Anode Of Microbial Fuel Cell Research Articles

MXene@Poly(diallyldimethylammonium chloride) Decorated Carbon Cloth for Highly Electrochemically Active Biofilms in Microbial Fuel Cells

AbstractThe anode characteristics are important to the performance of microbial fuel cells (MFCs) due to the influence on biofilm formation and extracellular electron transfer (EET). Herein, MXene was modified by the superhydrophilic cationic polymer poly(diallyldimethylammonium chloride) (PDDA) to prepare MXene@PDDA/carbon cloth (CC) as an anode for MFC. The unique anode combines the advantages of high conductivity, superhydrophilicity and biocompatibility. The anode facilitated the enrichment of electrochemical active bacterium and promoted the efficiency of EET process. MFCs based on MXene@PDDA/CC anodes can produce the remarkable power output and the satisfactory effluent removal efficiency through an external series resistance of 1 kΩ. The device can gain the maximum output voltage of 585 mV and the maximum power density of 811 mW m−2. The efficiencies of methyl orange decolorization and chemical oxygen demand were up to 79 % and 84 % after 12 h, respectively.

Evaluating Organic Acids As Oxidizable Fuels in R. Capsulatus-Based Bioelectrochemical Systems

The development of microbial fuel cells (MFCs) for wastewater treatment has recently gained significant attention in the bioremediation and renewable energy industries. Bacteria can be integrated into the anodes of MFCs to oxidize organic wastes, simultaneously producing electrical current and decontaminating wastewater. The photoheterotrophic purple bacterium Rhodobacter capsulatus has demonstrated photo-catalyzed electron transfer to carbon electrodes via exogenous quinone redox mediators, and tolerance to high salinity, opening opportunities for solar-powered MFC systems for treatment of saline wastewater. While the consumption of malate by R. capsulatus has been electrochemically analyzed previously, in this project, alternative target carbon sources were examined in order to improve electrochemical performance of these R. capsulatus systems. A combination of electrochemical techniques and biological assays were used to evaluate the relative viability of malate, lactate, succinate and propionate as oxidizable fuels. Specifically, cyclic voltammetry and amperometry data demonstrated that R. capsulatus generates distinctive bio-photocurrent densities depending on the fuel metabolized. Bioanodes with immobilized R. capsulatus cells oxidizing lactate (9.49 ± 1.89 µA cm-2) as the fuel yielded the greatest mediated bio-photocurrent densities compared to the other fuels, while those metabolizing propionate (1.33 ± 0.18 µA cm-2) generated the smallest current densities. In tandem with electrochemistry methods, growth curve assays and RNA sequencing were performed to further delve into the biological effects of altering the carbon source.

Biodegradation and metabolism of tetrabromobisphenol A in microbial fuel cell: Behaviors, dynamic pathway and the molecular ecological mechanism

Tetrabromobisphenol A (TBBPA) has aroused widespread pollution in industrial wastewater. Microbial fuel cell (MFC) was proved powerful in organics degradation and simultaneous resource recovery during wastewater treatment. However, the TBBPA biotransformation potential, pathway and the related molecular mechanism remain poorly understood. In this study, the enhanced degradation and detoxification performance of TBBPA in MFC anode was confirmed, evidenced by the shorter degradation period (2.3 times shorter) and less generation of bisphenol A. UPLC-QTOF-MS analysis verified TBBPA metabolism went through reductive debromination, hydrolytic debromination, oxidative ring cleavage and o-methylation. Accompanied with those biochemical processes, the metabolites underwent dynamic changes. The distinctly decreased abundance and fewer interactions with other functional genera for the potential reductive dehalogenators (Pseudomonas, etc.) possibly led to the suppressed reductive debromination (5.1%) in the closed bioanode. Otherwise, the more abundant potential function bacteria with more collaborated interrelations, including hydrolytic dehalogenators (Acinetobacter, etc.), aromatics degrading bacteria (Geobacter, Holophaga, etc.) and electroactive bacteria (Geobacter, Desulfovibrio, etc.) made great sense to the enhanced hydrolytic debromination and detoxification of TBBPA. This study revealed that MFC anode was beneficial to TBBPA degradation and provided theoretical support for the decomposition and transformation of micro-pollutants in the municipal sewage treatment coupled with MFC process.

