Si Ying Liu, Wipa Charles, Ralf Cord-Ruwisch et al.

Renewable Energy and Environmental Sustainability • 2023

Bioelectrochemical systems (BESs) can be integrated in situ into anaerobic digesters for increasing methane (CH 4 ) content of biogas. Using BES ex situ for improving biogas quality has recently been gaining attention. However, information on the process under thermophilic conditions is very limited. In this study, we placed a BES cathode in-line at the exit gas from a thermophilic anaerobic digester to convert carbon dioxide (CO 2 ) in the biogas into CH 4 . The performance of the ex situ BES reactor under thermophilic conditions was evaluated. When poising the cathode at −1.1 V versus Ag/AgCl in the ex situ BES reactor, CH 4 content increased from 50% to 85%. Of the incoming CO 2 73% was biologically converted to CH 4 and 23% absorbed by alkalinity generated in the cathode. The energy output as additional CH 4 as a percentage of the energy input to operate the BES was calculated at 56%. The biocathode of the BES reactor was dominated by Methanothermobacter spp., which are thermophilic hydrogen consuming methanogens. This study confirms that thermophilic BES can be used as an ex situ treatment process for enriching the CH 4 content of biogas. However, energy efficiency of the process was found to be limited by the lack of an energetically efficient anodic reaction. For industrial applications, optimisation of energy efficiency is an area for further research.

Michele Morgante, Nick Vlachopoulos, Anders Hagfeldt et al.

Journal of Physics: Energy • 2021

Abstract In recent years, one of the most important challenges of the 21st century is to satisfy the ever-increasing world’s energy demand. Many efforts are being undertaken to find alternative renewable energy sources, which ideally should outcompete fossil fuel use in all its aspects. In this respect, photo-assisted microbial bioelectrochemical cells (MBECs) in which the reduction of water to hydrogen takes place have been of considerable interest in recent years. Two categories of such systems have been investigated: MBECs with a semiconductor photocathode or photoanode, and hybrid systems, in which an MBEC cell with dark electrodes is coupled to an electrochemical photovoltaic cell. A common denominator of all these systems is the need of microorganisms at the anode, the action of which results in the generation of an electron flow by organic matter oxidation. The aim of this review is to describe the general working principles, with respect to both biochemical and electrochemical aspects, and the performance of various categories of hydrogen-generating photo-assisted MBECs.

Kiran Kuruvinashetti, Hemanth Kumar Tanneru, Pragasen Pillay et al.

Energy Technology • 2021

Biophotoelectrochemical cells are gaining prominence in recent years due to the necessity of sustainable power generation at both micro‐ and macroscale. Toward this direction, microphotosynthetic power cells (μ‐PSC) play a vital role in generating clean energy. The μ‐PSC generates sustainable power under light and in the dark through the photosynthesis and respiration of photosynthetic microorganisms or cells, such as cyanobacteria and green algae. Herein, particulars on μ‐PSCs from fundamentals to real‐time applications are provided. The state of the art of μ‐PSCs, in terms of the principle of operation, design, and materials is presented. μ‐PSCs reported to date are classified based on design, operating parameters, and photosynthetic organisms. In addition, details on the metrics and factors influencing the performance of μ‐PSCs are also discussed. The need for the development of mathematical and electrical equivalent models of μ‐PSCs and the progress in these areas are briefed. Current challenges for μ‐PSCs’ commercialization are identified as high cost and low power densities, and the factors that are leading to low power density and high cost are explored and are also discussed. In addition, the potential solutions to overcome these challenges are investigated.

Anna Espinoza-Tofalos, Matteo Daghio, Enza Palma et al.

Water • 2020

Bioelectrochemical systems (BESs) exploit the interaction between microbes and electrodes. A field of application thereof is bioelectrochemical remediation, an effective strategy in environments where the absence of suitable electron acceptors limits classic bioremediation approaches. Understanding the microbial community structure and genetic potential of anode biofilms is of great interest to interpret the mechanisms occurring in BESs. In this study, by using a whole metagenome sequencing approach, taxonomic and functional diversity patterns in the inoculum and on the anodes of three continuous-flow BES for the removal of phenol, toluene, and BTEX were obtained. The genus Geobacter was highly enriched on the anodes and two reconstructed genomes were taxonomically related to the Geobacteraceae family. To functionally characterize the microbial community, the genes coding for the anaerobic degradation of toluene, ethylbenzene, and phenol were selected as genetic markers for the anaerobic degradation of the pollutants. The genes related with direct extracellular electron transfer (EET) were also analyzed. The inoculum carried the genetic baggage for the degradation of aromatics but lacked the capacity of EET while anodic bacterial communities were able to pursue both processes. The metagenomic approach provided useful insights into the ecology and complex functions within hydrocarbon-degrading electrogenic biofilms.

Stefano Freguia, Maddalena Logrieco, Juliette Monetti et al.

Sustainability • 2019

Nutrient recovery from source-separated human urine has been identified by many as a viable avenue towards the circular economy of nutrients. Moreover, untreated (and partially treated) urine is the main anthropogenic route of environmental discharge of nutrients, most concerning for nitrogen, whose release has exceeded the planet’s own self-healing capacity. Urine contains all key macronutrients (N, P, and K) and micronutrients (S, Ca, Mg, and trace metals) needed for plant growth and is, therefore, an excellent fertilizer. However, direct reuse is not recommended in modern society due to the presence of active organic molecules and heavy metals in urine. Many systems have been proposed and tested for nutrient recovery from urine, but none so far has reached technological maturity due to usually high power or chemical requirements or the need for advanced process controls. This work is the proof of concept for the world’s first nutrient recovery system that powers itself and does not require any chemicals or process controls. This is a variation of the previously proposed microbial electrochemical Ugold process, where a novel air cathode catalyst active in urine conditions (pH 9, high ammonia) enables in situ generation of electricity in a microbial fuel cell setup, and the simultaneous harvesting of such electricity for the electrodialytic concentration of ionic nutrients into a product stream, which is free of heavy metals. The system was able to sustain electrical current densities around 3 A m–2 for over two months while simultaneously upconcentrating N and K by a factor of 1.5–1.7.

Eole Fukawa, Keisei Sowa, Yuki Kitazumi et al.

