Hang Yu, Yuhui Cao, Qingliang Zhao et al.

Frontiers in Environmental Science • 2022

A novel bioelectrochemical reactor assembled with cooperative cathodes of chemical cathode and bio-cathode (BERCC) and excess sludge as the anodic substrate obtained continuous and effective Cr(VI) reduction. Cooperative cathodes in BERCC stimulated the growth of electrochemically active microorganisms such as Geobacter sp. and Shewanella sp. in the anodic biofilm and produced 8.21 ± 0.64 mg C/(L·h) more electrons than the dual chemical cathodes in the bioelectrochemical reactor with dual chemical cathodes, which enhanced the electrons for electricity generation and Cr(VI) reduction by approximately 58.3% and 56.1 ± 5.6%, respectively.

Shelley D. Minteer

ECS Meeting Abstracts • 2019

Electrochemically interfacing bacteria with electrodes presents a dynamic new set of materials challenges. Bacteria naturally form biofilms on traditional electrode surfaces, but materials design can help promote extracellular electron transfer between the bacteria and the electrode within biofilms. This paper will discuss materials strategies for promoting biofilm formation, biofilm maintenance, and extracellular electron transfer within the film, as well as improving the lifetime of microbial bioelectrodes. We will discuss different strategies for biophotocurrent generation versus microbial fuel cells versus shock biosensors, including novel carbon materials, electrode treatments, redox polymers, and biopolymer engineering.

Qiaochu Liang, Takahiro Yamashita, Norihisa Matsuura et al.

Energies • 2019

Bioelectrochemical system (BES)-based reactors have a limited range of use, especially in aerobic conditions, because these systems usually produce current from exoelectrogenic bacteria that are strictly anaerobic. However, some mixed cultures of bacteria in aerobic reactors can form surface biofilms that may produce anaerobic conditions suitable for exoelectrogenic bacteria to thrive. In this study, we combined a BES with an aerobic trickling filter (TF) reactor for wastewater treatment and found that the BES-TF setup could produce electricity with a coulombic efficiency of up to 15% from artificial wastewater, even under aerobic conditions. The microbial communities within biofilms formed at the anodes of BES-TF reactors were investigated using high throughput 16S rRNA gene sequencing. Efficiency of reduction in chemical oxygen demand and total nitrogen content of wastewater using this system was >97%. Bacterial community analysis showed that exoelectrogenic bacteria belonging to the genera Geobacter and Desulfuromonas were dominant within the biofilm coating the anode, whereas aerobic bacteria from the family Rhodocyclaceae were abundant on the surface of the biofilm. Based on our observations, we suggest that BES-TF reactors with biofilms containing aerobic bacteria and anaerobic exoelectrogenic bacteria on the anodes can function in aerobic environments.

Geremia Sassetto, Laura Lorini, Agnese Lai et al.

Catalysts • 2024

A new membrane-less bioelectrochemical reactor configuration was developed for contaminated groundwater remediation. The new bioelectrochemical reactor configuration was inspired by the utilisation of a permeable reactive barrier (PBR) configuration with no separation membrane. The corresponding reactive zones were created by using graphite granules and mixed metal oxide (MMO) electrodes to stimulate the reductive and oxidative biological degradation of chlorinated aliphatic hydrocarbons. In the present study, the PBR-like bioelectrochemical reactor has been preliminarily operated with synthetic contaminated groundwater, testing the reductive dechlorination activity on cis-dichloroethylene (cisDCE). Moreover, to assess the effects of competing anions presence for the electron donor (i.e., the cathode), the synthetic wastewater contained sulphate and nitrate anions. In the PBR-like reactor operation, nearly all cisDCE was removed in the initial sampling port, with only VC detected as the observable RD product. During the same biotic test of the PRB reactor, the presence of both the reductive dechlorination and anions reduction was confirmed by the complete nitrate reduction in the cathodic chamber of the PRB reactor. On the contrary, sulphate reduction showed a lower activity; indeed, only 25% of the influent sulphate was removed by the PRB reactor.

Kumar Sonu, Monika Sogani, Zainab Syed et al.

Fuel Cells • 2022

AbstractThis study deals with the fabrication of a low‐cost ceramic anode made by blending the rice husk and mild steel dust with soil (RMS anode) for its application in plant microbial fuel cells (PMFCs). The high cost of electrode material has been a major concern in practical applications of the PMFC technology, but the present composition of waste materials such as rice husk, mild steel dust along with soil has served as an alternative low‐cost electrode material. Tagetes erecta plant has been used to produce clean and continuous electrical energy in the PMFC. The blending of rice husk has improved the porosity of the ceramic anode. The maximum power density recorded in PMFC with 50% rice husk anode was 1.4 mW/m2 as against 0.26 mW/m2 with the anode without rice husk. High biomass growth in terms of better plant height and higher chlorophyll content was also detected in the PMFC system within 60 working days.

