Microbial Fuel Cell

Membrane-less air-cathode microbial fuel cell (MFC), as one of the low-cost and potentially scalable modules in the bioelectrochemical technology, can treat wastewater and produce electricity without additional membrane and aeration cost. Nevertheless, the formation of biofilm (i.e., biofouling) on cathodes is observed to deteriorate the cathode performance. This study constructs an eight-unit membrane-less air-cathode MFC and aims to evaluate effects of cathodic biofouling on the performance of individual unit and the scale-up power efficiency during parallel connection. Results indicate cathodic biofoulings affect the cathodic performance by deteriorating both voltage and current output, further causing the performance variation among different cathodes. Moreover, the decrease of power densities by increasing the number of parallel-connected units is observed. Cyclic voltammetry demonstrates the onset potential decreases from 0.4 V to 0.1 V after cathodic biofouling. Electrochemical impedance spectroscopy reveals the polarization resistance of the biofouling cathode increases around two folds. In addition, we also find correlation between cathodic performance and microbial community and association between cathodic performance and unit position in the eight-unit MFC. Overall, our results suggest cathodic biofouling can be the key factor to limit the performance of parallel connection and warrant the need for further research to improve scale-up power efficiency.

By introducing the computer numerical control (CNC) engraving technology, this study fabricated the reusable CNC-fabricated membrane-less laminar flow microfluidic MFC (LMMFC) to develop the bioelectrochemical sensor and power source simultaneously. To verify its applicability, optimization of electroactive bacteria (EAB) cultivation and laminar-flow formation, performance of power density and long-term operation, and detection of Cr(VI) were evaluated. Results of EAB optimization showed under lower external resistance, shorter start-up time of current production, larger oxidation current, denser microbial distribution, and a higher percentage of Geobacter spp. were observed. Results of the laminar-flow operation indicated that increasing the density difference between two solutions and raising the anode flow velocity can minimize the interference of the diffusion zone. The power output of LMMFC could reach 2085 mW m-2 and achieve long-term stability for current production (~150 h). Regarding the detection of Cr(VI), low-concentration (0.1~1 ppm) and high-concentration (1-10 ppm) ranges reached the linear coefficient of determination of 0.98 and 0.97, respectively. Overall, these results suggest that an LMMFC which can both act as the power source and biosensor was successfully developed, showing potential for future self-power application.

In bioelectrochemical wastewater treatment systems, electrochemically active bacteria (EAB) in the anode can simultaneously treat wastewater and produce electricity via extracellular electron transfer. The anode potential has been reported as one way for selecting EAB; though, conflicting results of the relationship between applied potentials and the performance and community composition of EAB have been reported. In this study, we investigated the cultivation time and applied anode potentials (+0.2, 0,-0.2, and-0.4 V vs. Ag/AgCl) on the performance of current production and the compositions of the microbial community. Our results showed that the applied potentials affected the performance of current production, but the effect was substantially reduced with cultivation time. Particularly, the current gradually increased from negative to positive values with time for the applied anode potential at-0.4 V, implying the anode biofilm shifted from accepting electrons to producing electrons. In addition, principal coordinates analysis results indicated that microbial community compositions became closer to each other after long-term enrichment. Subsequently, principal component analysis demonstrated that systems with applied potentials from +0.2, 0 to-0.2 V and at-0.4 V were, respectively, reclassified into principal component 1 (higher-energy-harvesting group) and principal component 2 (lower-energy-harvesting group), implying in addition to cultivation time, the amount of energy available for bacterial growth is another key factor that influences EAB populations. Overall, this study has demonstrated that the selected cultivation time and the particular anode potentials applied in the study determine whether the applied anode potentials would affect the community and performance of EAB.

Long-term performance of bio-catalyzed and FePc-coated cathode MFCs were compared. Step-wise increase of biocathode potential to more than 500 mV was observed. Biocathode MFCs achieved better total nitrogen removal than FePc-coated cathode MFCs. Biocathode biofilm largely decreased polarization resistance of cathode material. Distinct microbial community between biocathode and FePc-coated cathode was found.

• A voltage reversal shock on the bio-cathode was observed during serial connection. • Self-recovery of voltage reversal in the biocathode was further observed. • The increase of biofilm capacitance was found on the recovered biocathode. • Thiothrix populations were highly enriched on the recovered biocathode biofilm. • Serially connected biocathode MFCs could drive an environmental sensor with a PMS.

Biological hydrogen production using photosynthetic algae and bacteria can result in the generation of large amounts of waste biomass. This biomass can be used to produce hydrogen gas by modifying microbial fuel cell (MFC) technologies to produce hydrogen instead of electricity. By applying a small voltage (0.25 V in practice), it is possible to generate pure hydrogen gas at the cathode in this modified MFC process known as a bioelectrochemically assisted microbial reactor (BEAMR). Using the BEAMR process we have produced ~3 mol-H 2 /mol-acetate. Linking this process with fermentation of sugars could produce 8-9 mol-H 2 /molglucose, at an energy equivalent of one mole of hydrogen. The process is not limited to sugars, as any biodegradable organic matter can be used, such as domestic wastewater and steam-exploded corn stover hydrolysates. Thus, it should be possible to link the BEAMR process with photosynthetic biohydrogen production in the form of algae, bacteria or crops, to create an overall sustainable biohydrogen process.

