Three-Dimensional Bimetallic Ammonium K-Eu Nitrate with a Rare (6,6)-Connected Ion Topology Exhibiting Structural Phase Transition and Photoluminescence Properties.

A K-Eu bimetallic ammonium metal-nitrate three-dimensional (3D) framework incorporating R-N-methyl-3-hydroxyquinuclidine, (RM3HQ)2KEu(NO3)6 (RM3HQ = R-N-methyl-3-hydroxyquinuclidine, 1), was characterized and reported. Distinguishing from the former hybrid rare-earth double perovskites, 1 adopts a mixed corner- and face-sharing K+/Eu3+-centered polyhedral connectivity to form a 3D inorganic framework, showing a rare (6, 6)-connected ion topology with a 66 framework. Notably, 1 exhibits clear phase transition, and the switchable thermodynamic behavior is confirmed by variable-temperature dielectric measurements and second-harmonic generation response. Moreover, 1 also shows photoluminescence properties. The activator Eu3+ plays a crucial role in this process, leading to a significant narrow emission at 592 nm with a photoluminescence quantum yield (PLQY) of 20.76%. The fluorescence lifetime (FLT) of 1 is 4.32 ms. This finding enriches the bimetallic hybrid system for potential electronic and/or luminescence applications.

Gas-Liquid Interface Route to Hybrid Copper Bromine Perovskite Single-Crystal Membrane with Dielectric Transitions and Ferromagnetic Exchanges.

Single-crystal membranes (SCMs) show great promise in the fields of sensors, light-emitting diodes, and photodetection. However, the growth of a large-area single-crystal membranes is challenging. We report a new organic-inorganic SCMs [HCMA]2CuBr4 (HCMA = cyclohexanemethylamine) crystallized at the gas-liquid interface. It also has low-temperature ferromagnetic order, high-temperature dielectric anomalies, and narrow band gap indirect semiconductor properties. Specifically, the reversible phase transition of the compound occurs at 350/341 K on cooling/heating and exhibits dielectric anomalies and stable switching performance near the phase transition temperature. The ferromagnetic exchange interaction in the inorganic octahedra and the organic layer enables ferromagnetic ordering at low-temperature 10 K. Finally, the single crystal exhibits an indirect semiconducting property with a narrow band gap of 0.99 eV. Such rich multichannel physical properties make it a potential application in photodetection, information storage and sensors.

Research Progress of Aluminum Alloy Welding/Plastic Deformation Composite Forming Technology in Achieving High-Strength Joints.

Fusion welding causes joint deterioration when joining aluminum alloys, which limits the use of aluminum alloy components in high-end equipment. This paper focuses on an overview of how to achieve high-strength aluminum alloy welded joints using welding/plastic deformation composite forming technology. The current technology is summarized into two categories: plastic deformation welding and plastic deformation strengthening. Plastic deformation welding includes friction stir welding, friction welding, diffusion welding, superplastic solid-state welding, explosive welding, and electromagnetic pulse welding. Plastic deformation strengthening refers to the application of plastic deformation to the weld seam or heat-affected zone, or even the whole joint, after welding or during welding, including physical surface modification and large-scale plastic deformation technology. Important processing parameters of plastic deformation welding and their effects on weld quality are discussed, and the microstructure is described. The effect of plastic deformation strengthening technology on the microstructure and performance evolution, including the hardness, tensile strength, fatigue property, residual stress, and hot cracking of aluminum alloy welded joints, and its evolution mechanism are systematically analyzed. Finally, this paper discusses the future development of plastic deformation strengthening technology and anticipates growing interest in this research area.

Tuning the luminescent properties of a three-dimensional perovskite ferroelectric (Me-Hdabco)CsI3via Sn(II) doping.

As promising functional materials, organic-inorganic hybrid metal halide perovskites have attracted significant interest because of their excellent photovoltaic performance. However, although considerable efforts have been made, three-dimensional (3D) metal halide perovskites beyond lead halides have been rarely reported. Herein, a new 3D organic-inorganic hybrid ferroelectric material (Me-Hdabco)CsI3 (1, Me-Hdabco = N-methyl-1,4-diazoniabicyclo[2.2.2]octane) was synthesized and characterized. 1 underwent a ferroelectric to paraelectric phase transition at Tc = 441 K, which was investigated by differential scanning calorimetry (DSC), dielectric measurements, and variable temperature structural analyses. Moreover, 1 shows a clear ferroelectric domain switching recorded by piezoelectric force microscopy. More interestingly, the pristine colorless crystal of 1 has no photoluminescence properties, while 10% Sn(II):(Me-Hdabco)CsI3 shows intense photoluminescence with a quantum yield of 8.90% under UV excitation. This finding will open up a new avenue to probe organic-inorganic hybrid multifunctional materials integrated ferroelectric and photoluminescence.

