Construction and performance analysis of a microbial electrochemical sensor for monitoring heavy metals in water environment / 生物工程学报

A microbial fuel cell (MFC)-based microbial electrochemical sensor was developed for real-time on-line monitoring of heavy metals in water environment. The microbial electrochemical sensor was constructed with staggered flow distribution method to optimize the parameters such as external resistance value and external circulation rate. The inhibition of concentration of simulated heavy metal wastewater on voltage under optimal parameters was analyzed. The results showed that the best performance of MFC electrochemical sensor was achieved when the external resistance value was 130 Ω and the external circulation rate was 1.0 mL/min. In this case, the microbial electrochemical sensors were responsive to 1-10 mg/L Cu2+, 0.25-1.25 mg/L Cd2+, 0.25-1.25 mg/L Cr6+ and 0.25-1.00 mg/L Hg2+ within 60 minutes. The maximum rejection rates of the output voltage were 92.95%, 73.11%, 82.76% and 75.80%, respectively, and the linear correlation coefficients were all greater than 0.95. In addition, the microbial electrochemical sensor showed a good biological reproducibility. The good performance for detecting heavy metals by the newly developed microbial electrochemical sensor may facilitate the real-time on-line monitoring of heavy metals in water environment.

Construction of conjugated polymer-exoelectrogen hybrid bioelectrodes and applications in microbial fuel cells / 生物工程学报

Microbial fuel cell (MFC) is a bioelectrochemical device, that enables simultaneous wastewater treatment and energy generation. However, a few issues such as low output power, high ohmic internal resistance, and long start-up time greatly limit MFCs' applications. MFC anode is the carrier of microbial attachment, and plays a key role in the generation and transmission of electrons. High-quality bioelectrodes have developed into an effective way to improve MFC performance. Conjugated polymers have advantages of low cost, high conductivity, chemical stability and good biocompatibility. The use of conjugated polymers to modify bioelectrodes can achieve a large specific surface area and shorten the charge transfer path, thereby achieving efficient biological electrochemical performance. In addition, bacteria can be coated with nano-scale conjugated polymer and effectively transfer the electrons generated by cells to electrodes. This article reviews the recently reported applications of conjugated polymers in microbial fuel cells, focusing on the MFC anode materials modified by conjugated polymers. This review also systematically analyzes the advantages and limitations of conjugated polymers, and how these composite hybrid bioelectrodes solve practical issues such as low energy output, high inner resistance, and long starting time.

Diversidad bacteriana en el biocátodo reductor de Cr(VI) de una Celda de Combustible Microbiana con puente salino / Bacterial diversity in the Cr(VI) reducing biocathode of a Microbial Fuel Cell with salt bridge

Although Cr(VI)-reducing and/or tolerant microorganisms have been investigated, there is no detailed information on the composition of the microbial community of the biocathode microbial fuel cell for Cr(VI) reduction. In this investigation, the bacterial diversity of a biocathode was analyzed using 454 pyrosequencing of the 16S rRNA gene. It was found that most bacteria belonged to phylum Proteobacteria (78.8%), Firmicutes (7.9%), Actinobacteria (6.6%) and Bacteroidetes (5.5%), commonly present in environments contaminated with Cr(VI). The dominance of the genus Pseudomonas (34.87%), followed by the genera Stenotrophomonas (5.8%), Shinella (4%), Papillibacter (3.96%), Brevundimonas (3.91%), Pseu-dochrobactrum (3.54%), Ochrobactrum (3.49%), Hydrogenophaga (2.88%), Rhodococcus (2.88%), Fluviicola (2.35%), and Alcaligenes (2.3%), was found. It is emphasized that some genera have not previously been associated with Cr(VI) reduction. This biocathode from waters contaminated with tannery effluents was able to remove Cr(VI) (97.83%) in the cathodic chamber. Additionally, through use of anaerobic sludge in the anodic chamber, the removal of 76.6% of organic matter (glucose) from synthetic waste water was achieved. In this study, an efficient biocathode for the reduction of Cr(VI) with future use in bioremediation, was characterized.

