Electrogenic Bacteria Research Articles

Synergistic degradation of o-chlorophenol in aerobic microbial fuel cells with a coupled photocatalytic-bioelectrochemical anode

An aerobic single-chamber microbial fuel cell (MFC) system coupled with a photocatalytic-bioelectrochemical anode is constructed for the synergistic degradation of o-chlorophenol (2-CP). Dissolved oxygen (DO) is utilized by photocatalytic and biological processes to enhance the removal of 2-CP. The degradation efficiency for 2-CP is significantly improved (DO decreases from 6.17 to 0.02 mg/L in 8 h), showing that the mean 2-CP removal efficiency (300 mg/L) is 67.1%, higher than those obtained with the anaerobic photocatalytic MFC (31.4%), aerobic MFC (20.5%), and anaerobic MFC (17.7%). Interesting, DO enhances the abundance of Geobacter sp. from 2.31 to 22.5% while enriching the biomass. In addition, the abundance of chlorophenol-degrading bacteria Azospirillum sp. and electrogenic bacteria Comamonadaceae fam. increase from 0.3 to 17.0% and 0.48 to 32.1% with illumination, respectively. Illumination and DO facilitate the cathodic oxidation-reduction reaction and upgrade electricity production from 134 to 255 mW/m2. The electrogenic bacteria rely on the electron transfer pathway of nicotinamide adenine dinucleotide dehydrogenase, succinate dehydrogenase, and terminal oxidase. Unlike the traditional anaerobic mode, the intimate coupling of photocatalysis and bio-electrocatalysis under aerobic conditions provides a more effective strategy for treating wastewater containing refractory pollutants and broadens the scope of MFC technology applications.

Performance of a dual-chamber microbial fuel cell as a biosensor for in situ monitoring Bisphenol A in wastewater

This research explores the possibilities of a dual-chamber microbial fuel cell as a biosensor to measure Bisphenol A (BPA) in wastewater. BPA is an organic compound and is considered to be an endocrine disruptor, affecting exposed organisms, the environment, and human health. The performance of the microbial fuel cells (MFCs) was first controlled with specific operational conditions (pH, temperature, fuel feeding rate, and organic loading rate) to obtain the best accuracy of the sensor signal. After that, BPA concentrations varying from 50 to 1000 μg L−1 were examined under the biosensor's cell voltage generation. The outcome illustrates that MFC generates the most power under the best possible conditions of neutral pH, 300 mg L−1 of COD, R 1000 Ω, and ambient temperature. In general, adding BPA improved the biosensor's cell voltage generation. A slight linear trend between voltage output generation and BPA concentration was observed with R2 0.96, which indicated that BPA in this particular concentration range did not real harm to the MFC's electrogenic bacteria. Scanning electron microscope (SEM) images revealed a better cover biofilm after BPA injection on the surface electrode compared to it without BPA. These results confirmed that electroactive biofilm-based MFCs can serve to detect BPA found in wastewaters.

Potential for Utilizing POME to Produce Biohydrogen Gas Using Microbial Electrolysis Cell

Palm oil mill effluent contains organic matter and microorganisms that can potentially be reused despite of its impact to the environment. Microbial electrolysis cell is a method that utilizes electrogenic bacteria to produce hydrogen gas. This study aims to explore the potential for utilizing palm oil mill effluent to produce hydrogen gas using microbial electrolysis cells. Experiments were conducted in a specially built MEC reactor with a 3.5 L capacity with 0.5, 1.0, and 1.5 V with carbon fiber cloth as electrodes. A gas analyzer was used to measure hydrogen gas over the course of 24 h at a 2 h interval. Palm oil mill effluent was utilized as a substrate, while distilled water was used as a control. Experiments demonstrate that the amount of hydrogen gas produced increases as the voltage increases, with values of 37 mg m-3 at 0.5 V, 136 mg m-3 at 1.0 V, and 358 mg m-3 at 1.5 V. When comparing the yield of hydrogen gas produced with distilled water substrate at 1.5 V, the yield of palm oil mill effluent substrate is always higher. This could be due to microbial activity increasing the rate of electrolysis of the substrate into hydrogen gas.

