Kô Takehara, Shinya Nakashima, Shinya Yamasaki et al.

Chemistry Letters • 2007

Abstract Bioluminescence reaction by bacterial luciferase has been successfully controlled by a controlled-potential electrolysis using platinum-mesh electrode to regenerate the reduced form of flavin mononucleotide (FMNH2), which is one of the substrates of the reaction. It was found that the regeneration of FMNH2 is facilitated by the adsorbed hydrogen atoms formed on a platinum electrode surface in the presence of phosphate ions.

L. Jourdin, S. Freguia, V. Flexer et al.

Environmental Science & Technology • 2016

The enhancement of microbial electrosynthesis (MES) of acetate from CO2 to performance levels that could potentially support practical implementations of the technology must go through the optimization of key design and operating conditions. We report that higher proton availability drastically increases the acetate production rate, with pH 5.2 found to be optimal, which will likely suppress methanogenic activity without inhibitor addition. Applied cathode potential as low as -1.1 V versus SHE still achieved 99% of electron recovery in the form of acetate at a current density of around -200 A m(-2). These current densities are leading to an exceptional acetate production rate of up to 1330 g m(-2) day(-1) at pH 6.7. Using highly open macroporous reticulated vitreous carbon electrodes with macropore sizes of about 0.6 mm in diameter was found to be optimal for achieving a good balance between total surface area available for biofilm formation and effective mass transfer between the bulk liquid and the electrode and biofilm surface. Furthermore, we also successfully demonstrated the use of a synthetic biogas mixture as carbon dioxide source, yielding similarly high MES performance as pure CO2. This would allow this process to be used effectively for both biogas quality improvement and conversion of the available CO2 to acetate.

A. Mulchandani, P. Mulchandani, I. Kaneva et al.

Analytical Chemistry • 1998

A potentiometric microbial biosensor for the direct measurement of organophosphate (OP) nerve agents was developed by modifying a pH electrode with an immobilized layer of Escherichia coli cells expressing organophosphorus hydrolase (OPH) on the cell surface. OPH catalyzes the hydrolysis of organophosporus pesticides to release protons, the concentration of which is proportional to the amount of hydrolyzed substrate. The sensor signal and response time were optimized with respect to the buffer pH, ionic concentration of buffer, temperature, and weight of cells immobilized using paraoxon as substrate. The best sensitivity and response time were obtained using a sensor constructed with 2.5 mg of cells and operating in pH 8.5, 1 mM HEPES buffer. Using these conditions, the biosensor was used to measure as low as 2 microM of paraoxon, methyl parathion, and diazinon. The biosensor had very good storage and multiple use stability. The use of cells with the metabolic enzyme expressed on cell surface as a biological transducer provides advantages of no resistances to mass transport of the analyte and product across the cell membrane and low cost due to elimination of enzyme purification, over the conventional microbial biosensors based on cells expressing enzyme intracellularly and enzyme-based sensors, respectively.

Yonggang Yang, Lei Yan, Jianhua Song et al.

RSC Advances • 2018

Sediment microbial fuel cells (SMFCs) is a promising technology for bioremediation, environmental monitoring and remote power supply in various water environments. Optimizing the anode/cathode surface area ratio (SAR a/c ) is important to enhance the power and decrease the cost of SMFCs. However, in fact, little information has been reported to optimize the SAR a/c of SMFCs in individual or stacked mode. This study comparatively analyzed the effects of electrode surface areas on the performance of single SMFCs and serial SMFC-stacks under separated- and connected-hydraulic conditions. The results suggested an optimal SAR a/c of 1 to 1.33 for both single and serial stacked SMFCs. Voltage reversal occurred in serial SMFC stacks with unoptimal SAR a/c but not in optimized stacks. The more the SAR a/c deviated from the optimal SAR a/c , the more easily the voltage reversal occurred ( i.e. lower reversal current). Compared to a separated-hydraulic environment, a connected-hydraulic environment showed no effect on the power generation of anode-limiting SMFC stacks but decreased the power generation and reversal current of cathode-limiting SMFCs, probably due to larger parasitic current. The results are important for the scale-up and application of SMFCs.

H. Ukeda, G. Wagner, U. Bilitewski et al.

Journal of Agricultural and Food Chemistry • 1992

A flow injection analysis system for the determination of short-chain fatty acids was developed incorporating a microbial electrode based on an oxygen electrode and Arthrobacter nicotiana immobilized behind a dialysis membrane. The system showed a high selectivity for short-chain fatty acids (C 4:0 -C 12:0 ), and the system response was linearly related to the concentration of butyric acid over the range 0.11-1.7 mM. The sampling freguency was approximately 20 samples/h at a carrier flow rate of 1.0 mL/min

M. T. Noori, G. Bhowmick, B. R. Tiwari et al.

Environmental Technology • 2018

ABSTRACT Waste generation from healthcare facilities now has become a concerning issue as it contain plastic and metals. Medicine wrappers are one of the major portions of healthcare solid waste, which impel intensive solid waste management practice due to fewer possibilities of deriving by-products. However, it can be recycled and used as an electrode material in microbial fuel cells (MFCs). An electrode material for application in MFCs is a crucial component, which governs total fabrication cost as well as power recovery, thus a cost-effective, stable and durable electrode is essential. In this endeavour, a new metallic (aluminium) waste material, a waste medicine wrapper (WMW), was evaluated for feasibility to be used as anode/cathode in MFCs. Based on the stability test under corrosive environment (1 N KCl), the WMW electrode sustained a maximum current of 46 mA during cyclic voltammetry (CV) and noted only 14% reduction in current at an applied voltage of +0.4 V after 2500 s in chronoamperometry, indicating its good stability. Power recovery from MFC using WMW was higher than the MFC using bare carbon felt as an anode (27 vs. 21 mW/m2). The entire analytical test results viz. CV, electrochemical impedance spectroscopy and power performance established WMW as an excellent anode rather than cathode material. GRAPHICAL ABSTRACT

Hao Zhu, Zhiwei Dong, Qiong Huang et al.