Jamile Mohammadi Moradian, Songmei Wang, Amjad Ali et al.

Catalysts • 2022

Although microbial fuel cells (MFCs) have been developed over the past decade, they still have a low power production bottleneck for practical engineering due to the ineffective interfacial bioelectrochemical reaction between exoelectrogens and anode surfaces using traditional carbonaceous materials. Constructing anodes from biomass is an effective strategy to tackle the current challenges and improve the efficiency of MFCs. The advantage features of these materials come from the well-decorated aspect with an enriched functional group, the turbostratic nature, and porous structure, which is important to promote the electrocatalytic behavior of anodes in MFCs. In this review article, the three designs of biomass-derived carbon anodes based on their final products (i.e., biomass-derived nanocomposite carbons for anode surface modification, biomass-derived free-standing three-dimensional carbon anodes, and biomass-derived carbons for hybrid structured anodes) are highlighted. Next, the most frequently obtained carbon anode morphologies, characterizations, and the carbonization processes of biomass-derived MFC anodes were systematically reviewed. To conclude, the drawbacks and prospects for biomass-derived carbon anodes are suggested.

Jianzhang Li

Highlights in Science, Engineering and Technology • 2025

The use of traditional fossil fuel energy has caused serious environmental pollution problems. It is becoming increasingly urgent to find a green and clean new energy source. Microbial fuel cells (MFCs) have attracted much attention due to their renewable capabilities and green characteristics. MFCs still has certain limitations in its application process, such as its internal complexity, high cost of electrode separators and unstable power generation. Introducing different types of nanomaterials to build MFCs can solve these existing problems. However, how the introduced nanomaterials improve the electrochemical properties of MFCs remains to be further analyzed. To this end, this research will discuss the mechanism by which different regulatory strategies based on nanomaterials alter the electrochemical behavior of MFCs. Specifically, this research will focus on the impact of nanomaterials-based modification on the electrochemical performance of MFCs, including structural changes, material composite and new material preparations. The results show that the introduction of nanomaterials significantly improves the power density, current density and stability of MFCs, while enhancing catalytic activity, microbial adhesion and electron transfer efficiency. In this research, the analysis of changes in the electrochemical properties of MFCs by nanomaterials is conducive to the synthesis of novel electrochemically active nanomaterials and the development of high-performance MFCs.

E. M. Milner, E. H. Yu

Fuel Cells • 2018

AbstractMicrobial fuel cells (MFCs) are a sustainable technology for the direct conversion of biodegradable organics in wastewater into electricity. In most MFCs, the oxygen reduction reaction (ORR) is used as the cathode reduction reaction. Aerobic biocathodes, which use bacteria as biocatalysts to catalyze the cathode ORR, provide self‐sustained, robust and highly active alternatives to chemical catalysts. However, further study of the effect of oxygen mass transfer to the biofilm and cathode materials design is needed. In the current work, two aerobic biocathodes were enriched in half‐cells, and oxygen mass transfer to the biofilm and the biofilm distribution in the porous electrode structure were investigated. It was found that mass transfer of oxygen to the aerobic biocathode was a significant factor affecting cathode ORR, evidenced by a strong correlation between the air flow rate and current. Additionally, it was found that the biofilm penetrates between 20–30% into the porous carbon electrode structure, which is likely due to oxygen mass transfer limitations. The performance of a MFC with biocatalysts at both anode and cathode (64 µW cm−2 peak power at an air flowrate of 1 L min−1) showed strong correlation with air flowrate, confirming the observation in the half‐cell system.

Y.‐G. Zhao, M. Ying, Y.‐B. Fu et al.

Fuel Cells • 2019

AbstractEnhancing the electrochemical performance of anode is a critical step for improving the power output of marine benthic microbial fuel cells (BMFCs). An active anode involving the akaganeite (β‐FeOOH)‐coated carbon felt was proposed in present study. Results showed that electrochemical performance of modified anode was significantly improved. The peak current density of oxidation reaction increased from 0.664 to 6.107 A m−2. The exchange current density was improved from 11.75 × 10−3 to 151.36 × 10−3 mA cm−2. Electron transfer resistance decreased from 13.4 to 1.407 Ω, while the surface capacitance dramatically increased. The maximum power density of the BMFCs equipped with modified anode approached to 504.2 mW m−2, 2.3 times higher than that with unmodified anode. Moreover, relative abundance of dissimilatory iron reducing bacteria (DIRB) on the modified anode increased. Finally, a molecule synergetic mechanism containing electrostatic interaction and bacteria recognition between DIRB and β‐FeOOH was proposed to interpret the improvement of modified anode.

