Article

Electron transfer and biofilm formation of Shewanella putrefaciens as function of anode potential. Bioelectrochemistry

Institute of Environmental and Sustainable Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany.
Bioelectrochemistry (Amsterdam, Netherlands) (Impact Factor: 4.17). 05/2012; 93. DOI: 10.1016/j.bioelechem.2012.05.002

ABSTRACT

Shewanellaceae are among the most widely studied electroactive microorganisms. In this report, we studied the influence of the applied electrode potential on the anodic current production of Shewanella putrefaciens NCTC 10695 under anoxic conditions. Furthermore, we used cyclic voltammetry (CV) and confocal laser scanning mi-croscopy (CLSM) to investigate the microbial electron transfer and biofilm formation. It is shown that the chro-noamperometric current density is increasing with increasing electrode potential from 3 μA cm − 2 at −0.1 V up to ~12 μA cm − 2 at +0.4 V (vs. Ag/AgCl), which is accompanied by an increasing amount of biomass deposited on the electrode. By means of cyclic voltammetry we demonstrate that direct electron transfer (DET) is dominat-ing and the planktonic cells play only a minor role.

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    • "For example, G. sulfurreducens showed different oxidation peaks (seven peaks) when wide range of anode potentials ( À 0.46 V to 0.60 V vs. Ag/AgCl) was applied, indicating the involvement of different extracellular redox components in electron transfer mechanisms[45]. In an alternative study, the performance of an MFC inoculated with Shewanella putrefaciens increased with a rise in anode potential and more positive potentials favored the biofilm formation and also increased the current density[46]. This is because the anode with a more positive redox potential enables the bacteria to oxidize the electron donor (substrates) more efficiently . "
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    ABSTRACT: Exoelectrogens are catalytic microorganisms competent to shuttle electrons exogenously to the electrode surface without utilizing artificial mediators. Diverse microorganisms acting as exoelectrogens in the fluctuating ambience of microbial fuel cells (MFCs) propose unalike metabolic pathways and incompatible, specific proteins or genes for their inevitable performance toward bioelectricity generation. A pivotal mechanism known as quorum sensing allows bacterial population to communicate and regulates the expression of biofilm-related genes. Moreover, it has been found that setting the anode potential affects the metabolism of the exoelectrogens and hence the output of MFCs. Microscopic, spectrometry investigations and gene deletion studies have confirmed the expression of certain genes for outer-membrane multiheme cytochromes and conductive pili, and their potential roles in the exoelectrogenic activity. Further, cyclic voltammetry has suggested the role of multifarious redox-active compounds secreted by the exoelectrogens in direct electron transport mechanisms. Besides, it also explores the various mechanisms of exoelectrogens with genetic and molecular approaches, such as biofilm formation, microbial metabolism, bioelectrogenesis, and electron transfer mechanisms from inside the exoelectrogens to the electrodes and vice versa. Copyright © 2015 John Wiley & Sons, Ltd.
    Full-text · Article · Feb 2015 · International Journal of Energy Research
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    • "Based on the small current densities due to the riboflavin redox reaction, it can be concluded that the catalytic activity of Shewanella at this stage appears to be dominated by DET mechanisms consistent with voltammagrams for Geobacter spp. biofilms [19] [20]. However, as the biofilm becomes more developed, complex and indeed larger (after 24-h of formation – Fig. 2), the presence of well-defined second EET mechanism appears at the onset of approximately −0.35 V vs Ag/AgCl (Fig. 3b). "
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    ABSTRACT: In this study, high-density planktonic cultures of Shewanella oneidensis MR-1 are grown aerobically to early stationary phase. After washing the cells and removing from original medium, the culture is exposed to an anaerobic environment in an electrochemical cell. An applied potential of −0.30 V vs Ag/AgCl is applied to the working electrode and the corresponding current is measured via chronoamperometry. Current begins to increase within 2 to 3 hours stabilizing at 5 hours. Cyclic voltammetry was measured at 5 hours indicating the initial stages a kinetically limited biofilm and again at 24 hours with an apparently more stable catalytic biofilm. At this point, the biofilm appears to suffer mass transport limitation as the catalytic wave dominates the shape of the voltammogram, similar to voltammograms reported for Geobacter spp. Polarization curves are also reported herein, further demonstrating a large increase of current near the oxidation potential of what is believed to be the terminal protein complex (MtrC/OmcA) of the trans-membrane cytochrome cascade, the Mtr pathway. Additional characterization and comparison between replicates of the biofilm is made using the idea of expanded uncertainty. This novel approach in reporting measured results for microbial fuel cells elucidates specific electrochemical parameters for appropriate comparison between systems and laboratories.
    Full-text · Article · Jul 2013 · Electrochimica Acta
    • "SHE) was regarded optimal for the performance of oxygen reducing biofilms [19]. While the use of set potential for efficient performance of bioanodes and biocathodes has received a great deal of attention [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20], only a limited number of reports have been published about the application of set potential to improve the degradation of recalcitrant organics [5] [17] [20]. In linkage with PCP degradation in the bioanodes [6] and biocathodes [8], in which there was still long biofilms acclimation time, slow PCP degradation and low power generation, optimal set potentials are expected to form efficient bioanodes and biocathodes with enhanced system performances for PCP degradation in MFCs. "
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    ABSTRACT: Bioanodes formed at an optimal potential of 200mV vs. SHE and biocathodes developed at -300mV vs. SHE in bioelectrochemical cells (BECs) enhanced the subsequent performances of microbial fuel cells (MFCs) compared to the un-treated controls. While the startup times were reduced to 320h (bioanodes) and 420-440h (biocathodes), PCP degradation rates were improved by 28.5% (bioanodes) and 21.5% (biocathodes), and power production by 41.7% (bioanodes) and 44% (biocathodes). Accordingly, there were less accumulated products of PCP de-chlorination in the biocathodes whereas PCP in the bioanodes was more efficiently de-chlorinated, resulting in the formation of a new product of 3,4,5-trichlorophenol (24.3±2.2μM at 96h). Charges were diverted to more generation of electricity in the bioanodes at 200mV while oxygen in the biocathodes at -300mV acted as a primary electron acceptor. Dominant bacteria known as recalcitrant organic degraders and/or exoelectrogens/electrotrophs included Desulfovibrio carbinoliphilus and Dechlorospirillum sp. on the bioanodes at 200mV, and Desulfovibrio marrakechensis, Comamonas testosteroni and Comamonas sp. on the biocathodes at -300mV. These results demonstrated that an optimal potential was a feasible approach for developing both bioanodes and biocathodes for efficient PCP degradation and power generation from MFCs.
    No preview · Article · May 2013 · Bioelectrochemistry (Amsterdam, Netherlands)
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