RSC Advances • 2019

Microbial electrosynthesis (MES) allows the transformation of CO2 into value-added products by coupling with renewable energy. The enhancement in the microbial activity and electron transfer rate via a new electrode modification method is essential for developing MES. Here, three groups of granular activated carbon decorated by Fe3O4 (Fe3O4/GAC) with mass fractions of 23%, 38% and 50% were prepared and compared with bare GAC. The volumetric acetate production rate of MES with Fe3O4/GAC-38% was the highest (0.171 g L−1 d−1), which was 1.4 times higher that of the control (bare GAC), and the final acetate concentration reached 5.14 g L−1 within 30 days. Linear sweep voltammetry and microbial community analyses suggested that Fe3O4/GAC facilitates extracellular electron transfer and improves the enrichment of electrochemically active bacteria. Fe3O4/GAC is an effective three-dimensional electrode material that enhances biofilm activity on GAC and improves MES efficiency.

T. Yamashita, Hiroshi Yokoyama

Biotechnology for Biofuels • 2018

BackgroundMetals are considered a suitable anode material for microbial fuel cells (MFCs) because of their high electrical conductivity. However, only a few types of metals have been used as anodes, and an extensive screening of metals has not yet been conducted. In this study, to develop a new metal anode for increased electricity generation in MFCs, 14 different metals (Al, Ti, Fe, Ni, Cu, Zn, Zr, Nb, Mo, Ag, In, Sn, Ta, and W) and 31 of their oxidized forms were comprehensively tested. Oxidized-metal anodes were prepared using flame oxidation, heat treatment, and electrochemical oxidation. The selected anodes were further evaluated in detail using air–cathode single-chambered MFCs.ResultsThe untreated Mo and electrochemically oxidized Mo anodes showed high averages of maximum power densities in the screening test, followed by flame-oxidized (FO) W, FO-Fe, FO-Mo, and Sn-based anodes. The untreated Mo and FO-W anodes were selected for further evaluation. X-ray analyses revealed that the surface of the Mo anode was naturally oxidized in the presence of air, forming a layer of MoO3, a known oxidation catalyst. A high maximum power density (1296 mW/m2) was achieved using the Mo anode in the MFCs, which was superior to that obtained using the FO-W anode (1036 mW/m2). The Mo anode, but not the FO-W anode, continued to produce current without detectable corrosion until the end of operation (350 days). Geobacter was abundant in both biofilms on the Mo and FO-W anodes, as analyzed by high-throughput sequencing of the 16S rRNA gene.ConclusionsThe screening test revealed that Mo, W, Fe, and Sn are useful MFC anode materials. The detailed analyses demonstrated that the Mo anode is a high-performance electrode with structural simplicity and long-term stability in MFCs. The anode can be easily prepared by merely shaping Mo materials to the desired forms. These properties would enable the large-scale preparation of the anode, required for practical MFC applications. This study also implies the potential involvement of Geobacter in the Mo and W cycles on Earth.

Lola Gonzalez Olias, P. Cameron, M. di Lorenzo

Frontiers in Energy Research • 2019

The growing use of herbicides in agriculture poses increasing concerns on the pollution of water systems worldwide. To be able to assess the presence of these compounds in waters and limit their impact on human health and ecosystems, the development of effective in-situ monitoring tools is key. Yet, many existing sensing technologies are not suitable for in-situ and remote applications, due to challenges in portability, durability, cost and power requirements. In this study, we explore for the first time the use of an algal-assisted cathode in a photosynthetic microbial fuel cell (p-MFC) as a self-powered dissolved oxygen probe for herbicides detection in water. The cathode is enriched with the alga Scenedesmus obliquus and two different electrode materials are tested, graphite felt and indium tin oxide, which mainly differ in porosity, surface roughness and transparency. Despite the much larger specific surface area of graphite felt compared to indium tin oxide, the current generated under light was only 10 times larger (109 ± 2µA vs. 10.5 ± 0.6 µA) and 8 times larger in the dark (37 ± 5 µA vs. 4.2 ± 0.6 µA). By generating a current output that correlates with the dissolved oxygen in the catholyte, the resulting p-MFCs could detect the EU legal atrazine concentration limit of 0.1 µg L-1. The use of graphite felt led to shorter response times and better sensitivity, as a result of the greater current baseline. In both cases, the current baseline was recovered after exposure of the sensor to frequent toxic events, thus showing the resilience of the cathodic biofilm and the potential of the p-MFCs for early warnings of herbicides pollution in water.

B. Logan, Emily Zikmund, Wulin Yang et al.

Environmental Science & Technology • 2018

Low solution conductivity is known to adversely impact power generation in microbial fuel cells (MFCs), but its impact on measured electrode potentials has often been neglected in the reporting of electrode potentials. While errors in the working electrode (typically the anode) are usually small, larger errors can result in reported counter electrode potentials (typically the cathode) due to large distances between the reference and working electrodes or the use of whole cell voltages to calculate counter electrode potentials. As shown here, inaccurate electrode potentials impact conclusions concerning factors limiting power production in MFCs at higher current densities. To demonstrate how the electrochemical measurements should be adjusted using the solution conductivity, electrode potentials were estimated in MFCs with brush anodes placed close to the cathode (1 cm) or with flat felt anodes placed further from the cathode (3 cm) to avoid oxygen crossover to the anodes. The errors in the cathode potential for MFCs with brush anodes reached 94 mV using acetate in a 50 mM phosphate buffer solution. With a felt anode and acetate, cathode potential errors increased to 394 mV. While brush anode MFCs produced much higher power densities than flat anode MFCs under these conditions, this better performance was shown primarily to result from electrode spacing following correction of electrode potentials. Brush anode potentials corrected for solution conductivity were the same for brushes set 1 or 3 cm from the cathode, although the range of current produced was different due to ohmic losses with the larger distance. These results demonstrate the critical importance of using corrected electrode potentials to understand factors limiting power production in MFCs.