Carbon material‐based anodes in the microbial fuel cells

AbstractFor the performance improvement of microbial fuel cells (MFCs), the anode becomes a breakthrough point due to its influence on bacterial attachment and extracellular electron transfer (EET). On other level, carbon materials possess the following features: low cost, rich natural abundance, good thermal and chemical stability, as well as tunable surface properties and spatial structure. Therefore, the development of carbon materials and carbon‐based composites has flourished in the anode of MFCs during the past years. In this review, the major carbon materials used to decorate MFC anodes have been systematically summarized, based on the differences in composition and structure. Moreover, we have also outlined the carbon material‐based hybrid biofilms and carbon material‐modified exoelectrogens in MFCs, along with the discussion of known strategies and mechanisms to enhance the bacteria‐hosting capabilities of carbon material‐based anodes, EET efficiencies, and MFC performances. Finally, the main challenges coupled with some exploratory proposals are also expounded for providing some guidance on the future development of carbon material‐based anodes in MFCs.

3D Anode Microbial Fuel Cell Characterization and Monitoring Coupling X-Ray Tomography and Electrochemical Impedance Spectroscopy

Entangled stainless steel single wire was used as a promising 3D anode for Microbial Fuel Cells (MFCs). Two complementary techniques were coupled to precisely characterize the anode structure and activity: X-Ray Computed Tomography (XRCT) and Electrochemical Impedance Spectroscopy (EIS). XRCT provides an acurate estimation of the pore distribution and size while EIS allows to check and monitor the electrochemical activity. Electrochemical measurements were performed with activated sludges and synthetic medium at an imposed potential of −0.2 V vs Ag/AgCl in a single chamber MFC. Modified Transmission Line Model was used to follow the evolution of the anode in both media including the formation and the growth on the biofilm.

Application of OPEFB Fibre Based Electrode in Microbial Fuel Cell System for Electricity Generation and Chlorophenol Degradation

Microbial fuel cell (MFC) has emerged as one of the potential technologies for sustainable bioelectrical energy recovery and reduction of recalcitrant wastes. The MFC performance is greatly influenced by the anode materials which serve as the support for exoelectrogenic bacteria attachment. In this study, oil palm empty fruit bunch (OPEFB) is proposed as an alternative anode material prepared via a direct carbonization process using tube furnace owing to its good conductivity property. The carbonization process was conducted under nitrogen gas flow at 900°C with a constant heating rate of 5°C/min. The anode was prepared by mixing the carbonized OPEFB with polytetrafluoroethylene (PTFE) binder. When used in MFC, the OPEFB-anode generated a maximum current density of 97.30 mA/m 2, which is comparatively higher than that of the conventional carbon cloth anode (76.24 mA/m 2). Our MFC system had also resulted considerable chemical oxygen demand (COD) and 2-chlorophenol reductions of 77% and 75%, respectively. This study could support future research on freely-available OPEFB materials for high performance MFC anode.

Modern trend of anodes in microbial fuel cells (MFCs): An overview

Microbial fuel cells (MFCs) is highly efficient bioelectrochemical systems in which bacteria are utilized to oxidize the organic substrate and produce electricity. The main component of an MFCs is the anode, in which bacterial attachment is promoted and the generation and transfer of electrons occurs. Therefore, the interest of introducing novel and innovative anode materials for attaining a high performance of MFCs is a concern that is growing in the modern era. In this review article, different conventional and modern anode materials are briefly discussed considering their advantages and limitations. Among all, the natural biomass-derived materials were found as one of the best sources to meet the present challenges to utilize them as anodes in MFCs. The natural derived anodes presented some limitations which can be addressed through metal oxide composites as described in this article. The oxidation mechanism of pollutants on the surface of anode along with their bacterial interactions are also briefly summarized. This review is limited to the performance and development of the anode in MFCs. • Comparison of anode materials for microbial fuel cells (MFCs) are well discussed. • Energy generation and pollutant oxidation mechanisms on anode are presented. • Utilization of natural biomass material to build the MFCs anode is promising. • Emerging trend in anodes: graphene derivatives and its composite-based material. • Addressing problems and future perspectives on the anode materials is critical.