SOLAR ENERGY ASSISTS SEDIMENT MICROBIAL FUEL CELL TO GENERATE GREEN ENERGY FROM LIQUID ORGANIC WASTE

Simultaneous liquid organic waste disposal and electricity generation were achieved by a solar-assist sediment microbial fuel cell (S-SMFC) in terms of an ecological and economical perspective. In this respect, 840 mL house environment liquid organic waste which contains 10% juice and 10% sugary tea were disposed by electrogenic bacteria and converted electricity with solar energy. A 100 F capacitor was easily charged 29 times with generated electricity. S-SMFC was disposed 10 mL more waste than control due to more electrical bacteria density on the graphite electrode. In this case, Proteobacteria and Firmucutes were categorized dominate bacteria groups, and they were found in the S-SMFC as 54% and 28%, respectively. Importantly, solar energy increased population density of these groups in the S-SMFC and the density on the graphite electrode increased more than 19% according to control. Some bacteria which were associated with electricity production in the S-SMFC were to Azospirillum fermentarium, Clostridium sp., Pseudomonas guangdongensis, Bacteroides sp., Azovibrio restrictus, Clostridium pascui, Levilinea saccharolytica, Seleniivibrio woodruffii, Geovibrio ferrireducens. Consequently, S-SMFC presents innovative, crucial and simple methodology in order to convert liquid organic waste into the green energy.

Syngas Fermentation to Acetate and Ethanol with Adaptative Electroactive Carboxydotrophs in Single Chambered Microbial Electrochemical System.

Microbial electrosynthesis system (MES; single-chambered) was fabricated and evaluated with carbon cloth/graphite as a working/counter electrode employing an enriched microbiome. Continuous syngas sparging (at working electrode; WE) enabled the growth of endo electrogenic bacteria by availing the inorganic carbon source. Applied potential (−0.5 V) on the working electrode facilitated the reduction in syngas, leading to the synthesis of fatty acids and alcohols. The higher acetic acid titer of 3.8 g/L and ethanol concentration of 0.2 g/L was observed at an active microbial metabolic state, evidencing the shift in metabolism from acetogenic to solventogenesis. Voltammograms evidenced distinct redox species with low charge transfer resistance (Rct; Nyquist impedance). Reductive catalytic current (−0.02 mA) enabled the charge transfer efficiency of the cathodes favoring syngas conversion to products. The surface morphology of carbon cloth and system-designed conditions favored the growth of electrochemically active consortia. Metagenomic analysis revealed the enrichment of phylum/class with Actinobacteria, Firmicutes/Clostridia and Bacilli, which accounts for the syngas fermentation through suitable gene loci.

Effects of bioelectricity generation processes on methane emission and bacterial community in wetland and carbon fate analysis

Wetlands are an important carbon sink for greenhouse gases (GHGs), and embedding microbial fuel cell (MFC) into constructed wetland (CW) has become a new technology to control methane (CH4) emission. Rhizosphere anode CW–MFC was constructed by selecting rhizome-type wetland plants with strong hypoxia tolerance, which could provide photosynthetic organics as alternative fuel. Compared with non-planted system, CH4 emission flux and power output from the planted CW–MFC increased by approximately 0.48 ± 0.02 mg/(m2·h) and 1.07 W/m3, respectively. The CH4 emission flux of the CW–MFC operated under open-circuit condition was approximately 0.46 ± 0.02 mg/(m2·h) higher than that under closed-circuit condition. The results indicated that plants contributed to the CH4 emission from the CW–MFC, especially under open-circuit mode conditions. The CH4 emission from the CW–MFC was proportional to external resistance, and it increased by 0.67 ± 0.01 mg/(m2·h) when the external resistance was adjusted from 100 to 1000 Ω. High throughput sequencing further showed that there was a competitive relationship between electrogenic bacteria and methanogens. The flora abundance of electrogenic bacteria was high, while methanogens mainly consisted of Methanothrix, Methanobacterium and Methanolinea. The form and content of element C were analysed from solid phase, liquid phase and gas phase. It was found that a large amount of carbon source (TC = 254.70 mg/L) was consumed mostly through microbial migration and conversion, and carbon storage and GHGs emission accounted for 60.38% and 35.80%, respectively. In conclusion, carbon transformation in the CW–MFC can be properly regulated via competition of microorganisms driven by environmental factors, which provides a new direction and idea for the control of CH4 emission from wetlands.Graphical