Mohita Sharma, Y. Alvarez-Gallego, W. Achouak et al.

Journal of Materials Chemistry A • 2019

(a) Pictograph and (b) schematic representation of the placement of multiple working electrodes with a single counter electrode and reference electrode using an N'Stat setup and (c) the schematic of the potentiostat interface connection with the electrochemical cell.

R. Rossi, B. Cario, C. Santoro et al.

Environmental Science & Technology • 2019

Direct comparisons of microbial fuel cells based on maximum power densities are hindered by different reactor and electrode sizes, solution conductivities, and materials. We propose an alternative method here, the electrode potential slope (EPS) analysis, to enable quantitative comparisons based on anode and cathode area-based resistances and operating potentials. Using EPS analysis, the brush anode resistance ( RAn = 10.6 ± 0.5 mΩ m2) was shown to be 28% lower than the resistance of a 70% porosity diffusion layer (70% DL) cathode ( RCat = 14.8 ± 0.9 mΩ m2) and 24% lower than the solution resistance ( RΩ = 14 mΩ m2) (acetate in a 50 mM phosphate buffer solution). Using a less porous cathode (30% DL) did not impact the cathode resistance but did reduce the cathode performance due to a lower operating potential. With low-conductivity domestic wastewater ( RΩ = 87 mΩ m2), both electrodes had higher resistances [ RAn = 75 ± 9 mΩ m2, and RCat = 54 ± 7 mΩ m2 (70% DL)]. Our analysis of the literature using EPS analysis shows how electrode resistances can easily be quantified to compare system performance when the electrode distances are changed or the sizes of the electrodes are different.

M. S. Hamed, H. Majdi, Basim O. Hasan

ACS Omega • 2020

In recent decades, there has been huge interest in exploring cost-effective and sustainable ways for energy production using fuel cells. In this study, different electrode materials, namely, nickel, stainless steel, brass, and graphite were used to investigate the energy production in double chamber microbial fuel cells. Yeast microorganisms (MOs) (Saccharomyces cerevisiae) were used at different concentrations for electricity production under different operating conditions with glucose as a substrate. The produced current and potential of the electrode were measured for ranges of operating conditions such as MO concentration (1–8 g/L), flow velocity (0–600 rpm), and aeration of the catholyte. It was found that there was a different performance exhibited by each electrode material, with nickel and graphite giving the highest efficiency. Increasing the flow velocity and aeration in the cathode compartment led to increasing the produced current while the flow and aeration in the anode compartment had a negative effect on the produced current. Simultaneous aeration and agitation gave high produced current values, while high agitation with aeration reduced the efficacy. The increased concentration of substrate glucose showed different influences on the produced current depending on electrode materials.

R. Mickol, Brian J. Eddie, A. P. Malanoski et al.

Applied and Environmental Microbiology • 2021

Microbial electrochemical technologies (METs) rely on electroactive bacteria to catalyze energy-generating and energy storage reactions at electrodes. Known electroactive bacteria are not equally capable of both reactions, and METs are typically configured to be unidirectional. ABSTRACT Electroactive bacteria are living catalysts, mediating energy-generating reactions at anodes or energy storage reactions at cathodes via extracellular electron transfer (EET). The Cathode-ANode (CANode) biofilm community was recently shown to facilitate both reactions; however, the identities of the primary constituents and underlying molecular mechanisms remain unknown. Here, we used metagenomics and metatranscriptomics to characterize the CANode biofilm. We show that a previously uncharacterized member of the family Desulfobulbaceae, Desulfobulbaceae-2, which had <1% relative abundance, had the highest relative gene expression and accounted for over 60% of all differentially expressed genes. At the anode potential, differential expression of genes for a conserved flavin oxidoreductase (Flx) and heterodisulfide reductase (Hdr) known to be involved in ethanol oxidation suggests a source of electrons for the energy-generating reaction. Genes for sulfate and carbon dioxide reduction pathways were expressed by Desulfobulbaceae-2 at both potentials and are the proposed energy storage reactions. Reduction reactions may be mediated by direct electron uptake from the electrode or from hydrogen generated at the cathode potential. The Desulfobulbaceae-2 genome is predicted to encode at least 85 multiheme (≥3 hemes) c-type cytochromes, some with as many as 26 heme-binding domains, that could facilitate reversible electron transfer with the electrode. Gene expression in other CANode biofilm species was also affected by the electrode potential, although to a lesser extent, and we cannot rule out their contribution to observed current. Results provide evidence of gene expression linked to energy storage and energy-generating reactions and will enable development of the CANode biofilm as a microbially driven rechargeable battery. IMPORTANCE Microbial electrochemical technologies (METs) rely on electroactive bacteria to catalyze energy-generating and energy storage reactions at electrodes. Known electroactive bacteria are not equally capable of both reactions, and METs are typically configured to be unidirectional. Here, we report on genomic and transcriptomic characterization of a recently described microbial electrode community called the Cathode-ANode (CANode). The CANode community is able to generate or store electrical current based on the electrode potential. During periods where energy is not needed, electrons generated from a renewable source, such as solar power, could be converted into energy storage compounds to later be reversibly oxidized by the same microbial catalyst. Thus, the CANode system can be thought of as a living “rechargeable battery.” Results show that a single organism may be responsible for both reactions demonstrating a new paradigm for electroactive bacteria.