Electrochemically active bacteria (EAB) on the cathodes of microbial fuel cells (MFCs) can remove metals from the catholyte, but the fate of metals in the cells has not been examined in the presence of multiple metals. To study the relative uptake and fate of Cr(VI) and Cd(II) in cells, fluorescence probes were used to determine the amount and location of these metals in four different EAB on the biocathodes of MFCs. When both metals were present, less Cr(VI) was removed but Cd(II) uptake was not appreciably affected. As a consequence, the imaging of Cr(III) ions was lower than that using individual fluorescence probes for single Cr(III) ions in each EAB, compared to negligible changes in images for Cd(II) ions in the presence of either both Cr(VI) and Cd(II) or Cd(II) alone. The concentration of Cr(III) ions in the cells consistently increased over time, while that of Cd(II) ions decreased following an initial increase. Cr or Cd uptake could not be detected using a scanning electro...

Given our vast methane reserves and the difficulty in transporting methane without substantial leaks, the conversion of methane directly into electricity would be beneficial. Microbial fuel cells harness electrical power from a wide variety of substrates through biological means; however, the greenhouse gas methane has not been used with much success previously as a substrate in microbial fuel cells to generate electrical current. Here we construct a synthetic consortium consisting of: (i) an engineered archaeal strain to produce methyl-coenzyme M reductase from unculturable anaerobic methanotrophs for capturing methane and secreting acetate; (ii) micro-organisms from methane-acclimated sludge (including Paracoccus denitrificans) to facilitate electron transfer by providing electron shuttles (confirmed by replacing the sludge with humic acids), and (iii) Geobacter sulfurreducens to produce electrons from acetate, to create a microbial fuel cell that converts methane directly into si...

Activated carbon (AC) air cathodes were constructed using variable amounts of carbon (43-171 mg cm ) and an inexpensive binder (10 wt% polytetrafluoroethylene, PTFE), and with or without a porous cloth wipe-based diffusion layer (DL) that was sealed with PDMS. The cathodes with the highest AC loading of 171 mg cm 22 , and no diffusion layer, produced 1255 ¡ 75 mW m 22 and did not appreciably vary in performance after 1.5 months of operation. Slightly higher power densities were initially obtained using 100 mg cm 22 of AC (1310 ¡ 70 mW m 22 ) and a PDMS/wipe diffusion layer, although the performance of this cathode decreased to 1050 ¡ 70 mW m 22 after 1.5 months, and 1010 ¡ 190 mW m 22 after 5 months. AC loadings of 43 mg cm 22 and 100 mg cm 22 did not appreciably affect performance (with diffusion layers). MFCs with the Pt catalyst and Nafion binder initially produced 1295 ¡ 13 mW m 22 , but the performance decreased to 930 ¡ 50 mW m 22 after 1.5 months, and then to 890 ¡ 20 mW m 22 after 5 months. Cathode performance was optimized for all cathodes by using the least amount of PTFE binder (10%, in tests using up to 40%). These results provide a method to construct cathodes for MFCs that use only inexpensive AC and a PTFE, while producing power densities similar to those of Pt/C cathodes. The methods used here to make these cathodes will enable further tests on carbon materials in order to optimize and extend the lifetime of AC cathodes in MFCs.

Oxygen intrusion into the anode chamber through proton exchange membrane can result in positive redox conditions in fed-batch, two chamber MFCs at the end of a cycle when the substrate is depleted. A slight increase in dissolved oxygen to 0.3 mg/L during MFC operation was not found to adversely affect power generation over subsequent cycles if sufficient substrate (acetate) was provided. Purging the anode chamber with air or pure oxygen for up to 10 days and 10 hrs also did not affect power generation, as power rapidly returned to previous levels when the chamber was sparged with nitrogen gas. When MFCs are connected in series, voltage reversal can occur resulting in a positive voltage applied to the anode biofilm. To investigate if this adversely affected the bacteria, voltages of 1, 2, 3, 4, and 9 V, were applied for 1 hr to the MFC before reconnecting it back to a fixed external load (1,000 Ω). A voltage of <2 V did not affect power generation. However, applying 3 V resulted i...

Waste Not The organic matter in wastewater is a potentially vast and sustainable energy source; however, most wastewater treatment plants consume energy. Cusick et al. (p. 1474 , published online 1 March) combined a microbial fuel cell with a reverse-electrodialysis system to boost the voltage output and the power density over a simple microbial fuel cell. The use of ammonium bicarbonate as a fuel for reverse electrodialysis while microorganisms simultaneously turn organic matter into electricity not only allows for the capturing of waste heat, but could eventually produce enough energy to offset the energy used in conventional wastewater treatment systems.

Carbon brush electrodes have been used to provide high surface areas for bacterial growth and high power densities in microbial fuel cells (MFCs). A high-temperature ammonia gas treatment has been used to enhance power generation, but less energy-intensive methods are needed for treating these electrodes in practice. Three different treatment methods are examined here for enhancing power generation of carbon fiber brushes: acid soaking (CF-A), heating (CF-H), and a combination of both processes (CF-AH). The combined heat and acid treatment improve power production to 1370 mW m -2 , which is 34% larger than the untreated control (CF-C, 1020 mW m -2 ). This power density is 25% higher than using only acid treatment (1100 mW m -2 ) and 7% higher than that using only heat treatment (1280 mW m -2 ). XPS analysis of the treated and untreated anode materials indicates that power increases are related to higher N1s/C1s ratios and a lower C-O composition. These findings demonstrate efficient and simple methods for improving power generation using graphite fiber brushes, and provide insight into reasons for improving performance that may help to further increase power through other graphite fiber modifications.