Electrogenic Staphylococcus warneri in lactate-rich skin

The electrogenicity of environmental bacteria has been thoroughly explored and has been known to have the unique capability of decomposing hazardous chemicals for environmental remediation. However, electrogenic bacteria in human skin in regards to their electrical properties and locations have not yet been determined. Here, electrodermal activities and metabolite compositions at different locations of arm skin were assessed. Compared to the uppermost part of arm, we found that the forearm elicited high electrodermal activity and carried abundant lactate and alpha-ketoglutarate, two components commonly present in sweat. Upon culturing bacteria from the forearm, an iron-resistant strain of Staphylococcus warneri (S. warneri) was identified through 16S ribosomal RNA sequencing. Voltage changes induced by S. warneri in the presence of glucose were detected by two voltmeters of different electrode materials, demonstrating the electrogenicity of skin bacteria. Furthermore, we discovered that S. warneri has the ability to metabolize lactate to generate electricity. The results of this study reveal changes in skin conductance caused by bacterial electricity that are mediated by skin endogenous molecules and may provide a novel method of monitoring environmental skin insults.

A miniaturized bioelectricity generation device using plant root exudates to feed electrogenic bacteria

This paper presents a miniaturized plant-microbial fuel cell (mPFMC) as an assay tool that can examine different combinations of plants and electrogenic bacteria to maximize bioelectricity generation. The plant is grown in a miniature plant growth chamber (PGC). Root exudates of the plant provide carbon-containing organic matter to support the catalytic reaction of the bacteria inoculated and grown on the carbon cloth anode of a miniature microbial fuel cell (MFC). The mPFMC utilizes a semipermeable hydrophilic filtering membrane to separate the PGC from the MFC. This membrane allows retaining the bacteria inside the MFC for inoculation and growth and prevents them from entering the PGC; however, the membrane still permits the root exudates into the MFC as the sole carbon source to the bacteria grown on the anode of the device. A pilot proof-of-concept study was conducted to validate the mPMFC, by using it to examine electricity generation of the device with different varieties of model organisms, including rice plant cultivars Kitaake and IR24, and bacterial species Shewanella oneidensis strain MR-1 and Pseudomonas aeruginosa strain PA14. The plant cultivars were grown hydroponically without using soils, thus eliminating the effect of soil microorganisms and nutrients on the bioelectricity generation of the device. The present mPFMC has high compactness with the dimensions of 25 × 25 × 29 mm3, consumes only 3 mL volume of plant growth medium and less than 1 mL volume of anolyte and catholyte each, and produces electricity within only several hours after the plants are loaded into the device. The present technology will allow large-scale parallel screening of different combinations of small plants and electrogenic bacteria and their strains for bioelectricity generation.

Enhanced degradation of high-concentrated 2,4,6 trichlorophenol-containing wastewater by micron-grade high iron-containing fly ash/loofah sponge biochar: Metagenomic functional succession

In order to strengthen the treatment of phenolic wastewater by anaerobic biotechnology, micron-grade high iron-containing fly ash/loofah sponge biochar (MHIFA/LsBC) was prepared and added to anaerobic activated sludge. It was domesticated and cultured in anaerobic bottle by a constant temperature oscillation incubator. Its promoting effect on the anaerobic degradation of high-concentrated 2,4,6-trichlorophenol (2,4,6-TCP) wastewater and its effect on the composition and function of microbial community were studied. The results indicated that with MHIFA/LsBC, the final removal rates of COD and 2,4,6-TCP in R1 (75.6% and 75.1%) were 2.1 and 1.81 times than those of the control group, respectively. The maximum methane yield was 107.25 mL/d. MHIFA/LsBC addition resulted in higher biomass and conductivity, and simultaneously increased the concentration of EPS and coenzyme F420. Microbial community analysis indicated that the enriched electrogenic bacteria Pseudomonas might perform DIET with Methanothrix through bioelectrical connection assisted by MHIFA/LsBC, and promote the anaerobic degradation of 2,4,6-TCP. As the functional genus induced by MHIFA/LsBC, Pseudomonas promoted the degradation and transformation of phenolic pollutants, and Azotobacter played a keystone role in metabolism for hydrogen production by preserving the NADH/NAD+ balance.

