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This study investigated the molecular mechanism behind the highly efficient performance of nitrogen-doped carbon dots (NCDs)-assisted microbial electrosynthesis systems (MESs). The impact of NCDs (C:N precursor = 1:0.5-1:3) on acetogens was examined in the biocathode. The highest electrocatalytic performance was observed with NCDs 1:1 . The maximum acetate production rate of 1.9 ± 0.1 mM d -1 was achieved in NCDs 1:1 - modified MESs, which was 26.7-216.7 % higher than other MESs (0.6-1.5 mM d -1 ). With NCDs 1:1 modified, the biocathode exhibited a 129.3-186.8 % increase in the abundance of Sporomusa, and 38.5-104.6 % increase in cytochrome expression (cydAB, cybH). Transcriptome confirmed that cytochromes played a crucial role in the extracellular electron uptake (EEU) of NCDs 1:1 -modified Sporomusa. NCDs 1:1 enhanced EEU efficiency, thereby increasing the two H + -pumping steps and accelerating microbial CO 2 fixation. These results provide valuable insights into increasing CO 2 fixation by maximizing EEU efficiency in acetogens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Extracellular electron transfer (EET) is a significant pathway to transport electrons between bacteria and electrode in microbial electrosynthesis systems (MESs). To enhance EET in the MES, a high-conductivity polymer, polypyrrole (PPy), was coated on the surface of mixed culture acetogens in situ and the PPy-coated bacteria were inoculated on the cathode of MES. The charge transfer resistance of PPy-coated biocathode was 33%-70% of that with PPy-uncoated. Acetate production rate and Faradic efficiency in PPy-coated biocathodes increased by 3 to 6 times. After 960 h operation, Acetobacterium, Desulfovibrio, and Acinetobacter dominate the community on the coated and uncoated biocathode. Quinone loop and NADH dehydrogenase to ubiquinone were involved in electron transfer pathway of biocathode and stimulated by PPy coating. Low-level expression of C-type cytochromes on biocathode indicated its less important role in inward EET. The study provided useful information for applications of high-conductivity chemicals in microbial electrosynthesis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Flexible control of CH 4 /H 2 ratio in biohythane is important to its applications but remains a challenge. Herein, a dual-cathode bioelectrochemical system (BES) was developed for achieving biohythane production with controllable composition through adjusting external resistance. The BES was started as a microbial electrolysis cell to produce hydrogen in both cathodes ("H 2 -cathode") and then evolved to produce methane production in one cathode with inoculation of anaerobic sludge ("CH 4 -cathode"). When increasing the external resistance of the H 2 -cathode from 10 to 330 Ω, its H 2 production decreased from 173 ± 11 to 8 ± 2 L m -3  d -1 . This redistribution of electrons has benefited the CH 4 -cathode that had an increased CH 4 production from 25 ± 3 to 90 ± 5 L m -3  d -1 . The CH 4 /H 2 ratio increased from 0.14 to 11, making biohythane more applicable to natural gas engines. Those results will help to formulate a BES-based approach to accomplish controllable biohythane production., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This study aimed to investigate the graphene oxide (GO) conversion by the sulfate-reducing biocathode and its modified effects on performance of the microbial electrolysis cell (MEC). Biocathodes were acclimated with autotrophic sulfate-reducing cultures using medium containing 500 mg L -1 sulfate. Sulfate reductive rate in the MEC was 230 and 135 g m -3  d -1 , respectively, with and without 30 mg L -1 GO addition. Raman measurements showed that GO was efficiently reduced to graphene by the biocathode within 24 h. Higher electrochemical activity and smaller charge transfer resistance were detected on biofilm with GO affected. With high electrical conductivity of 307 ± 36 μS cm -1 , pili substance were observed on GO affected biofilm. As dominated by Desulfovibrio sp., the biocathode could use GO as the sole electron acceptor and maintained high activity. The results from this study should provide useful information for applications of nanomaterials in the biocathode MEC., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate the development of cathodic biofilm and its effect on methane production in a single-chamber microbial electrolysis cell (MEC). The MEC with 1 g/L acetate was successfully operated within 31 cycles (∼2400 h). The maximum methane production rate and average current capture efficiency in