Microbial fuel cells (MFCs) produce bioelectricity from a wide variety of organic and inorganic substrates. Chitin can be used as a slowly degrading substrate in MFCs and thus as a long-term fuel to sustain power by these devices in remote locations. However, little is known about the effects of particle size on power density and length of the power cycle (longevity). We therefore examined power generation from chitin particles sieved to produce three average particle sizes (0.28, 0.46 and 0.78 mm). The longevity increased from 9 to 33 days with an increase in the particle diameter from 0.28 to 0.78 mm. Coulombic efficiency also increased with particle size from 18% to 56%. The maximum power density was lower for the largest (0.78 mm) particles (176 mW m -2 ), with higher power densities for the 0.28 mm (272 mW m -2 ) and 0.46 mm (252 mW m -2 ) particle sizes. The measured lifetimes of these particles scaled with particle diameter to the 1.3 power. Application of a fractal dissolution model indicates chitin particles had a threedimensional fractal dimension between 2 and 2.3. These results demonstrate particles can be used as a sustainable fuel in MFCs, but that particle sizes will need to be controlled to achieve desired power levels.

Biocathodes in bioelectrochemical systems (BESs) can be used to convert CO 2 into diverse organic compounds through a process called microbial electrosynthesis. Unfortunately, start-up of anaerobic biocathodes in BESs is a difficult and time consuming process. Here, a pre-enrichment method was developed to improve start-up of anaerobic facultatively autotrophic biocathodes capable of using cathodes as the electron donor (electrotrophs) and CO 2 as the electron acceptor. Anaerobic enrichment of bacteria from freshwater bog sediment samples was first performed in batch cultures fed with glucose and then used to inoculate BES cathode chambers set at -0.4 V (versus a standard hydrogen electrode; SHE). After two weeks of heterotrophic operation of BESs, CO 2 was provided as the sole electron acceptor and carbon source. Consumption of electrons from cathodes increased gradually and was sustained for about two months in concert with a significant decrease in cathode chamber headspace CO 2 . The maximum current density consumed was -34 ± 4 mA/m 2 . Biosynthesis resulted in organic compounds that included butanol, ethanol, acetate, propionate, butyrate, and hydrogen gas. Bacterial community analyses based on 16S rRNA gene clone libraries revealed Trichococcus palustris DSM 9172 (99% sequence identity) as the prevailing species in biocathode communities, followed by Oscillibacter sp. and Clostridium sp. Isolates from autotrophic cultivation were most closely related to Clostridium propionicum (99% sequence identity; ZZ16), Clostridium celerecrescens (98-99%; ZZ22, ZZ23), Desulfotomaculum sp. (97%; ZZ21), and Tissierella sp. (98%; ZZ25). This pre-enrichment procedure enables simplified start-up of anaerobic biocathodes for applications such as electrofuel production by facultatively autotrophic electrotrophs.

Although microbial fuel cells (MFCs) generate much lower power densities than hydrogen fuel cells, the characteristics of the cathode can also substantially affect electricity generation. Cathodes used for MFCs are often either Ptcoated carbon electrodes immersed in water that use dissolved oxygen as the electron acceptor or they are plain carbon electrodes in a ferricyanide solution. The characteristics and performance of these two cathodes were compared using a two-chambered MFC. Power generation using the Pt-carbon cathode and dissolved oxygen (saturated) reached a maximum of 0.097 mW within 120 h after inoculation (wastewater sludge and 20 mM acetate) when the cathode was equal size to the anode (2.5 × 4.5 cm). Once stable power was generated after replacing the MFC with fresh medium (no sludge), the Coulombic efficiency ranged from 63 to 78%. Power was proportional to the dissolved oxygen concentration in a manner consistent with Monod-type kinetics, with a half saturation constant of K DO ) 1.74 mg of O 2 /L. Power increased by 24% when the cathode surface areas were increased from 22.5 to 67.5 cm 2 and decreased by 56% when the cathode surface area was reduced to 5.8 cm 2 . Power was also substantially reduced (by 78% to 0.02 mW) if Pt was not used on the cathode. By using ferricyanide instead of dissolved oxygen, the maximum power increased by 50-80% versus that obtained with dissolved oxygen. This result was primarily due to increased mass transfer efficiencies and the larger cathode potential (332 mV) of ferricyanide than that obtained with dissolved oxygen (268 mV). A cathode potential of 804 mV (NHE basis) is theoretically possible using dissolved oxygen, indicating that further improvements in cathode performance with oxygen as the electron acceptor are possible that could lead to increased power densities in this type of MFC.

Voltages produced by microbial fuel cells (MFCs) cannot be sustainably increased by linking them in series due to voltage reversal, which substantially reduces stack voltages. It was shown here that MFC voltages can be increased with continuous power production using an electronic circuit containing two sets of multiple capacitors that were alternately charged and discharged (every one second). Capacitors were charged in parallel by the MFCs, but linked in series while discharging to the circuit load (resistor). The parallel charging of the capacitors avoided voltage reversal, while discharging the capacitors in series produced up to 2.5 V with four capacitors. There were negligible energy losses in the circuit compared to 20-40% losses typically obtained with MFCs using DC-DC converters to increase voltage. Coulombic efficiencies were 67% when power was generated via four capacitors, compared to only 38% when individual MFCs were operated with a fixed resistance of 250 U. The maximum power produced using the capacitors was not adversely affected by variable performance of the MFCs, showing that power generation can be maintained even if individual MFCs perform differently. Longer capacitor charging and discharging cycles of up to 4 min maintained the average power but increased peak power by up to 2.6 times. These results show that capacitors can be used to easily obtain higher voltages from MFCs, allowing for more useful capture of energy from arrays of MFCs.