Improving the performance of biotrickling filter microbial fuel cells in treating exhaust gas by adjusting the oxygen content of the anode tank

A biotrickling filter (BTF) was combined with a microbial fuel cell (MFC) to remove ethyl acetate from exhaust gas while generating electricity in the process. The results indicated that the use of carbide porous ceramic rings (CPCR) as auxiliary anodes produced more biomass and exhibited a high average removal efficiency (98%), making it a superior microorganism growth carrier compared with carbon coke. When CPCR was used as the cathode in the BTF-MFC, the maximum power density (PD) was 5.64–14.8% of that achieved when carbon cloth was used as the cathode, revealing that CPCR is not a suitable cathode. The maximum elimination capacity (EC) and output voltage of the two-stage BTF-MFC (tBTF-MFC) were only 69.4% and 68.4% of those of the single-stage BTF-MFC (sBTF-MFC), presumably because of voltage reversal. Although the output voltage and EC in the tBTF-MFC were less than those in the sBTF-MFC, the follow-up field application involves stacking multiple small MFCs to remove high-concentration pollutants and generate a high power output. Additionally, continuously adding sodium sulfite decreased the average dissolved oxygen; generated an averaged closed-circuit voltage of 477 mV; and produced a maximum PD of 71.7 mW/m3. These findings demonstrated that the aforementioned method can effectively improve the problem of oxygen and MFC anodes competing for electrons, thus delivering a method that enhances MFC performance through controlling the amount of oxygen in practical applications.

Self-assembled oil palm biomass-derived modified graphene oxide anode: An efficient medium for energy transportation and bioremediating Cd (II) via microbial fuel cells

Although microbial fuel cells (MFCs) rank among the most promising bioelectrochemical approaches for generating energy while removing pollutants from wastewater, their relatively poor performance, largely due to electrode material that hinder their applicability, has limited their commercial viability. Thus, in our study, self-assembled modified graphene oxide (GO) anodes were developed from oil palm (Elaeis guineensis) biomass, and several techniques were applied to assess the physiochemical properties of material synthesized with waste material. Ultimately, the waste material was an excellent source for generating energy in the form of anodes in MFCs. The bioinspired modified GO anodes demonstrated greater energy output (135.96 mA/m2) of more than eight times the unmodified GO anodes (15.65 mA/m2), even though the source of inoculation was synthetic wastewater with 100 ppm of Cd (II) solution. To our knowledge, no work has reported removing Cd (II) from synthetic wastewater by using waste-derived anodes via MFCs. This paper reports on the utilization of waste-derived organic waste (oil palm trunk sap) as an organic substrate which is a healthy source of nutrients for bacteria in an inoculated media. Along with evidence of their electrochemical and biological character, the primary result achieved (i.e., 90% removal efficiency) supports using MFCs on an industrial scale.

In-situ alkaline pretreatment of waste activated sludge in microbial fuel cell enhanced power production

Energy recovery from waste activated sludge (WAS) by microbial fuel cell (MFC) can simultaneously address energy issue and environmental concerns. Pretreatments are vital to enhancing energy recovery and sludge reduction with WAS as power source in MFC. The commonly applied two-stage process, which separates WAS pretreatment with electricity generation, decreases the cost-effectiveness of MFC with WAS as power source. It is of great practical importance to investigate the feasibility of one-stage process for simultaneous sludge pretreatment and electricity generation. Herein, a one-stage alkaline MFC (anode chamber controlled at pH 9.0) is constructed to recover energy from in-situ alkaline pretreated WAS. Results show that alkaline MFC achieves excellent performance of electricity generation with high voltage output (0.74 V) and high power density (0.65 W m−2). The total chemical oxygen demand removal of WAS is >40%. No greenhouse gas (CH4 and CO2) are released from the alkaline MFC with WAS as power source. The enhanced electricity generation performance in the alkaline MFC is investigated through three aspects, including internal resistance, degradation of soluble organics, and shift of microbial community. This work offers a promising alternative for energy recovery with WAS as renewable power source.