Aunque se ha investigado sobre los microorganismos reductores y/o tolerantes de Cr(VI), no hay información detallada sobre la composición de la comunidad microbiana del cátodo de una Celda de Combustible Microbiana para la reducción de Cr(VI). En esta investigación se analizó la diversidad bacteriana de un biocátodo usando pirosecuenciación 454 del gen 16S rRNA. Se encontró que la mayoría de las bacterias pertenecieron a los filos Proteobac-teria (78,8%), Firmicutes (7,9%), Actinobacteria (6,6%) y Bacteroidetes (5,5%), comúnmente presentes en ambientes contaminados con Cr(VI). Se encontró como género dominante a Pseudomonas (34,87%), seguido por los géneros Stenotrophomonas (5,8%), Shinella (4%), Papil-libacter (3,96%), Brevundimonas (3,91%), Pseudochrobactrum (3,54%), Ochrobactrum (3,49%), Hydrogenophaga (2,88%), Rhodococcus (2,88%), Fluviicola (2,35%) y Alcaligenes (2,3%). Se destaca que algunos géneros no han sido previamente asociados con la reducción de Cr(VI). Este biocátodo procedente de aguas contaminadas con efluentes de curtiembres fue capaz de remover Cr(VI) (97,83%) en la cámara catódica. Adicionalmente, a través del uso de lodo anaeróbico en la cámara anódica, se logró la remoción del 76,6% de materia orgánica (glucosa) a partir de agua residual sintética. En este estudio se caracterizó un eficiente biocátodo para la reducción de Cr(VI) con futuro uso en biorremediación.

Use of Glycerol as Substrate for Electricity Generation Using Citrobacter sp. in a Double Chambered Microbial Fuel Cell

Microbial fuel cells (MFCs) have the potential to convert organic substratesinto electricity thus facilitating the strategies of renewable energy production. In recentyears the exploration for newer energy resources for MFC has widened and in thiscontext, the use of glycerol in bioenergy production was investigated to check itsefficacy in electricity generation. Thus, the power generation of a double-chamberedMFC was observed with glycerol as the substrate and Citrobacter sp. as the bacteriumof interest. Here, the MFC system yielded a power density of 79.42 mW/m² with carboncloth as the electrodes and Nafion as the proton exchange membrane. Further, the MFCsystem was optimized for the ambient temperature, in which the maximum voltage andcurrent were obtained at 35⁰C. In the study, the Citrobacter sp. showed its bestperformance at the optimum temperature of 350C. Likewise, the optimal pH for the MFCsystem in which the electrical output was high was observed in the pH value of 7.4.Moreover, the anodic bacterial biofilm analysis under confocal microscope providedevidence of the presence of live bacteria which were responsible for the efficientcurrent generation of the MFC system.

The behaviour of membrane less sediment microbial fuel cell in the terms of bioremediation and power generation 108-112

@#Aims: To study the performance of SMFC in the terms of power generation and toxic metals removal. This study was also focused on the characterization of SMFC electro-microbiology. Methodology and results: A SMFC was designed and loaded with sediment and overlying water. This SMFC was synchronized with wireless data logger acquisition system. The toxic metals removal capacity was measured by atomic absorption spectroscopy. The characterization of SMFC bacteria was done by 16S rRNA.In this study the experiments were carried out in a dual-chamber SMFC with external resistances 30 kΩ-50 Ω. The SMFC was produced power about 630 mV with maximum power density 40 mW/m2and current density 250 mA/m2. After 120 days of operation, SMFC removed cadmium and copper about 22.6 and 150 mg/kg, respectively. The SMFC also showed high cadmium (86%) and copper (90%) removal at pH 7.0 and temperature 40 °C. The most dominant bacterial community at anode and cathode was identified as Pseudomonas spp. which could be function as exoelectrogen. Conclusion, significance and impact of the study: The results indicated that the SMFC system could be applied as a long term and effective tool for the removal of cadmium and copper contaminated sediments and supply power for commercial devices. The Pseudomonas spp. may be used as a genetic donor for the other non-exoelectrogens strains.