High-performance microbial fuel cell (MFC) air cathodes were constructed using a combination of inexpensive materials for the oxygen reduction cathode catalyst and the electrode separator. A poly(vinyl alcohol) (PVA)-based electrode separator enabled high coulombic efficiencies (CEs) in MFCs with activated carbon (AC) cathodes without significantly decreasing power output. MFCs with AC cathodes and PVA separators had CEs (43%-89%) about twice those of AC cathodes lacking a separator (17%-55%) or cathodes made with platinum supported on carbon catalyst (Pt/C) and carbon cloth (CE of 20%-50%). Similar maximum power densities were observed for AC-cathode MFCs with (840 ± 42 mW/m 2 ) or without (860 ± 10 mW/m 2 ) the PVA separator after 18 cycles (36 days). Compared to MFCs with Pt-based cathodes, the cost of the AC-based cathodes with PVA separators was substantially reduced. These results demonstrated that AC-based cathodes with PVA separators are an inexpensive alternative to expensive Pt-based cathodes for construction of larger-scale MFC reactors.

The improvement in electricity generation during the enrichment process of a microbial consortium was analyzed using an air-cathode microbial fuel cell (MFC) repeatedly fed with acetate that was originally inoculated with sludge from an anaerobic digester. The anodic maximum current density produced by the anode biofilm increased from 0.12 mA/cm 2 at day 28 to 1.12 mA/cm 2 at day 105. However, the microbial cell density on the carbon cloth anode increased only three times throughout this same time period from 0.21 to 0.69 mg protein/cm 2 , indicating that the biocatalytic activity of the consortium was also enhanced. The microbial activity was calculated to have a per biomass anode-reducing rate of 374 μmol electron g protein -1 min -1 at day 28 and 1,002 μmol electron g protein -1 min -1 at day 105. A bacterial community analysis of the anode biofilm revealed that the dominant phylotype, which was closely related to the known exoelectrogenic bacterium, Geobacter sulfurreducens, showed an increase in abundance from 32% to 70% of the total microbial cells. Fluorescent in situ hybridization observation also showed the increase of Geobacter-like phylotypes from 53% to 72%. These results suggest that the improvement of microbial current generation in microbial fuel cells is a function of both microbial cell growth on the electrode and changes in the bacterial community highly dominated by a known exoelectrogenic bacterium during the enrichment process.

A microbial fuel cell (MFC) is a relatively new type of fixed film bioreactor for wastewater treatment, and the most effective methods for inoculation are not well understood. Various techniques to enrich electrochemically active bacteria on an electrode were therefore studied using anaerobic sewage sludge in a two-chambered MFC. With a porous carbon paper anode electrode, 8 mW/m 2 of power was generated within 50 h with a Coulombic efficiency (CE) of 40%. When an iron oxide-coated electrode was used, the power and the CE reached 30 mW/m 2 and 80%, respectively. A methanogen inhibitor (2-bromoethanesulfonate) increased the CE to 70%. Bacteria in sludge were enriched by serial transfer using a ferric iron medium, but when this enrichment was used in a MFC the power was lower (2 mW/m 2 ) than that obtained with the original inoculum. By applying biofilm scraped from the anode of a working MFC to a new anode electrode, the maximum power was increased to 40 mW/m 2 . When a second anode was introduced into an operating MFC the acclimation time was not reduced and the total power did not increase. These results suggest that these active inoculating techniques could increase the effectiveness of enrichment, and that start up is most successful when the biofilm is harvested from the anode of an existing MFC and applied to the new anode.

Activated carbon (AC) is a cost-effective catalyst for the oxygen reduction reaction (ORR) in air-cathode microbial fuel cells (MFCs). To enhance the catalytic activity of AC cathodes, AC powders were pyrolyzed with iron ethylenediaminetetraacetic acid (FeEDTA) at a weight ratio of FeEDTA:AC = 0.2:1. MFCs with FeEDTA modified AC cathodes and a stainless steel mesh current collector produced a maximum power density of 1580 ± 80 mW/m 2 , which was 10% higher than that of plain AC cathodes (1440 ± 60 mW/m 2 ) and comparable to Pt cathodes (1550 ± 10 mW/m 2 ). Further increases in the ratio of FeEDTA:AC resulted in a decrease in performance. The durability of AC-based cathodes was much better than Pt-catalyzed cathodes. After 4.5 months of operation, the maximum power density of Pt cathode MFCs was 50% lower than MFCs with the AC cathodes. Pyridinic nitrogen, quaternary nitrogen and iron species likely contributed to the increased activity of FeEDTA modified AC. These results show that pyrolyzing AC with FeEDTA is a cost-effective and durable way to increase the catalytic activity of AC.

Hydrogen gas has tremendous potential as an environmentally acceptable energy carrier for vehicles, but most hydrogen is generated from nonrenewable fossil fuels such as natural gas. Here, we show that efficient and sustainable hydrogen production is possible from any type of biodegradable organic matter by electrohydrogenesis. In this process, protons and electrons released by exoelectrogenic bacteria in specially designed reactors (based on modifying microbial fuel cells) are catalyzed to form hydrogen gas through the addition of a small voltage to the circuit. By improving the materials and reactor architecture, hydrogen gas was produced at yields of 2.01–3.95 mol/mol (50–99% of the theoretical maximum) at applied voltages of 0.2 to 0.8 V using acetic acid, a typical dead-end product of glucose or cellulose fermentation. At an applied voltage of 0.6 V, the overall energy efficiency of the process was 288% based solely on electricity applied, and 82% when the heat of combustion of...