ECS Meeting Abstracts • 2024

The interest in the use of redox enzymes for the construction of efficient biodevices has grown to achieve an environmentally friendly society. “Bioelectrocatalysis,” in which enzymatic reaction and electrode reactions are coupled, is a fundamental technology for various electrochemical biomimetics (e.g., biosensors, biofuel cells, and bioreactors). In particular, the reaction in which an enzyme directly shuttles electrons to an electrode without any external electron mediators is called a direct electron transfer (DET)-type reaction. Thanks to its mediator-less configuration, DET-type reaction is advantageous in biocompatibility and design freedom, enabling us to develop ideal bio-devices. However, the number of enzymes performing DET-type reactions (DET-type enzyme) is very limited, which is one of the major problems for developing the aforementioned biodevices. Thus, there has been considerable interest in studies for creating new DET-type enzymes using existing enzymes as templates. To tackle the issue, fundamental research on their catalytic reaction mechanisms is essential. D-Fructose dehydrogenase (FDH) from Gluconobacter japonicus NBRC3260, a membrane-bound heterotrimeric flavohemoprotein capable of intense DET-type bioelectrocatalysis, has been widely investigated. FDH forms heterotrimetric structures composed of the catalytic large subunit, the chaperonic small subunit, and the membrane-bound cytochrome c subunit. Although the catalytic center is flavin adenine dinucleotide (FAD), the details for substrate oxidation remain unclear. Thanks to its extremely high DET-type activity and its covalently-bound cofactors, FDH is regarded as the model DET-type enzyme. Several researchers have already revealed the enzyme properties, focusing on DET from the viewpoints of enzyme engineering and electrochemistry. In addition, the three-dimensional (3D) structure of FDH was first revealed in 2022 with cryo-electron microscopy (cryo-EM) analysis, enabling us to discuss the enzyme from the perspective of structural biology and bioinformatics. In this study, we intend to understand the catalytic mechanism of FDH, such as substrate recognition or catalysis. First, we performed enzyme-substrate docking simulation and homology search to estimate critical amino acid residues in the catalytic reaction. These results indicated that three amino acid residues around FAD (N1146, H1147, and N1190) were the critical residues. Site-directed FDH variants focused on the residues (Namely, N1146A, N1146Q, H1147A, and N1190A) were expressed, purified, and evaluated. Next, the electrochemical properties of variants were evaluated with enzyme-modified rotating disk electrodes at 2000 rpm, pH 4.5, and 25 °C. From the cyclic voltammogram, we found that the mutations to H1147 or N1190 brought remarkable declines in DET-type activities, implying the importance of the two residues for the catalytic reaction. Substrate concentration dependence of the variants on the catalytic currents (Michaelis-Menten plot) revealed that the mutation into N1146 or H1147 resulted in increases in Michaelis constants, which indicates that the two residues seemed to have roles in fructose recognition. Because the two N1146 variants (N1146A or N1146Q) maintained sufficient activities, we examined substrate characteristics for various sugars and confirmed that the relative activity of N1146Q with D-tagatose, the C4 epimer of D-fructose, was improved over that of recombinant FDH. Finally, we also discuss the properties of variants from structural biology. The structures of the variants were successfully analyzed with cryo-EM analysis, and the N1146A, N1146Q, H1147A, and N1190A resolutions were 2.4, 3.1, 2.8, and 3.0 Å, respectively. The overall quaternary structures remained almost unchanged, indicating that each point mutation did not disrupt the protein structure. The direction and position of the amino acid residues of each variant differed slightly around the mutation sites. When using their structure for enzyme-substrate docking simulation, a good relationship between docking scores and Michaelis constants of the variants was observed. This means that the decline in the affinity between the variants and the substrate can be explained in structural biology. In the simulation, on the other hand, we obtained different results when using in-silico variants (computationally constructed), implying room for improvement in the current protein structure prediction methods. In summary, we investigated the mechanisms underlying the catalytic activity of FDH using enzyme engineering, electrochemistry, structural biology, and bioinformatics. H1147 and N1190 are particularly important for catalytic activity, with H1147 mainly functioning as a basic catalyst. N1146, H1147, and N1190 contribute to the recognition of the fructose molecules. In the future, our understanding of the fundamental reaction mechanism is expected to lead to the computational design and creation of various DET-type enzymes with FDH as a template.

A. Carucci, G. Erby, G. Puggioni et al.

Water Science and Technology • 2022

Abstract Growing food and biomass production at the global scale has determined a corresponding increase in the demand for and use of nutrients. In this study, the possibility of recovering nitrogen from agro-industrial digestate using bioelectrochemical systems was investigated: two microbial electrolysis cells (MECs) were fed with synthetic and real digestate (2.5 gNH4+-N L−1). Carbon felt and granular graphite were used as anodes in MEC-1 and MEC-2, respectively. As to synthetic wastewater, the optimal nitrogen load (NL) for MEC-1 and -2 was 1.25 and 0.75 gNH4+-N d−1, respectively. MEC-1 showed better performance in terms of NH4+-N removal efficiency (39 ± 2.5%) and recovery rate (up to 70 gNH4+-N m−2d−1), compared to MEC-2 (33 ± 4.7% and up to 30 gN m−2d−1, respectively). At the optimal hydraulic retention time, lower NH4+-N removal efficiencies and recovery rates were observed when real digestate was fed to MEC-1 (29 ± 6.6% and 60 ± 13 gNH4+-N m−2d−1, respectively) and MEC-2 (21 ± 7.9% and 10 ± 3.6 gNH4+-N m−2d−1, respectively), likely due to the higher complexity of the influent. The average energy requirements were 3.6–3.7 kWh kgNremoved−1, comparable with values previously reported in the literature and lower than conventional ammonia recovery processes. Results are promising and may reduce the need for costly and polluting processes for nitrogen synthesis.

Marco Zeppilli, Edoardo Dell’Armi, Lorenzo Cristiani et al.

Water • 2019

An innovative bioelectrochemical reductive/oxidative sequential process was developed and tested on a laboratory scale to obtain the complete mineralization of perchloroethylene (PCE) in a synthetic medium. The sequential bioelectrochemical process consisted of two separate tubular bioelectrochemical reactors that adopted a novel reactor configuration, avoiding the use of an ion exchange membrane to separate the anodic and cathodic chamber and reducing the cost of the reactor. In the reductive reactor, a dechlorinating mixed inoculum received reducing power to perform the reductive dechlorination of perchloroethylene (PCE) through a cathode chamber, while the less chlorinated daughter products were removed in the oxidative reactor, which supported an aerobic dechlorinating culture through in situ electrochemical oxygen evolution. Preliminary fluid dynamics and electrochemical tests were performed to characterize both the reductive and oxidative reactors, which were electrically independent of each other, with each having its own counterelectrode. The first continuous-flow potentiostatic run with the reductive reactor (polarized at −450 mV vs SHE) resulted in obtaining 100% ± 1% removal efficiency of the influent PCE, while the oxidative reactor (polarized at +1.4 V vs SHE) oxidized the vinyl chloride and ethylene from the reductive reactor, with removal efficiencies of 100% ± 2% and 92% ± 1%, respectively.

Miriam Edel, Laura-Alina Philipp, Jonas Lapp et al.

Extremophiles • 2022

Abstract The interaction of bacteria and archaea with electrodes is a relatively new research field which spans from fundamental to applied research and influences interdisciplinary research in the fields of microbiology, biochemistry, biotechnology as well as process engineering. Although a substantial understanding of electron transfer processes between microbes and anodes and between microbes and cathodes has been achieved in mesophilic organisms, the mechanisms used by microbes under extremophilic conditions are still in the early stages of discovery. Here, we review our current knowledge on the biochemical solutions that evolved for the interaction of extremophilic organisms with electrodes. To this end, the available knowledge on pure cultures of extremophilic microorganisms has been compiled and the study has been extended with the help of bioinformatic analyses on the potential distribution of different electron transfer mechanisms in extremophilic microorganisms.

