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Journal ArticleDOI

Efficient reduction of nitrobenzene to aniline with a biocatalyzed cathode.

28 Oct 2011-Environmental Science & Technology (American Chemical Society)-Vol. 45, Iss: 23, pp 10186-10193
TL;DR: Investigation of the conversion of NB to aniline (AN), a less toxic endproduct that can easily be mineralized, using a fed-batch bioelectrochemical system with microbially catalyzed cathode indicated that the cathode was dominated by an Enterococcus species closely related toEnterococcus aquimarinus.
Abstract: Nitrobenzene (NB) is a toxic compound that is often found as a pollutant in the environment. The present removal strategies suffer from high cost or slow conversion rate. Here, we investigated the conversion of NB to aniline (AN), a less toxic endproduct that can easily be mineralized, using a fed-batch bioelectrochemical system with microbially catalyzed cathode. When a voltage of 0.5 V was applied in the presence of glucose, 88.2 ± 0.60% of the supplied NB (0.5 mM) was transformed to AN within 24 h, which was 10.25 and 2.90 times higher than an abiotic cathode and open circuit controlled experiment, respectively. AN was the only product detected during bioelectrochemical reduction of NB (maximum efficiency 98.70 ± 0.87%), whereas in abiotic conditions nitrosobenzene was observed as intermediate of NB reduction to AN (decreased efficiency to 73.75 ± 3.2%). When glucose was replaced by NaHCO(3), the rate of NB degradation decreased about 10%, selective transformation of NB to AN was still achieved (98.93 ± 0.77%). Upon autoclaving the cathode electrode, nitrosobenzene was formed as an intermediate, leading to a decreased AN formation efficiency of 71.6%. Cyclic voltammetry highlighted higher peak currents as well as decreased overpotentials for NB reduction at the biocathode. 16S rRNA based analysis of the biofilm on the cathode indicated that the cathode was dominated by an Enterococcus species closely related to Enterococcus aquimarinus.
Citations
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Journal ArticleDOI
TL;DR: This perspective review provides a comprehensive summary on the mechanisms of the new bioelectrochemical system (BES) platform technology for efficient and low cost remediation, including petroleum hydrocarbons, chlorinated solvents, perchlorate, azo dyes, and metals, and it discusses the potential new uses of BES approach for some emerging contaminants remediation.

244 citations


Cites background from "Efficient reduction of nitrobenzene..."

  • ...Microbially catalyzed cathode with supplemental power later on showed even higher removal rate (A. Wang et al., 2011)....

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  • ...The cathodic reduction of Hg(II) in MFCs was complex due to mixed products, including Hg22+, Hg0, and Hg2Cl2 (Z. Wang et al., 2011)....

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Journal ArticleDOI
TL;DR: The importance of aryl amines as raw materials for various applications has spurred extensive research in developing economic processes for the reduction of nitroarenes as mentioned in this paper, and developing green methodologies is now a compelling discipline for synthetic organic chemists.
Abstract: The importance of aryl amines as raw materials for various applications has spurred extensive research in developing economic processes for the reduction of nitroarenes. Developing green methodologies is now a compelling discipline for synthetic organic chemists. The recent surge in nanochemistry has led to the development of some interesting applications in nitro reduction processes. This review discusses some recent examples of reports in this field. The different methods are classified based on the source of hydrogen utilized during reduction and the mechanism involved in the reduction process.

228 citations

Journal ArticleDOI
TL;DR: With the biocathode BES, antibacterial activity of CAP was completely removed and nitro group reduction combined with dechlorination reaction enhanced detoxication efficiency of CAP.
Abstract: Chlorinated nitroaromatic antibiotic chloramphenicol (CAP) is a priority pollutant in wastewaters A fed-batch bioelectrochemical system (BES) with biocathode with applied voltage of 05 V (served as extracellular electron donor) and glucose as intracellular electron donor was applied to reduce CAP to amine product (AMCl2) The biocathode BES converted 871 ± 42% of 32 mg/L CAP in 4 h, and the removal efficiency reached 960 ± 09% within 24 h Conversely, the removal efficiency of CAP in BES with an abiotic cathode was only 730 ± 32% after 24 h When the biocathode was disconnected (no electrochemical reaction but in the presence of microbial activities), the CAP removal rate was dropped to 620% of that with biocathode BES Acetylation of one hydroxyl of CAP was noted exclusive in the biocatalyzed process, while toxic intermediates, hydroxylamino (HOAM), and nitroso (NO), from CAP reduction were observed only in the abiotic cathode BES Electrochemical hydrodechlorination and dehalogenase were respon