Les piles microbianes o microbial fuel cells (MFC) són uns sistemes bioelectroquímcs que permeten l’obtenció d’energia elèctrica a partir d’energia química tenint com a catalitzador a un microorganisme electrogènic que oxida el combustible o matèria orgànica contaminant (font de l’energia química) i transfereix els electrons obtinguts a un electrode (ànode) el qual està connectat a un càtode a través d’un material conductor que conté una resistència al mig.

Background Natural products are an important source of drugs and other commercially interesting compounds, however their isolation and production is often difficult. Metabolic engineering, mainly in bacteria and yeast, has sought to circumvent some of the associated problems but also this approach is impeded by technical limitations. Here we describe a novel strategy for production of diverse natural products, comprising the expression of an unprecedented large number of biosynthetic genes in a heterologous host. Results As an example, genes from different sources, representing enzymes of a seven step flavonoid pathway, were individually cloned into yeast expression cassettes, which were then randomly combined on Yeast Artificial Chromosomes and used, in a single transformation of yeast, to create a variety of flavonoid producing pathways. Randomly picked clones were analysed, and approximately half of them showed production of the flavanone naringenin, and a third of them produced ...

Microbial fuel cell (MFC) has become a great attraction amongst most researchers, where degradation of waste takes place simultaneously produces electricity. Using an efficient organism and a better proton exchange membrane gives out good electricity. In this study, Exiguobacterium sp SU-5 was isolated from soil and used for producing electricity against carboxy methyl cellulose (CMC) in Nafion membrane and Salt bridge fitted MFC, where both act as proton exchange membrane. The organism was found to produce more electricity in Nafion membrane fitted MFC. Later the organism was subjected to produce electricity against kitchen waste and the kitchen waste was also checked for BOD, COD and other water analysis before and after the treatment. The organism could produce more electricity in Nafion membrane fitted MFC and found to reduce chloride, fluoride and hardness of water.

This study presents a new miniature-microbial fuel cell (MFC) platform which has been built by using polydimethylsiloxane (PDMS). The MFC design includes PDMS soft chambers featuring carbon cloth electrode, gold nanoparticles and a delivery system of electrolytes (mcL). Bioelectricity was generated using Pseudomonas aeruginosa cultivated on simple nutrient medium. P.aeruginosa in the anode chamber forms biofilm and generates electrons which flow from anode to cathode through external load and generates current while protons pass through the salt bridge to cathode chamber. These mini-MFC exhibited fast start-ups, reproducible voltage generation, and enhanced power densities up to approximately 2.1mV.

In this study, the antitoxicity performance of the traditional anaerobic baffled reactor (ABR) and the newly constructed membraneless anaerobic baffled reactor coupled with microbial fuel cell (ABR-MFC) was compared for the treatment of simulated printing and dyeing wastewater under the same hydraulic residence time. The sludge performances of ABR-MFC and ABR were evaluated on the dye removal rate, extracellular polymer (EPS) content, sludge particle size, methane yield, and the surface morphology of granular sludge. It was found that the maximum power density of the ABR-MFC reactor reached 1226.43 mW/m 3 , indicating that the coupled system has a good power generation capacity. The concentration of the EPS in the ABR-MFC reactor was about 3 times that in the ABR, which could be the result of the larger average particle size of sludge in the ABR-MFC reactor than in the ABR. The dye removal rate of the ABR-MFC reactor (91.71%) was higher than that of the ABR (1.49%). The methane production and microbial species in the ABR-MFC system were higher than those in the ABR. Overall, the MFC embedded in the ABR can effectively increase the resistance of the reactor, promote the formation of granular sludge, and improve the performance of the reactor for wastewater treatment.

Microbial fuel cells (MFCs) have emerged as a viable method for bioremediation of toxic metals while also producing energy. In this paper, we examine the issue of organic substrate as a source of metabolism for microbe growth in MFC, as well as its significance for metal ion degradation in tandem with energy production. This study focused on the use of commercial sugar as an organic substrate in a single-chamber MFC. The MFC was operated for 27 days, with the highest voltage of 150 mV achieved on day 12, and toxic metal bioremediation efficiencies of 89%, 76.45%, and 89.45% for Pb2+, Cd2+, and Hg2+, respectively. Every 24 hours, the organic substrate (sugar solution) was fed into the cell. This study’s mechanism of metal ion degradation and electron transport is also thoroughly described. In addition, some future views have been highlighted.

Fuel cell efficiency can be improved by using progressive electrodes and electrolytes. Green nanomaterials and green technologies have been explored for the manufacturing of high-performance electrode and electrolyte materials for fuel cells. Platinum-based electrodes have been replaced with green materials and nanocomposites using green fabrication approaches to attain environmentally friendly fuel cells. In this regard, ecological and sustainable electrode- and electrolyte-based membrane electrode assemblies have also been designed. Moreover, green nanocomposites have been applied to form the fuel cell electrolyte membranes. Among fuel cells, microbial fuel cells have gained research attention for the incorporation of green and sustainable materials. Hence, this review essentially focuses on the potential of green nanocomposites as fuel cell electrode and electrolyte materials and application of green synthesis techniques to attain these materials. The design of and interactions w...

A METland is an innovative treatment wetland (TW) that relies on the stimulation of electroactive bacteria (EAB) to enhance the degradation of pollutants. The METland is designed in a short-circuit mode (in the absence of an external circuit) using an electroconductive bed capable of accepting electrons from the microbial metabolism of pollutants. Although METlands are proven to be highly efficient in removing organic pollutants, the study of in situ EAB activity in full-scale systems is a challenge due to the absence of a two-electrode configuration. For the first time, four independent full-scale METland systems were tested for the removal of organic pollutants and nutrients, establishing a correlation with the electroactive response generated by the presence of EAB. The removal efficiency of the systems was enhanced by plants and mixed oxic–anoxic conditions, with an average removal of 56 g of chemical oxygen demand (COD) mbed material–3 day–1 and 2 g of total nitrogen (TN) mbed ...