Velichkova P, Bratkova S, Angelov A et al.

Journal of Ecology & Natural Resources • 2025

Simple electron donors (such as lactate, ethanol, glucose, etc.) in the process of microbial sulfate reduction are well studied. In search of new substrates for sulfate-reducing bacteria, multicomponent organic products were investigated. The application of distillery wastewater (vinasse and ethanol stillage) as electron donors in a microbial sulfate reduction process with an integrated microbial fuel cell was studied. The results were compared with those of lactate as a control. The influence of the rate of volumetric sulfate loading on the rate of microbial processes was studied using six different hydraulic retention times: 14, 18, 22, 26, 30 and 34 hours. During the process, sulfate-reducing bacteria incompletely oxidize organic matter in the used distillery wastewater and generate large amounts of acetic acid, and propionic acids as a product of other microbiological processes. The rates of sulfate and organic removal for all three substrates increase with increasing retention time. In the case of vinasse and stillage at the 34th hour, sulfate removal was 98%, and organics removal was 48 and 44%, respectively. The open circuit voltage values for both fuel cells with wastewaters were highest at the 22nd hour. The results showed that vinasse and ethanol stillage were suitable electron donors in the process of microbial sulfate reduction and the resulting metabolites can be a substrate for other anaerobic processes.

Youssef A. Youssef, Mohamed E. Abuarab, Ahmed Mahrous et al.

RSC Advances • 2023

Coupling CWs with MFCs enhanced ibuprofen removal. Eichhornia crassipes remarkably contributed to ibuprofen removal. CW-MFC represents a technically and economically feasible option for pharmaceutical wastewater treatment and electricity production.

Yaser Abdollahfard, Mehdi Sedighi, Mostafa Ghasemi

Sustainability • 2023

Microbial fuel cells have recently received considerable attention as a potential source of renewable energy. Due to its complex and hybrid nature, it has significant nonlinear features and substantial hysteresis behavior, making it hard to optimize and control its power generation directly. This study modeled power density and COD removal using random forest regression and gradient boost regression trees. System inputs are three key parameters that affect performance and commercialization. There is a range of 0.1–0.5 mg/cm2 of Pt, a degree of sulfonation of sulfonated polyether-etherketone varying from 20% to 80%, and a cathode aeration rate of 10–150 mL/min. Based on the model’s accuracies, gradient boost regression was selected for power density prediction and random forest for COD removal prediction. Particle swarm optimization was used as the optimization algorithm after selecting the best models to maximize COD removal and power density. It was found that DS was the most critical parameter for COD removal, and Pt was the most critical parameter for power density. There is a different optimal input value for each model. In order to maximize power density, DS (%) must be 67.7087, Pt (mg/cm2) must be 0.3943, and Aeration (mL/min) must be 117.7192. To maximize COD removal, the DS (%) must be 75.8816, the Pt (mg/cm2) must be 0.3322, and the Aeration (mL/min) must be 75.1933.

Himanshu Kachroo, Ravi Shankar, Prasenjit Mondal

International Journal of Chemical Reactor Engineering • 2024

Abstract Microbial fuel cell (MFC) employs microbial communities as biocatalysts to convert chemical energy from organic substrates to electrical energy. The investigation of MFC incorporated with anaerobic mixed cultures and sulfonated polystyrene (SPS) membrane is of interest for this research due to its competency in generating renewable biological energy and wastewater treatment. Methylene blue was an effective redox mediator in this study. The reactor optimization was performed via the Design of Experiments (DOE) approach using Minitab software. The performance of the batch reactor was optimal with the operating conditions of temperature 30 °C, pH 7, and mediator concentration 250 μM. The contour plots and ANOVA specified that mediator concentration was the most influential parameter that affects MFC performance. MFC fed with 250 μM methylene blue concentration generated a maximum voltage of 0.33 V, current (density) of 4.08 A/m2, power (density) of 1.34 W/m2. The COD removal was 82.4 % at the end of the batch cycle of seven days. The data obtained from the experiments showed that small amounts of a mediator (250 μM) in wastewater elevate the bio-electricity output of the MFC reactor by 1.22 folds.

Jesada Lawan, Siriwan Wichai, Choopong Chuaypen et al.