Evaluation of extracellular electron transfer in Pseudomonas aeruginosa by co-expression of intermediate genes in NAD synthetase production pathway.

Pseudomonas aeruginosa (PA) is an electrogenic bacterium, in which extracellular electron transfer (EET) is mediated by microbially-produced phenazines, especially pyocyanin. Increasing EET rate in electrogenic bacteria is key for the development of biosensors and bioelectrofermentation processes. In this work, the production of pyocyanin, Nicotinamide Adenine Dinucleotide (NAD) and NAD synthetase by the electrogenic strain PA-A4 is determined using a Microbial Fuel Cell (MFC). Effects of metabolic inhibition and enhancement of pyocyanin and NAD synthetase on NAD/NADH levels and electrogenicity was demonstrated by short chronoamperometry measurements (0-48h). Combined overexpression of two intermediate NAD synthetase production genes-nicotinic acid mononucleotide adenyltransferase (nadD) and quinolic acid phosphoribosyltransferase (nadC) genes, which are distant on the PA genomic map, enabled co-transcription and increased NAD synthetase activity. The resulting PA-A4 nadD + nadC shows increases in pyocyanin concentration, NAD synthetase activity, NAD/NADH levels, and MFC potential, all significantly higher than its wild type. Extracellular respiratory mechanisms in PA are linked with NAD metabolism, and targeted increased yield of NAD could directly lead to enhanced EET. A previous attempt at enhancing NAD synthetase for electrogenicity by targeting the terminal NAD synthetase gene (nadE) in standard P. aeruginosa PA01 had earlier been reported. Our work however, poses another route to electrogenicity enhancement in PA using; a combination of nadD and nadC. Further experiments are needed to understand specific intracellular mechanisms governing how over-expression of nadD and nadC induced activity of NadE protein. These findings significantly advance the knowledge of the versatility of NAD biosynthetic genes in PA electrogenicity.

The use of a self-generated current in a coupled MFC-AnMBR system to alleviate membrane fouling

In this study, we developed a coupled microbial fuel cell-anaerobic membrane bioreactor (MFC-AnMBR) system to degrade and remove membrane foulants, rather than preventing foulants from reaching the membrane surface through electrostatic repulsion. The MFC-AnMBR system consists of a conductive membrane as the MFC anode and an MBR filter membrane. The operating time of an experimental group with a 0.38-mA current was extended to 89 days longer than that of a control group (no cleaning during the operating period). Fourier-transform infrared spectroscopy indicated that the main membrane foulants were polysaccharides, proteins, and lipids. The concentrations of polysaccharides and proteins were significantly lower in the experimental group than in the control group. In confocal laser scanning microscopy, membrane surface proteins, α-polysaccharides, and β-polysaccharides decreased in the experimental group by 45.34%, 57.19%, and 26.46% compared to the control group. Three-dimensional excitation–emission matrix fluorescence spectroscopy and molecular weight (MW) analysis revealed that foulants deposited on the anode film surface were degraded into substances with low MW more effectively in the experimental group than in the control group. Two-dimensional heterogeneous correlation spectroscopy and high-throughput sequencing revealed that protein-like substances were degraded in both the control and experimental groups, but degradation of polysaccharide-like substances was more efficient in the experimental group. The degradation of polysaccharide-like and protein-like substances can be attributed to bacteria involved in anaerobic fermentation and electrogenic bacteria. Therefore, in the presence of electrons, polysaccharide-like substances with high MW can be converted into hydroxy-containing compounds with low MW, which are more readily degraded and utilized by microorganisms, thereby preventing membrane fouling.

Elucidation of complex respiratory chains: a straightforward strategy to monitor electron transfer between cytochromes.