A Study on Polythiophene Modified Carbon Cloth as Anode in Microbial Fuel Cell for Lead Removal

In this study, the performance of carbon cloth (CC) modified with iodine (I2) doped polythiophene nanoparticles (PTh-NP) as an anode was investigated in a double chamber microbial fuel cell (MFC) for the purpose of simultaneous power generation and lead (Pb2+) removal using Shewanella putrefaciens as the biocatalyst. The CC with I2 doped PTh-NP displayed good electrochemical characteristics compared to pristine CC and the CC with undoped PTh-NP. A further increase in the electrical conductivity using the modified CC with biofilm was observed, which matured after 51 h, as evident from cyclic voltametry. The removal of lead for concentrations, viz., 20 ppm, 30 ppm, and 40 ppm, was analyzed. The optimum concentration was found to be 30 ppm with a maximum power density of 0.84 W/m2 and a current density of 1.45 A/m2 at an optimum resistance of 250 ohms. At the end of the process, total organic carbon (TOC) and Pb2+ removal of 95.1% and 89.6%, respectively, were obtained at the optimum concentration. Hence, this study demonstrates the possibility of utilizing MFC for treating low concentrated metal wastewater.

Construction of conjugated polymer-exoelectrogen hybrid bioelectrodes and applications in microbial fuel cells

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

Enhanced Electrocatalytic Sludge Derived Carbon for High-Efficiency Anode of Microbial Fuel Cells

Enhanced Electrocatalytic Sludge Derived Carbon for High-Efficiency Anode of Microbial Fuel Cells

Improvement of Renewable Bioenergy Production in Microbial Fuel Cells with Saponin Supplementation

Microbial fuel cell (MFC) is one of renewable biofuel production technology that directly converts biomass to electricity. Cellulosic biomass is particularly attractive renewable resources for its low cost and abundance and neutral carbon balance. However, methanogenesis remains as a major factor limiting MFC performance. The current study reports that saponin addition at 0.05% w/v dose to anolyte in MFCs inhibited methanogenesis and improves power generation and cellulose fermentation. Mediator-less two chamber H-type MFCs were prepared using rumen fluid as anode inocula at 20% v/v of anolyte to convert finely ground pine tree (Avicel) at 2%, w/v to electricity. Saponin was added to the anode of MFC at 0.005% or 0.05% v/v dosage for treatment. MFC power and current across an external resistor were measured daily for 10d. On d10, collected gases from anode compartment were measured for total gas volume and analyzed for gas composition on gas chromatography. Supplementation of saponin to MFC at 0.005% did not have any effects on electricity generation or biogas production and composition. Saponin at 0.05% dose reduced 10% of methane production and increased 40% of CO2 production and 6.4% of total gas production for 10d MFC operation. Voltage across resistor prior to treatment addition (d0) was 164.75 ± 9.07 mV. In control group, voltage across resistor did not change (P = 0.9153) with time course and mean was 167.8 ± 8.20 mV ranged from 157 to 174.5 mV during 10d operation. In 0.05% Saponin group, voltage across resistor increased (P 0.0001) after d2 and mean was 187.3 ± 4.30 mV ranged between 161.5 and 204.0 mV and the 10d mean of voltage across resistor in 0.05% Saponin was greater (P 0.0001) than in control group. 0.05% Saponin also had greater voltage across resistor at d5 (P = 0.0030) and d6 (P = 0.0246) than control. End point potential increased (P 0.0001) in 0.05% Saponin after d2. 0.05% Saponin had greater (P 0.0001) in 0.05% Saponin. Power density increased (P 0.0001) after d2 in 0.05% Saponin. 0.05% Saponin MFCs had greater (P 0.0001) overall mean of 10d operation. The current study provides strong background for potential use of saponin and saponin containing natural resources for methanogenesis inhibitor and cellulolysis enhancer in MFC and also cellulolysis reactors.

