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Solid-phase microbial fuel cell (SMFC) can accelerate the removal of organic pollutants through the electrons transfer between microorganisms and anodes in the process of generating electricity. Thus, the characteristics of the anode material will affect the performance of SMFCs. In this study, corn stem (CS) is first calcined into a 3D macroporous electrode, and then modified with carbon nanotubes (CNTs) through electrochemical deposition method. Scanning electron microscope analysis showed the CS/CNT anode could increase the contact area on the surface. Furthermore, electrochemical impedance spectroscopy and cyclic voltammetry analysis indicated the electrochemical double-layer capacitance of the CS/CNT anode increased while its internal resistance decreased significantly. These characteristics are crucial for increasing bacterial adhesion capability and electron transfer rate. The maximum output voltage of the SMFC with CS/CNT anode was 158.42 mV, and the removal rate of petroleum hydrocarbon (PH) reached 42.17%, 2.72 times that of unmodified CS. In conclusion, CNT-modified CS is conducive to improve electron transfer rate and microbial attachment, enhancing the removal efficiency of PH in soil.

Microbial electrosynthesis (MES) is an electrochemical reduction technology that converts carbon dioxide (CO2) efficiently into chemicals by electrically driving microorganisms attached to electrodes. However, due to the limited solubility of CO2 and hydrogen (H2), low mass transfer efficiency affects the performance of MES. In this study, fillers were introduced into the MES system and combined with a vertical or horizontal cathode. Through the barrier and shearing effect of fillers, it realized the reduction of bubbles volume, the increase of gas residence time and the optimization of mass transfer rate, thereby providing a sufficient substrate supply for the biocatalyst. The results showed that MES with horizontal cathode and 4 series of fillers generated the highest acetate production rate (0.18 gL−1 day−1), which was 1.6 times that of the control group. Furthermore, the acetate concentration reached 5.28 ± 0.2 g L−1 within 30 days. Scanning electron microscope and microbial community analyses showed that the filler was beneficial to the growth of biofilm on cathodes and fillers, and improved the enrichment of Acetobacterium. The presence of fillers significantly enhanced the performance of MES and demonstrated the potential as a new and simple strategy for the MES reactor improvement.

Microbial electrosynthesis (MES) is a promising technology through which carbon dioxide is converted into chemicals via bioelectrochemcal reaction. In this study, a natural loofah sponge (LS) was directly converted into a 3D macroporous carbon cathode through carbonization. The LS was codecorated with polydopamine and Mo2C (Mo2C/N-doped LS). Results revealed that the acetate production rate of MES with Mo2C/N-doped LS increased by 2.5 times compared with that of carbon felt. The maximum acetate concentration of 6.08 g L−1 and 64% of coulomb efficiency (CE) were obtained in MES with Mo2C/N-doped LS. Electrochemistry, scanning electron microscopy, and microbial community analyses showed that Mo2C/N-doped LS contributed to biofilm formation and improved the enrichment of electrochemically active bacteria. Thus, this study introduced a promising method for the fabrication of 3D cathodes with a high electrocatalytic activity from low-cost sustainable natural materials to improve MES efficiency.

Solid-phase microbial fuel cells (SMFCs) are promising clean energy that can convert soil/sediment organic matter into usable electricity. However, the practical application of SMFCs require to inc...

Microbial electrosynthesis (MES) is an electrochemical reduction technique where microorganisms attached to electrodes are used as catalysts for CO2 reduction into chemicals. In situ grown molybden...