Jungho Jang, Byoung Wook Jeon, Yong Hwan Kim

Scientific Reports • 2018

Abstract The conversion of carbon dioxide to formate is a fundamental step for building C1 chemical platforms. Methylobacterium extorquens AM1 was reported to show remarkable activity converting carbon dioxide into formate. Formate dehydrogenase 1 from M. extorquens AM1 (MeFDH1) was verified as the key responsible enzyme for the conversion of carbon dioxide to formate in this study. Using a 2% methanol concentration for induction, microbial harboring the recombinant MeFDH1 expressing plasmid produced the highest concentration of formate (26.6 mM within 21 hours) in electrochemical reactor. 60 μM of sodium tungstate in the culture medium was optimal for the expression of recombinant MeFDH1 and production of formate (25.7 mM within 21 hours). The recombinant MeFDH1 expressing cells showed maximum formate productivity of 2.53 mM/g-wet cell/hr, which was 2.5 times greater than that of wild type. Thus, M. extorquens AM1 was successfully engineered by expressing MeFDH1 as recombinant enzyme to elevate the production of formate from CO 2 after elucidating key responsible enzyme for the conversion of CO 2 to formate.

Nhlanganiso Ivan Madondo, Emmanuel Kweinor Tetteh, Sudesh Rathilal et al.

Bioengineering • 2021

Conventionally, the anaerobic digestion of industrial effluent to biogas constitutes less than 65% methane, which warrants its potential methanation to mitigate carbon dioxide and other anthropogenic gas emissions. The performance of the anaerobic digestion process can be enhanced by improving biochemical activities. The aim of this study was to examine the synergistic effect of the magnetite and bioelectrochemical systems (BES) on anaerobic digestion by comparing four digesters, namely a microbial fuel cell (MFC), microbial electrolysis cell (MEC), MEC with 1 g of magnetite nanoparticles (MECM), and a control digester with only sewage sludge (500 mL) and inoculum (300 mL). The MFC digester was equipped with zinc and copper electrodes including a 100 Ω resistor, whereas the MEC was supplied with 0.4 V on the electrodes. The MECM digester performed better as it improved microbial activity, increased the content of methane (by 43% compared to 41% of the control), and reduced contaminants (carbon oxygen demand, phosphates, colour, turbidity, total suspended solids, and total organic carbon) by more than 81.9%. Current density (jmax = 25.0 mA/m2) and electrical conductivity (275 µS/cm) were also high. The prospects of combining magnetite and bioelectrochemical systems seem very promising as they showed a great possibility for use in bioelectrochemical methane generation and wastewater treatment.

Daniele Cecconet, Silvia Bolognesi, Luca Piacentini et al.

Water • 2021

Greywater normally represents the largest fraction of wastewater generated in buildings and may be suitable for non-potable reuse after on-site treatment. Conventional technologies for greywater treatment include sequencing batch reactors, membrane filtration, and membrane biological reactors. Even though these can be very effective, they are highly energy consuming and may negatively impact the energy balance of the building where they are installed. Microbial fuel cells (MFCs) have emerged as a sustainable technology for contaminant removal and energy production from a variety of substrates. In this study, the application of MFCs for greywater treatment is reported, with a particular focus on the analysis of energy losses, in view of non-potable reuse. MFCs were fed with different types of greywater, characterized by either high or low conductivity, because greywater’s conductivity may greatly differ based on its origin; in either case, organic matter (chemical oxygen demand; COD) removal was higher than 85% and not influenced by the influent conductivity, coupled with a maximum power production of 0.46 mW L−1 and 0.38 mW L−1. Electrolyte overpotentials were dramatically higher in the case of low conductivity greywater (20% vs. 10%, compared to high conductivity influent); these overpotentials are related to the conductivity of the influent, showing that low conductivity hindered energy generation, but not COD removal. Polarization and power curves showed higher internal resistance in the case of low conductivity, confirming the overpotentials’ analysis. Results showed the feasibility of the use of MFCs in greywater treatment, with potential to reduce the energy demand connected to its reuse compared to conventional technologies; coupling with a disinfection stage would be necessary to fully comply with most non-potable reuse regulations.

Anirudh Bhanu Teja Nelabhotla, Carlos Dinamarca

Applied Sciences • 2019

Anaerobic digestion (AD) is a widely used technique to treat organic waste and produce biogas. This article presents a practical approach to increase biogas yield of an AD system using a microbial electrosynthesis system (MES). The biocathode in MES reduces carbon dioxide with the supplied electrons and protons (H+) to form methane. We demonstrate that the MES is able to produce biogas with over 90% methane when fed with reject water obtained from a local wastewater treatment plant. The optimised cathode potential was observed in the range of −0.70 V to −0.60 V and optimised feed pH was around 7.0. With autoclaved feed, these conditions allowed methane yields of about 9.05 mmol/L(reactor)-day. A control experiment was then carried out to make a comparison between open circuit and MES methanogenesis. The highest methane yield of about 22.1 mmol/L(reactor)-day was obtained during MES operation that performed 10–15% better than the open circuit mode of operation. We suggest and describe an integrated AD-MES system, by installing MES in the reject water loop, as a novel approach to improve the efficiency and productivity of existing waste/wastewater treatment plants.

Dipankar Deb, Ravi Patel, Valentina E. Balas

Processes • 2020

A microbial fuel cell (MFC) is a potentially viable renewable energy option which promises effective and commercial harvesting of electrical power by bacterial movement and at the same time also treats wastewater. Microbial fuel cells are complicated devices and therefore research in this field needs interdisciplinary knowledge and involves diverse areas such as biological, chemical, electrical, etc. In recent decades, rapid strides have taken place in fuel cell research and this technology has become more efficient. For effective usage, such devices need advanced control techniques for maintaining a balance between substrate supply, mass, charge, and external load. Most of the research work in this area focuses on experimental work and have been described from the design perspective. Recently, the development in mathematical modeling of such cells has taken place which has provided a few mathematical models. Mathematical modeling provides a better understanding of the operations and the dynamics of MFCs, which will help to develop control and optimization strategies. Control-oriented bio-electrochemical models with mass and charge balance of MFCs facilitate the development of advanced nonlinear controllers. This work reviews the different mathematical models of such cells available in the literature and then presents suitable parametrization to develop control-oriented bio-electrochemical models of three different types of cells with their uncertain parameters.

Silvia Bolognesi, Daniele Cecconet, Arianna Callegari et al.