Modified graphene oxide anode: A bioinspired waste material for bioremediation of Pb2+ with energy generation through microbial fuel cells

• Natural lignin biomass – derived materials is the potential source for synthesis of graphene derivatives. • Lignin-based GO and its metallic composite-derived anode for MFCs is successfully fabricated. • The modified anode offered higher power density (1350 × 10 −3 mW/m 2 ) than the unmodified GO-anode. • Pb 2+ reduction from synthetic waster was 91.07% in case of the modified anode. Nowadays, Microbial fuel cells (MFCs) technology has received a great attention as a promising and sustainable technology to generate electricity and reduce environmental pollution. However, low energy generation and fabrication cost-issue of anode material hamper the commercial viability of MFCs. In this study, oil palm biomass waste-derived graphene derivatives (L-GO) was used as an anode in a double chamber of MFCs. Furthermore, to improve the electron transportation rate, composite based anode (L-GO/ZnO) was fabricated to generate energy and concurrently remediate the Pb 2+ supplemented wastewater. The setup with L-GO/ZnO anode showed 91.07% removal efficiency of metal ions (Pb 2+ ) while 85% removal efficiency was exhibited by L-GO anode. Moreover, the composite anode (L-GO/ZnO) delivered maximum power density (1350 × 10 −3 mW/m 2 ) and current density (142.98 mA/m 2 ) which are higher than L-GO anode (power density = 20 × 10 −3 mW/m 2 and current density = 17.54 mA/m 2 ). The anode performance was well supported by electrochemical and physicochemical analyses. The results of the fabricated anodes showed that oil palm biomass can be used as a promising and low-cost material to enhance the anode performance of MFCs.

Specific Desulfuromonas Strains Can Determine Startup Times of Microbial Fuel Cells

Microbial fuel cells (MFCs) can generate electricity simultaneously with wastewater treatment. For MFCs to be considered a cost-effective treatment technology, they should quickly re-establish a stable electroactive microbial community in the case of system failure. In order to shorten startup times, temporal studies of anodic biofilm development are required, however, frequent sampling can reduce the functionality of the system due to electroactive biomass loss; therefore, on-line monitoring of the microbial community without interfering with the system’s stability is essential. Although all anodic biofilms were composed of Desulfuromonadaceae, MFCs differed in startup times. Generally, a Desulfuromonadaceae-dominated biofilm was associated with faster startup MFCs. A positive PCR product of a specific 16S rRNA gene PCR primer set for detecting the acetate-oxidizing, Eticyclidine (PCE)-dechlorinating Desulfuromonas group was associated with efficient MFCs in our samples. Therefore, this observation could serve as a biomarker for monitoring the formation of an efficient anodic biofilm. Additionally, we successfully enriched an electroactive consortium from an active anode, also resulting in a positive amplification of the specific primer set. Direct application of this enrichment to a clean MFC anode showed a substantial reduction of startup times from 18 to 3 days.

Oxygen-deficient TiO2 decorated carbon paper as advanced anodes for microbial fuel cells

A free-standing oxygen-deficient hydrogenated TiO2 nanorod arrays decorated carbon paper (CP) electrode (TiO2-x NRAs/CP) is fabricated by a facile thermal reduction approach and developed as a robust anode for microbial fuel cells (MFCs). The oriented 3D nanostructure provides a fast electron transportation pathway for the electron transfer and large accessible areas for bacterial colonization. Also, the introduction of oxygen defects into TiO2 can further enhance its bio- and electrochemical activity as well as biocompatibility. Consequently, the MFCs with TiO2-x NRAs/CP as anode delivers a maximum power density of 2576.3±33 mW m−2, which is much larger than the MFCs with pristine TiO2 NRAs/CP and CP anode. This work demonstrates the first use of oxygen-deficient TiO2 NRAs/CP as an advanced anode for MFCs and provides a new path for performance improvement for metallic oxide anode MFCs.

Microbial fuel cells with enhanced bacterial catalytic activity and stability using 3D nanoporous stainless steel anode

The activity and stability of the anode biofilm control the produced power by microbial fuel cells (MFCs). In this study, 3D nanoporous stainless steel (SS) was used as an anode material in MFCs to enhance both the biofilm growth and its adhesion to the support electrode, which would improve the catalytic activity and stability of MFCs anode biofilm. The effect of varying the annealing atmosphere on the SS performance was studied and correlated with the change in the oxidation states of the surface elements. Annealing the SS, before or after anodization, is found to have a major contribution to the biofilm growth due to the presence of more biocompatible components at the SS surface. The high roughing of the SS via anodization as well as the formation of the 3D nanoporous film has a huge contribution to the biofilm stability, especially when the MFC is generating high power. The best SS anode annealed in O2 atmosphere produced 430 mW/m2 compared to 0.01 mW/m2 produced by the as-received SS.

