Effect of treatment on electron transfer mechanism in microbial fuel cell

<i>Harvesting Energy using Biocatalysts</i>

Probing mechanisms for microbial extracellular electron transfer (EET) using electrochemical and microscopic characterisations

The mechanisms of electron transfer of association of chemoorganotrophic bacteria to the anode in microbial fuel cells are summarized in the survey. These mechanisms are not mutually exclusive and are divided into the mechanisms of mediator electron transfer, mechanisms of electron transfer with intermediate products of bacterial metabolism and mechanism of direct transfer of electrons from the cell surface. Thus, electron transfer mediators are artificial or synthesized by bacteria riboflavins and phenazine derivatives, which also determine the ability of bacteria to antagonism. The microorganisms with hydrolytic and exoelectrogenic activity are involved in electron transfer mechanisms that are mediated by intermediate metabolic products, which are low molecular carboxylic acids, alcohols, hydrogen etc. The direct transfer of electrons to insoluble anode is possible due to membrane structures (cytochromes, pili, etc.). Association of microorganisms, and thus the biochemical mechanisms of electron transfer depend on the origin of the inoculum, substrate composition, mass transfer, conditions of aeration, potentials and location of electrodes and others, that are defined by technological and design parameters.

Investigating the mechanism of thylakoid direct electron transfer for photocurrent generation

Hierarchical modulation of extracellular electron transfer processes in microbial fuel cell anodes for enhanced power output through improved Geobacter adhesion

Microbial fuel cells (MFCs) are a promising technology that uses microorganisms to simultaneously generate bioelectricity while treating wastewater. To further improve the performance of the MFC, it is essential to understand and evaluate the electron transfer mechanism. However, redesigning the electron transfer mechanism of MFCs through an experimental approach is costly and time-consuming. Hence, in this study, a numerical modeling approach is implemented through the Nernst-Monod kinetic equation, which is validated by experimental results. A nanowire conductive transferring pathway is considered between the microorganisms and anode electrodes of a batch-type MFC. Moreover, two types of bacteria are utilized such as the Shewanella oneidensis MR-1 and Shewanella putrefacient with substrate concentrations of 0.5 M sodium lactate. The results have shown that the limiting current density of the MFC from the computational model is 1514 mA m−2. On the other hand, the current density from the experimental approach for Shewanella oneidensis MR-1 is 497 mA m−2 while for Shewanella putrefacient is 140 mA m−2. The anode activation loss of 491 Ω is lower than the cathode activation loss of 643 Ω, which indicates the relative influence of the cathode activation loss on the bioelectricity generation of the MFC. In addition, the results revealed that the nanowire electron transfer mechanism in the anode biofilm was less affected by the concentration losses. This then indicates that the physical mechanism of the nanowire electron transfer can be effectively used to investigate the batch-type MFCs. In turn, the results of this study will contribute to the development of an improved MFC.

Linking carbon, nitrogen and sulfur cycles: Electron transfer model for nitrate and sulfate dependent anaerobic oxidation of methane.

Understanding the extracellular electron transfer mechanisms of electroactive bacteria could help determine their potential in microbial fuel cells (MFCs) and their microbial syntrophy with redox-active minerals in natural environments. However, the mechanisms of extracellular electron transfer to electrodes by sulfate-reducing bacteria (SRB) remain underexplored. Here, we utilized double-chamber MFCs with carbon cloth electrodes to investigate the extracellular electron transfer mechanisms of Desulfovibrio vulgaris Hildenborough (DvH), a model SRB, under varying lactate and sulfate concentrations using different DvH mutants. Our MFC setup indicated that DvH can harvest electrons from lactate at the anode and transfer them to cathode, where DvH could further utilize these electrons. Patterns in current production compared with variations of electron donor/acceptor ratios in the anode and cathode suggested that attachment of DvH to the electrode and biofilm density were critical for effective electricity generation. Electron microscopy analysis of DvH biofilms indicated DvH utilized filaments that resemble pili to attach to electrodes and facilitate extracellular electron transfer from cell to cell and to the electrode. Proteomics profiling indicated that DvH adapted to electroactive respiration by presenting more pili- and flagellar-related proteins. The mutant with a deletion of the major pilus-producing gene yielded less voltage and far less attachment to both anodic and catholic electrodes, suggesting the importance of pili in extracellular electron transfer. The mutant with a deficiency in biofilm formation, however, did not eliminate current production indicating the existence of indirect extracellular electron transfer. Untargeted metabolomics profiling showed flavin-based metabolites, potential electron shuttles.IMPORTANCEWe explored the application of Desulfovibrio vulgaris Hildenborough in microbial fuel cells (MFCs) and investigated its potential extracellular electron transfer (EET) mechanism. We also conducted untargeted proteomics and metabolomics profiling, offering insights into how DvH adapts metabolically to different electron donors and acceptors. An understanding of the EET mechanism and metabolic flexibility of DvH holds promise for future uses including bioremediation or enhancing efficacy in MFCs for wastewater treatment applications.