S. Spiess, J. Kucera, H. Seelajaroen et al.

Biosensors • 2021

Sustainable technologies for energy production and storage are currently in great demand. Bioelectrochemical systems (BESs) offer promising solutions for both. Several attempts have been made to improve carbon felt electrode characteristics with various pretreatments in order to enhance performance. This study was motivated by gaps in current knowledge of the impact of pretreatments on the enrichment and microbial composition of bioelectrochemical systems. Therefore, electrodes were treated with poly(neutral red), chitosan, or isopropanol in a first step and then fixed in microbial electrolysis cells (MECs). Four MECs consisting of organic substance-degrading bioanodes and methane-producing biocathodes were set up and operated in batch mode by controlling the bioanode at 400 mV vs. Ag/AgCl (3M NaCl). After 1 month of operation, Enterococcus species were dominant microorganisms attached to all bioanodes and independent of electrode pretreatment. However, electrode pretreatments led to a decrease in microbial diversity and the enrichment of specific electroactive genera, according to the type of modification used. The MEC containing isopropanol-treated electrodes achieved the highest performance due to presence of both Enterococcus and Geobacter. The obtained results might help to select suitable electrode pretreatments and support growth conditions for desired electroactive microorganisms, whereby performance of BESs and related applications, such as BES-based biosensors, could be enhanced.

Shiv Singh, Amol Pophali, R. Omar et al.

Chemical Communications • 2021

A facile and single-step nickel oxide-dispersed in situ grown 3-D graphitic forest engrained carbon foam (NiO-CNF-CF)-based electrode was fabricated for high-performance microbial fuel cells (MFCs). The metal oxide, graphitic contents, biocompatibility, stability and large surface area available in the material for biofilm formation rendered the prepared electrode competent for wastewater treatment and bioenergy (0.79 V and 1.955 W m-2) generation with a coulombic efficiency of 85.66%.

Zi‐Ai Xu, Xiao‐Meng Ma, Yu-tong Shi et al.

International Journal of Energy Research • 2022

Microbial electrocatalysis showed great potential for waste energy harvesting and CO2 upgrading. The conventional electrodes with three‐dimensional (3D) architectures hold promise for efficient microbial electrocatalysis, but they were designed as macroporous structure with microfibers in all three dimensions, which could not concurrently improve the mass transfer and microbes penetration. In this study, a high‐performance 3D electrode assembled from bulk two‐dimensional (2D) structures derived from natural wood was fabricated by hydrothermal treatment for surface activation and followed by pyrolysis. This 2D/3D hybrid structure guaranteed high surface area and multi‐transportation‐pathways, which endowed the wood electrode attracted more bacterial cells, facilitated the interfacial electron transfer between cells and electrode. As a result, the wood electrode delivered 8.3 times higher power output (483 vs 52 mW/m2) and 3.1 times higher formic acid production (3.3 vs 0.8 mM) than conventional carbon cloth electrode in microbial electrocatalysis system. This work provided new strategy for high‐performance wood electrode fabrication and unveiled the mechanism of microbial electrocatalysis with natural biomass electrode.

G. S. Lekshmi, K. Bazaka, S. Ramakrishna et al.

Materials Horizons • 2022

Microbial electrosynthesis (MES) is a sustainable approach to address greenhouse gas (GHG) emissions using anthropogenic carbon dioxide (CO2) as a building block to create clean fuels and highly valuable chemicals. The efficiency of MES-based CO2 conversion is closely related to the performance of electrode material and, in particular, the cathode for which carbonaceous materials are frequently used. Compared to expensive metal electrodes, carbonaceous materials are biocompatible with a high specific surface area, wide range of possible morphologies, and excellent chemical stability, and their use can maximize the growth of bacteria and enhance electron transfer rates. Examples include MES cathodes based on carbon nanotubes, graphene, graphene oxide, graphite, graphite felt, graphitic carbon nitride (g-C3N4), activated carbon, carbon felt, carbon dots, carbon fibers, carbon brushes, carbon cloth, reticulated vitreous carbon foam, MXenes, and biochar. Herein, we review the state-of-the-art MES, including thermodynamic and kinetic processes that underpin MES-based CO2 conversion, as well as the impact of reactor type and configuration, selection of biocompatible electrolytes, product selectivity, and the use of novel methods for stimulating biomass accumulation. Specific emphasis is placed on carbonaceous electrode materials, their 3D bioprinting and surface features, and the use of waste-derived carbon or biochar as an outstanding material for further improving the environmental conditions of CO2 conversion using carbon-hungry microbes and as a step toward the circular economy. MES would be an outstanding technique to develop rocket fuels and bioderived products using CO2 in the atmosphere for the Mars mission.

Xiaojing Liu, Kang Zhang, Yidan Sun et al.

SusMat • 2023

Upgrading of atmospheric CO2 into high‐value‐added acetate using renewable electricity via electrocatalysis solely remains a great challenge. Here, inspired by microbial synthesis via biocatalysts, we present a coupled system to produce acetate from CO2 by bridging inorganic electrocatalysis with microbial synthesis through formate intermediates. A 3D Bi2O3@CF integrated electrode with an ice‐sugar gourd shape was fabricated via a straightforward hydrothermal synthesis strategy, wherein Bi2O3 microspheres were decorated on carbon fibers. This ice‐sugar gourd‐shaped architecture endows electrodes with multiple structural advantages, including synergistic contribution, high mass transport capability, high structural stability, and large surface area. Consequently, the resultant Bi2O3@CF exhibited a maximum Faradic efficiency of 92.4% at −1.23 V versus Ag/AgCl for formate generation in 0.5 M KHCO3, exceeding that of Bi2O3/CF prepared using a conventional electrode preparation strategy. Benefiting from the high formate selectivity, unique architecture, and good biocompatibility, the Bi2O3@CF electrode attached with enriched CO2‐fixing electroautotrophs served as a biocathode. As a result, a considerable acetate yield rate of 0.269 ± 0.009 g L−1 day−1 (a total acetate yield of 3.77 ± 0.12 g L−1 during 14‐day operation) was achieved in the electrochemical–microbial system equipped with Bi2O3@CF.