Environmental Science and Pollution Research • 2021

Abstract Despite solid wastes’ landfill disposal limitation due to recent European legislation, landfill leachate disposal remains a significant problem and will be for many years in the future, since its production may persist for years after a site’s closure. Among process technologies proposed for its treatment, microbial fuel cells (MFCs) can be effective, achieving both contaminant removal and simultaneous energy recovery. Start-up and operation of two dual-chamber MFCs with different electrodes’ structure, fed with mature municipal solid waste landfill leachate, are reported in this study. Influent (a mix of dairy wastewater and mature landfill leachate at varying proportions) was fed to the anodic chambers of the units, under different conditions. The maximum COD removal efficiency achieved was 84.9% at low leachate/dairy mix, and 66.3% with 7.6% coulombic efficiency (CE) at a leachate/dairy ratio of 20%. Operational issues and effects of cells’ architecture and electrode materials on systems’ performance are analyzed and discussed.

Azhan Ahmad, Monali Priyadarshani, Sovik Das et al.

Journal of Basic Microbiology • 2022

Abstract Bioelectrochemical systems (BESs) are a unique group of wastewater remediating technology that possesses the added advantage of valuable recovery with concomitant wastewater treatment. Moreover, due to the application of robust microbial biocatalysts in BESs, effective removal of emerging contaminants (ECs) can be accomplished in these BESs. Thus, this review emphasizes the recent demonstrations pertaining to the removal of complex organic pollutants of emerging concern present in wastewater through BES. Owing to the recalcitrant nature of these pollutants, they are not effectively removed through conventional wastewater treatment systems and thereby are discharged into the environment without proper treatment. Application of BES in terms of ECs removal and degradation mechanism along with valuables that can be recovered are discussed. Moreover, the factors affecting the performance of BES, like biocatalyst, substrate, salinity, and applied potential are also summarized. In addition, the present review also elucidates the occurrence and toxic nature of ECs as well as future recommendations pertaining to the commercialization of this BES technology for the removal of ECs from wastewater. Therefore, the present review intends to aid the researchers in developing more efficient BESs for the removal of ECs from wastewater.

Parisa Ebrahimzadeh, Nahid Navidjouy, Hassan Khorsandi et al.

ChemElectroChem • 2024

Abstract Bioelectrochemical systems (BES) is a new and expanding technology that can simultaneously convert chemical energy into electrical energy by removing nutrients. The present study investigated the BES in removing nitrogen compounds and produce electricity. To this end, a BES reactor with two chambers of cathode and anode and nafion 117 membrane was used as a separator between the two chambers. Then, the BES performance at different concentrations of COD and primary ammonium at different retention times was investigated to remove nitrogen compounds and organic matter. Voltage, current and power density were measured. The results showed that the maximum COD removal efficiency was 73.2 % for the substrate concentration of 2000 mg/L, which decreased to 72.6 % when the substrate concentration increased to 10000 mg/L. The maximum removal efficiency of nitrogen compounds was 83.4 % at COD 10000 mg/L and the initial ammonium concentration was 50 mg/L. The maximum voltage, current and power density in this phase were 391 mV, 460 mA/m 2 , 63/48 mW/m 2 , respectively. The results of the study showed that BES can be used as a suitable method to remove high amounts of ammonium in wastewater and organic materials and simultaneously produce electricity.

Shengjin Ke, Xuhui Jiang, Xi Zhang et al.

Journal of Physics: Conference Series • 2024

Abstract Bioelectrochemical systems (BESs) serve as an emerging renewable energy technology that presents great potential for wastewater treatment and energy recovery. Microbial desalination cell (MDC), as a type of BES, is capable of desalination while realizing wastewater treatment and recycling of electric energy, which has become a research hotspot in recent years. However, research that has been conducted tends to focus only on the desalination capacity of the MDC and pays less attention to its electricity generation performance. The electricity derived from the recovery of chemical energy in the wastewater by the system has also not been well utilized. In this study, a microbial reverse-electrodialysis cell (MRC), which is capable of obtaining the salt difference energy from high-salt wastewater, was constructed and coupled with an electrodialysis cell (EDC), ultimately constructing a new type of BES named MRC-EDC. It can synchronize the recovery of chemical energy and salt difference in high-salt wastewater, realizing the in-situ use of electric energy and wastewater desalination. The maximum power production performance of MRC-EDC reached 2.44 W m −2 , which was 67.1% higher than that of conventional MFC. The COD removal rate of the system reached 34.16% after 10 h of operation, and the average desalination rate per hour was 5.15%. This study provides a reference for the construction of high-efficiency BESs.

Anagha Bindu, Sudipa Bhadra, Soubhagya Nayak et al.

Open Life Sciences • 2024

Abstract Bioelectrochemical biosensors offer a promising approach for real-time monitoring of industrial bioprocesses. Many bioelectrochemical biosensors do not require additional labelling reagents for target molecules. This simplifies the monitoring process, reduces costs, and minimizes potential contamination risks. Advancements in materials science and microfabrication technologies are paving the way for smaller, more portable bioelectrochemical biosensors. This opens doors for integration into existing bioprocessing equipment and facilitates on-site, real-time monitoring capabilities. Biosensors can be designed to detect specific heavy metals such as lead, mercury, or chromium in wastewater. Early detection allows for the implementation of appropriate removal techniques before they reach the environment. Despite these challenges, bioelectrochemical biosensors offer a significant leap forward in wastewater monitoring. As research continues to improve their robustness, selectivity, and cost-effectiveness, they have the potential to become a cornerstone of efficient and sustainable wastewater treatment practices.

N. Evelin Paucar, Chikashi Sato

Processes • 2021

The world is facing serious threats from the depletion of non-renewable energy resources, freshwater shortages and food scarcity. As the world population grows, the demand for fresh water, energy, and food will increase, and the need for treating and recycling wastewater will rise. In the past decade, wastewater has been recognized as a resource as it primarily consists of water, energy-latent organics and nutrients. Microbial fuel cells (MFC) have attracted considerable attention due to their versatility in their applications in wastewater treatment, power generation, toxic pollutant removal, environmental monitoring sensors, and more. This article provides a review of MFC technologies applied to the removal and/or recovery of nutrients (such as P and N), organics (COD), and bioenergy (as electricity) from various wastewaters. This review aims to provide the current perspective on MFCs, focusing on the recent advancements in the areas of nutrient removal and/or recovery with simultaneous power generation.

Bhim Sen Thapa, Soumya Pandit, Sanchita Bipin Patwardhan et al.

Sustainability • 2022

Pharmaceutical wastewater (PWW) is rapidly growing into one of the world’s most serious environmental and public health issues. Existing wastewater treatment systems carry numerous loopholes in supplying the ever-increasing need for potable water resulting from rises in population, urbanization, and industrial growth, and the volume of wastewater produced is growing each day. At present, conventional treatment methods, such as coagulation, sedimentation, oxidation, membrane filtration, flocculation, etc., are used to treat PWW. In contrast to these, the application of microbial fuel cells (MFCs) for decontaminating PWW can be a promising technology to replace these methods. MFC technologies have become a trending research topic in recent times. MFCs have also garnered the interest of researchers worldwide as a promising environmental remediation technique. This review extensively discusses the flaws in standalone conventional processes and the integration of MFCs to enhance electricity production and contaminant removal rates, especially with respect to PWW. This article also summarizes the studies reported on various antibiotics and wastes from pharmaceutical industries treated by MFCs, and their efficiencies. Furthermore, the review explains why further research is needed to establish the actual efficiency of MFCs to achieve sustainable, environmentally friendly, and cost-effective wastewater treatment. A brief on technoeconomic impacts has also been made to provide a glimpse of the way these technologies might replace present-day conventional methods.