Cytochromes are electron transfer (ET) proteins essential in various biological systems, playing crucial roles in the respiratory chains of bacteria. These proteins are particularly abundant in electrogenic microorganisms and are responsible for the efficient delivery of electrons to the cells' exterior. The capability of sending electrons outside the cells open new avenues to be explored for emerging biotechnological applications in bioremediation, microbial electrosynthesis, and bioenergy fields. To develop these applications, it is critical to identify the different redox partners and to elucidate the stepwise ET along the respiratory paths. However, investigating direct ET events between proteins with identical features in nearly all spectroscopic techniques is extremely challenging. Nuclear magnetic resonance (NMR) spectroscopy offers the possibility to overcome this difficulty by analysing the alterations of the spectral signatures of each protein caused by electron exchange events. The uncrowded NMR spectral regions containing the heme resonances of the cytochromes display unique and distinct signatures in the reduced and oxidized states, which can be explored to monitor ET within the redox complex. In this study, we present a strategy for a fast and straightforward monitorization of ET between c-type cytochromes, using as model a triheme periplasmic cytochrome and a membrane-associated monoheme cytochrome from the electrogenic bacterium Geobacter sulfurreducens. The comparison between the 1D 1H NMR spectra obtained for samples containing the two cytochromes and for samples containing the individual proteins clearly demonstrated a unidirectional ET within the redox complex. This strategy provides a simple and straightforward means to elucidate complex biologic respiratory ET chains.

Ceramic-microbial fuel cell (C-MFC) for waste water treatment: A mini review

Microbial fuel cell (MFC) is a bio-electrochemical system that utilizes the activity of electrogenic bacteria to generate electricity. When wastewater is used as feed in MFC, its organic constituents are hydrolyzed and oxidized by the bacteria. Hence, this technology is a source of clean electricity while simultaneously treating wastewater. Over the years much research has been done to improve its efficiency as well as to reduce the cost of implementation and functioning. However, scalability and commercialization of this technology still faces several challenges. This mini review discusses the use of ceramics in MFCs using wastewater feed as a method of overcoming the current technological challenges. Ceramics can be used as separators, chassis or electrode, conferring facile chemical and structural stability. The material is low-cost, environment-friendly and easily available. Studies reporting stacked configurations have been mentioned, and those that have reported field studies and technology oriented practical applications. Critical analysis of the scalability of the use of ceramics for the dual purpose of electricity generation as well as wastewater treatment has been done in this review. Future research directives towards potential sustainable commercialization have also been mentioned. C-MFC is a promising technology and the primary aim of this review is to help enhance the knowledge base for the optimization of use of ceramics in MFC to achieve large-scale clean electricity generation and sewage treatment.

Electrogenic Bacteria Promise New Opportunities for Powering, Sensing, and Synthesizing.

Considerable research efforts into the promises of electrogenic bacteria and the commercial opportunities they present are attempting to identify potential feasible applications. Metabolic electrons from the bacteria enable electricity generation sufficient to power portable or small-scale applications, while the quantifiable electric signal in a miniaturized device platform can be sensitive enough to monitor and respond to changes in environmental conditions. Nanomaterials produced by the electrogenic bacteria can offer an innovative bottom-up biosynthetic approach to synergize bacterial electron transfer and create an effective coupling at the cell-electrode interface. Furthermore, electrogenic bacteria can revolutionize the field of bioelectronics by effectively interfacing electronics with microbes through extracellular electron transfer. Here, these new directions for the electrogenic bacteria and their recent integration with micro- and nanosystems are comprehensively discussed with specific attention toward distinct applications in the field of powering, sensing, and synthesizing. Furthermore, challenges of individual applications and strategies toward potential solutions are provided to offer valuable guidelines for practical implementation. Finally, the perspective and view on how the use of electrogenic bacteria can hold immeasurable promise for the development of future electronics and their applications are presented.

Introducing electrolysis to enhance anaerobic digestion resistance to acidification.