Xiaojun Han, Chao Li, Daming Yong

Sensors and Materials • 2019

A whole-cell-based amperometric biosensor was fabricated using Escherichia coli cells immobilized on a glassy carbon electrode to detect mercury, cadmium, and zinc ions. E. coli cells were immobilized by the cross-linking method using bovine serum albumin (BSA) in glutaraldehyde (GA) vapor. The principle of the microbial electrode sensor is the inhibition of alkaline phosphatase (AP) enzyme activity by heavy metal ions. Therefore, by monitoring the oxidation current of the product generated by AP in a metal ion solution, its concentration was determined. The Michaelis–Menten constant (Km) for AP was evaluated to be 2.23 mmol/L. The E. coli-based biosensor has detection limits of 5.58 × 10−11 mol/L for mercury ion, 5.10 × 10−10 mol/L for cadmium ion, and 1.38 × 10−9 mol/L for zinc ion. The prepared biosensor can respond steadily for seven days.

Nobuyoshi Kitajima, Kana Ueda, Takayuki Ohshima et al.

Textile Research Journal • 2007

We have been studying pulsed electric field (PEF) inactivation of various bacteria, which is based on the destruction of biological membrane due to applying pulsed electric field. In this study, we report a novel treatment system based on the textile electrode, combination of polyester fiber and 0.2 mmφ metal wire. The efficiency of PEF inactivation of Escherichia coli cells depended on the peak voltage and the conductivity of the target solutions. Higher efficiency of PEF sterilization could be achieved with 7 kV of peak voltage and lower solution conductivity. When the solution conductivity was lower, some materials, which seemed to be bacterial residue, were sedimented on high voltage electrode.

Y Maoyu, Y Zhang

Applied and Environmental Microbiology • 1989

Microbial cell populations in polluted water were determined by using a fuel cell-type electrode. The electrode was composed of a Pt anode, a Pt-K3Fe(CN)6-K4Fe(CN)6 cathode, and a cation-exchange membrane for separating two electrode compartments. The principle of microbial cell number determination is based on sensing a redox dye reduced by microorganisms with the electrode. Sample solutions containing microorganisms, a redox dye (thionine), and peptone were purged with oxygen-free nitrogen during the determination. A linear relationship was obtained between the increasing rate of current and the number of microbial cells measured by the colony count method above 10(4) cells per ml. The determination time varied with the number of microbial cells determined from 20 to 60 min for 3.6 x 10(6) and 3.6 x 10(4) cells per ml, respectively.

Atieh Ebrahimi, Daryoush Yousefi Kebria, Ghasem Najafpour Darzi

Water Science and Technology • 2017

The microbial desalination cell (MDC) is known as a newly developed technology for water and wastewater treatment. In this study, desalination rate, organic matter removal and energy production in the reactors with and without desalination function were compared. Herein, a new design of plain graphite called roughened surface graphite (RSG) was used as the anode electrode in both microbial fuel cell (MFC) and MDC reactors for the first time. Among the three type of anode electrodes investigated in this study, RSG electrode produced the highest power density and salt removal rate of 10.81 W/m3 and 77.6%, respectively. Such a power density was 2.33 times higher than the MFC reactor due to the junction potential effect. In addition, adding the desalination function to the MFC reactor enhanced columbic efficiency from 21.8 to 31.4%. These results provided a proof-of-concept that the use of MDC instead of MFC would improve wastewater treatment efficiency and power generation, with an added benefit of water desalination. Furthermore, RSG can successfully be employed in an MDC or MFC, enhancing the bio-electricity generation and salt removal.

Hooshyar Hossini, Abbas Rezaee, Bita Ayati et al.

RSC Advances • 2015

In this study, the feasibility of ammonium and total nitrogen removal from aqueous solution using a simultaneous nitrification and denitrification process was studied in a membraneless bio-electrochemical system with a novel electrode.

Tadashi Matsunaga, Isao Karube, Shuichi Suzuki

Applied and Environmental Microbiology • 1979

Determinations of microbial populations were carried out by using a new electrode system composed of two electrodes. Each electrode was constructed from a platinum anode and a silver peroxide cathode. The anode of the reference electrode was covered with cellulose dialysis membrane. The response time of the electrode system was 15 min in culture broth, and current differences between the two electrodes were proportional to populations of microbial cells in cultures of Saccharomyces cerevisiae and Lactobacillus fermentum . Current differences were reproducible; the average relative error was 5%. Furthermore, cell populations of S. cerevisiae in a fermentor could be continuously estimated by using this electrochemical method.

Motohiko Hikuma, Tatsuru Kubo, Takeo Yasuda et al.

Biotechnology and Bioengineering • 1979

Abstract A microbial electrode consisting of immobilized microorganisms, a gas permeable Teflon membrane, and an oxygen electrode was prepared for the continuous determination of methyl and ethyl alcohols. Immobilized Trichosporon brassicae was employed for a microbial electrode sensor for ethyl alcohol. When a sample solution containing ethyl alcohol was injected into a microbial electrode system, the current of the electrode decreased markedly with time until a steady state was reached. The response time was within 10 min by the steady state method and within 6 min by the pulse method. A linear relationship was observed between the current decrease and the concentration of ethyl alcohol below 22.5 mg/liter. The current was reproducible within ± 6% of the relative error when a sample solution containing 16.5 mg/liter ethyl alcohol. The standard deviation was 0.5 mg/liter in 40 experiments. The selectivity of the microbial electrode sensor for ethyl alcohol was satisfactory. The microbial electrode sensor was applied to a fermentation broth of yeasts and satisfactory comparative results were obtained (correlation coefficient 0.98). The current output of the microbial electrode sensor was almost constant for more than three weeks and 2100 assays. A microbial electrode sensor using immobilized bacteria for methyl alcohol was also described.