228 citations

Journal ArticleDOI
TL;DR: The extensively studied exoelectrogenic bacteria Shewanella and Geobacter showed that both directions for electron transfer would be possible and could catalyze various bioelectrochemical reductions.
Abstract: Extracellular electron transfer in microorganisms has been applied for bioelectrochemical synthesis utilizing microbes to catalyze anodic and/or cathodic biochemical reactions. Anodic reactions (electron transfer from microbe to anode) are used for current production and cathodic reactions (electron transfer from cathode to microbe) have recently been applied for current consumption for valuable biochemical production. The extensively studied exoelectrogenic bacteria Shewanella and Geobacter showed that both directions for electron transfer would be possible. It was proposed that gram-positive bacteria, in the absence of cytochrome C, would accept electrons using a cascade of membrane-bound complexes such as membrane-bound Fe-S proteins, oxidoreductase, and periplasmic enzymes. Modification of the cathode with the addition of positive charged species such as chitosan or with an increase of the interfacial area using a porous three-dimensional scaffold electrode led to increased current consumption. The extracellular electron transfer from the cathode to the microbe could catalyze various bioelectrochemical reductions. Electrofermentation used electrons from the cathode as reducing power to produce more reduced compounds such as alcohols than acids, shifting the metabolic pathway. Electrofuel could be generated through artificial photosynthesis using electrical energy instead of solar energy in the process of carbon fixation.

227 citations


Cites methods from "Efficient reduction of nitrobenzene..."

  • ...The direct reduction process was studied in fumarate reduction to succinate [47], nitrate reduction to nitrite [48], nitrobenzene reduction to aniline [86], and hexavalent chromium reduction [18]....

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Journal ArticleDOI
TL;DR: In this article, the impact of redox potentials on gene expression, protein biosynthesis and metabolism as well as redox-potential control strategies for more efficient production of fermentation products are reviewed.

201 citations


Cites background from "Efficient reduction of nitrobenzene..."

  • ...…and S. cerevisiae (Na et al., 2007) and butanol production by C. acetobutylicum (Peguin and Soucaille, 1996) as well as mixed cultures for methane and hydrogen production from organic wastes (Jeon et al., 2009b; Wang et al., 2011) and biodegradation of recalcitrant pollutants (Mu et al., 2010)....

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  • ...acetobutylicum (Peguin and Soucaille, 1996) as well as mixed cultures for methane and hydrogen production from organic wastes (Jeon et al., 2009b; Wang et al., 2011) and biodegradation of recalcitrant pollutants (Mu et al....

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References
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Journal ArticleDOI
TL;DR: Version 4 of MEGA software expands on the existing facilities for editing DNA sequence data from autosequencers, mining Web-databases, performing automatic and manual sequence alignment, analyzing sequence alignments to estimate evolutionary distances, inferring phylogenetic trees, and testing evolutionary hypotheses.
Abstract: We announce the release of the fourth version of MEGA software, which expands on the existing facilities for editing DNA sequence data from autosequencers, mining Web-databases, performing automatic and manual sequence alignment, analyzing sequence alignments to estimate evolutionary distances, inferring phylogenetic trees, and testing evolutionary hypotheses. Version 4 includes a unique facility to generate captions, written in figure legend format, in order to provide natural language descriptions of the models and methods used in the analyses. This facility aims to promote a better understanding of the underlying assumptions used in analyses, and of the results generated. Another new feature is the Maximum Composite Likelihood (MCL) method for estimating evolutionary distances between all pairs of sequences simultaneously, with and without incorporating rate variation among sites and substitution pattern heterogeneities among lineages. This MCL method also can be used to estimate transition/transversion bias and nucleotide substitution pattern without knowledge of the phylogenetic tree. This new version is a native 32-bit Windows application with multi-threading and multi-user supports, and it is also available to run in a Linux desktop environment (via the Wine compatibility layer) and on Intel-based Macintosh computers under the Parallels program. The current version of MEGA is available free of charge at (http://www.megasoftware.net).