The phenomenon that the anaerobic system is inhibited by acid has always been a bottleneck hindering the application of anaerobic digestion (AD) technology. We tried to introduce electrolysis into AD to improve the acidification resistance, and eventually the productivity of the energy. In a batch fermentation device, the ability of electrochemical anaerobic digestion (EAD) to resist acidification was evaluated in current intensity, electrode potential, AC impedance, microbial community, pH value, and volatile fatty acids (VFAs). The results showed that the average concentration of VFAs in EAD was 32.9% lower than that in AD, the energy efficiency of EAD is 53.25% higher than AD, indicating that EAD has stronger anti-acidification ability and energy conversion efficiency than AD. When the EAD reaches a steady state, the current intensity fluctuates in the range of 7-12mA, the electrode potential difference is maintained at 600 ± 5mV, and the internal resistance decreases from 3333.3 ± 16Ω at startup to 68.9 ± 1.4Ω at the steady state, indicating that the EAD has stronger resistance to acidification may be due to the degradation of some VFAs on the electrode surface. Furthermore, the 16S rRNA sequencing analysis showed that the dominant electricity-producing bacteria on EAD anode surface were Clostridium, Hydrogenophaga and Trichloromonas, with a relative abundance of 40.32%, while the relative abundance of electrogenic bacteria in AD bulk solution and EAD bulk solution were about 1/2 and 1/4 that of EAD anode film, suggesting that the electricity-producing bacteria on the electrode surface play an important role in the degradation of VFAs.

Reading the ground: Understanding the response of bioelectric microbes to anthropogenic compounds in soil based terrestrial microbial fuel cells.

Electrogenic bacteria produce power in soil based terrestrial microbial fuel cells (tMFCs) by growing on electrodes and transferring electrons released from the breakdown of substrates. The direction and magnitude of voltage production is hypothesized to be dependent on the available substrates. A sensor technology was developed for compounds indicative of anthropological activity by exposing tMFCs to gasoline, petroleum, 2,4-dinitrotoluene, fertilizer, and urea. A machine learning classifier was trained to identify compounds based on the voltage patterns. After 5 to 10 days, the mean voltage stabilized (+/- 0.5 mV). After the entire incubation, voltage ranged from -59.1 mV to 631.8 mV, with the tMFCs containing urea and gasoline producing the highest (624 mV) and lowest (-9 mV) average voltage, respectively. The machine learning algorithm effectively discerned between gasoline, urea, and fertilizer with greater than 94% accuracy, demonstrating that this technology could be successfully operated as an environmental sensor for change detection.

A dual chamber microbial fuel cell based biosensor for monitoring copper and arsenic in municipal wastewater

This study investigated a dual-chamber microbial fuel cell-based biosensor (DC-MFC-B) for monitoring copper and arsenic in municipal wastewater. Operational conditions, including pH, flow rate, a load of organic substrate and external resistance load, were optimized to improve the biosensor's sensitivity. The DC-MFC-B's toxicity response was established under the electroactive bacteria inhibition rate function to a specific heavy metal level as well as the recovery of the DC-MFC-B. Results show that the DC-MFC-B was optimized at the operating conditions of 1000 Ω external resistance, COD 300 mg L−1 and 50 mM K3Fe(CN)6 as a catholyte solution. The voltage output of the DC-MFC-B decreased with increasing in the copper and arsenic concentrations. A significant linear relationship between the maximum voltage of the biosensor and the heavy metal concentration was obtained with a coefficient of R2 = 0.989 and 0.982 for copper and arsenic, respectively. The study could detect copper (1–10 mg L−1) and arsenic (0.5–5 mg L−1) over wider range compared to other studies. The inhibition ratio for both copper and arsenic was proportional to the concentrations, indicating the electricity changes are mainly dependent on the activity of the electrogenic bacteria on the anode surface. Moreover, the DC-MFC-B was also recovered in few hours after being cleaned with a fresh medium. It was found that the concentration of the toxicant effected on the recovery time and the recovery time was varied between 4 and 12 h. In short, this work provided new avenues for the practical application of microbial fuel cells as a heavy metal biosensor.