Microbial electrosynthesis (MES) is an emerging technology through which autotrophic microorganisms can directly uptake electrons or indirectly uptake electrons through H2 in the cathode for reducing CO2 to chemicals. In this study, the performance of MES with engineered Clostridium ljungdahlii was improved by electrochemically depositing a nickel phosphide (Ni–P) catalyst on the cathode. The acetate production rate of MES with 15 cycles was 0.17 g L–1 day–1, which was 1.7 times higher than that of MES without the catalyst. The corresponding butyrate production rate was remarkably enhanced at 0.1 g L–1 day–1, which was 2.5 times higher than that of MES without the catalyst. Electrochemical studies, scanning electron microscopy, and confocal scanning laser microscopy showed that Ni–P could accelerate the release of hydrogen and promote biofilm formation. These results also implied that more H2 evolution could provide more reducing power for butyrate production in the presence of Ni–P. This study attempted to provide effective strategies for the accumulation of C4 products in MES.

Microbial electrosynthesis (MES) is an emerging strategy for converting electrical energy into chemical energy. Many efforts have been made toward the enhancement of cathode-microorganism interacti...

Microbial electrosynthesis (MES) is a novel CO

BACKGROUND: p‐Chloronitrobenzene (p‐CNB) is easily accumulated in the environment and subsequently is a threat to humans and the ecosystem. The anaerobic process as an important pathway for p‐CNB degradation has a relatively low degradation rate. This study illustrated that the strain Pseudomonas fluorescens was evaluated as the biocatalyst for bioaugmentation to enhance the p‐CNB removal in bioelectrochemical system (BES). RESULTS: When the initial p‐CNB concentration was 100 mg L⁻¹, the p‐CNB removal efficiency reached 100% at 12 h in BES with P. fluorescens. All the p‐CNB removal efficiencies in BES were higher than that in anaerobic degradation and electrocatalysis. Meantime, the highest total organic carbon (TOC) removal efficiency was obtained at 89.8% after augmentation with P. fluorescens. During the bioaugmentation, microbial community analysis showed that the main abundance changes were in Pseudomonas, Romboutsia and Macellibacteroides. The cyclic voltammetry (CV) showed BES with bioaugmentation had the highest activity in reducing p‐CNB and hydrogen evolution. Combined with intermediates analysis, bioaugmentation possibly stimulated nitro reduction and hydrodechlorination rate in p‐CNB reduction. CONCLUSION: These results demonstrate that BES with P. fluorescens bioaugmentation could serve as a potential treatment process for p‐CNB removal. © 2019 Society of Chemical Industry

In this paper, a graphene/Fe2O3 (G/Fe2O3) modified anode was prepared through a simple one-step hydrothermal reduction method to improve the performance of microbial fuel cell (MFC). The power density of MFC with the G/Fe2O3 anode was 334 ± 4 mW/m2, which was 1.72 times and 2.59 times that of MFC with a graphene anode and an unmodified anode, respectively. Scanning electron microscopy and iron reduction rate experiment showed that G/Fe2O3 materials had good biocompatibility. Furthermore, microbial community analysis results indicated that the predominant populations on the anode biofilm belonged to Enterobacteriaceae, and the abundance of Desulfovibrio increased in the presence of the Fe2O3. Thus, the combination of graphene and Fe2O3 provided high electrical conductivity to facilitate extracellular electron transfer (EET) and improved biocompatibility to promote the cable bacteria formation and enhance electron transport efficiency over long distances. Therefore, G/Fe2O3 is an effective anode material for enhancing the performance of MFCs.

Background Microbial electrosynthesis (MES) is a biocathode-driven process, in which electroautotrophic microorganisms can directly uptake electrons or indirectly via H2 from the cathode as energy sources and CO2 as only carbon source to produce chemicals. Results This study demonstrates that a hydrogen evolution reaction (HER) catalyst can enhance MES performance. An active HER electrocatalyst molybdenum carbide (Mo2C)-modified electrode was constructed for MES. The volumetric acetate production rate of MES with 12 mg cm−2 Mo2C was 0.19 ± 0.02 g L−1 day−1, which was 2.1 times higher than that of the control. The final acetate concentration reached 5.72 ± 0.6 g L−1 within 30 days, and coulombic efficiencies of 64 ± 0.7% were yielded. Furthermore, electrochemical study, scanning electron microscopy, and microbial community analyses suggested that Mo2C can accelerate the release of hydrogen, promote the formation of biofilms and regulate the mixed microbial flora. Conclusion Coupling a HER catalyst to a cathode of MES system is a promising strategy for improving MES efficiency. Electronic supplementary material The online version of this article (10.1186/s13068-019-1413-z) contains supplementary material, which is available to authorized users.