29,021 citations

Journal ArticleDOI
TL;DR: A database containing 16S rRNA gene sequences of all prokaryotic type strains was generated and a web-based tool, named EzTaxon, was constructed to achieve identification of isolates based on pairwise nucleotide similarity values and phylogenetic inference methods.
Abstract: 16S rRNA gene sequences have been widely used for the identification of prokaryotes. However, the flood of sequences of non-type strains and the lack of a peer-reviewed database for 16S rRNA gene sequences of type strains have made routine identification of isolates difficult and labour-intensive. In the present study, we generated a database containing 16S rRNA gene sequences of all prokaryotic type strains. In addition, a web-based tool, named EzTaxon, for analysis of 16S rRNA gene sequences was constructed to achieve identification of isolates based on pairwise nucleotide similarity values and phylogenetic inference methods. The system developed provides users with a similarity-based search, multiple sequence alignment and various phylogenetic analyses. All of these functions together with the 16S rRNA gene sequence database of type strains can be successfully used for automated and reliable identification of prokaryotic isolates. The EzTaxon server is freely accessible over the Internet at http://www.eztaxon.org/

2,051 citations

Journal ArticleDOI
TL;DR: Enrichment by repeated transfer of a bacterial consortium harvested from the anode compartment of a biofuel cell in which glucose was used increased the output and selected organisms capable of mediating the electron transfer either by direct bacterial transfer or by excretion of redox components.
Abstract: Microbial fuel cells hold great promise as a sustainable biotechnological solution to future energy needs. Current efforts to improve the efficiency of such fuel cells are limited by the lack of knowledge about the microbial ecology of these systems. The purposes of this study were (i) to elucidate whether a bacterial community, either suspended or attached to an electrode, can evolve in a microbial fuel cell to bring about higher power output, and (ii) to identify species responsible for the electricity generation. Enrichment by repeated transfer of a bacterial consortium harvested from the anode compartment of a biofuel cell in which glucose was used increased the output from an initial level of 0.6 W m−2 of electrode surface to a maximal level of 4.31 W m−2 (664 mV, 30.9 mA) when plain graphite electrodes were used. This result was obtained with an average loading rate of 1 g of glucose liter−1 day−1 and corresponded to 81% efficiency for electron transfer from glucose to electricity. Cyclic voltammetry indicated that the enhanced microbial consortium had either membrane-bound or excreted redox components that were not initially detected in the community. Dominant species of the enhanced culture were identified by denaturing gradient gel electrophoresis and culturing. The community consisted mainly of facultative anaerobic bacteria, such as Alcaligenes faecalis and Enterococcus gallinarum, which are capable of hydrogen production. Pseudomonas aeruginosa and other Pseudomonas species were also isolated. For several isolates, electrochemical activity was mainly due to excreted redox mediators, and one of these mediators, pyocyanin produced by P. aeruginosa, could be characterized. Overall, the enrichment procedure, irrespective of whether only attached or suspended bacteria were examined, selected for organisms capable of mediating the electron transfer either by direct bacterial transfer or by excretion of redox components.

1,234 citations

Journal ArticleDOI
TL;DR: Results show that electromethanogenesis can be used to convert electrical current produced from renewable energy sources (such as wind, solar, or biomass) into a biofuel (methane) as well as serving as a method for the capture of carbon dioxide.
Abstract: New sustainable methods are needed to produce renewable energy carriers that can be stored and used for transportation, heating, or chemical production. Here we demonstrate that methane can directly be produced using a biocathode containing methanogens in electrochemical systems (abiotic anode) or microbial electrolysis cells (MECs; biotic anode) by a process called electromethanogenesis. At a set potential of less than −0.7 V (vs Ag/AgCl), carbon dioxide was reduced to methane using a two-chamber electrochemical reactor containing an abiotic anode, a biocathode, and no precious metal catalysts. At −1.0 V, the current capture efficiency was 96%. Electrochemical measurements made using linear sweep voltammetry showed that the biocathode substantially increased current densities compared to a plain carbon cathode where only small amounts of hydrogen gas could be produced. Both increased current densities and very small hydrogen production rates by a plain cathode therefore support a mechanism of methane pro...

1,015 citations