Chemosphere • 2021

For wastewater treatment, sediment microbial fuel cells (SMFCs) have advantages over traditional microbial fuel cells in cost (due to their membrane-less structure) and operation (less intensive maintenance). Nevertheless, the technical obstacles of SMFCs include their high internal electrical resistance due to sediment in the anode chamber and slow oxygen reduction reaction (ORR) in the cathode chamber, which is responsible for their low power density (PD) (0.2-50 mW/m2). This study evaluated several SMFC improvements, including anode and cathode chamber amendment, electrode selection, and scaling the chamber size up to obtain optimally constructed single-chamber SMFCs to treat fat, oil, and grease (FOG) trap effluent. The chemical oxygen demand (COD) removal efficiency, PD, and electrical energy conversion efficiency concerning theoretically available chemical energy from FOG trap effluent treatment (%ECWW) were examined. Packing biochar in the anode chamber reduced its electrical resistance by 5.76 times, but the improvement in PD was trivial. Substantial improvement occurred when packing the cathode chamber with activated carbon (AC), which presumably catalyzed the ORR, yielding a maximum PD of 109.39 mW/m2, 959 times greater than without AC in the cathode chamber. This SMFC configuration resulted in a COD removal efficiency of 85.80 % and a %ECWW of 99.74 % in 30 days. Furthermore, using the most appropriate electrode pair and chamber volume increased the maximum PD to 1787.26 mW/m2, around 1.7 times greater than the maximum PD by SMFCs reported thus far. This optimally constructed SMFC is low cost and applicable for household wastewater treatment.

Jimmy Kuo, Daniel Liu, Chorng-Horng Lin

Bioengineering (Basel, Switzerland) • 2023

Sediment microbial fuel cells (MFCs) were developed in which the complex substrates present in the sediment could be oxidized by microbes for electron production. In this study, the functional prediction of microbial communities of anode-associated soils in sediment MFCs was investigated based on 16S rRNA genes. Four computational approaches, including BugBase, Functional Annotation of Prokaryotic Taxa (FAPROTAX), the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2), and Tax4Fun2, were applied. A total of 67, 9, 37, and 38 functional features were statistically significant. Among these functional groups, the function related to the generation of precursor metabolites and energy was the only one included in all four computational methods, and the sum total of the proportion was 93.54%. The metabolism of cofactor, carrier, and vitamin biosynthesis was included in the three methods, and the sum total of the proportion was 29.94%. The results suggested that the microbial communities usually contribute to energy metabolism, or the metabolism of cofactor, carrier, and vitamin biosynthesis might reveal the functional status in the anode of sediment MFCs.

Peng Xu, En-Rong Xiao, Feng He et al.

Chemosphere • 2020

Settled algae may be used as nutrient for macrophyte establishment, but also can induce marked macrophyte decline during deep anaerobic decomposition. Sediment microbial fuel cells (SMFCs) may promote the utilization of algae-derived nutrients and relieve bio-toxicity from settled algae to submerged macrophytes, thus facilitating plant production. To test these hypotheses, a 62-day comparative study was designed and conducted in microcosms with the following six treatments: control (open-circuit SMFC), plant (open-circuit SMFC with plants), algae (open-circuit SMFC with algae), algae-plant (open-circuit SMFC with algae and plants), algae-SMFC (closed-circuit SMFC with algae), and algae-plant-SMFC (closed-circuit SMFC with algae and plants). The results showed that the presence of Hydrilla verticillata improved the power generation of SMFCs when algae were used as substrates during the whole operation. The decomposition of sedimented algae experienced two periods since the injection. During the slight decomposition period (14-38 day), the algal retention in sediments was enhanced by H.&#xa0;verticillata as a nutrient source. Nitrogen (N) assimilation in plant shoots was facilitated under electrogenesis due to a simultaneous increase of algae-derived dissolved inorganic carbon (DIC) and ammonium (NH4+) in the water column. At the end of the 38th day, the biomass of H.&#xa0;verticillata were increased by 21.4% and 52.3%, respectively, in the algae-plant and algae-plant-SMFC, compared with that in plant treatment. Obvious NH4+-stress was exerted on H.&#xa0;verticillata during the following intense algal decomposition period (38-62 day). Compared with shoots, roots of H.&#xa0;verticillata were more sensitive to the biotoxicity of algae-derived NH4+. The electrogenetic process diverted the degradation pathway from acetoclastic methanogenesis to electrogenesis via redox cycle, resulting in delayed algal decomposition in algae-SMFC treatment. In addition, electrogenesis enhanced the removal of algae-derived N. As a result, NH4+ toxicity to plant roots was effectively alleviated, and sedimented algae served as a stable nutrient source for plant development. Stable transfer rate of algae-derived N from sediments to plant roots was observed, while the assimilation rate of algae-derived N from water column to plant shoots showed a constant increase in the algae-plant-SMFC treatment. Electrogenesis enhanced N-fixing capacity belonged to rhizosphere of H.&#xa0;verticillata, evidenced by greater enrichment of some plant growth-promoting rhizobacteria (PGPRs), including Bradyrhizobium, Mycobacterium, Paenibacillus, Mesorhizobium, and Roseomonas in the algae-plant-SMFC treatment. At the end of the experiment, marked increases in the production of H.&#xa0;verticillata in algae-plant-SMFC were observed, with 90.1% and 32.8%, respectively, when compared with algae-plant and plant treatments (p&#xa0;<&#xa0;0.05). SMFC application could be used as a strategy to promote the growth of submerged macrophytes in algae-rich sediments.