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

Microbial electrosynthesis (MES) is a novel CO2 utilization technology. Biocatalysts in this process may use electrons obtained from a photovoltaic system to reduce CO2 to chemicals and realize energy conversion from solar energy to chemical energy. The photoelectric material CuO/g-C3N4 was directly introduced into the MES system using mixed culture as biocatalyst in this study. CuO/g-C3N4 can effectively absorb light and presents satisfactory electron and hole separation ability. Photogenerated electrons from CuO/g-C3N4 enhanced the electron transfer rate and reduced cathodic charge transfer resistance. CuO/g-C3N4 mainly improved the electron supply of electroautotrophic microorganisms through direct electron transfer rather than indirect electron transfer via hydrogen. Photogenerated holes can combine electrons from anode and provide extra driving force to improve the MES performance. Furthermore, the CuO/g-C3N4 photocathode also improved the biocatalytic activity by increasing the total amount of biocatalyst and regulating cathodic microbial community composition. Acetate production rate in MES with the CuO/g-C3N4 photocathode was 2.6 times higher than that of the control group. This study provides a new strategy for semiconductor photocathodes to improve the MES performance with mixed culture.

Microbial electrosynthesis (MES) is an electricity-driven technology for the microbial reduction of CO2 to organic commodities. However, the limited solubility of CO2 in a solution and the inefficient electron transfer make it impossible for microorganisms to obtain an efficient surface for catalytic interaction, thus resulting in the low efficiency of MES. To address this, we introduce a multifunctional perovskite-based cathode material Pr0.5(Ba0.5Sr0.5)0.5Co0.8Fe0.2O3-δ-carbon felt (Pr0.5BSCF-CF), which provides a simultaneously significant increase in CO2 absorption and hydrogen production. As a result, the volumetric acetate production rate of MES obtained by Pr0.5BSCF-CF is 0.24 ± 0.01 g L-1 day-1, and it achieves a maximum acetate titer of 13.74 ± 0.20 g L-1 within 70 days. An adequate supply of CO2 and H2 also provides a sufficient amount of substrates and energy for the self-replication of the biocatalysts in the MES reactor. This effect not only increases the amount of biocatalysts but also optimizes the functions of the biocatalysts; the above benefits further improve the production efficiency of the MES system. This strategy demonstrates that the development of perovskite-based multifunctional cathodes with a simultaneous supplementation of substrates and electrons is a promising approach toward improving the MES efficiency.

It has been brought to our attention that in our article, explanations about cable bacteria are not rigorous. We apologize for these and note the specific reporting issues and errors below, with their corrections.

Background The conversion of CO2 into high value-added products has a very important environmental and economic significance. Microbial electrosynthesis (MES) is a promising technology, which adopts a bioelectrochemical system to transform CO2 into organic chemicals. Results In this study, Clostridium scatologenes ATCC 25775T, an anaerobic acetogenic bacterium, demonstrated its utility as a biocatalyst in a MES system, for the first time. With the cathodic potential of the MES system decreased from − 0.6 to − 1.2 V (vs. Ag/AgCl), the current density of the MES, and the production of organic chemicals, increased. Combining the genetic analysis and the results of the wet lab experiments, we believe C. scatologenes may accept electrons directly from the cathode to reduce CO2 into organic compounds at a potential of − 0.6 V. The acetic and butyric acid reached a maximum value of 0.03 and 0.01 g/L, respectively, and the maximum value of total coulombic efficiency was about 84%, at the potential of − 0.6 V. With the decrease in cathodic potentials, both direct electron transfer and exogenous electron shuttle, H2 might be adopted for the C. scatologenes MES system. At a potential of − 1.2 V, acetic acid, butyric acid and ethanol were detected in the cathodic chamber, with their maximum values increasing to 0.44, 0.085 and 0.015 g/L, respectively. However, due to the low H2 utilization rate by the C. scatologenes planktonic cell, the total coulombic efficiency of the MES system dropped to 37.8%. Conclusion Clostridium scatologenes is an acetogenic bacterium which may fix CO2 through the Wood–Ljungdahl pathway. Under H2 fermentation, C. scatologenes may reduce CO2 to acetic acid, butyric acid and ethanol. It can also be used as the biocatalyst in MES systems.