N. Thepsuparungsikul, N. Phonthamachai, H. Y. Ng

Water Science and Technology • 2012

The microbial fuel cell (MFC) is a novel and innovative technology that could allow direct harvesting of energy from wastewater through microbial activity with simultaneous oxidation of organic matter in wastewater. Among all MFC parts, electrode materials play a crucial role in electricity generation. A variety of electrode materials have been used, including plain graphite, carbon paper and carbon cloth. However, these electrode materials generated only limited electricity or power. Recently, many research studies have been conducted on carbon nanotubes (CNTs) because of their unique physical and chemical properties that include high conductivity, high surface area, corrosion resistance, and electrochemical stability. These properties make them extremely attractive for fabricating electrodes and catalyst supports. In this study, CNT-based electrodes had been developed to improve MFC performance in terms of electricity generation and treatment efficiency. Multi-walled carbon nanotubes (MWCNTs) with carboxyl groups have been employed to fabricate electrodes for single-chamber air-cathode MFCs. The quality of the prepared MWCNTs-based electrodes was evaluated by morphology, electrical conductivity and specific surface area using a field emission scanning electron microscope, four-probe method and Brunauer–Emmerr–Teller method, respectively. The performance of MFCs equipped with MWCNT-based electrodes was evaluated by chemical analysis and electrical monitoring and calculation. In addition, the performance of these MFCs, using MWCNTs as electrodes, was compared against that using commercial carbon cloth.

Isao Karube, Tadashi Matsunaga, Satoshi Mitsuda et al.

Biotechnology and Bioengineering • 1977

Abstract Two different types of biochemical oxygen demand (BOD) sensors using microbial electrodes were prepared. First, a microbial electrode using the bacteria–collagen membrane and oxygen electrode was used for the determination of BOD. When the electrode was inserted in a sample solution containing glucose and glutamic acid (model waste water), the current of the electrode decreased markedly with time until a steady state was reached. A linear relationship was observed between the steady state current and the concentration of the standard solution containing glucose–glutamic acid or the BOD of the solution. The BOD of industrial waste waters can be estimated within 15 min by using the microbial electrode. No decrease in current output was observed over a ten day period. The reproducibility was determined using the same sample (10% of the standard solution) and was found to be 26.2 ± 2.0 μA (7.5% of the relative standard deviation). Next, a biofuel cell utilizing microbial electrode (immobilized Clostridium butyricum –platinum electrode) was applied to the estimation of the BOD of waste waters. The current of the biofuel cell was decreased markedly with time until a steady state was reached. The steady state current was in all cases attained within 30–40 min at 37°C. A linear relationship was obtained between the steady state current and BOD. The BOD of industrial waste waters can be estimated by using the biofuel cell. Relative error of the BOD estimation was within ±10%. The current output of the biofuel cell was almost constant for 30 days.

Cesar Iñiguez, Roumen Zlatev, Margarita Stoytcheva et al.

ECS Transactions • 2011

The Reversible Hydrogen Electrode (RHE) potential depends on the pH and the H2 pressure which determines the disolved hydrogen concentration according to the Henry law. RHE was applied as hydrogen sensor for real time bacterial hydrogen production rate evaluation employing the photosynthetic Rodobacter Capsulatus strain IR3 in 10 ml reactor containing RCV medium. The reliable determination of the produced H2 volume for determination of the process rate requires big reactor volumes since the H2 production rate is small, measured in mL/hour and the precise measurements of small gas volumes is very complicated. The RHE potential monitoring however allows real time determination of the generated H2 and hence the process rate without consumption of great reagent amounts.

T. Sangeetha, M. Muthukumar

Environmental Progress &amp; Sustainable Energy • 2013

Microbial fuel cells (MFC) are hybrid bioelectrochemical devices, which generate electrical energy through the oxidation of organic matter catalyzed by bacteria. In this research, the influence of electrode distance and different electrode materials on power production and chemical oxygen demand (COD) removal using raw sago‐processing wastewater were studied. Effect of electrode distance on MFC performance was carried out by varying it as 10, 12 and 15 cm. This study revealed that electrode distance of 10 cm resulted in increased power production with a voltage of 900 mV (millivolts), current of 9.0 mA (milliamps) at 100 Ω and COD removal of 94% compared to electrode distance of 12 and 15 cm. Graphite electrodes were good in power production compared to aluminum, stainless steel, and iron electrodes. Biofilm examination on the anode showed the presence of gram‐negative rod ( E. coli) bacteria which might have contributed for power production . © 2012 American Institute of Chemical Engineers Environ Prog, 32: 390‐395, 2013

Matthew A. Williams, Justin P. Koeln, Andrew G. Alleyne

Volume 1: Adaptive and Intelligent Systems Control; Advances in Control Design Methods; Advances in Non-Linear and Optimal Control; Advances in Robotics; Advances in Wind Energy Systems; Aerospace Applications; Aerospace Power Optimization; Assistive Robotics; Automotive 2: Hybrid Electric Vehicles; Automotive 3: Internal Combustion Engines; Automotive Engine Control; Battery Management; Bio Engineering Applications; Biomed and Neural Systems; Connected Vehicles; Control of Robotic Systems • 2015

This two-part paper presents the development of a hierarchical control framework for the control of power flow throughout large-scale systems. Part II presents the application of the graph-based modeling framework and three-level hierarchical control framework to the power systems of an aircraft. The simplified aircraft system includes an engine, electrical, and thermal systems. A graph based approach is used to model the system dynamics, where vertices represent capacitive elements such as fuel tanks, heat exchangers, and batteries with states corresponding to the temperature and state of charge. Edges represent power flows in the form of electricity and heat, which can be actuated using control inputs. The aircraft graph is then partitioned spatially into systems and subsystems, and temporally into fast, medium, and slow dynamics. These partitioned graphs are used to develop models for each of the three levels of the hierarchy. Simulation results show the benefits of hierarchical control compared to a centralized control method.