Membrane-less microbial fuel cell: effect of pH on the electricity generation powered by municipal food waste

Fossil fuels have supported the industrialization and economic growth of countries during the past centuries and it is clear that they cannot indefinitely sustain in a longer time. In this study, membrane-less microbial fuel cell (ML-MFC) with mediators-less and air cathode had potential solution to generate electricity power and at the same time could reduce the abundant of food waste (1.64 kg/daily, around 8 tonnes/year) which dumped in the landfill and it’s cost effective device. The ML-MFC operated electrochemically incorporate electrogenic bacteria (EB) acted as a biocatalyst in order to produce electricity. The performance and optimization performance of food waste was evaluated using one-factor-at-a-time (OFAT) method and it was focused to pH for power generation. To determine the generated electricity the polarization curve was used to evaluate the performance of ML-MFC. The chemical oxygen demand (COD) of food waste was studied. The optimization of pH condition in ML-MFC was ranging from 7 to 9. Results showed that pH 8 was the optimum pH for EB strain, Bacillus Subtilis, with the high voltage (807 mV), EB biomass (15.46 mg/L), and power density (373.3 mW/m2) generated. Clearly the pH environment condition affected the efficiency of ML-MFC performance. The increase in EB biomass also increased the voltage in the ML-MFC, proving that EB biomass and voltage were associated with growth.

Catalytic membrane cathode integrated in a proton exchange membrane-free microbial fuel cell for coking wastewater treatment

BackgroundCoking wastewater (CW) is characterized by complex composition, high concentration and toxicity, thereby challenging the treatment technologies. Traditional microbial fuel cell (MFC) is deficient in effluent quality and capital cost. Therefore, integrating the catalytic electrode membrane in separation process in MFC is promising for actual wastewater treatment, while replacing proton exchange membrane (PEM) to reduce cost. MethodsA CNF-CFO/PM membrane (blended with carbon nanofiber-CoFe2O4, polyvinylidene fluoride) was prepared via casting and phase inversion. By using this membrane as cathode, activated carbon-loaded electrogenic bacteria as bio-anode, the catalytic membrane cathode-MFC system (CM-MFC) was constructed with quartz sand separating layer (QSL) replacing PEM. Significant findingsModification with CNF-CFO catalyst effectively improved the catalytic and anti-fouling (membrane foulants) property of membrane cathode. The optimal activity of CM-MFC was achieved under 36 h (HRT), with the COD decreasing from 4325.0-5074.3 mg L−1 to 50.0-92.8 mg L−1, and the stable output voltage of ∼0.40 V. The high-throughput sequencing results clarified that the enriched electrogenic bacteria coexisted with other anaerobic bacteria in the anodic chamber and functioned for electron transfer and organics removal. Integrating with the catalysis and filtration processes of membrane cathode, the effluent quality after primary treatment in the anodic chamber was further enhanced.

Co, N co-doped hierarchical porous carbon as efficient cathode electrocatalyst and its impact on microbial community of anode biofilm in microbial fuel cell

The exploration of low-cost, long-term stable, and highly electrochemically active cathode catalysts is important for the practical application of microbial fuel cell (MFC). In this work, a series of the 3D hierarchical porous Co–N–C (3DHP Co–N–C) materials are designed and synthesized by a metal-organic framework ZIF-67 as a precursor and SiO2 sphere of different sizes as the hard template. The 3DHP Co–N–C-2 with 129 nm macropore exhibits excellent ORR performance in 0.1 M KOH solution with a half-wave potential of 0.80 V vs. RHE and superior durability than Pt/C (20%) due to the specific macropore-mesopore-micropore structure that exposes a large number of active sites and accelerates the electrolyte transport and oxygen diffusion. The MFC with 3DHP Co–N–C-2 as the cathode catalysts shows excellent performance with a maximum power density of 426.9±7.87 mW m−2 and favorable durability after 50 d of operation. In addition, 16s rDNA results reveal the presence of different dominant electrogenic bacteria and different abundance of important non-electrogenic bacteria in the anode biofilm in MFCs using cathode catalysts with different ORR activity. And 3DHP Co–N–C-2 was found to be beneficial to the synergistic effect of electrogenic and non-electrogenic bacteria. This study explores electrocatalysts in terms of both electrocatalytic activity and anode microorganisms, providing new and comprehensive insights into the power generation of MFC.