the MEC reached 93 L/m 3 ·d and 82%, respectively. Distinct stratification of Methanobacteriaceae within cathodic biofilm was observed after 9 cycles of operation. The relative abundance of Methanobacteriaceae in the microbial community increased from 45.3% (0-15 μm), 57.6% (15-30 μm), 66.9% (30-45 μm) to 77.2% (45-60 μm) within the cathodic biofilm. The methane production rates were positively correlated with the mcrA gene copy numbers in the cathodic biofilm. Our results should be useful to understand the mechanism of methane and hydrogen production in the MEC., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate the feasibility to improve the tetramethyl ammonium hydroxide (TMAH) production in the microbial electrolysis desalination and chemical-production cell (MEDCC) with long anode of 48 cm. Different concentrations of tetramethylammonium chloride (0.3-0.7 M) and applied voltages (1.5-3.5 V) were tested in the MEDCC. With 0.6 M of tetramethylammonium chloride as the raw material and under the applied voltage of 3.5 V, the maximum TMAH production rate in the MEDCC reached 1.13 ± 0.12 mmol/h, which was 9.4 times higher than those previously reported in the MEDCCs. The maximum current density of 41.0 ± 4.0 A/m 2 in the MEDCC was obtained, which was the highest value in the bioelectrochemical systems using the carbon cloth or carbon brush as the anode so far. Our results should provide a promising method to improve the TMAH production and boost the MEDCC application., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The aim of this study was to improve performance of the microbial electrolysis desalination and chemical-production cell (MEDCC) using enlarged anode and high applied voltages. MEDCCs with anode lengths of 9 and 48cm (i.e., the 9cm-anode MEDCC and 48cm-anode MEDCC, respectively) were tested under different voltages (1.2-3.0V). Our results demonstrated for the first time that the MEDCC could maintain high performance even under the applied voltage higher than that for water dissociation (i.e., 1.8V). Under the applied voltage of 2.5V, the maximum current density in the 48cm-anode MEDCC reached 32.8±2.6A/m 2 , which is one of the highest current densities reported so far in the bioelectrochemical system (BES). The relative abundance of Geobacter was changed along the anode length. Our results show the great potential of the BES with enlarged anode and high applied voltages., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate the feasibility and optimization of formic acid production in the microbial electrolysis desalination and chemical-production cell (MEDCC). The maximum current density in the MEDCC with 72cm of the anode fiber length (72-MEDCC) reached 24.0±2.0A/m 2 , which was much higher than previously reported. The maximum average formic acid production rate in the 72-MEDCC was 5.28 times higher than that in the MEDCC with 24cm of the anode fiber length (37.00±1.15vs. 7.00±0.25mg/h). High performance in the 72-MEDCC was attributed to small membrane spacing (1mm), high flow rate (1500μL/min) on the membrane surface and high anode biomass. The minimum electricity consumption of 0.34±0.04kWh/kg in the 72-MEDCC was only 3.1-18.8% of those in the EDBMs. The MEDCC should be a promising technology for the formic acid production., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The aim of this study is to investigate the effect of sulfate-reducing bacteria on performance of a mixed culture microbial electrosynthesis system (MES). The two-chamber MESs were operated under different cathode potentials (-0.5, -0.6, -0.7, and -0.8V) with or without addition of 6mM sulfate. At -0.7V, acetate production and electrons harvesting in the MES with the sulfate addition were 31.81mM and 5152C, respectively, which improved by 2.7 and 2.4times compared to that without sulfate. With sulfate, the biomass, proportion of live cells, and electrochemical activity of cathode biofilm were enhanced at all the potentials. At -0.7V, the relative abundance of Acetobacterium and Desulfovibrionaceae was 14.2% and 36.7% with sulfate, respectively, compared to 17.4% and 7.3% without sulfate. At -0.7 and -0.8V, the sulfate-reducing bacteria can promote the electron transfer of cathode biofilm and enhance the acetate production., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate the microbial stratification structure within cathodic biofilm of the microbial fuel cell (MFC) using the freezing microtome method. Experiments were conducted in a single-chamber air-cathode MFC with 0.8g/L maltodextrin as substrate for ∼30d operation. The maximum power density was 945±10mW/m 