Kenneth E. Richter, Jennifer M. Ayers

Applied Sciences • 2018

Here we present an approach to predicting sediment microbial fuel cell performance based on environmental conditions. Sediment total organic carbon and water temperature were found to be important determinants in predicting the power output from microbial fuel cells in shallow sediments (<100 m) in San Diego. We extrapolated data from the in situ San Diego experiments to predict MFC performance in shallow sediments in other locations, namely the Gulf of Mexico and the Yellow Sea. Finally, using laboratory data of MFC performance in deep water (~1000 m) sediment samples, we extend our predictions to ocean sediments worldwide. We predict low power output from the deep sea (microwatts) relative to the shallow sediments (milliwatts), and attribute that to a possible lack of electrogenic bacteria in the sediments, lower sediment permeability, or a greater proportion of refractory organic matter reaching the bottom.

Onur Can TÜRKER

Eskişehir Technical University Journal of Science and Technology A - Applied Sciences and Engineering • 2022

Simultaneous liquid organic waste disposal and electricity generation were achieved by a solar-assist sediment microbial fuel cell (S-SMFC) in terms of an ecological and economical perspective. In this respect, 840 mL house environment liquid organic waste which contains 10% juice and 10% sugary tea were disposed by electrogenic bacteria and converted electricity with solar energy. A 100 F capacitor was easily charged 29 times with generated electricity. S-SMFC was disposed 10 mL more waste than control due to more electrical bacteria density on the graphite electrode. In this case, Proteobacteria and Firmucutes were categorized dominate bacteria groups, and they were found in the S-SMFC as 54% and 28%, respectively. Importantly, solar energy increased population density of these groups in the S-SMFC and the density on the graphite electrode increased more than 19% according to control. Some bacteria which were associated with electricity production in the S-SMFC were to Azospirillum fermentarium, Clostridium sp., Pseudomonas guangdongensis, Bacteroides sp., Azovibrio restrictus, Clostridium pascui, Levilinea saccharolytica, Seleniivibrio woodruffii, Geovibrio ferrireducens. Consequently, S-SMFC presents innovative, crucial and simple methodology in order to convert liquid organic waste into the green energy.

Nannan Zhao

E3S Web of Conferences • 2020

To investigate the removal effect of pollutants in mariculture sediment by sediment microbial fuel cell (SMFC) and its power generation capacity, the effects of external resistance, cathode pH and cathode dissolved oxygen concentration (DO) on the SMFC system were investigated. The results showed that the optimal parameters for SMFC were as follows: external resistance = 1500 Ω, pH = 8.5 and DO = 5 mg·L-1. In these situations, the power generation performance and organic degradation effect were both the best. The maximum output voltages were 585, 606, and 587 mV, respectively; the removal rates of COD in sediment were 75.51%, 84.21% and 86.63%, respectively; and the removal rates of ammonia nitrogen in sediment were 80.34%, 98.91% and 90.24%, respectively. The SMFC system had a certain degradation ability to pollutants such as COD and ammonia nitrogen in the sediment of the marine aquaculture areas, which had a broad application prospect.

Desmond Ato Koomson, Jingyu Huang, Guang Li et al.