Chen Zhang, Tao Yang, Wei Gao et al.

Volume 1: Additive Manufacturing; Manufacturing Equipment and Systems; Bio and Sustainable Manufacturing • 2019

Abstract The growing resource shortage and environmental concerns have forced mankind to develop and utilize renewable energy sources. The penetration of solar photovoltaic (PV) power in the electricity market has been increasing over the past few decades due to its low construction costs, zero pollution nature, and enormous support from governments. However, the intermittency and randomness of PV power also cause huge grid fluctuations which limit its integration in the system. An accurate forecasting of solar PV power generation and optimization of operation and maintenance (O&amp;M) management are essential for further development of the solar PV farms. A great number of related researches have been done in recent years. A review of PV power generation forecasting techniques together with their brief applications on the optimization of O&amp;M management is presented in this paper. Machine learning methods are thought to be the most suitable at the present stage because of their ease of implementation and their capability in processing non-linear, complex data sets. Typical forecasting accuracy measures are summarized and further applications of PV power forecasting on the O&amp;M management are also presented.

Fulai Yao, Qingbin Gao

Volume 1: Aerospace Applications; Advances in Control Design Methods; Bio Engineering Applications; Advances in Non-Linear Control; Adaptive and Intelligent Systems Control; Advances in Wind Energy Systems; Advances in Robotics; Assistive and Rehabilitation Robotics; Biomedical and Neural Systems Modeling, Diagnostics, and Control; Bio-Mechatronics and Physical Human Robot; Advanced Driver Assistance Systems and Autonomous Vehicles; Automotive Systems • 2017

This paper proposes a novel approach for optimizing the total power output of a generalized power station with identical generators by analyzing the characteristics of the efficiency function. The introduced treatment yields the maximum total power supply and the maximum overall efficiency for the generalized power station. To achieve these, the input factor for each generator is kept the same, and the optimal switch points are selected to be the same efficiency points of two operating methods.

Rahul Sarpeshkar

• 2010

This book provides, for the first time, a broad and deep treatment of the fields of both ultra low power electronics and bioelectronics. It discusses fundamental principles and circuits for ultra low power electronic design and their applications in biomedical systems. It also discusses how ultra energy efficient cellular and neural systems in biology can inspire revolutionary low power architectures in mixed-signal and RF electronics. The book presents a unique, unifying view of ultra low power analog and digital electronics and emphasizes the use of the ultra energy efficient subthreshold regime of transistor operation in both. Chapters on batteries, energy harvesting, and the future of energy provide an understanding of fundamental relationships between energy use and energy generation at small scales and at large scales. A wealth of insights and examples from brain implants, cochlear implants, bio-molecular sensing, cardiac devices, and bio-inspired systems make the book useful and engaging for students and practicing engineers.

Jayesh M. Sonawane, C. Ezugwu, P. Ghosh

ACS Sensors • 2020

Environmental pollution has been a continuous threat to sustainable development and global well-being. It has become a significant concern worldwide to combat the ecological crisis using low-cost innovative technologies. Biological oxygen demand (BOD) is a key indicator to comprehend the quality of water to guarantee environmental safety and human health; however, none of the present technology is capable of online monitoring of the water at the source. Microbial fuel cell (MFC) is a promising technology for simultaneous power generation and wastewater treatment. MFCs have also shown fascinating applications to measure and detect the toxic pollutants present in wastewater. These are the bioreactors where exoelectrogenic microorganisms catalyze the conversion of the inherent chemical energy stored in organic compounds to electrical energy. Sensors employ energy conversion to measure BOD, which is considered an international index for the detection of organic material load present in wastewater. The MFC based BOD sensors have gone through a wide range of advancement from mediator to mediator-less, double chamber to single-chamber, and large size to miniature. There have been detailed studies to improve the accuracy and reproducibility of the sensors for commercial applications. Additionally, multi-stage MFC based BOD biosensors and miniature MFC-BOD sensors have also been ubiquitous in recent years. A considerable amount of work has been carried out to improve the performance of these devices by fabricating the proton exchange membranes and altering catalysts at the cathode. However, there remains a dearth for the fabrication of the devices in aspects like suitable microbes, proton exchange membranes, and cheaper catalysts for cathodes for effective real-time monitoring of wastewater. In this review, an extensive study has been carried out on various MFC based BOD sensors. The efficiency and drawbacks associated with the different MFC based BOD sensors have been critically evaluated, and future perspectives for their development have been investigated. The breath of work compiled in this review will accelerate further research in MFC based BOD biosensors. It will be of great importance to broad ranges of scientific researchers and industrialists.

Xiang Zhou, S. Fang, Xueqi Leng et al.