2 in the MFC. Maltodextrin resulted in the relative abundance of Candidatus Saccharibacteria of 37.0% in the anodic biofilm. Different bacterial communities were identified in different layers within the cathodic biofilm. The relative abundance of Enterococcus was 3.7%, 10.5%, and 1.6% in the top (100-150μm), middle (50-100μm), and bottom (0-50μm) layers, respectively. Higher bacterial viability was observed within the top and bottom layers of the cathodic biofilm. Understanding the stratification of bacterial community in cathodic biofilm should be important to control the cathodic biofilm in the MFC., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The aim of this study was to develop an efficient bioanode microbial electrosynthesis system (MES) to convert carbon dioxide into acetate using bioenergy from the wastewater. The bioanode MESs were constructed using proton exchange membrane (PEM) and bipolar membrane (BPM) as separator, respectively, and operated under different voltages (i.e., 0.8, 1.0, 1.2, and 1.4V). Since BPM could dissociate H 2 O into H + and OH - in situ to buffer the pH change in the chambers, the BPM-MES achieved 238% improvement in cathodic acetate production rate, 45% increase in anodic substrate removal efficiency, and more than five times enhancement in current output, as compared to the PEM-MES. The biomass on the surface of anode and cathode, and the relative abundance of Acetobacterium in the cathode of BPM-MES was higher than that in PEM-MES. Bioanode MES with BPM should be a useful microbial electrosynthesis strategy for acetate production using bioenergy from wastewater treatment., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate different microbial electrolysis desalination cells for malic acid production. The systems included microbial electrolysis desalination and chemical-production cell (MEDCC), microbial electrolysis desalination cell (MEDC) with bipolar membrane and anion exchange membrane (BP-A MEDC), MEDC with bipolar membrane and cation exchange membrane (BP-C MEDC), and modified microbial desalination cell (M-MDC). The microbial electrolysis desalination cells performed differently in terms of malic acid production and energy consumption. The MEDCC performed best with the highest malic acid production rate (18.4 ± 0.6 mmol/Lh) and the lowest energy consumption (0.35 ± 0.14 kWh/kg). The best performance of MEDCC was attributable to the neutral pH condition in the anode chamber, the lowest internal resistance, and the highest Geobacter percentage of the anode biofilm population among all the reactors., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The aim of this study was to utilize the biocathode microbial electrolysis cell (MEC) for sulfate removal from wastewater. Experiments were conducted using the two-chambered MEC under fed-batch and continuous flow modes, respectively, with different cathode potentials. With the fed-batch operation, the average reductive rate of sulfate was 0.49 mg d(-1) and the sulfide concentration increased to 3.1 ± 0.7 mg L(-1) in the catholyte. Sulfate removal rate and electron production rate in the continuous flow mode were 49% and 11 times higher than in the fed-batch mode. With cathode potentials from -0.6 to -1.0 V, electron recovery efficiencies ranged from 5.3% to 50% with the maximum obtained at -0.8 V. The maximum sulfate removal efficiency of (39 ± 9.2)% was achieved at -0.9 V. This study suggests the MEC can be a valuable alternative to remove sulfate in wastewater treatment., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Performance of a two-chamber microbial fuel cell (MFC) was evaluated with the influence of cathodic dissolved oxygen (DO). The maximum voltage, coulombic efficiency and maximum power density outputs of MFC decreased from 521 to 303 mV, 52.48% to 23.09% and 530 to 178 mW/m(2) with cathodic DO declining. Furthermore, a great deal of total phosphorus (TP) was removed owing to chemical precipitation (about 80%) and microbial absorption (around 4-17%). COD was first removed in anode chamber (>70%) then in cathode chamber (<5%). Most of nitrogen was removed when the cathodic DO was at low levels. Chemical precipitates formed in cathode chamber were verified as phosphate, carbonate and hydroxyl compound with the aid of scanning electron microscope capable of energy dispersive spectroscopy (SEM-EDS), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR)., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

