp, light-dependent redox gradients that regulate microbial respiration on specific electron acceptors as a function of depth. In this work, a benthic phototrophic microbial mat from Hot Lake, a hypersaline, epsomitic lake located near Oroville in north-central Washington, was used to develop a microscale electrochemical method to study local electron transfer processes within the mat. To characterize the physicochemical variables influencing electron transfer, we initially quantified redox potential, pH, and dissolved oxygen gradients by depth in the mat under photic and aphotic conditions.

Mass transfer studies of Geobacter sulfurreducens biofilms on rotating disk electrodes.

Electrochemical impedance spectroscopy has received significant attention recently as a method to measure electrochemical parameters of Geobacter sulfurreducens biofilms. Here, we use electrochemical impedance spectroscopy to demonstrate the effect of mass transfer processes on electron transfer by G. sulfurreducens biofilms grown in situ on an electrode that was subsequently rotated.

Microscale gradients of oxygen, hydrogen peroxide, and pH in freshwater cathodic biofilms.

Cathodic reactions in biofilms employed in sediment microbial fuel cells is generally studied in the bulk phase. However, the cathodic biofilms affected by these reactions exist in microscale conditions in the biofilm and near the electrode surface that differ from the bulk phase. Understanding these microscale conditions and relating them to cathodic biofilm performance is critical for better-performing cathodes.

Microscale gradients and their role in electron-transfer mechanisms in biofilms.

The chemical and electrochemical gradients in biofilms play a critical role in electron-transfer processes between cells and a solid electron acceptor. Most of the time, electron-transfer processes have been investigated in the bulk phase, for a biofilm electrode or for an isolated component of a biofilm. Currently, the knowledge of chemical and electrochemical gradients in living biofilms respiring on a solid surface is limited.

pH, redox potential and local biofilm potential microenvironments within Geobacter sulfurreducens biofilms and their roles in electron transfer.

The limitation of pH inside electrode-respiring biofilms is a well-known concept. However, little is known about how pH and redox potential are affected by increasing current inside biofilms respiring on electrodes. Quantifying the variations in pH and redox potential with increasing current is needed to determine how electron transfer is tied to proton transfer within the biofilm.

Redox and pH microenvironments within Shewanella oneidensis MR-1 biofilms reveal an electron transfer mechanism.

The goal of this research was to quantify the variations in redox potential and pH in Shewanella oneidensis MR-1 biofilms respiring on electrodes. We grew S. oneidensis MR-1 on a graphite electrode, which was used to accept electrons for microbial respiration.