Emre Cevik, Mohammed A. Gondal, Noha Alqahtani et al.

Biotechnology and Bioengineering • 2023

Abstract The power performance of the bio‐electrochemical fuel cells (BEFCs) depends mainly on the energy harvesting ability of the anode material. The anode materials with low bandgap energy and high electrochemical stability are highly desirable in the BEFCs. To address this issue, a novel anode is designed using indium tin oxide (ITO) modified by chromium oxide quantum dots (CQDs). The CQDs were synthesized using facile and advanced pulsed laser ablation in liquid (PLAL) technique. The combination of ITO and CQDs improved the optical properties of the photoanode by exhibiting a broad range of absorption in the visible to UV region. A systematic study has been performed to optimize the amount of CQDs and green Algae (Alg) film grown using the drop casting method. Chlorophyll ( a , b , and total) content of algal cultures (with different concentrations) were optimized to investigate the power generation performance of each cell. The BEFC cell (ITO/Alg10/Cr3//Carbon) with optimized amounts of Alg and CQDs demonstrated enhanced photocurrent generation of 120 mA cm −2 at a photo‐generated potential of 24.6 V m −2 . The same device exhibited a maximum power density of 7 W m −2 under continuous light illumination. The device also maintained 98% of its initial performance after 30 repeated cycles of light on–off measurements.

Fatemeh Poureshghi Oskouei, Nga Phuong Dong, Subhashis Das et al.

ECS Meeting Abstracts • 2022

Microbial fuel cells (MFCs) harness the metabolism of microorganisms, converting chemical energy into electrical energy. Improving both Anode and Cathode design is thus of great significance to enhance the MFC performance and its commercial application. For the performance improvement of MFCs, the anode becomes a breakthrough point due to its influence on bacterial attachment and extracellular electron transfer (EET). On the other hand, air cathodes have considerable influence on the maximum power of air-driven MFCs. The cathodes used in MFCs need to have high catalytic activity for oxygen reduction, but they should be inexpensive watertight,and easy to manufacture. As the first part of this work, carbon felt was electrochemically and chemically treated by electrolyzing in nitric acid and phosphate buffer followed by soaking in aqueous ammonia. The treated and untreated carbon felts were utilized as anodes in MFCs, and current production was compared while the cathode was stainless steel mesh (SS-316L) in both cases. The treated carbon felt displays strong interaction with the microbial biofilm of Shewanella baltica 20 facilitating electron transfer from exoelectrogens to the anode. An MFC equipped with a treated carbon felt as anode has significantly lower charge-transfer resistance and achieves considerably better performance than one equipped with an untreated carbon felt anode. The enhanced electron transfer is attributed to newly generated carboxyl containing functional groups on the treated carbon felt. In the second part of the present study, SS-316L as a cathode was modified using phase inversion process to construct a poly vinylidenefluoride (PVDF) binder and an activated carbon catalyst according to the procedure reported previously. Finally, the MFC with treated carbon felt anode and PVDF air cathode was tested. The MFC with both modified anode and cathode achieves considerably better performance than one with a traditional carbon felt anode and SS-316L cathode. The maximum current density, power density, and energy recovery, and sensitivity of the biofilm to the heavy metals are significantly improved.

Xiaoqi Fan, Yun Zhou, Xueke Jin et al.

Carbon Energy • 2021

Abstract For the performance improvement of microbial fuel cells (MFCs), the anode becomes a breakthrough point due to its influence on bacterial attachment and extracellular electron transfer (EET). On other level, carbon materials possess the following features: low cost, rich natural abundance, good thermal and chemical stability, as well as tunable surface properties and spatial structure. Therefore, the development of carbon materials and carbon‐based composites has flourished in the anode of MFCs during the past years. In this review, the major carbon materials used to decorate MFC anodes have been systematically summarized, based on the differences in composition and structure. Moreover, we have also outlined the carbon material‐based hybrid biofilms and carbon material‐modified exoelectrogens in MFCs, along with the discussion of known strategies and mechanisms to enhance the bacteria‐hosting capabilities of carbon material‐based anodes, EET efficiencies, and MFC performances. Finally, the main challenges coupled with some exploratory proposals are also expounded for providing some guidance on the future development of carbon material‐based anodes in MFCs.

Hindatu Yusuf, Mohamad Suffian Mohamad Annuar, Ramesh Subramaniam et al.

Chemical Engineering & Technology • 2019

Abstract Hydrophobic bacterial polyhydroxyalkanoates were rendered amphiphilic by grafting with poly(ethylene glycol) methacrylate, followed by compositing with carbon nanotubes. The polymer graft composite as an anode material encouraged superior biofilm surface growth; thus enhancing electrochemical activities in microbial fuel cells and resulting in higher current and power densities. The internal resistance of the cell was greatly reduced due to improved electron transfer from the biofilm to the anode.

Tahira Yaqoob, Malika Rani, Arshad Mahmood et al.

Materials • 2021

MXene/Ag2CrO4 nanocomposite was synthesized effectively by means of superficial low-cost co-precipitation technique in order to inspect its capacitive storage potential for supercapacitors. MXene was etched from MAX powder and Ag2CrO4 spinel was synthesized by an easy sol-gel scheme. X-Ray diffraction (XRD) revealed an addition in inter-planar spacing from 4.7 Å to 6.2 Å while Ag2CrO4 nanoparticles diffused in form of clusters over MXene layers that had been explored by scanning electron microscopy (SEM). Energy dispersive X-Ray (EDX) demonstrated the elemental analysis. Raman spectroscopy opens the gap between bonding structure of as-synthesized nanocomposite. From photoluminence (PL) spectra the energy band gap value 3.86 eV was estimated. Electrode properties were characterized by applying electrochemical observations such as cyclic voltammetry along with electrochemical impedance spectroscopy (EIS) for understanding redox mechanism and electron transfer rate constant Kapp. Additionally, this novel work will be an assessment to analyze the capacitive behavior of electrode in different electrolytes such as in acidic of 0.1 M H2SO4 has specific capacitance Csp = 525 F/g at 10 mVs−1 and much low value in basic of 1 M KOH electrolyte. This paper reflects the novel synthesis and applications of MXene/Ag2CrO4 nanocomposite electrode fabrication in energy storage devices such as supercapacitors.

Elizabeth C. A. Trindade, Regina V. Antônio, Ricardo Brandes et al.