The performance enhancement of constructed wetlands can be achieved through the coupling with microbial electrochemical technologies (MET). MET is a setup designed to mimic metabolic electrons exchange with insoluble donors and acceptors with the aid of electroactive bacteria and external electrical circuits. An alternative MET that dispenses of electrodes and circuits but uses an electro-conductive biofilter is called Microbial Electrochemical-based Constructed Wetland (METland). Previously it has been demonstrated that a METland has higher biodegradation rates than horizontal flow constructed wetlands, however given its novelty there are still uncertainties related to the removal of pollutants, including their microbial activity. The genetic characterization of microbial communities of a METland is desirable, but is time and resource consuming, then a characterization alternative could be based on functional analysis of the microbial communities. Community-level physiological profile (CLPP) is a useful method to evaluate the functional diversity of microbial communities based on the carbon source utilization pattern (CSUP). Therefore, this study was focused on the microbial characterization of laboratory scale METland based on CLPP analysis. The study included the characterization of microbial communities attached to two carbon-based electro-conductive materials (calcined petroleum coke from crushed electrodes -PK-A; calcined petroleum coke with low sulphur and nitrogen content -PK-LSN), in planted and non-planted set-ups. Variations on the metabolic activity of tested systems were identified and it seems to be related to the characteristics of the material, rather than the presence / absence of plants. In general, CSUP show differences along flow pathway, as well as among the tested systems, being carbohydrates and carboxylic/acetic acids the most consumed carbon sources, followed by polymers, amides/amines and amino acids. Also, were established some correlations between the utilization of carbon sources and the removal of pollutants. The obtained results provide useful insight into the spatial dynamics of METland systems.

Microbial electrochemical technologies (MET) rely on the presence of the metabolic activity of electroactive bacteria for the use of solid-state electrodes for oxidizing different kind of compound, that could lead to the synthesis of chemicals, bioremediation of polluted matrices, the treatment of contaminants of interest, as well as the recovery of energy. Keeping in mind those possibilities, since the beginning of the present century, there has been a growing interest in the use of electrochemical technologies for wastewater treatment, and if possible with simultaneous power generation. In the last years, there has been a growing interest to explore the possibility of merging MET with constructed wetlands, to offer a new option of intensified wetland system that could keep a high performance with a lower footprint. Based on that interest, this paper explains the general principles of MET, and the different known extracellular electron transfer mechanisms ruling the interaction bet...

The increase of industrial discharges is the first cause of the contamination of water bodies. The bacterial survival strategies contribute to the equilibrium restoration of ecosystems being useful tools for the development of innovative environmental biotechnologies. The aim of this work was to study the Cu(II) and Cd(II) biosensing, removal and recovery, mediated by whole cells, exopolymeric substances (EPS) and biosurfactants of the indigenous and non-pathogenic Pseudomonas veronii 2E to be applied in the development of wastewater biotreatments. An electrochemical biosensor was developed using P. veronii 2E biosorption mechanism mediated by the cell surface associated to bound exopolymeric substances. A Carbon Paste Electrode modified with P. veronii 2E (CPEM) was built using mineral oil, pre-washed graphite power and 24 h-dried cells. For Cd(II) quantification the CPEM was immersed in Cd(II) (1–25 μM), detected by Square Wave Voltammetry. A similar procedure was used for 1–50 μM...

In this study, electrogenic microbial communities originating from a single source were multiplied using our custom-made, 96-well-plate-based microbial fuel cell (MFC) array. Developed communities operated under different pH conditions and produced currents up to 19.4 A/m3 (0.6 A/m2) within 2 days of inoculation. Microscopic observations [combined scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS)] revealed that some species present in the anodic biofilm adsorbed copper on their surface because of the bioleaching of the printed circuit board (PCB), yielding Cu2 + ions up to 600 mg/L. Beta- diversity indicates taxonomic divergence among all communities, but functional clustering is based on reactor pH. Annotated metagenomes showed the high presence of multicopper oxidases and Cu-resistance genes, as well as genes encoding aliphatic and aromatic hydrocarbon-degrading enzymes, corresponding to PCB bioleaching. Metagenome analysis revealed a high abundance of Di...

We demonstrate a single chamber, 96-well plate based Microbial Fuel Cell (MFC). This invention is aimed at robust selection of electrogenic microbial community under specific conditions, (pH, external resistance, inoculum) that can be altered within the 96 well plate array. Using this device, we selected and multiplicated electrogenic microbial communities fed with acetate and lactate that can operate under different pH and produce current densities up to 19.4 A/m3 (0.6 A/m2) within 5 days past inoculation. Moreover, studies shown that Cu mobilization through PCB bioleaching occurred, thus each community was able to withstand presence of Cu2+ ions up to 600 mg/L. Metagenome analysis reveals high abundance of Dietzia spp., previously characterized in MFCs, but not reported to grow at pH 4, as well as novel species, closely related to Actinotalea ferrariae, not yet associated with electrogenicity. Microscopic observations (combined SEM and EDS) reveal that some of the species present ...