Microbial electrosynthesis (MES) is a biocathode-driven process, producing high-value chemicals from CO2. Here, an in situ self-assembled graphene oxide (rGO)/biofilm was constructed, in MES, for high efficient acetate production. GO has been successfully reduced by electroautotrophic bacteria for the first time. An increase, of 1.5 times, in the volumetric acetate production rate, was obtained by self-assembling rGO/biofilm, as compared to the control group. In MES with rGO/biofilm, a volumetric acetate production rate of 0.17gl-1d-1 has been achieved, 77% of the electrons consumed, were recovered and the final acetate concentration reached 7.1gl-1, within 40days. A three-dimensional rGO/biofilm was constructed enabling highly efficient electron transfer rates within biofilms, and between biofilm and electrode, demonstrating that the development of 3D electroactive biofilms, with higher extracellular electron transfer rates, is an effective approach to improving MES efficiency.

BACKGROUND Microbial electrosynthesis (MES) is a biocathode-driven process, producing high-value chemicals, from CO2. However, the low efficiency of the biocathode hinders the MES process efficiency significantly. RESULTS A novel 3D graphene–nickel foam (G-NF) cathode has been fabricated, by hydrothermal approach for the improvement of microbially-catalyzed reduction at the MES cathode. An increase of 1.8 times in the volumetric acetate production rate was obtained, compared with the untreated nickel foam. In MES with G-NF, a volumetric acetate production rate of 3.11 mmol L-1 day-1 has been achieved; 70% of the electrons consumed were recovered and the final acetate concentration reached 5.46 g L-1 within 28 days. CONCLUSION The hierarchical porous G-NF cathode improved bacterial colonization and the efficiency of mass, nutrients and protons transfer due to its 3D composition; the graphene coating considerably increased the effective surface area for microbial adhesion, as well as the electron transfer rate of biofilm in the MES. This study attempted to improve the efficiency of the biocathode, and provides a promising large electrode for large-scale MES devices. © 2017 Society of Chemical Industry

Tetracycline (TC) is the second most commonly used antibiotic despite its high toxicity and persistence. In this study, a new approach for the anaerobic biodegradation of TC in a microbial fuel cell (MFC), with glucose–TC mixtures as the substrate, under gradient acclimation conditions was explored. Within 7 days, approximately 79.1% of TC was degraded by the MFC. This value was higher than that obtained through a traditional anaerobic method (14.9%). The TC degradation rates in MFCs with a closed circuit were 31.6% higher than those in MFCs with an open circuit. Furthermore, zebrafish assessment showed that no toxicity was observed after MFC treatment. Microbial community analysis was performed on the anode of the MFCs under gradient acclimation conditions, and the results showed that TC was effectively degraded by the synergy of fermentative bacteria, acid-producing bacteria and electrogenic bacteria. This work confirmed that the anaerobic biodegradation of TC by MFCs is a cost-effective and environmentally friendly method.