Effect of Anode Electrode Modified with Carbon Nanomaterials of Microbial Fuel Cell-based Sensor on Detection Sensitivity of Water Toxicity / 分析化学

The low sensitivity of microbial fuel cell ( MFC)-biosensor is one of the bottlenecks in its practical application. To investigate the effect of anode electrode modified with carbon nanomaterials on the sensitivity of water toxicity detection of MFC-based biosensor, graphite felts ( GF ) were modified using two carbon nanomaterials of multi-walled carbon nanotubes ( MWNT ) and conductive carbon black ( GCB ) . MFC biosensors were started up with the anode electrodes, and the results showed that resistance of the GCB and MWNT-modified electrode was smaller than that of unmodified electrode, and the order of MFC power output was GCB/GF-MFC (2. 63 W/m2)>MWNT/GF-MFC (2. 56 W/m2)>GF-MFC (2. 09 W/m2). Then, 3, 5-dichlorophenol poison ( DCP) was used as a model toxicant in toxicity test, the order of toxicity inhibition ratios of 10 mg/L DCP to three MFC biosensor was MWNT/GF-MFC (31. 8% )>GCB/GF-MFC (26. 3% )>GF-MFC (20. 1% ). The sensitivity for toxicity detection by MFC biosensors with anode electrode modified with carbon nanomaterials was improved, and MWNT/GF-MFC had the highest sensitivity. The result of the study may promote the application of MFC biosensor in water pollution monitoring.

Isolation of Electrogenic Microorganisms with Potential to Reduce Hexavalent Chromium / Aislamiento de microorganismos electrogénicos con potencial para reducir cromo hexavalente

RESUMEN Se realizó el aislamiento de microorganismos cultivables a partir de la biopelícula formada sobre el ánodo de una celda de combustible microbiana puesta en operación durante 30 días; los microorganismos aislados fueron evaluados en su capacidad de producir energía en celdas de combustible microbianas y de reducir el cromo hexavalente, Cr (VI). Se aislaron cinco microorganismos, los cuales fueron caracterizados mediante análisis del gen del ARNr 16S, el cual ubicó a los microorganismos en cuatro géneros bacterianos: Exiguobacterium (CrMFC1), Acinetobacter (CrMFC2), Aeromonas (CrMFC3 y CrMFC5), y Serratia (CrMFC4). Todas las cepas aisladas mostraron actividad electrogénica y capacidad para reducir cromo hexavalente; la cepa de Acinetobacter CrMFC2 mostró el mejor desempeño electroquímico al registrar una densidad de potencia máxima de 18,61 mW/m²; las demás cepas mostraron valores de densidad de potencia máxima entre 4,6 mW/m² y 7.1 mW/m². Las cepas de Aeromonas CrMFC5 y Exiguobacterium CrMFC1 mostraron las mejores tasas de reducción de cromo al ser capaces de reducir el 100% del Cr (VI) en menos de 24 horas, destacándose la cepa de Aeromonas CrMFC5 la cual redujo el 100 % de Cr (VI) en 10 horas; las demás cepas redujeron el 100 % del contaminante al cabo de 28 a 30 horas. Los microorganismos aislados en este estudio son escasamente conocidos por su capacidad electrogénica y de reducir el Cr (VI); no obstante, se muestran promisorios para su utilización en sistemas mixtos que involucren la producción de energía acoplada a sistema de biorremediación de aguas contaminadas con cromo.