Synthesis, dielectric, magnetic, and photoluminescence properties of two new hybrid rare-earth double perovskites.

Two new organic-inorganic hybrid double perovskites (R3HQ)4CsSm(NO3)8 (1) (R3HQ = (R)-(-)-3-quinuclidinol) and (R3HQ)4CsEu(NO3)8 (2) were synthesized and characterized. Compounds 1 and 2 exhibit obvious phase transitions at 379 and 375 K, respectively, confirmed by differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction. The rapid switching between high- and low-dielectric states makes it a typical dielectric material with a switchable dielectric constant for thermal stimulus response. Furthermore, 1 and 2 show attractive photoluminescence and paramagnetic behavior, and the fluorescence quantum yield of 2 reached 14.6%. These results show that compounds 1 and 2 can be used as excellent candidates for multifunctional intelligent materials, which also provides a new way for development of multifunctional materials.

Carbamazepine degradation and genome sequencing of a novel exoelectrogen isolated from microbial fuel cells.

Extracellular electron transfer and pharmaceutical products degradation mechanisms of electrochemical active microbial are helpful in optimizing electricity generation and biotoxic contaminants removal for microbial fuel cells (MFCs). An exoelectrogenic bacterial strain (designated as LYK-6) capable of degrading carbamazepine was first isolated from MFCs operated with carbamazepine as unique fuel. The strain LYK-6 was identified as the member of Pseudomonas genus according to morphological characteristics and 16S rRNA gene sequence analysis. Carbamazepine degradation rate of the strain LYK-6 was determined as 56.28% in inorganic salt medium using carbamazepine as sole carbon source. There were two oxidation peaks located at -0.044 V and 0.288 V revealed with differential pulse voltammetry analysis of the strain LQK-6. The maximum voltage of MFCs inoculated the strain LYK-6 reached to 187 mV when the MFCs fed with carbamazepine. The complete genome of the strain LYK-6 was of 4,454,672 bp in length and encoding 4209 protein genes. Genome annotation and functional gene analysis showed that the strain LYK-6 had significant genes encoding proteins responsible for the degradation of carbamazepine. The results demonstrated that the strain LYK-6 was promising application for the treatment of carbamazepine contaminant water by MFCs. This finding increases the known diversity of exoelectrogens.

Performance of bioelectrode based on different carbon materials in bioelectrochemical anaerobic digestion for methanation of maize straw.

The performance of the bioelectrochemical anaerobic digestion (BEAD) reactor was investigated with different carbon material-modified electrodes for the methanation of maize straw. The carbon material-modified electrodes used titanium (Ti) mesh modified with carbon nanotube (CNT), carbon black (CB), and activated carbon (AC). The maximum cumulative methane production obtained in the Ti-CNT reactor was (616.4 ± 9.3) mL/g VS, while the maximum methane production rate in the Ti-AC reactor was (61.9 ± 1.0) mL/g VS.d.The electroactive bacteria were well enriched by the different electrodes, and the enriched electroactive bacteria further facilitate the direct interspecies electron transfer (DIET) for methane production. Additionally, we found the phylum Firmicutes showed a linear relationship to methanogenic performance, as well as the Genus Proteiniborus. The Ti-CNT electrode shows better performance by the electrochemical analysis. These findings provide critical knowledge for the large-scale use of the BEAD process and the treatment of maize straw.

Influence of electrostatic field and conductive material on the direct interspecies electron transfer for methane production.