This chapter describes the principle of current generation in microbial fuel cells (MFCs), and the mechanisms of electron transfer in these MFCs, viz., direct electron transfer, mediated electron transfer, and direct oxidation of exported catabolites. The components of MFCs as well as the uses of MFCs are presented. The MFCs can be used in wastewater treatment, as power source of environmental sensors, for hydrogen production, for renewable electricity production, and as BOD sensors.

This study introduces the utilization of self-powered microbial fuel cell (MFC)-based biosensors for the detection of biotoxicity in wastewater. Current MFC-based biosensors lack specificity in distinguishing between different pollutants. To address this limitation, a novel approach is introduced, capitalizing on the adaptive capabilities of anodic biofilms. By acclimating these biofilms to specific pollutants, an enhancement in the selectivity of MFC biosensors is achieved. Notably, electrochemically active bacteria (EAB) were cultivated on 3D porous carbon felt with and without a model toxicant (target analyte), resulting in the development of toxicant-resistant anodic biofilms. The model toxicants, Pb2+ ions and the antibiotic neomycin sulfate (NS), were deployed at a concentration of 1 mg L-1 during MFC operation. The influence of toxicity on biofilm growth and power production was investigated through polarization and power density curves. Concurrently, the electrochemical activity of both non-adapted and toxicity-adapted biofilms was investigated using cyclic voltammetry. Upon maturation and attainment of peak powers, the MFC reactors were evaluated individually as self-powered biosensors for pollutant detection in fresh wastewater, employing the external resistor (ER) mode. The selected ER, corresponding to the maximum power output, was positioned between the cathode and anode of each MFC, enabling output signal tracking through a data logging system. Subsequent exposure of mature biofilm-based MFC biosensors to various concentrations of the targeted toxicants revealed that non-adapted mature biofilms generated similar current-time profiles for both toxicity models, whereas toxicity-adapted biofilms produced distinctive current-time profiles. Accordingly, these results suggested that merely by adapting the anodic biofilm to the targeted toxicity, distinct and identifiable current-time profiles can be created. Furthermore, these toxicity-adapted and non-adapted biofilms can be employed to selectively detect the pollutant via the differential measurement of electrical signals. This differentiation offers a promising avenue for selective pollutant detection. To the best of our current knowledge, this approach, which harnesses the natural adaptability of biofilms for enhanced sensor selectivity, represents a pioneering effort in the realm of MFC-based biosensing.

Electron transfer mechanism in Shewanella loihica PV-4 biofilms formed at graphite electrode

Exoelectrogens: Recent advances in molecular drivers involved in extracellular electron transfer and strategies used to improve it for microbial fuel cell applications

Increasing industrialization and urbanization have contributed to a significant rise in wastewater discharge and exerted extensive pressure on the existing natural energy resources. Microbial fuel cell (MFC) is a sustainable technology that utilizes wastewater for electricity generation. MFC comprises a bioelectrochemical system employing electroactive biofilms of several aerobic and anaerobic bacteria, such as Geobacter sulfurreducens, Shewanella oneidensis, Pseudomonas aeruginosa, and Ochrobacterum pseudiintermedium. Since the electroactive biofilms constitute a vital part of the MFC, it is crucial to understand the biofilm-mediated pollutant metabolism and electron transfer mechanisms. Engineering electroactive biofilm communities for improved biofilm formation and extracellular polymeric substances (EPS) secretion can positively impact the bioelectrochemical system and improve fuel cell performance. This review article summarizes the role of electroactive bacterial communities in MFC for wastewater treatment and bioelectricity generation. A significant focus has been laid on understanding the composition, structure, and function of electroactive biofilms in MFC. Various electron transport mechanisms, including direct electron transfer (DET), indirect electron transfer (IET), and long-distance electron transfer (LDET), have been discussed. A detailed summary of the optimization of process parameters and genetic engineering strategies for improving the performance of MFC has been provided. Lastly, the applications of MFC for wastewater treatment, bioelectricity generation, and biosensor development have been reviewed.

Constructed mathematical model for nanowire electron transfer in microbial fuel cells

3 - Electron transfer mechanisms in biofilms