Microbial electrosynthesis (MES) is potentially useful for the biological conversion of carbon dioxide into value-added chemicals and biofuels. The study evaluated several limiting factors that affect MES performance. Among all these factors, the optimization of the applied cell voltage, electrode spacing, and trace elements in catholytes may significantly improve the MES performance. MES was operated under the optimal condition with an applied cell voltage of 3 V, an electrode spacing of 8 cm, 2× salt solution, and 8× trace element of catholyte for 100 days, and the maximum acetate concentration reached 7.8 g L−1. The microbial community analyses of the cathode chamber over time showed that Acetobacterium, Enterobacteriaceae, Arcobacter, Sulfurospirillum, and Thioclava were the predominant genera during the entire MES process. The abundance of Acetobacterium first increased and then decreased, which was consistent with that of acetate production. These results provided useful hints for replacing the potentiostatic control of the cathodes in the future construction and operation of MES. Such results might also contribute to the practical operation of MES in large-scale systems.

Microbial electrosynthesis (MES) allows the transformation of CO

In this paper, a graphene/Fe

Additional file 1. Additional information.

In this study, we demonstrate the effect of iron sheet on the output power of sediment microbial fuel cells (SMFCs). An SMFC with iron sheet present, but not in the circuit (SMFC-GF-iron) displayed a maximum power density of 63 mW m−2, whereas we find 37 mW m−2 for that SMFC with the iron sheet not present (SMFC-GF). Furthermore, the SMFC with an iron sheet in the circuit (SMFC-iron) had a maximum power density of 170 mW m−2. The effect of sheet iron, out of the circuit, was to improve the iron reduction microbial activity, while, within the circuit, it produced a large number of electrons from the electrochemical corrosion yielding higher power production. The study suggests that the addition of iron sheet to an SMFC is an easy and effective method for enhancing the output power of SMFCs.

Microbial electrosynthesis (MES) is an electricity-driven bioreduction of carbon dioxide to a multicarbon chemical process. The structure of catalysts with a high biocompatibility and an enhanced microbe–electrode electron transfer rate is required to improve production rates. Here, carbon felt (CF) cathodes modified with molybdenum disulfide (MoS2) were prepared via a simple one-step hydrothermal method with three different preparation temperatures (160 °C,180 °C, and 240 °C). Results showed that the hydrogen evolution reaction (HER) activity of CF with MoS2 catalysts was higher than that of bare CF. The CF with MoS2 nanoflowers obtained at 180 °C showed the highest volumetric acetate production rate (0.2 g L−1 d−1), which was 2.2 times that of the bare CF, and the final acetate concentration of 6 g L−1 was reached within 30 days. Electrochemical impedance spectroscopy and microbial community analyses suggested that the CF with MoS2 obtained at 180 °C facilitated extracellular electron transfer and improved the enrichment of Acetobacterium and Arcobacter. Scanning electron microscopy revealed that a porous nanoflower structure at 180 °C was conducive to microbial colonization and an increase in indirect and direct electron transfer rates. Graphene-like MoS2 nanoflower was excellent and cost-effective materials for cathode modification to improve MES efficiency.

It has been brought to our attention that in our article, explanations about cable bacteria are not rigorous. We apologize for these and note the specific reporting issues and errors below, with their corrections.

The electricity-driven bioreduction of carbon dioxide to multi-carbon organic compounds, particularly acetate, has been achieved in microbial electrosynthesis (MES). MES performance can be limited by the amount of cathode surface area available for biofilm formation and slow substrate mass transfer. Here, a fluidized three-dimensional electrode, containing granular activated carbon (GAC) particles, was constructed via MES. The volumetric acetate production rate increased by 2.8 times through MES with 16 g L-1 GAC (0.14 g L-1 d-1) compared with that of the control (no GAC), and the final acetate concentration reached 3.92 g L-1 within 24 days. Electrochemical, scanning electron microscopy, and microbial community analyses suggested that GAC might improve the performance of MES by accelerating direct and indirect (via H2) electron transfer because GAC could provide a high electrode surface and a favorable mass transport. This study attempted to improve the efficiency of MES and presented promising opportunities for MES scale-up.