The influence of electrostatic field on the direct interspecies electron transfer (DIET) pathways for methane production was investigated in a batch bioelectrochemical anaerobic digester (BEAD). The ultimate methane production and methane yield in the BEAD reactor saturated to 925 ± 29 mL/L and 309.9 ± 9.6 mL CH4/g COD, respectively, which were much higher than 616 ± 3 mL/L and 205.4 ± 205.4 mL CH4/g COD in the anaerobic digester (AD). In the cyclic voltammogram (CV) for bulk solution, the oxidation peak current was 0.52 mA in the BEAD reactor, which was higher than 0.24 mA of AD reactor. This shows that the oxidizing ability of microorganisms was greatly improved in the BEAD reactor. Anaerolineaceae, a well-known electroactive bacterial family, was well enriched in the BEAD reactor. It indicates that the electrostatic field can enrich the electroactive bacteria and activate the DIET pathways for methane production. Moreover, the conductive material (activated carbon) further improved the performance of BEAD reactor, implies that the conductivities of bulk solution is one of the important parameters for the DIET pathways.

Three-dimensional carbon-based anodes promoted the accumulation of exoelectrogens in bioelectrochemical systems.

To achieve deep understandings on the effects of structure and surface properties of anode material on the performance of bioelectrochemical systems, the present research investigated the bacterial community structures of biofilms attached to different three-dimensional anodes including carbon felt and materials derived from pomelo peel, kenaf stem, and cardboard with 454 pyrosequencing analysis based on the bacterial 16S rRNA gene. The results showed that bacterial community structures, especially the relative abundance of exoelectrogens, were significantly related to the types of adopted three-dimensional anode materials. Proteobacteria was the shared predominant phylum, accounting for 55.4%, 52.1%, 66.7%, and 56.1% for carbon felt, cardboard, pomelo peel, and kenaf stem carbon, respectively. The most abundant OTU was phylogenetically related to the well-known exoelectrogen of Geobacter, with a relative abundance of 16.3%, 19.0%, 36.3%, and 28.6% in carbon felt, cardboard, pomelo peel, and kenaf stem, respectively. Moreover, another exoelectrogen of Pseudomonas sp. accounted for 4.9% in kenaf stem and 3.9% in carbonboard, respectively. The results implied the macrostructure and properties of different anode materials might result in different niches such as hydrodynamics and substrate transport dynamics, leading to different bacterial structure, especially different relative abundance of exoelectrogens, which consequently affected the performance of bioelectrochemical systems. PRACTITIONER POINTS: Bioelectrochemical systems (BESs) represent a novel biotechnology platform to simultaneously treat wastewaters and produce electrical power. Three-dimensional materials derived from nature plant as anode to promote electricity output from BESs and reduce the construct cost of BESs. Macrostructure of the three-dimensional anode material affected phylotype richness and phylogenetic diversity of microorganisms in anodic biofilm of BESs. Geobacter as well-known exoelectrogen was the most abundant in biofilm attached to three-dimensional anode.

Changes in bacterial community structure and humic acid composition in response to enhanced extracellular electron transfer process in coastal sediment.

Humic acids are one of the main organic matters in sediments and contribute importantly to the marine biogeochemical cycles. Extracellular electron transfer is a ubiquitous natural process and has potentials to change the macrostructure of humic acids which can act as an electron shuttle. By setting up marine sediment microbial fuel cells, the present study revealed that enhanced extracellular electron transfer process could increase the content of C and H, but decrease the O content in humic acids, which could result in an increased aromaticity and decreased polarity of humic acids, whereas no significant changes occurred to the humification degree of the humic acids. Specific bacterial groups as potential exoelectrogens including Proteobacteria (especially Pseudomonas strains) and Firmicutes were enriched under enhanced extracellular electron transfer process, indicating that they were active to exchange electrons and might play important roles during the changes of humic acids, while the relative abundance of Verrucomicrobia and Bacteroidetes was reduced during these processes. The results of the present research shed lights on the relation between exoelectrogens and the transformation of humic acids in coastal sediment, while the microbial process and mechanisms behind it require further study.

Recent achievements in enhancing anaerobic digestion with carbon- based functional materials.

Carbon-based materials such as graphite, graphene, biochar, activated carbon, carbon cloth and nano-tube, and maghemite and magnetite carbons are capable for adsorbing chemicals onto their surfaces. Currently, this review is to highlight the relevance of carbons in enhancing hydrogen or methane production. Some key roles of carbons in improving cell growth, enrichment and activity, and accelerating their co-metabolisms were elaborated with regard to their effects on syntrophic communities, interspecies electron transfer, buffering capacity, biogas upgrading, and fertilizer nutrient retention and land application. Carbons can serve as a habitation for microbial immobilization, and a provision for bioelectrical connections among cells, and provide some essential elements for anaerobes. Besides, an outlook on the possible options towards the large scale and improvement solutions has been provided. Further studies in this area could be encouraged to intend and operate continuous mode by designing carbon-amended bioreactor with stability and reliability.