Journal of Applied Polymer Science • 2020

Abstract Microbial fuel cells (MFC) are of great interest for new sources of renewable energies from the waste of biomass and debris. This work aimed was to develop an anode electrode of the carbon fiber‐embedded of bacterial cellulose/polyaniline (CF/BC/PANI) nanocomposite for MFC applications. For this purpose, carbon fiber was wrapped onto bacterial cellulose (BC) fibers network during the BC synthesis. The CF/BC/PANI was obtained by polyaniline polymerization on the BC nanofibers as a scaffold. To characterize the electrode, scanning electron microscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis analysis were carried out. The electrical conductivity was determined by measuring the resistivity. MFC using the CF/BC/PANI electrode was monitored and the maximum current density generated was 0.009 mA/cm 2 . The results obtained from the CF/BC/PANI demonstrate great potential for the use as an MFC electrode, as well as a microenvironment favorable to a microbial biofilm formation.

Gopa Nandikes, Shaik Gouse Peera, Lakhveer Singh

Energies • 2021

Microbial fuel cells (MFCs) are biochemical systems having the benefit of producing green energy through the microbial degradation of organic contaminants in wastewater. The efficiency of MFCs largely depends on the cathode oxygen reduction reaction (ORR). A preferable ORR catalyst must have good oxygen reduction kinetics, high conductivity and durability, together with cost-effectiveness. Platinum-based electrodes are considered a state-of-the-art ORR catalyst. However, the scarcity and higher cost of Pt are the main challenges for the commercialization of MFCs; therefore, in search of alternative, cost-effective catalysts, those such as doped carbons and transition-metal-based electrocatalysts have been researched for more than a decade. Recently, perovskite-oxide-based nanocomposites have emerged as a potential ORR catalyst due to their versatile elemental composition, molecular mechanism and the scope of nanoengineering for further developments. In this article, we discuss various studies conducted and opportunities associated with perovskite-based catalysts for ORR in MFCs. Special focus is given to a basic understanding of the ORR reaction mechanism through oxygen vacancy, modification of its microstructure by introducing alkaline earth metals, electron transfer pathways and the synergistic effect of perovskite and carbon. At the end, we also propose various challenges and prospects to further improve the ORR activity of perovskite-based catalysts.

Zhengying Guo, Peng Xu, Shiqing Zhou et al.

Sensors • 2025

Excessive levels of heavy metal pollutants in the environment pose significant threats to human health and ecosystem stability. Consequently, the accurate and rapid detection of heavy metal ions is critically important. A AgNPs@CeO2/Nafion composite was prepared by dispersing nano-ceria (CeO2) in a Nafion solution and incorporating silver nanoparticles (AgNPs). The morphology, microstructure, and electrochemical properties of the modified electrode materials were systematically characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and cyclic voltammetry (CV). By leveraging the oxygen vacancies and high electron transfer efficiency of CeO2, the strong adsorption capacity of Nafion, and the superior conductivity of AgNPs, an AgNPs@CeO2/Nafion/GCE electrochemical sensor was developed. Under optimized conditions, trace Pb2+ in water was detected using square wave anodic stripping voltammetry (SWASV). The sensor demonstrated a linear response for Pb2+ within the concentration range of 1–100 μg·L−1, with a detection limit of 0.17 μg·L−1 (S/N = 3). When applied to real water samples, the method achieved recovery rates between 93.7% and 110.3%, validating its reliability and practical applicability.

Anh Vu Nguyen, Bin Lai, Lorenz Adrian et al.

Microbial Biotechnology • 2021

Summary Pseudomonas putida ( P. putida ) is a microorganism of interest for various industrial processes, yet its strictly aerobic nature limits application. Despite previous attempts to adapt P. putida to anoxic conditions via genetic engineering or the use of a bioelectrochemical system (BES), the problem of energy shortage and internal redox imbalance persists. In this work, we aimed to provide the cytoplasmic metabolism with different monosaccharides, other than glucose, and explored the physiological response in P. putida KT2440 during bioelectrochemical cultivation. The periplasmic oxidation cascade was found to be able to oxidize a wide range of aldoses to their corresponding (keto‐)aldonates. Unexpectedly, isomerization of the ketose fructose to mannose also enabled oxidation by glucose dehydrogenase, a new pathway uncovered for fructose metabolism in P. putida KT2440 in BES. Besides the isomerization, the remainder of fructose was imported into the cytoplasm and metabolized. This resulted in a higher NADPH/NADP + ratio, compared to glucose. Comparative proteomics further revealed the upregulation of proteins in the lower central carbon metabolism during the experiment. These findings highlight that the choice of a substrate in BES can target cytosolic and periplasmic oxidation pathways, and that electrode‐driven redox balancing can drive these pathways in P . putida under anaerobic conditions.

Pholoso Calvin Motsaathebe, Omolola Ester Fayemi

Nanomaterials • 2022

Ascorbic acid (AA) is an essential vitamin in the body, influencing collagen formation, as well as norepinephrine, folic acids, tryptophan, tyrosine, lysine, and neuronal hormone metabolism. This work reports on electrochemical detection of ascorbic acid (AA) in oranges using screen-print carbon electrodes (SPCEs) fabricated with multi-walled carbon nanotube- antimony oxide nanoparticle (MWCNT-AONP) nanocomposite. The nanocomposite-modified electrode displayed enhanced electron transfer and a better electrocatalytic reaction towards AA compared to other fabricated electrodes. The current response at the nanocomposite-modified electrode was four times bigger than the bare electrode. The sensitivity and limit of detection (LOD) at the nanocomposite modified electrode was 0.3663 [AA]/µM and 140 nM, respectively, with linearity from 0.16–0.640 μM and regression value R2 = 0.985, using square wave voltammetry (SWV) for AA detection. Two well-separated oxidation peaks were observed in a mixed system containing AA and serotonin (5-HT); and the sensitivity and LOD were 0.0224 [AA]/µA, and 5.85 µΜ, respectively, with a concentration range from 23 to 100 µM (R2 = 0.9969) for AA detection. The proposed sensor outperformed other AA sensors reported in the literature. The fabricated electrode showed great applicability with excellent recoveries ranging from 99 to 107 %, with a mean relative standard deviation (RSD) value of 3.52 % (n = 3) towards detecting AA in fresh oranges.

Thomas Fudge, Isabella Bulmer, Kyle Bowman et al.

Water • 2021

Traditional wastewater treatment methods have become aged and inefficient, meaning alternative methods are essential to protect the environment and ensure water and energy security worldwide. The use of microbial electrolysis cells (MEC) for wastewater treatment provides an innovative alternative, working towards circular wastewater treatment for energy production. This study evaluates the factors hindering industrial adoption of this technology and proposes the next steps for further research and development. Existing pilot-scale investigations are studied to critically assess the main limitations, focusing on the electrode material, feedstock, system design and inoculation and what steps need to be taken for industrial adoption of the technology. It was found that high strength influents lead to an increase in energy production, improving economic viability; however, large variations in waste streams indicated that a homogenous solution to wastewater treatment is unlikely with changes to the MEC system specific to different waste streams. The current capital cost of implementing MECs is high and reducing the cost of the electrodes should be a priority. Previous pilot-scale studies have predominantly used carbon-based materials. Significant reductions in relative performance are observed when electrodes increase in size. Inoculation time was found to be a significant barrier to quick operational performance. Economic analysis of the technology indicated that MECs offer an attractive option for wastewater treatment, namely greater energy production and improved treatment efficiency. However, a significant reduction in capital cost is necessary to make this economically viable. MEC based systems should offer improvements in system reliability, reduced downtime, improved treatment rates and improved energy return. Discussion of the merits of H2 or CH4 production indicates that an initial focus on methane production could provide a stepping-stone in the adoption of this technology while the hydrogen market matures.