ABSTRACT Isolation of cultivable microorganisms was made from the biofilm formed on the anode of a microbial fuel cell put into operation for 30 days; isolated microorganisms were evaluated for their ability to produce energy and reduce the hexavalent chromium Cr (VI). Five microorganisms were isolated, which were characterized by analysis of 16S rRNA gene, placing them in four bacterial genera: Exiguobacterium (CrMFC1), Acinetobacter (CrMFC2), Aeromonas (CrMFC3 and CrMFC5) and Serratia (CrMFC4). All isolates showed electrogenic activity and ability to reduce hexavalent chromium; the Acinetobacter CrMFC1 strain showed the best electrochemical performance registering a maximum power density of 18.61 mW/m²; the other strains showed values of maximum power density between 4.6 mW/m² and 7.1 mW/m². Strains Aeromonas CrMFC5 and Exiguobacterium CrMFC1 showed the best rates of chromium reduction being able to reduce 100 % of the Cr (VI) in less than 24 hours, the Aeromonas CrMFC5 strain was the most efficient, reducing 100 % of Cr (VI) in 10 hours; the other strains reduced 100% of the contaminant after 28 to 30 hours. The microorganisms isolated in this study are hardly known for their electrogenic capacity and for reducing Cr (VI); however, show promise for their use in combined systems involving energy production system coupled to bioremediation of chromium contaminated water.

Bacterial Diversity Associated with Anodic Biofilms in Microbial Fuel Cells Fed with Wastewater / Diversidad bacteriana asociada a biopelículas anódicas en celdas de combustible microbianas alimentadas con aguas residuales

RESUMEN. El presente trabajo evaluó la diversidad bacteriana asociada a las biopelículas formadas sobre los ánodos de celdas de combustible microbianas, por medio del análisis del gen del ARNr 16S y observaciones por microscopía electrónica de barrido. Se construyeron celdas de combustible microbianas de una cámara que permanecieron en operación durante 30 días utilizando muestras ambientales como inóculo y único sustrato energético; las celdas fueron monitoreadas en función de la producción de energía durante el desarrollo del experimento; al finalizar los ensayos, se realizó la caracterización molecular y observaciones mediante microscopía electrónica de barrido a las biopelículas formadas. Se reportan valores de densidad de potencia máxima de 4,85 mW/m² para el agua residual doméstica y de 1,85 mW/m² para el caso del agua residual industrial, con disminuciones de 71 % de la DBO para el agua residual doméstica y de 59 % de la DBO para el caso del agua residual industrial. Se logró la recuperación de 15 secuencias únicas provenientes de la amplificación del gen del ARNr 16S obtenidas a partir de las biopelículas formadas sobre los ánodos. El análisis filogenético ubicó estas secuencias en la clase Deltaproteobacteria. Los dos sustratos ambientales contienen una importante e interesante diversidad microbiana, mostrándolos promisorios para la construcción y operación de MFC y la implementación de procesos de biodegradación de materia orgánica.

ABSTRACT. This study evaluated the bacterial diversity associated with biofilms formed on the anode of microbial fuel cells (MFC), by analyzing the 16S rRNA gene and observations by scanning electron microscopy. Single chambered MFC were constructed and kept in operation for 30 days using environmental samples as inoculum and sole energy substrate; the MFC were monitored as a function of energy production in the course of the experiment; at endpoint, molecular characterization and observations using scanning electron microscopy was performed to the formed biofilms. Values of maximum power density of 4.85 mW/m2 for domestic wastewater and 1.85 mW/m2 in the case of industrial wastewater are reported, with declines of 71 % of the BOD for domestic wastewater and 59 % of the BOD in the case of industrial wastewater. Recovery of 15 unique sequences from the amplification of 16S rRNA gene obtained from the biofilms formed on the anodes was accomplished. Phylogenetic analysis placed these sequences in the Deltaproteobacteria class. The two environmental substrates contain an important and interesting microbial diversity, showing them very promising for the construction and operation of MFC and implementing biodegradation of organic material.