The prognostic value of shock index for the outcomes of acute myocardial infarction patients: A systematic review and meta-analysis.

BACKGROUND: Several studies have revealed that high shock index (SI) is a risk factor for acute myocardial infarction (AMI) patients. These studies do not give a systematic review in this issue. Therefore, we conducted a systematic review and meta-analysis to determine the effect of high SI on the prognosis of AMI patients. METHODS: We did a systematic search of PubMed, Embase, and the Cochrane Library, using various combinations of keywords such as "shock index," "shock-index," "acute myocardial infarction," "ST elevation myocardial infarction," "non-ST segment elevation myocardial infarction," "STEMI," "NSTEMI," "AMI," and "MI" for eligible studies published up to December 23, 2016. The 3 primary outcomes for this analysis were all-cause in-hospital mortality, short-term adverse outcomes, and long-term adverse outcomes. RESULTS: Database searches retrieved 226 citations. Finally, 8 studies enrolling 20,404 patients were eventually included in the analysis. High SI was associated with an increased in-hospital mortality (pooled RR = 10.96, 95% CI: 2.00-59.94, P = .01). Adverse outcomes were significantly higher in the high SI group compared to the low SI group (pooled RR = 1.93, 95% CI: 1.10-3.39, P = .02; I = 95%). Individuals with high SI had an increased risk of long-term adverse outcomes (pooled RR = 2.31, 95% CI: 1.90-2.81, P < .001) compared to low SI. CONCLUSION: High SI may increase the in-hospital mortality, short-term, and long-term adverse outcomes in AMI patients.

Effect of electrode potentials on the microbial community of photo bioelectrochemical systems.

Increasing attention is being paid to the adoption of photoautotrophic microbes in bioelectrochemical systems (BESs) because of the advantages of self-sustainability. Biased potential on the anode was capable of adjusting the performance of non-photo BESs, and the microbial community structure was also changed; however, few studies have been conducted to investigate the effects of potential on microbial community structure in photo-BESs. In this work, the response of microbial community structure to different potentials (i.e., 0, 0.2, 0.4 and 0.6 V vs. Ag/AgCl) was characterized with 454 pyrosequencing. Four samples were collected and they generated 42865 16S rDNA sequencing reads with an average length of 429 bp. The potential at 0.2 V resulted in the highest current density (378.8 mA m-2) and showed a strong selection for γ-proteobacteria (30.8% of the sequences). α-Diversity analysis showed that microbial diversity increased with increased potential. Rhodopseudomonas palustris was dominant among known exoelectrogens in the biofilm biased at 0.4 V. The results provided an insight into the mechanism of potential regulation on the performance of photo-BESs and changes in microbial community structure.

Modulation of the Acetone/Butanol Ratio during Fermentation of Corn Stover-Derived Hydrolysate by Clostridium beijerinckii Strain NCIMB 8052.

Producing biobutanol from lignocellulosic biomass has shown promise to ultimately reduce greenhouse gases and alleviate the global energy crisis. However, because of the recalcitrance of a lignocellulosic biomass, a pretreatment of the substrate is needed which in many cases releases soluble lignin compounds (SLCs), which inhibit growth of butanol-producing clostridia. In this study, we found that SLCs changed the acetone/butanol ratio (A/B ratio) during butanol fermentation. The typical A/B molar ratio during Clostridium beijerinckii NCIMB 8052 batch fermentation with glucose as the carbon source is about 0.5. In the present study, the A/B molar ratio during batch fermentation with a lignocellulosic hydrolysate as the carbon source was 0.95 at the end of fermentation. Structural and redox potential changes of the SLCs were characterized before and after fermentation by using gas chromatography/mass spectrometry and electrochemical analyses, which indicated that some exogenous SLCs were involved in distributing electron flow to C. beijerinckii, leading to modulation of the redox balance. This was further demonstrated by the NADH/NAD+ ratio and trxB gene expression profile assays at the onset of solventogenic growth. As a result, the A/B ratio of end products changed significantly during C. beijerinckii fermentation using corn stover-derived hydrolysate as the carbon source compared to glucose as the carbon source. These results revealed that SLCs not only inhibited cell growth but also modulated the A/B ratio during C. beijerinckii butanol fermentation.IMPORTANCE Bioconversion of lignocellulosic feedstocks to butanol involves pretreatment, during which hundreds of soluble lignin compounds (SLCs) form. Most of these SLCs inhibit growth of solvent-producing clostridia. However, the mechanism by which these compounds modulate electron flow in clostridia remains elusive. In this study, the results revealed that SLCs changed redox balance by producing oxidative stress and modulating electron flow as electron donors. Production of H2 and acetone was stimulated, while butanol production remained unchanged, which led to a high A/B ratio during C. beijerinckii fermentation using corn stover-derived hydrolysate as the carbon source. These observations provide insight into utilizing C. beijerinckii to produce butanol from a lignocellulosic biomass.