Marie Abadikhah, Frank Persson, Anne Farewell et al.

ISME Communications • 2024

Abstract In microbial electrolysis cells (MECs), microbial communities catalyze conversions between dissolved organic compounds, electrical energy, and energy carriers such as hydrogen and methane. Bacteria and archaea, which catalyze reactions on the anode and cathode of MECs, interact with phages; however, phage communities have previously not been examined in MECs. In this study, we used metagenomic sequencing to study prokaryotes and phages in nine MECs. A total of 852 prokaryotic draft genomes representing 278 species, and 1476 phage contigs representing 873 phage species were assembled. Among high quality prokaryotic genomes (>95% completion), 55% carried a prophage, and the three Desulfobacterota spp. that dominated the anode communities all carried prophages. Geobacter anodireducens, one of the bacteria dominating the anode communities, carried a CRISPR spacer showing evidence of a previous infection by a Peduoviridae phage present in the liquid of some MECs. Methanobacteriaceae spp. and an Acetobacterium sp., which dominated the cathodes, had several associations with Straboviridae spp. The results of this study show that phage communities in MECs are diverse and interact with functional microorganisms on both the anode and cathode.

Dilan Akagunduz, Rumeysa Cebecioglu, Murat Ozdemir et al.

Water Science and Technology • 2021

Abstract In this study, hydrogen production was analyzed along with methane and carbon dioxide generation using paroxetine, venlafaxine, and o-desmethylvenlafaxine (ODV) as substrates in single-chamber microbial electrolysis cells (MECs). Combinations of all three drugs were examined at concentrations of 750 ng/mL and 170 ng/mL. At the beginning of MEC operations using a 750 ng/mL mixture of drugs, there was no hydrogen or methane, but carbon dioxide was detected. When the concentration of the drug mixture was reduced to 170 ng/mL, MECs produced hydrogen and methane gas. Removal of the drugs during MEC operations was also analyzed using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Paroxetine, venlafaxine and ODV drugs were removed up to 99% by MECs. In conclusion, MECs could offer an alternative treatment method for wastewaters containing psychoactive pharmaceuticals with the added benefit of fuel hydrogen generation.

Hasika Suresh, Rhea Patel, Kundan Saha et al.

ECS Meeting Abstracts • 2024

Promoting extracellular electron transfer (EET) in bacteria has many widespread applications including wastewater treatment and environmental remediation. With the development of synthetic biology technologies that can alter microbial electron transfer routes and enhance their electrogenic capacity, there is a need for high throughput systems to identify the responsible genes and the consequent metabolic pathways in an expeditious way. Conventional platforms utilizing single electrodes, or electrochemical cells, and colorimetric detection suffer from low sensitivity and low throughput. Moreover, they require bulky equipment for readout and fluid handling. Moving towards a nuanced miniaturized electrochemical detection, we propose individually addressable microwells used to monitor electron flux from EET-capable bacteria with the ability to screen a large number of electroactive bacteria for various applications. Materials and method : The device is simple and fabricated with cost-effective electrodes. Carbon felt is used as the working electrode to improve bacterial entrapment and assist in capturing maximum electrons donated by the electroactive bacteria. Silver-silver chloride ink (Ag/AgCl) as the reference electrode will help maintain the potential of with respect to the working electrode. Conductive carbon ink as the counter electrode will promote current collection. The proposed device has the elements of a traditional three electrode system arranged in two different planes resulting in a 3D configuration of electrodes. The reference and counter electrode are on the bottom plane with acrylic wells housed right above each electrode pair, while the working electrode is used in the cross-bar architecture from the top plane as shown in Figure 1(a). The fabrication steps are illustrated in Figure 1(b). This system can be scaled to have 10000 microwells on a single platform with individual addressability of each micro-well array. With this layout, connections from the innermost wells can be drawn effortlessly without any signal damping from the surrounding wells. As a proof of concept, we have fabricated a 9 by 9 array (20cm by 20 cm) as shown in Figure 1(a) . Five strains of Shewanella oneidensis MR-1, the wild type organism and four modified strains overexpressing variants of MtrA (unmodified MtrA, IV-205, IV-261 and an empty vector), were screened for their current producing capacity [1]. Results: A bacterial load of OD 600 = 0.065 was sufficient to give a reliable current signal. For each strain, the working electrode was biased at 0.205 V with respect to the reference electrode (Ag/AgCl), and the resulting chronoamperometry signal was recorded as shown in Figure 1(c) . The values obtained helped identify the current-producing capacity of each mutant. Among them, the highest peak current was given by mtr A + (20 μA), and IV – 261 gave a low peak current (2 μA) within 3 minutes, validating the difference in the genetic make-up and EET capabilities. Technical and biological replicates were also conducted for all the 5 strains. The average standard deviation for the technical and biological replicates (n=3, OD 600 =0.065) was 0.09 μA and 0.56 μA respectively. A similar current trend for the same set of strains was obtained by Ian et al., [1] using a traditional bioelectrochemical system, thus validating our platform’s functionality and integrity. This system allows for parallel screening of wild type and mutant variations of multiple electroactive bacteria as demonstrated. The high throughput feature enabled by this device can also find application to characterize mutants generated by directed evolution workflows. Additionally, mechanical and electrical multiplexing can further improve the electronic instrumentation and connections between the wells for parallel readout and will also minimize human intervention during the current measurements. Chronoamperometry measurements is an important technique to characterize EET. Thus, a low-cost system like ours will help do that in a shorter time frame with minimal bacterial inoculum and for a larger number of electroactive bacterial species. In conclusion, we aim to show that a 3D carbon felt platform is miniaturized, and can be scaled to understand and characterize EET from electroactive bacteria in a high throughput manner. References Ian J. Campbell, Joshua T. Atkinson, Matthew D. Carpenter, Dru Myerscough, Lin Su, Caroline M. Ajo-Franklin, and Jonathan J. Silberg Biochemistry 2022 61 (13), 1337-1350 Figure 1

N I I M Jamlus, M N Masri, S K Wee et al.

IOP Conference Series: Earth and Environmental Science • 2021

Abstract Electroactive bacteria can transfer electrons to electrodes to generate electricity in the microbial fuel cell (MFC). Electroactive bacteria can generate energy for growth via the oxidation of organic compounds and transfer electrons to the electrodes that serve as the terminal electron acceptor. In this study, electricity generation in a double chamber evaluated MFC by four newly isolated electroactive bacteria strains (ESPK 22, ESPK 26, KP20, and KP22). ESPK22 and ESPK26 were previously identified as gram-positive Bacillus genera, while KP20 and KP22 belong to gram-negative Klebsiella genera. Among all the strains tested, the gramnegative KP20 strain shows the highest electricity generation value is 222.08 mV and the lowest electricity generation was ESPK26 of 44.82 mV.