During 2015-2017 we have conducted experiments in Japan to test the capacity of microbial fuel cells (MFC) to treat different types of wastewaters (swine farm, domestic, yeast fermentation, winery, etc.) and concomitantly collecting DNA samples from MFC anodic and planktonic bacterial communities. W e analyzed these metagenomes in UK, using our new bioinformatics tool (ASAR) that allow integration of phylogenetic and functional data. Characteristic MFC communities and the associated functional signatures were shown to reflect effective waste water treatment. We also found that the fraction of opportunistic pathogenic bacteria DNA was reduced in metagenomes from MFC communities during swine waste treatment. The highest loss was recorded for Enterobacteriaceae family (such as Yersinia, Vibrio, and Shigella). The abundance of virulent genes responsible for adhesion, secretion systems, invasion and intracellular survival, as well as antibiotic resistance, associated with Firmicutes and ...

The development of bioelectrochemical systems reinforces the necessity for the identification and engineering of electroactive bacteria with improved performance and novel biochemical properties. In this study, using a newly designed 96-well-plate array of microbial fuel cells (MFCs), we compared the electroactive capabilities of microbial communities derived from four mine drainages. The maximum power density of individual wells after two weeks of inoculation was 102 mW/m 3 , whereas the maximum current density was 1.6 A/m 3 . Transferring communities from individual wells into larger MFCs comprising low (20 mg/L) and high (200 mg/L) concentrations of Cu yielded maximum power densities of 445 and 58 mW/m 3 , respectively, with up to a 3.7 fold decrease in Cu 2+ ions within 24 h. Electrochemical data analysis revealed that microbial consortia can be distinguished based on their electrochemical profiles. Our results showed that a 96-well MFC array is a suitable platform for high-throughput screening, selection, and subsequent source of enriched electroactive consortia. The quantitative and comparative analysis followed by principal component analysis indicated that the initial environmental conditions, as well as physical and chemical parameters of the lakes were crucial to develop an efficient electroactive community. Further applications of the proposed platform include genetic engineering, phenotype screening, and mutagenesis studies of both microbial communities and single cultures. This is the first time that a high-throughput MFC platform is used to evaluate the performance of multiple electroactive consortia towards Cu removal.

Soil pollution by Petroleum contaminants are a major threat to the ecosystem that they are responsible for such dangers as mutation, carcinogenesis, and environmental toxicity. In this study, bioremediation of the bio-slurry reactor containing soil with different concentrations of pyrene were surveyed by transgenic Pseudomonas putida KT2440 (with manganese peroxidase 2 gene (mnp2) from Pleurotus ostreatus fungus). At first step of the study, five different genera were identified in the soil sample the most abundant genus belonged to pseudomonas. In the second step, soil bio-slurry reactors were treated with different concentration of pyrene (50, 100, 200, 400 ppm) for 1, 5, 10, 15, and 20 days. According to GC analysis, two concentrations of 100 ppm and 200 ppm of pyrene after 10 and 15 days of the treatment times were selected as optimum reactors. The efficiency of pyrene removal was investigated in bio-slurry reactors with wild-type and transgenic Pseudomonas putida KT2440. The results showed that the percentage of pyrene degradation for 100 and 200 ppm concentrations were 22.56%, 13.97%, 26.08%, and 15.59% in the bio-slurry reactors containing wild-type bacteria after 10 and 15 days of the treatment, respectively. Furthermore, the percentage of pyrene degradation for 100 and 200 ppm concentrations were 22.56%, 26.06%, 38.4%, and 23.74% in the bio-slurry reactors containing transgenic bacteria after 10 and 15 days of the treatment, respectively. Therefore, it seems that the bio-slurry reactor has more ability for pyrene bioremediation in the soil in the presence of the transgenic Pseudomonas putida KT2440 containing mnp2 gene.

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Microbial Fuel Cells (MFCs) are a promising technology for treating wastewater in a sustainable manner. In potential applications, low temperatures substantially reduce MFC performance. To better understand the effect of temperature and particularly how bioanodes respond to changes in temperature, we investigated the current generation of mixed-culture and pure-culture MFCs at two low temperatures, 10°C and 5°C. The results implied that the mixed-culture MFC sustainably performed better than the pure-culture (Shewanella) MFC at 10°C, but the electrogenic activity of anodic bacteria was substantially reduced at the lower temperature of 5°C. At 10°C, the maximum output voltage generated with the mixed-culture was 540-560mV, which was 10%-15% higher than that of Shewanella MFCs. The maximum power density reached 465.3±5.8mW/m(2) for the mixed-culture at 10°C, while only 68.7±3.7mW/m(2) was achieved with the pure-culture. It was shown that the anodic biofilm of the mixed-culture MFC had...

The capacity of a small-scale pilot wastewater treatment plant (WWTP) to treat synthetic and real wastewater using the selective ion flow cell (SIFC) technology (SIC patent title 37239) was evaluated; for this purpose, a one-factorial experimental design was carried out with samples of synthetic wastewater prepared in the laboratory. The relevant factor used was the flow of the sample, and the response variables were hydrogen production (clean energy) and different physicochemical parameters: COD, fats and oils, color, pH, conductivity and total solids. The results obtained show that the best flow for treating wastewater was 50 ml/min with a hydraulic retention time (HRT) of 5.33 h, reducing synthetic wastewater quality parameters such as COD by 90.54 wt %, fats and oils by 93.8 wt %, apparent color by 90.7%, true color by 85.4%, conductivity by 80.9% and total solids by 83.7 wt %, which comply with Resolution No. 0631 of 2015 for discharges in Colombia.