Mixed cellulose ester filter as a separator for air-diffusion cathode microbial fuel cells.

Separator is important to prevent bio-contamination of the catalyst layer of air-diffusion cathode microbial fuel cells (MFCs). Mixed cellulose ester filter (MCEF) was examined as a separator for an air-cathode MFC in the present study. The MCEF-MFC produced a maximum power density of 780.7 ± 18.7 mW/m2, which was comparable to 770.9 ± 35.9 mW/m2 of MFC with Nafion membrane (NFM) as a separator. Long-term examination demonstrated a more stable performance of the MCEF-MFC than NFM-MFC. After 25 cycles, the maximum voltage of the MCEF-MFC decreased by only 1.3% from 425.1 ± 4.3 mV (initial 5 cycles) to 419.5 ± 2.3 mV (last 5 cycles). However, it was decreased by 9.1% from 424.8 ± 5.7 to 386 ± 2.5 mV for the NFM-MFC. The coulombic efficiency (CE) of the MCEF-MFC did not change (from 3.11 ± 0.09% to 3.13 ± 0.02%), while it decreased by 9.12% from 3.18 ± 0.04% to 2.89 ± 0.02% for the NFM-MFC. The MCEF separator was with less biofouling than the NFM separator over 60 days' operation, which might be the reason for the more table long-term performance of the MCEF-MFC. The results demonstrated that MCEF was feasible as a separator to set up good-performing and cost-effective air-diffusion cathode MFC.

[Influence of Carbonization Temperature on Bacterial Community of the Biological Carbon Electrode Based on High-throughput Sequencing Technology].

Microbial diversity of anodic biofilm in bioelectrochemical systems with hemp rod carbonized at 1000 and 1800℃ as anode was investigated using Solexa high-throughput sequencing technology. The results showed that a total of 4231 and 5263 optimized 16S rRNA gene sequences were gained from the electrode biofilm on the hemp rod carbonized at 1000 and 1800℃, respectively. At the level of 97% similarity, 1187 and 1338 OTUs were obtained for electrode biofilm carbonized at 1000 and 1800℃, respectively. The result of α diversity analysis showed that microbial diversity increased with decreasing carbonization temperature. Dominant phylum for both biofilms were Proteobacteria, Firmicutes and Bacteroidetes, which accounted for 66%, 10% and 9%, respectively for 1000℃, while 71%, 7% and 9%, respectively for 1800℃. Beside the coexisting phylum, some unique species were also discovered, demonstrating that carbonization temperature did not only influence the electrode structure, but also affected the microbial community structure.

[Comparative Analysis of the Bacterial Community on Anodic Biofilms in Sediment Microbial Fuel Cell Under Open and Closed Circuits].

To investigate the differences in microbial community of anodic biofilms under open and closed circuits, sediment microbial fuel cell (SMFCs) reactors connecting with a 5 kΩ external resistance and open circuit during the start-up period were operated individually. Anodic biofilms were collected and analyzed using Solexa high-throughput sequencing technology. A total of 3936 and 3930 operational taxonomic units (OTUs) were obtained from the anodic biofilms under open and closed circuits, respectively. After 97% similarity merging, 1581 and 1551 OTUs were finally determined from open and close circuit biofilms, respectively. The analysis of α diversity showed that bacterial diversity of anodic biofilm under open circuit was higher than that under closed circuit. The dominant bacterial were Proteobacteria, Firmicutes and Bacteroidetes for both open and closed circuits. They accounted for 59.79%, 12.54% and 9.02% under open circuit biofilm respectively; and these values were 63.02%, 10.01% and 3.60% in the closed circuit biofilm respectively, and Geobacter accounted for 16.55% in the closed circuit biofilm. The present study demonstrated that the electron transfer process during start-up period affected the microbial community structure of the anodic biofilms.