Membranes • 2021

The recirculatory microbial desalination cell-microbial electrolysis cell (MDC-MEC) coupled system is a novel technology that generates power, treats wastewater, and supports desalination through eco-friendly processes. This study focuses on the simultaneous efficient removal of Fe2+ and Pb2+ in the MEC and ammonium ions in the MDC. It also evaluates the performances of dual-chambered MEC (DCMEC) and single-chambered MEC (SCMEC), coupled with MDC with Ferricyanide as catholyte (MDCF) in heavy metals (Pb2+ and Fe2+) removal, in addition to the production of voltage, current, and power within a 48-h cycle. The SCMEC has a higher Pb2+ (74.61%) and Fe2+ (85.05%) removal efficiency during the 48-h cycle than the DCMEC due to the simultaneous use of microbial biosorption and the cathodic reduction potential. The DCMEC had a higher current density of 753.62 mAm-2 than that of SCMEC, i.e., 463.77 mAm-2, which influences higher desalination in the MDCF than in the SCMEC within the 48-h cycle. The MDCF produces a higher voltage (627 mV) than Control 1, MDC (505 mV), as a power source to the two MECs. Stable electrolytes' pH and conductivities provide a conducive operation of the coupled system. This study lays a solid background for the type of MDC-MEC coupled systems needed for industrial scale-up.

Yang Cui, Bin Lai, Xinhua Tang

Biosensors • 2019

The microbial fuel cell (MFC) is a promising environmental biotechnology that has been proposed mainly for power production and wastewater treatment. Though small power output constrains its application for directly operating most electrical devices, great progress in its chemical, electrochemical, and microbiological aspects has expanded the applications of MFCs into other areas such as the generation of chemicals (e.g., formate or methane), bioremediation of contaminated soils, water desalination, and biosensors. In recent decades, MFC-based biosensors have drawn increasing attention because of their simplicity and sustainability, with applications ranging from the monitoring of water quality (e.g., biochemical oxygen demand (BOD), toxicants) to the detection of air quality (e.g., carbon monoxide, formaldehyde). In this review, we summarize the status quo of MFC-based biosensors, putting emphasis on BOD and toxicity detection. Furthermore, this review covers other applications of MFC-based biosensors, such as DO and microbial activity. Further, challenges and prospects of MFC-based biosensors are briefly discussed.

Anshika Varshney, Lokendra Sharma, Chetan Pandit et al.

Applied biochemistry and biotechnology • 2022

The sustainable development of human society in today's high-tech world depends on some form of eco-friendly energy source because existing technologies cannot keep up with the rapid population expansion and the vast amounts of wastewater that result from human activity. A green technology called a microbial fuel cell (MFC) focuses on using biodegradable trash as a substrate to harness the power of bacteria to produce bioenergy. Production of bioenergy and wastewater treatment are the two main uses of MFC. MFCs have also been used in biosensors, water desalination, polluted soil remediation, and the manufacture of chemicals like methane and formate. MFC-based biosensors have gained a lot of attention in the last few decades due to their straightforward operating principle and long-term viability, with a wide range of applications including bioenergy production, treatment of industrial and domestic wastewater, biological oxygen demand, toxicity detection, microbial activity detection, and air quality monitoring, etc. This review focuses on several MFC types and their functions, including the detection of microbial activity.

Xiaoyu Han, Youpeng Qu, Da Li et al.

Chemosphere • 2020

Saline-sodic soil is widely distributed around the world and has induced severe impacts on ecosystems and agriculture. Plant microbial desalination cell (PMDC) and soil microbial desalination cell (SMDC) were constructed to migrate excessive salt in the soil in this study. Compared with SMDC, PMDCs generated higher voltage ranging from 150&#xa0;mV to 410&#xa0;mV (500&#x3a9;) and the maximum power density reached 34&#xa0;mW/m2. Higher desalinization efficiency was obtained by PMDCs, the soil conductivity reduced from initial 2.4&#xa0;mS/cm to 0.4&#xa0;&#xb1;&#xa0;0.1&#xa0;mS/cm and pH decreased from initial 10.4 to 8.2&#xa0;&#xb1;&#xa0;0.1. Soils desalination in PMDCs was achieved through multiple pathways, including ion migration in PMDCs driven by electrokinetic process, plant absorption and bioremediation by plant roots and anode microorganism activity. Geobacter was the dominant electrogenic bacteria at the PMDC anode. The electrochemical and desalinating performance of PMDCs was enhanced by plants and provided a new method for remediation of saline-sodic soil.

Xianyue Jing, Shanshan Chen, Xing Liu et al.