Detection of toxic substances in microbial fuel cells / 生物工程学报

Microbial fuel cells (MFCs) is a highly promising bioelectrochemical technology and uses microorganisms as catalyst to convert chemical energy directly to electrical energy. Microorganisms in the anodic chamber of MFC oxidize the substrate and generate electrons. The electrons are absorbed by the anode and transported through an external circuit to the cathode for corresponding reduction. The flow of electrons is measured as current. This current is a linear measure of the activity of microorganisms. If a toxic event occurs, microbial activity will change, most likely decrease. Hence, fewer electrons are transported and current decreases as well. In this way, a microbial fuel cell-based biosensor provides a direct measure to detect toxicity for samples. This paper introduces the detection of antibiotics, heavy metals, organic pollutants and acid in MFCs. The existing problems and future application of MFCs are also analyzed.

Progresses and Prospects of Microbial Fuel Cell in Analytical Applications / 分析化学

Microbial fuel cell ( MFC ) is a type of energy device in which exoelectrogens are harnessed for directly converting the chemical energy of organic matter into electric energy. In addition to researches on the development of high-performance MFC, we have witnessed a rapid progress in the analytical application of MFCs. The MFC-based biosensors are simple and easy to operate, and they can also be used to monitor target online without external power sources, thus attracting more and more attention. Here, we summarize and discuss the progress on using MFCs for measuring biological oxygen demand ( BOD ) , volatile fatty acids, pollutant and toxic compounds, microbial activities and other substances. Furthermore, the design principle of MFC-based biosensors is clarified. The outlook and future prospect of MFC-based biosensors are also discussed in the end.

Application of Electrochemically Active Bacteria as Anodic Biocatalyst in Microbial Fuel Cells / 分析化学

Microbial fuel cell ( MFC ) is a novel device with the function to produce energy and degrade organic materials. The characteristics of anodic electrochemically active bacteria and catalytic activity are one of key factors to affect MFC performance. This review summarized the enrichment, source, taxonomy, physiological and biochemical characteristics and electricity production ability of electrochemically active bacteria.

Design of a microbial fuel cell and its transition to microbial electrolytic cell for hydrogen production by electrohydrogenesis.

Anaerobic bacteria were isolated from industrial wastewater and soil samples and tested for exoelectrogenic activity by current production in double chambered microbial fuel cell (MFC), which was further transitioned into a single chambered microbial electrolytic cell to test hydrogen production by electrohydrogenesis. Of all the cultures, the isolate from industrial water sample showed the maximum values for current = 0.161 mA, current density = 108.57 mA/m2 and power density = 48.85 mW/m2 with graphite electrode. Maximum voltage across the cell, however, was reported by the isolate from sewage water sample (506 mv) with copper as electrode. Tap water with KMnO4 was the best cathodic electrolyte as the highest values for all the measured MFC parameters were reported with it. Once the exoelectrogenic activity of the isolates was confirmed by current production, these were tested for hydrogen production in a single chambered microbial electrolytic cell (MEC) modified from the MFC. Hydrogen production was reported positive from co-culture of isolates of both the water samples and co-culture of one soil and one water sample. The maximum rate and yield of hydrogen production was 0.18 m3H2/m3/d and 3.2 mol H2/mol glucose respectively with total hydrogen production of 42.4 mL and energy recovery of 57.4%. Cumulative hydrogen production for a five day cycle of MEC operation was 0.16 m3H2/m3/d.

Progress in Research of Electrigens in Microbial Fuel Cell / 微生物学通报

Electricigens play an important role in microbial fuel cell(MFC) . This review provides an introduction of different electricigens on theirs taxonomical group,biochemical,physiological and morphological characteristics. The ability of electricity production of electricigens and electron transfer mechanisms in microbial fuel cells are also concluded. The prospect of waste water treatment and bio-electricity production is underlined,it is point out in this review that the future research of microorganism for MFC should be focused on enrichment,adaptation,modification and optimization by multi-strains application to improve the performances of MFC.