Microbial community structures differentiated in a single-chamber air-cathode microbial fuel cell fueled with rice straw hydrolysate.

BACKGROUND: The microbial fuel cell represents a novel technology to simultaneously generate electric power and treat wastewater. Both pure organic matter and real wastewater can be used as fuel to generate electric power and the substrate type can influence the microbial community structure. In the present study, rice straw, an important feedstock source in the world, was used as fuel after pretreatment with diluted acid method for a microbial fuel cell to obtain electric power. Moreover, the microbial community structures of anodic and cathodic biofilm and planktonic culturewere analyzed and compared to reveal the effect of niche on microbial community structure. RESULTS: The microbial fuel cell produced a maximum power density of 137.6 ± 15.5 mW/m2 at a COD concentration of 400 mg/L, which was further increased to 293.33 ± 7.89 mW/m2 through adjusting the electrolyte conductivity from 5.6 mS/cm to 17 mS/cm. Microbial community analysis showed reduction of the microbial diversities of the anodic biofilm and planktonic culture, whereas diversity of the cathodic biofilm was increased. Planktonic microbial communities were clustered closer to the anodic microbial communities compared to the cathodic biofilm. The differentiation in microbial community structure of the samples was caused by minor portion of the genus. The three samples shared the same predominant phylum of Proteobacteria. The abundance of exoelectrogenic genus was increased with Desulfobulbus as the shared most abundant genus; while the most abundant exoelectrogenic genus of Clostridium in the inoculum was reduced. Sulfate reducing bacteria accounted for large relative abundance in all the samples, whereas the relative abundance varied in different samples. CONCLUSION: The results demonstrated that rice straw hydrolysate can be used as fuel for microbial fuel cells; microbial community structure differentiated depending on niches after microbial fuel cell operation; exoelectrogens were enriched; sulfate from rice straw hydrolysate might be responsible for the large relative abundance of sulfate reducing bacteria.

Isolation, identification and characterization of an electrogenic microalgae strain.

Extracellular electron transfer involving microbes is important as it closely reflects the ability of cells to communicate with the environment. However, there are few reports on electron transfer mechanisms of pure microalgae and a lack of any model alga to study the transfer processes. In the present study, nine green microalgae species were isolated from wastewater and characterized in terms of their ability to transfer electrons between cells and an electrode. One species showed direct electron transfer via membrane-associated proteins and indirect electron transfer via secreted oxygen. The microalga was identified as Desmodesmus sp. based on phylogenetic analysis and electron microscopy. Electrochemical tests demonstrated that Desmodesmus sp. was able to act as a cathodic microorganism. Stable current densities of -0.24, 35.54 and 170 mA m(-2) were achieved at potentials of +0.2, -0.2 and -0.4 V, respectively, under illumination. Dissolved oxygen concentration measurement showed gradients within the microalgae biofilm: 18.3 mg L(-1) in light decreasing to 4.29 mg L(-1) in the dark. This study diversified the exoelectrogen library and provided a potential model microalga to explore the associated mechanism of extracellular electron transfer.

In situ probing the effect of potentials on the microenvironment of heterotrophic denitrification biofilm with microelectrodes.

Bio-electrochemical reactor provides a promising technology to remove nitrogen contaminants in water. In this study, a heterotrophic biofilm for denitrification process was developed, and stable total nitrogen removal efficiencies (>80%) were achieved. Fluorescence in situ hybridization showed that genes norB mainly transcribed in inner biofilm while genes nosZ showed similar transcription activities in the entire biofilm. The microelectrodes of pH and nitrous oxide (N2O) were applied to profile the microenvironment of denitrification biofilm. In all measurements, the microenvironment pH decreased as a function of biofilm depth. The highest N2O concentration of 90 µM in biofilm was detected when the bulk solution pH was 7.3, and an applied potential of -0.2V did not decrease the yield of N2O in biofilm at pH 7.3. Nevertheless, pH 9.5 or an applied potential of -0.4V seemed not to suppress the yield of N2O in biofilm.