The Science of the total environment • 2021

Potassium (K+)-channel-based electrical signaling can coordinate microbial actions at a distance that provides an evolutionary advantage to cell communities. Electroactive cells are usually cultured surrounded by an electric field which provided stronger electrical signaling than the K+-mediated electrical signaling. Whether the K+ signaling also plays a role in coordinating the behavior of electroactive microorganisms has not been accurately demonstrated. Thus, we constructed a K+-channel-deficient strain &#x394;gsuK of Geobacter sulfurreducens to directly investigate roles of K+ signaling in electroactive biofilm formation for the first time. The &#x394;gsuK strain exhibited significantly inferior biofilm formation (i.e., biomass, thickness and component) and consequently showed weaker electrical performance (i.e., start-up time, current output, electrochemical catalytic behavior and charge transfer resistance) than the wild-type strain. Individual electric generation capacity and the expression of genes involved in biofilm formation and electrical performance in the single cell did not significantly change with the deletion of gsuK, indicating that K+ signaling indeed influenced the recruiting behavior of planktonic cell but not the functioning of the single cell related to biofilm formation or electric generation. This study is intended to provide an in-depth understanding of electroactive biofilm formation and serve as a basis for optimizing its electrical performance via strengthening the recruitment behavior.

Yue Dong, Mingrui Sui, Yiying Jiang et al.

The Science of the total environment • 2022

Plasticizer plays an imperceptible role in interfering with the structure and function of wastewater biofilms, but the inherent influence mechanism still remains unknown. Here, the responses in electrochemical, structural, microbial properties of electroactive biofilm (EAB) to plasticizer (dibutyl phthalate, DBP) were comprehensively elucidated, especially for the property variation of extracellular polymeric substances (EPS). The biofilm-0 in DBP-absent environment contributed to 22.9% and 63.9% higher current, compared to those in 1&#xa0;mg/L and 10&#xa0;mg/L DBP environment (biofilm-1 and biofilm-10). Chronic exposure to high-concentration DBP significantly boosted the content and distribution width of polysaccharide in EPS, but the electron exchange capacity of EPS decreased 76.6% to 0.146&#xa0;&#x3bc;mol e-/mg EPS for biofilm-10. The bacteria were subjected to metabolic function loss, in terms of esterase activity and membrane integrity, by using flow cytometry. The DBP exposure also imposed selective pressure on enrich EPS-secretion-related bacteria, while the Geobacter species decreased from 71.2% (biofilm-0) to 55.8% (biofilm-10). Consequently, the DBP exposure suppressed the pollutant degradation rate, which provided new insights into the EAB role as a promising core for wastewater treatment in plasticizer-existing environments.

Gemma Reguera

FEMS microbiology ecology • 2017

Geobacter bacteria are the only microorganisms known to produce conductive appendages or pili to electronically connect cells to extracellular electron acceptors such as iron oxide minerals and uranium. The conductive pili also promote cell-cell aggregation and the formation of electroactive biofilms. The hallmark of these electroactive biofilms is electronic heterogeneity, mediated by coordinated interactions between the conductive pili and matrix-associated cytochromes. Collectively, the matrix-associated electron carriers discharge respiratory electrons from cells in multilayered biofilms to electron-accepting surfaces such as iron oxide coatings and electrodes poised at a metabolically oxidizable potential. The presence of pilus nanowires in the electroactive biofilms also promotes the immobilization and reduction of soluble metals, even when present at toxic concentrations. This review summarizes current knowledge about the composition of the electroactive biofilm matrix and the mechanisms that allow the wired Geobacter biofilms to generate electrical currents and participate in metal redox transformations.

Samantha R McCuskey, Yude Su, Dirk Leifert et al.

Advanced materials (Deerfield Beach, Fla.) • 2019

Composites, in which two or more material elements are combined to provide properties unattainable by single components, have a historical record dating to ancient times. Few include a living microbial community as a key design element. A logical basis for enabling bioelectronic composites stems from the phenomenon that certain microorganisms transfer electrons to external surfaces, such as an electrode. A bioelectronic composite that allows cells to be addressed beyond the confines of an electrode surface can impact bioelectrochemical technologies, including microbial fuel cells for power production and bioelectrosynthesis platforms where microbes produce desired chemicals. It is shown that the conjugated polyelectrolyte CPE-K functions as a conductive matrix to electronically connect a three-dimensional network of Shewanella oneidensis MR-1 to a gold electrode, thereby increasing biocurrent &#x2248;150-fold over control biofilms. These biocomposites spontaneously assemble from solution into an intricate arrangement of cells within a conductive polymer matrix. While increased biocurrent is due to more cells in communication with the electrode, the current extracted per cell is also enhanced, indicating efficient long-range electron transport. Further, the biocomposites show almost an order-of-magnitude lower charge transfer resistance than CPE-K alone, supporting the idea that the electroactive bacteria and the conjugated polyelectrolyte work synergistically toward an effective bioelectronic composite.