Najwa Najihah Mohamad Daud, Mohamad Nasir Mohamad Ibrahim, Asim Ali Yaqoob et al.

Fuel • 2024

Ashish Yewale, Ravi N. Methekar, Shailesh G. Agrawal

ECS Meeting Abstracts • 2018

Sustainability and resource management is one of the major concerns for scientific community now days. In this context, in many fields of research, the focus is centred on the re-utilization of used resources with no further damage to the environment. Microbial fuel cell (MFC) is one of the technologies, where electricity is generated from waste-water. MFC is an electrochemical device that converts organic matter directly into the electricity with high efficiency. MFCs offer certain advantages such as minimum sludge production, cost effective and operation at normal condition. Despite its wide range of potential applications and ease of feed stocks, commercialisation of this technology did not realized till now 1 . The major limitations for the commercialization are the scale up of the process 2 and continuous operations. To perform continuous operation for longer time, it is extremely important to understand the dynamics of the system. Dynamics of the system can be understood by performing exhaustive experiments and analysing the data thus obtained. But performing exhaustive experiments is a time consuming as well expensive task. The other approach is to model the system to understand the dynamics. In literature very few researcher worked on the modeling of continuous microbial fuel cell (CMFC). Although batch modeling of MFC have been reported earlier, a very few studies had focused on understanding the dynamics of the system. First dynamic study was carried out by Zhang et al 3 , and there model is based on electron transfer using mediator. Later, Picioreanu et al 4 modeled the bio-film development on the anode electrode in MFC. Marcus et al 5 and Pinto et al 6 developed 1-D model for multispecies electron donor and acceptor for bio-film anode based on the material balance, Ohm’s law and Nernst-Monod kinetics to describe the rate of electron donor oxidation. In 2017, Esfandyari et al 7 , developed batch process model considering direct electron transfer through bio-film to the electron acceptor. In this talk, we will present a continuous model developed for MFC and dynamic analysis of potential controlled variables. Dynamic analysis will provide deeper insights of the various physical phenomena of the microbial fuel cell. In present work, model presented by Esfandyari et al 7 which is a batch model is taken as the basis. Batch model developed in this work is validated with the work of Esfandyari 7 and Picioreanu et al 4 for typical dynamic responses. The batch model is then converted into the dual chamber continuous model. In continuous model, substrate (Lactate) and oxygen is continuously fed to the anode and cathode chamber respectively as shown in Figure 1. Coolant is supplied through the jacket to maintain the required operating temperature of the cell. Bacteria species Shewanella is used as the catalyst to oxidise electron donor. The electrons produced are then reaching the cathode electrode via external circuit producing the power. Protons migrate to the cathode through the proton exchange membrane. In the cathode chamber, transferred electrons and migrated protons are reacted with dissolved oxygen to produce water. To understand the dynamic of the MFC, the step change study of the important parameters i.e. substrate concentration, current produced and coolant flow have been simulated. The simulation result of this model is shown in Figure 2, where time variations of the current shows first order dynamic. The settling time observed to be approximately 20 days. It is also noted that the current obtained from the same size of fuel cell in continuous system is higher than the batch. Once the impact of pH is accounted into the model, the dynamic analysis with respective various potential manipulated variables i.e. pH of the solution, flow rate of the substrate and coolant flow rate will be studied to get further insight of the microbial fuel cell. The model, thus developed will be used as a system for devising an effective control and optimization strategies for the microbial fuel cell. References: J. Chouler, G. Padgett, P. Cameron, K. Peruss, M. Titirici, I. Ieropoulos, and M. Lorenzo, Electrochimica Acta, 196 , 89-98,(2016) S. Choi, Biosensors and Bioelectronic , 69 , 8-25 (2015). X. Zhang and A. Halme, B iotechnology Letters , 17 (8), 809-814 (1995). C. Picioreanua, I. Head, K. Katuri, M. van Loosdrecht, K. Scott, Water Research , 41 , 2921-2940 (2007). A. Marcus, C. Torres, B. Rittmann, Biotechnology and Bioengineering , 98 (6), 1171-1182 (2007). R. Pinto, B. Srinivasan, M. Manuel, B. Tartakovsky, Bioresource Technology , 101 (14), 5256-5265 (2010). Figure 1

Jianfei Wang, Kexin Ren, Yan Zhu et al.

BioTech • 2022

The microbial fuel cell has been considered a promising alternative to traditional fossil energy. It has great potential in energy production, waste management, and biomass valorization. However, it has several technical issues, such as low power generation efficiency and operational stability. These issues limit the scale-up and commercialization of MFC systems. This review presents the latest progress in microbial community selection and genetic engineering techniques for enhancing microbial electricity production. The summary of substrate selection covers defined substrates and some inexpensive complex substrates, such as wastewater and lignocellulosic biomass materials. In addition, it also includes electrode modification, electron transfer mediator selection, and optimization of operating conditions. The applications of MFC systems introduced in this review involve wastewater treatment, production of value-added products, and biosensors. This review focuses on the crucial process of microbial fuel cells from preparation to application and provides an outlook for their future development.

Rodrigo Valladares Linares, Jorge Domínguez-Maldonado, Ernesto Rodríguez-Leal et al.

Water • 2019

The most important operational expense during wastewater treatment is electricity for pumping and aeration. Therefore, this work evaluated operational parameters and contaminant removal efficiency of a microbial fuel cell stack system (MFCSS) that uses no electricity. This system consists of (i) septic tank primary treatment, (ii) chamber for secondary treatment containing 18 MFCs, coupled to an energy-harvesting circuit (EHC) that stores the electrons produced by anaerobic respiration, and (iii) gravity-driven disinfection (sodium hypochlorite 5%). The MFCSS operated during 60 days (after stabilization period) and it was gravity-fed with real domestic wastewater from a house (5 inhabitants). The flow rate was 600 ± 100 L∙d−1. The chemical oxygen demand, biological oxygen demand, total nitrogen and total phosphorous were measured in effluent, with values of 100 ± 10; 12 ± 2; 9.6 ± 0.5 and 4 ± 0.2 mg∙L−1, and removal values of 86%, 87%, 84% and 64%, respectively. Likewise, an EHC (ultra-low energy consumption) was built with 6.3 V UCC® 4700 µF capacitors that harvested and stored energy from MFCs in parallel. Energy management was programmed on a microcontroller Atmega 328PB®. The water quality of the treated effluent complied with the maximum levels set by the Mexican Official Standard NOM-001-SEMARNAT-1996-C. A cost analysis showed that MFCSS could be competitive as a sustainable and energy-efficient technology for real domestic wastewater treatment.