In this study, the microbial electrolysis cell (MEC) was examined for treatment of wastewater containing nickel ion (Ni(2+)). Effects of initial Ni(2+) concentrations in catholyte, pH values of catholyte, and applied voltages on MEC performance were determined. Results showed that the Ni(2+) removal efficiency with the MEC was three times higher than those with an electrolysis cell and a microbial fuel cell. Ni(2+) removal efficiencies decreased from 99 ± 0.6% to 33 ± 4.2% with the initial Ni(2+) concentrations from 50 to 1000 mg/L, while the mass removal of Ni(2+) increased consistently with the initial concentrations. Ni(2+) removal efficiencies in the MEC increased from 51 ± 4.6% to 67 ± 5.3% with the applied voltages from 0.5 to 1.1 V. These results demonstrate that the MEC can be an alternative process to effectively remove Ni(2+) from wastewater., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The microbial electrolysis desalination and chemical-production cell (MEDCC) is a device to desalinate seawater, and produce acid and alkali. The objective of this study was to enhance the desalination and chemical-production performance of the MEDCC using two types of stack structure. Experiments were conducted with different membrane spacings, numbers of desalination chambers and applied voltages. Results showed that the stack construction in the MEDCC enhanced the desalination and chemical-production rates. The maximal desalination rate of 0.58 ± 0.02 mmol/h, which was 43% higher than that in the MEDCC, was achieved in the four-desalination-chamber MEDCC with the AEM-CEM stack structure and the membrane spacing of 1.5mm. The maximal acid- and alkali-production rates of 0.079 ± 0.006 and 0.13 ± 0.02 mmol/h, which were 46% and 8% higher than that in the MEDCC, respectively, were achieved in the two-desalination-chamber MEDCC with the BPM-AEM-CEM stack structure and the membrane spacing of 3mm., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Rapid startup of microbial fuel cells (MFCs) and other bioreactors is desirable when treating wastewaters. The startup time with unamended wastewater (118 h) was similar to that obtained by adding acetate or fumarate (110-115 h), and less than that with glucose (181 h) or Fe(III) (353 h). Initial current production took longer when phosphate buffer was added, with startup times increasing with concentration from 149 h (25 mM) to 251 h (50 mM) and 526 h (100 mM). Microbial communities that developed in the reactors contained Betaproteobacteria, Acetoanaerobium noterae, and Chlorobium sp. Anode biomass densities ranged from 200 to 600 μg/cm(2) for all amendments except Fe(Ш) (1650 μg/cm(2)). Wastewater produced 91 mW/m(2), with the other MFCs producing 50 mW/m(2) (fumarate) to 103mW/m(2) (Fe(III)) when amendments were removed. These experiments show that wastewater alone is sufficient to acclimate the reactor without the need for additional chemical amendments., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In this study, the microbial fuel cell (MFC) was combined with the Fenton-like technology to simultaneously generate electricity and degrade refractory contaminants in both anode and cathode chambers. The maximum power density achieved was 15.9 W/m(3) at an initial pH of 3.0 in the MFC. In the anode chamber, approximately 100% of furfural and 96% COD were removed at the end of a cycle. In the cathode chamber, the Fenton-like reaction with FeVO(4) as a catalyst enhanced the removal of AO7 and COD. The removal rates of AO7 and COD reached 89% and 81%, respectively. The optimal pH value and FeVO(4) dosage toward degrading AO7 were about 3.0 and 0.8 g, respectively. Furthermore, a two-way catalyst mechanism of FeVO(4) and the contaminant degradation pathway in the MFC were explored., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The effect of nitrobenzene (NB) on electricity generation and simultaneous biodegradation of NB were studied with two types of microbial fuel cells (MFCs): a ferricyanide-cathode MFC with NB as the anodic reactant and a NB-cathode MFC. Compared to controls without NB, the presence of NB in the anode of the first MFC decreased maximum voltage outputs, maximum power densities and Coulombic efficiencies. No electricity was generated from the first MFC using NB as the sole fuel; however, the second MFC using NB as the electron acceptor generated electricity successfully with a maximum voltage of 400mV. NB was degraded completely within 24h in both anode and cathode chambers. Denaturing gradient gel electrophoresis (DGGE) profiles demonstrated that the presence of NB caused changes in relative abundance of the dominant bacterial species and emergence of new bacteria on the anodes., (Copyright 2010 Elsevier Ltd. All rights reserved.)