The wide presence of antibiotics in the environment has raised concerns about their potential impact on ecological and human health. This study was conducted to evaluate the degradation of antibiotics (chlortetracycline (CTC) and oxytetracycline (OTC)) in microbial fuel cells (MFCs) and the change of toxicity. The degradation rates of 60 mg L−1 CTC and OTC in the MFCs were 74.2% and 78%, respectively, within 7 days. The degradation ability of the two antibiotics followed the order of OTC > CTC. Toxicity test results of the zebrafish illustrated the toxicity of OTC and CTC was largely eliminated by MFC treatment. Furthermore, possible degradation pathways of CTC and OTC were speculated using LC-MS analysis. High-throughput sequencing analysis indicated that Petrimonas, Azospirillum, Dokdonella, Burkholderia and Stenotrophomonas were the predominant genera in the MFC anode biofilm. Therefore, this work is of great significance for future studies on the treatment of antibiotics in wastewater by MFCs.

In this paper, we developed an environmental friendly, cost effective, simple and green approach to reduce graphene oxide (GO) by a sulfate-reducing bacterium Desulfovibrio desulfuricans. The D. desulfuricans reduces exfoliated GO to reduced graphene oxide (rGO) at 25 °C in an aqueous solution without any toxic and environmentally harmful reducing agents. The rGO was characterized with X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscope, X-ray Photoelectron Spectroscopy and Raman Spectroscopy. The analysis results showed that rGO had excellent properties and multi-layer graphene sheets structure. Furthermore, we demonstrated that D. desulfuricans, one of the primary bacteria responsible for the biocorrosion of various metals, might reduce GO to rGO on the surface of copper and prevented the corrosion of copper, which confirmed that electrophoretic deposition of GO on the surface of metals had great potential on the anti-biocorrosion applications.

To demonstrate that an enhanced sediment microbial fuel cell (SMFC) system can accelerate the degradation of cellulose in fresh water sediments as the accumulation of cellulose in lake sediments may aggravate the lake marsh, increase organic matter content and result in rapid deterioration of water quality and damage the ecosystem. After 330 days the highest cellulose removal efficiency (72.7 ± 2.1 %) was achieved in the presence of a SMFC with a carbon nanotube decorated cathode, followed by a SMFC without the cathode decoration (64.4 ± 2.8 %). The lowest cellulose removal efficiency (47.9 ± 2.1 %) was in the absence of SMFC. The sediment characterization analysis confirmed that the carbon nanotube decorated cathode enhances the electron transfer rate in the SMFC and improves the dissolved organic matter oxidation rate. This study offers a relatively simple and promising new method for cellulose degradation in sediment.

Cobalt oxide/nanocarbon hybrid materials (graphene and carbon nanotube) are used as alternative cathode catalysts for oxygen reduction reaction in air-cathode microbial fuel cell (MFC) for the first time. Electrochemical results reveal that these hybrid materials exhibit high catalytic performance. In MFCs, the maximum power density of 469 ± 17 mW m−2 is achieved from the Co3O4/NCNT cathode, which is 5.3 times larger than that of the NCNT cathode. This value is competitive with those obtained using Pt/C (603 ± 23 mW m−2). Therefore, Co3O4/NCNT nanocomposite is an efficient and cost-effective cathode catalyst for practical MFC applications.

Low toxic and highly biocompatible graphene-based nanomaterials are in high demand within the biomedical fields. In this study, a highly biocompatible bacterially reduced graphene oxide (BRGO) was prepared by a “Generally Recognized As Safe” (GRAS) strain Bacillus subtilis 168 mediated with Vitamin K3 (VK3). The hypothesis of VK3 mediating electron transfer between succinate:quinine oxidoreductase, from B. subtilis 168, and graphene oxide (GO) was proposed. BRGO was characterized by Raman spectroscopy, XPS and XRD and showed excellent properties. Furthermore, BRGO illustrates greater biocompatibility, with less toxicity, than GO and chemically reduced graphene oxide (CRGO) by zebrafish toxicity assessment, which demonstrates its great potential in various biomedical applications.