Accounts of Chemical Research • 2021

ConspectusNature's evolution over billions of years has led to the development of different kinds of twisted structures in a variety of biological species. Twisted fibers from nanoscale- to micrometer-scale diameter have been prepared by mimicking natural twisted structures. Mechanically inserting twist in a yarn is an efficient and important method, which generates internal stress, changes the macromolecular orientation, and increases compactness. Recently, twist insertion has been found to produce interesting fiber properties, including chemical, mechanical, electrical, and thermal properties. This Account summarizes recent progress in how twist insertion affects the chemical and physical properties of fibers and describes their applications in artificial spider silk, artificial muscles, refrigeration, and electricity generation.Twist and associated chirality widely arise in nature from molecules to nano- and microscale materials to macroscopic objects such as DNA, RNA, peptides, and chromosomes. Such twisted architectures play an important role in improving the mechanical properties and enabling biological functions. Inspired by the beauty and interesting properties of twisted structures, a wide range of artificial chiral materials with twisted or coiled structures have been prepared, from organic and inorganic nanorods, nanotubes, and nanobelts to macroscopic architectures and buildings.An efficient way to prepare twisted materials is by inserting twist in fibers or yarns, which is an ancient technique used to make yarns or ropes (Wang, R., et al. Science 2019, 366, 216-221. Mu, J., et al. Science 2019, 365, 150-155). During the twisting process, torque is generated in fibers or yarns, the structure of the polymer chains becomes helically oriented, and the fibers in a yarn become more compact. Therefore, the twisting of fibers and yarns can produce novel chemical, mechanical, electrical, and thermal properties (Dou, Y., et al. Nat. Commun. 2019, 10, 1-10. Kim, S. H., et al. Science 2017, 357, 773-778). This Account focuses on the novel properties generated by twist insertion. The mechanical stress and strain can be optimized in a yarn by twist insertion, and different types of fibers exhibit rather different mechanisms.In the first section, we will focus on recent progress in improving the mechanical properties of twisted fibers, including carbon nanotube yarns, single-filament fibers, and hydrogel fibers. Torque was generated by twist insertion in a fiber or a yarn, and the balance of internal torsional stress can be changed by causing a change in yarn volume. This will result in twist release and torsional and tensile actuations of the yarn, which will be described in the second section. Twisting a yarn generally makes it more compact, which will result in a mechanically induced change in capacitance, supercapacitance, and other useful electrochemical properties when a conducting yarn is in an electrolyte. Such processes were used to develop novel devices for twist-based electricity generation, called twistrons, which will be discussed in the third section. Twist insertion or release also changes the polymer chain orientation or crystal structure, resulting in changes in entropy. This is called the twistocaloric effect, which was used to develop a new cooling method, and will be discussed in the last section.

M. Q. Duong, Thai Dinh Pham, T. Nguyen et al.

Energies • 2019

This paper presents an effective biogeography-based optimization (BBO) for optimal location and sizing of solar photovoltaic distributed generation (PVDG) units to reduce power losses while maintaining voltage profile and voltage harmonic distortion at the limits. This applied algorithm was motivated by biogeography, that the study of the distribution of biological species through time and space. This technique is able to expand the searching space and retain good solution group at each generation. Therefore, the applied method can significantly improve performance. The effectiveness of the applied algorithm is validated by testing it on IEEE 33-bus and IEEE 69-bus radial distribution systems. The obtained results are compared with the genetic algorithm (GA), the particle swarm optimization algorithm (PSO) and the artificial bee colony algorithm (ABC). As a result, the applied algorithm offers better solution quality and accuracy with faster convergence.

Xiaobing Yan, Qianlong Zhao, A. Chen et al.

Small • 2019

Memristors with nonvolatile memory characteristics have been expected to open a new era for neuromorphic computing and digital logic. However, existing memristor devices based on oxygen vacancy or metal-ion conductive filament mechanisms generally have large operating currents, which are difficult to meet low-power consumption requirements. Therefore, it is very necessary to develop new materials to realize memristor devices that are different from the mechanisms of oxygen vacancy or metal-ion conductive filaments to realize low-power operation. Herein, high-performance and low-power consumption memristors based on 2D WS2 with 2H phase are demonstrated, which show fast ON (OFF) switching times of 13 ns (14 ns), low program current of 1 µA in the ON state, and SET (RESET) energy reaching the level of femtojoules. Moreover, the memristor can mimic basic biological synaptic functions. Importantly, it is proposed that the generation of sulfur and tungsten vacancies and electron hopping between vacancies are dominantly responsible for the resistance switching performance. Density functional theory calculations show that the defect states formed by sulfur and tungsten vacancies are at deep levels, which prevent charge leakage and facilitate the realization of low-power consumption for neuromorphic computing application.

Xue Qi, Sheng-Ping Chen, A. Jin et al.

Optical Engineering • 2015

Abstract. We design a seven-core photonic crystal fiber with specifically designed dispersion and group velocity profile which is optimized for high-power visible supercontinuum (SC) generation pumped by ∼1-μm pulsed lasers. The fiber has both a large air-filling fraction and a large effective mode field area. Additionally, the in-phase supermode of this fiber exhibits an even field distribution after mode modification. The simulation results suggest that it has a great potential to generate a high-power SC extending to 400 nm, which is highly desirable in biological applications.

B. Lóránt, G. Tardy

Periodica Polytechnica Chemical Engineering • 2022

To limit global warming, ratio of renewable sources in the energy mix has to be considerably raised in the following years. While application of e.g. wind and solar power usually generates fluctuations in the electric grid, biogas produced in anaerobic processes is an easy-to-store renewable energy source. Raw biogas contains generally ~55–70% methane and ~30–45% carbon-dioxide. Although raw biogas can be utilized directly for combustion or combined heat and power generation (CHP), its methane content can be raised to >95% by upgrading technologies, thus it can be valorized. By upgrading and cleaning, the quality of the upgraded biogas may reach the quality of the natural gas and it may be injected to the gas grid or used as fuel for devices optimized for natural gas. Several physico-chemical upgrading methods are available on the market (e.g. high pressure water scrubbing, pressure swing adsorption, membrane technology, etc.) to remove the carbon-dioxide content of the biogas. Opposite to the physico-chemical methods, where basically the CO2 removal is the main goal, in biological biogas upgrading technologies microorganisms are applied to convert the carbon-dioxide content of the biogas to methane (chemoautotrophic upgrading), or algal biomass (photoautotrophic upgrading). The expectations are high towards biological biogas upgrading technologies in the field of energy storage linked with carbon-dioxide capture. In this paper, latest research results concerning biological biogas upgrading are summarized, viability and competitiveness of this technology is discussed together with the most important future development directions.