Silver in the linings The bacterium Shewanella oneidensis is well known to use extracellular electron sinks, metal oxides and ions in nature or electrodes when cultured in a fuel cell, to power the catabolism of organic material. However, the power density of microbial fuel cells has been limited by various factors that are mostly related to connecting the microbes to the anode. Cao et al . found that a reduced graphene oxide–silver nanoparticle anode circumvents some of these issues, providing a substantial increase in current and power density (see the Perspective by Gaffney and Minteer). Electron microscopy revealed silver nanoparticles embedded or attached to the outer cell membrane, possibly facilitating electron transfer from internal electron carriers to the anode. —MAF

The study introduces the benthic microbial fuel cell lander (BMFC Lander)-an newly constructed modification to an untethered instrumented seafloor platform or ''ocean lander" for probing deep-sea energy potential at depths exceeding 1000 meters below the sea surface over long timescales (two to five months). The BMFC Lander's design includes a detachable anode that permits the re-use of its electrical and anode components in subsequent deployments. Six BMFC Landers successfully deployed in the Southern California bight that hosted a variety of water depth and temperature conditions for testing BMFC performance, demonstrating their reliability as platforms for deployment, energy generation and recovery. Four Lander's BMFC payloads generated a combined total energy density of approximately 30 W hrs m-2 from the seafloor. Organic feedstock (chitin) shortened the time to discharge potential and enhanced power production for two BMFCs in deep-sea sediments despite increased depths and lower temperatures. The BMFC Landers, with a low-cost overhead, are adaptable to support a variety of low-power sensors for tracking water parameters.

A Microbial Fuel Cell (MFC) was conceived by using garden soil as a source to culture. It was then utilized as a bio-catalyst to decompose waste organic matter, reduce pollution from the soil, and produce energies. The MFC was composed of a bio-anode inoculated with a mixture of garden compost leachate and an abiotic stainless steel cathode. Besides, the bio-anode consisted of a Nafion membrane modified with carbon. The microorganisms agglomerated under polarization and formed electroactive bio-film onto bio-anode. In the preliminary test of MFC, potassium hexacyanoferrate has been utilized as catholyte, to enhance the reduction of proton and electrons resulting in a higher voltage. However, this electrolyte is toxic and oxidized rapidly, thus substituted by the hydrochloric acid. The results showed that the MFC with modified Nafion, gave relatively high current-density 379 mA/m2 in two days, whereas the conventional biofuel cell without modification attained the current-density 292...

The microbial fuel cell (MFC) is emerging as a potential technology for extracting energy from wastes/wastewater while they are treated. The major hindrance in MFC commercialization is lower power generation due to the sluggish transfer of electrons from the biocatalyst (bacteria) to the anode surface and inefficient microbial consortia for treating real complex wastewater. To overcome these concerns, a traditional carbon felt (CF) electrode modification was carried out by iron oxide (Fe 3 O 4 ) nanoparticles via facile dip-and-dry methods, and mixed sulfate-reducing bacteria (SRBs) were utilized as efficient microbial consortia. In the modified CF electrode with SRBs, a considerable improvement in the bioelectrochemical operation was observed, where the power density (309 ± 13 mW/m 2 ) was 1.86 times higher than bare CF with SRBs (166 ± 11 mW/m 2 ), suggesting better bioelectrochemical performance of an SRB-enriched Fe 3 O 4 @CF anode in the MFC. This superior activity can be assigned to the lower charge transfer resistance, higher conductance, and increased number of catalytic sites of the Fe 3 O 4 @CF electrode. The SRB-enriched Fe 3 O 4 @CF anode also assists in enhancing MFC performance in terms of COD removal (>75%), indicating efficient biodegradability of tannery wastewater and a higher electron transfer rate from SRBs to the conductive anode. These findings demonstrate that a combination of the favorable properties of nanocomposites such as Fe 3 O 4 @CF anodes and efficient microbes for treating complex wastes can encourage new directions for renewable energy-related applications.

This paper comprehensively reviews whey, a by-product of cheese production, as a raw material for various biotechnological applications. It addresses its unique composition, the environmental impact of its inadequate disposal, and the opportunities it offers to develop high-value products in line with circular economy and sustainability principles. Using the PRISMA methodology, a systematic search was conducted in various databases (Science Direct, Scopus, and Google Scholar) with specific inclusion and exclusion criteria. Studies from the last five years were considered, focusing on food applications, the production of bioproducts (such as lactic acid, biopolymers, bioethanol, biomass, and enzymes), and the use of whey as a culture medium for the expression of recombinant proteins. It is concluded that the use of whey in biotechnological applications mitigates the environmental impact associated with its disposal and represents an economic and sustainable alternative for the industrial production of bioproducts. The integration of pretreatment technologies, experimental designs, and improvements in producing strains brings these processes closer to competitive conditions in the industry, opening new perspectives for innovation in the fermentation sector.

Electrodes based on graphite, graphene, and carbon nanomaterials have been used in the anode chamber of microbial fuel cells (MFCs). Carbon quantum dots (C-dots) are a class of versatile nanomaterials hitherto not reported in MFCs. C-dots previously synthesized from coconut husk were reported to possess hydroxyl and carboxyl functional groups on their surface. The presence of these functional groups on a carbon matrix conferred on the C-dots the ability to conduct and transfer electrons. Formation of silver nanoparticles from silver nitrate upon addition of C-dots confirmed their reducing ability. DREAM assay using a mixed microbial culture containing C-dots showed a 172% increase in electron transfer activity and thus confirmed the involvement of C-dots in supplementing redox activity of a microbial culture. Addition of C-dots as a suspension in the anode chamber of an MFC resulted in a 22.5% enhancement in maximum power density. C-dots showed better performance as electron shuttle...