Impregnated thermoset pre-pressurized carbon composite electrodes in microbial fuel cell: Compositional functionalities influence on ORR with reference to graphite

Advancement in developing specific compositional functionalities of electrodes that are energy-recovery efficient, cost-effective, durable and catalytically active is particularly challenging for microbial fuel cell (MFC) operation due to its bio-compatibility requirement. Compositional characteristics of the electrodes influence the electron charge-discharge rates, oxidation-reduction reaction and biofilm formation. In this study, compact carbon-carbon composite electrode (C/C composite), fabricated by high pressure hot-pressing method followed by densified low-pressure impregnation thermosetting carbonization, was evaluated as both anode and cathode in dual-chambered MFC with varied combinations with graphite electrode. Fed-batch experiments were operated with four combinations of electrode using 3 g/l glucose in designed synthetic wastewater as anolyte and oxygenated water as catholyte. C/C composite as cathode and graphite as anode (MFC-GC) depicted comparatively higher power density (0.37 W/m2) and current (2 A/m2) than the other configurations. Improved oxidation–reduction rate (ORR) kinetics enabled higher bioelectrogenic activity in MFC-GC with respect to the elemental and surface functionalities of C/C composite electrode. Bioelectrochemical analysis showed increased charge-transfer capacitance and electron flux while lowering the system losses in MFC-GC. The capability of C/C composite electrodes as cathode due to presence of higher oxygen functionalities and surface properties increased the oxidation-reduction rate kinetics towards higher energy output during MFC operation.

Effects of biofilm transfer and electron mediators transfer on Klebsiella quasipneumoniae sp. 203 electricity generation performance in MFCs

BackgroundExtracellular electron transfer (EET) is essential in improving the power generation performance of electrochemically active bacteria (EAB) in microbial fuel cells (MFCs). Currently, the EET mechanisms of dissimilatory metal-reducing (DMR) model bacteria Shewanella oneidensis and Geobacter sulfurreducens have been thoroughly studied. Klebsiella has also been proved to be an EAB capable of EET, but the EET mechanism has not been perfected. This study investigated the effects of biofilm transfer and electron mediators transfer on Klebsiella quasipneumoniae sp. 203 electricity generation performance in MFCs.ResultsHerein, we covered the anode of MFC with a layer of microfiltration membrane to block the effect of the biofilm mechanism, and then explore the EET of the electron mediator mechanism of K. quasipneumoniae sp. 203 and electricity generation performance. In the absence of short-range electron transfer, we found that K. quasipneumoniae sp. 203 can still produce a certain power generation performance, and coated-MFC reached 40.26 mW/m2 at a current density of 770.9 mA/m2, whereas the uncoated-MFC reached 90.69 mW/m2 at a current density of 1224.49 mA/m2. The difference in the electricity generation performance between coated-MFC and uncoated-MFC was probably due to the microfiltration membrane covered in anode, which inhibited the growth of EAB on the anode. Therefore, we speculated that K. quasipneumoniae sp. 203 can also perform EET through the biofilm mechanism. The protein content, the integrity of biofilm and the biofilm activity all proved that the difference in the electricity generation performance between coated-MFC and uncoated-MFC was due to the extremely little biomass of the anode biofilm. To further verify the effect of electron mediators on electricity generation performance of MFCs, 10 µM 2,6-DTBBQ, 2,6-DTBHQ and DHNA were added to coated-MFC and uncoated-MFC. Combining the time–voltage curve and CV curve, we found that 2,6-DTBBQ and 2,6-DTBHQ had high electrocatalytic activity toward the redox reaction of K. quasipneumoniae sp. 203-inoculated MFCs. It was also speculated that K. quasipneumoniae sp. 203 produced 2,6-DTBHQ and 2,6-DTBBQ.ConclusionsTo the best of our knowledge, the three modes of EET did not exist separately. K. quasipneumoniae sp.203 will adopt the corresponding electron transfer mode or multiple ways to realize EET according to the living environment to improve electricity generation performance.