For Cr(VI)-removal microbial fuel cell (MFC), a more efficient biocathode in MFCs is required to improve the Cr(VI) removal and electricity generation. RVC-CNT electrode was prepared through the electrophoretic deposition of carbon nanotube (CNT) on reticulated vitreous carbon (RVC). The power density of MFC with an RVC-CNT electrode increased to 132.1 ± 2.8 mW m −2 , and 80.9% removal of Cr(VI) was achieved within 48 h; compared to only 44.5% removal of Cr(VI) in unmodified RVC. Cyclic voltammetry, energy-dispersive spectrometry and X-ray photoelectron spectrometry showed that the RVC-CNT electrode enhanced the electrical conductivity and the electron transfer rate; and provided more reaction sites for Cr(VI) reduction. This approach provides process simplicity and a thickness control method for fabricating three-dimensional biocathodes to improve the performance of MFCs for Cr(VI) removal.

N-Acetylneuraminic acid lyase (NAL, E.C. number 4.1.3.3) is a Class I aldolase that catalyzes the reversible aldol cleavage of N-acetylneuraminic acid (Neu5Ac) from pyruvate and N-acetyl-D-mannosamine (ManNAc). Due to the high Neu5Ac cleavage activity in most isozyme forms, the enzyme catalyzes the rate-limiting step of two biocatalytic reactions producing Neu5Ac in industry. We report the biochemical characterization of a novel NAL from a "GRAS" (General recognized as safe) strain C. glutamicum ATCC 13032 (CgNal). Compared to all previously reported NALs, CgNal exhibited the lowest kcat/Km value for Neu5Ac and highest kcat/Km values for ManNAc and pyruvate, which makes CgNal favor industrial Neu5Ac synthesis process in a non-equilibrium condition. The recombinant CgNal reached the highest expression level (480 mg/L culture), and the highest reported yield of Neu5Ac was achieved (194 g/L, 0.63 M). All these unique properties make CgNal a promising biocatalyst for industrial Neu5Ac biosynthesis. Additionally, although showing the best Neu5Ac synthesis activity among the NAL family, CgNal is more related to dihydrodipicolinate synthase (DHDPS) by phylogenetic analysis. The activities of CgNal towards both NAL's and DHDPS' substrates are fairly high, which indicates CgNal a bi-functional enzyme. The sequence analysis suggests that CgNal might have adopted a unique set of residues for substrates recognition.

A multi-walled, carbon nanotube (MWNT)-modified graphite felt (GF) cathode was fabricated to improve the performance of sediment microbial fuel cells (SMFC). Three types of MWNT-modified GF cathodes were prepared by different electrophoretic deposition (EPD) times. Maximum power density of SMFC with MWNT-GF*** cathode at 60 min EPD was 215 ± 9.9 mW m(-2). This was 1.6 times that of SMFC with a bare GF cathode. Cyclic voltammetry and the amount of biomass showed that biomass density and electrochemical activity increased as the electrophoretic deposition time extended. Therefore the electrode possesses the highest catalytic behavior toward O2 reduction reaction. This simple process of carbon nanotube modification of a cathode by EPD can serve as an effective technique to improve the performance of SMFC.

One major limiting factor for sediment microbial fuel cells (SMFC) is the low oxygen reduction rate in the cathode. The use of the photosynthetic process of the algae is an effective strategy to increase the oxygen availability to the cathode. In this study, SMFCs were constructed by introducing the algae ( Chlorella vulgaris ) to the cathode, in order to generate oxygen in situ . Cyclic voltammetry and dissolved oxygen analysis confirmed that C. vulgaris in the cathode can increase the dissolved oxygen concentration and the oxygen reduction rate. We showed that power generation of SMFC with algae-assisted cathode was 21 mW m −2 and was further increased to 38 mW m −2 with additional carbon nanotube coating in the cathode, which was 2.4 fold higher than that of the SMFC with bare cathode. This relatively simple method increases the oxygen reduction rate at a low cost and can be applied to improve the performance of SMFCs.

BACKGROUND For a microbial fuel cell (MFC), the anode material plays a key part in power generation. Modification of conventional carbon-based anode materials is an effective strategy to improve MFC performance. RESULTS Two different zeolites, namely, mobil catalytic materials number 41 (MCM-41) and NaX, were used to modify graphite felt anodes and compared with unmodified anodes in dual-chamber MFCs. Fourier transform infrared analysis verified that MCM-41 and NaX zeolites were successfully coated onto the bare graphite felt surface. Results showed that NaX zeolite is a favorable, affordable material for anode modification of MFCs. This zeolite improved MFC performance considerably. Its maximum power density (215.3 ± 6.4 mW m−2) and CE value (50.0% ± 2.0%) were 152.1% and 36.2% higher than those of the unmodified anode, respectively. According to scanning electron microscopy, cyclic voltammetry, and the amount of anode biomass, the superhydrophilicity of the NaX zeolite-modified anode was a vital reason for thick anode biofilm formation and accelerated anodic bio-electrochemical reactions. The improved specific surface area of the anode and properties of the microporous NaX zeolite were responsible for the enhancement of MFC performance. CONCLUSIONS Graphite felt anode modified by NaX zeolite resulted in improved power generation by a MFC. © 2013 Society of Chemical Industry

In this study, two types of biomass ( Acorus calamus leaves and wheat straw) were added to a matrix of sediment and soil inside the anode of solid phase microbial fuel cells (SMFCs) in order to increase their output power. SMFC containing 3% leaves in their sediment had a maximum power density of 195 mW m −2 in contrast to 4.6 mW m −2 of that SMFC without leaves. Similarly, SMFC containing 1% wheat straw in their soil environment had a maximum power density of 167 mW m −2 . It suggests that the addition of biomass in appropriate proportions increases contact opportunities between the matrix, the anode and the added biomass, increases organic matter content, and enhances cellulase activity, thus serving as an important method for enhancing output power in SMFCs.

A 10 L upflow microbial fuel cell (UMFC) was constructed for simultaneous carbon and nitrogen removal. During the 6-month operation, the UMFC constantly removed carbon and nitrogen, and then generated electricity with synthetic wastewater as substrate. At 5.0 mg L−1 dissolved oxygen, 100 Ω external resistance, and pH 6.5, the maximum power density (Pmax) and nitrification rate for the UMFC was 19.5 mW m−2 and 17.9 mg·(L d)−1, respectively. In addition, Pmax in the UMFC with chicken manure wastewater as substrate was 16 mW m−2, and a high chemical oxygen demand (COD) removal efficiency of 94.1% in the UMFC was achieved at 50 mM phosphate-buffered saline. Almost all ammonia in the cathode effluent was effectively degraded after biological denitrification in the UMFC cathode. The results can help to further develop pilot-scale microbial fuel cells for simultaneous carbon and nitrogen removal.

SiO 2 : Sm 3+ nanotube arrays with excellent antireflective property at 1.06 μm were synthesized by a template-assisted sol–gel process. The molecular structure, morphology and optical properties of the fabricated SiO 2 :Sm 3+ nanotube arrays were investigated by a Fourier transform infrared spectroscope (FTIR), a Scanning electron microscope (SEM), and a spectro-fluorometer, respectively. The experimental results demonstrate that the SiO 2 :Sm 3+ nanotube arrays were formed via the AAO membrane during the sol–gel process. The remarkable antireflective characteristic of about 0.166% at 1.06 μm was attributed to the drastic decrease of effective refraction index which enhances the matching effect between air and substrate. As well as the absorption performance of Sm3+ at 1.06 μm which consumes the energies of incident light.