Xing Liu, Yin Ye, Zhishuai Zhang et al.

Environmental science &amp; technology • 2023

Sustaining a metabolically active electroactive biofilm (EAB) is essential for the high efficiency and durable operation of microbial fuel cells (MFCs). However, EABs usually decay during long-term operation, and, until now, the causes remain unknown. Here, we report that lysogenic phages can cause EAB decay in Geobacter sulfurreducens fuel cells. A cross-streak agar assay and bioinformatic analysis revealed the presence of prophages on the G. sulfurreducens genome, and a mitomycin C induction assay revealed the lysogenic to lytic transition of those prophages, resulting in a progressive decay in both current generation and the EAB. Furthermore, the addition of phages purified from decayed EAB resulted in accelerated decay of the EAB, thereafter contributing to a faster decline in current generation; otherwise, deleting prophage-related genes rescued the decay process. Our study provides the first evidence of an interaction between phages and electroactive bacteria and suggests that attack by phages is a primary cause of EAB decay, having significant implications in bioelectrochemical systems.

Yuqing Yan, Xin Wang, Anis Askari et al.

The Science of the total environment • 2021

Microbial cooperation widely exists in anaerobic reactors degrading complex pollutants, conventionally studied separately inside the biofilm or the planktonic community. Recent experiments discovered the mutualism between the planktonic bacteria and electroactive biofilm treating propionate, an end-product usually accumulated in anaerobic digesters. Here, a one-dimensional multispecies model found the preference on acetate-based pathway over the hydrogen-based in such community, evidenced by the fact that acetate-originated current takes 66% of the total value and acetate-consuming anode-respiring bacteria takes over 80% of the biofilm. Acetate-based anodic respiration most apparently influences biofilm function while propionate fermentation is the dominant planktonic bio-reaction. Additionally, initial planktonic propionate level shows the ability of coordinating the balance between these two extracellular electron transfer pathways. Increasing the propionate concentration from 2 to 50&#xa0;mM would increase the steady hydrogen-originated current by 210% but decrease the acetate-originated by 26%, suggesting a vital influence of the planktonic microbial process to the metabolic balance in biofilm. Best strategy to promote the biofilm activity is to increase the biomass density and biofilm conductivity simultaneously, which would increase the current density by 875% without thickening the biofilm thickness or prolonging the growth apparently.

Yuanzhao Ding

Bacteria • 2024

This paper explores the intriguing parallels between bacterial behavior and human actions, specifically the tendency of bacteria to adhere to surfaces, construct bacterial “houses” known as a biofilm matrix, nurture growth and reproduction within the biofilm matrix, and disperse upon maturity. Termed as the bacterial “houses”, biofilm matrices exert significant influence on various aspects of human life. A well-structured biofilm matrix serves as the foundation for establishing biofilm reactors capable of efficiently removing heavy metal pollutants from water. Conversely, a dysfunctional biofilm matrix can lead to infections and subsequent illnesses in the human body. Therefore, the study of the biofilm matrix emerges as pivotal. Employing a bibliographic study methodology, this paper analyzes 1000 web of science articles in the field, investigating key keywords, influential countries/regions, organizations, and their interconnections. The findings illuminate the primary themes in biofilm matrix research and offer insights into future directions for this critical field of study.

Veerraghavulu Sapireddy, Krishna P. Katuri, Ali Muhammad et al.

npj Biofilms and Microbiomes • 2021

AbstractMaintaining functional stability of microbial electrolysis cell (MEC) treating wastewater depends on maintaining functional redundancy of efficient electroactive bacteria (EAB) on the anode biofilm. Therefore, investigating whether efficient EAB competing for the same resources (electron donor and acceptor) co-exist at the anode biofilm is key for the successful application of MEC for wastewater treatment. Here, we compare the electrochemical and kinetic properties of two efficient acetoclastic EAB, Geobacter sulfurreducens (GS) and Desulfuromonas acetexigens (DA), grown as monoculture in MECs fed with acetate. Additionally, we monitor the evolution of DA and GS in co-culture MECs fed with acetate or domestic wastewater using fluorescent in situ hybridization. The apparent Monod kinetic parameters reveal that DA possesses higher jmax (10.7 ± 0.4 A/m2) and lower KS, app (2 ± 0.15 mM) compared to GS biofilms (jmax: 9.6 ± 0.2 A/m2 and KS, app: 2.9 ± 0.2 mM). Further, more donor electrons are diverted to the anode for respiration in DA compared to GS. In acetate-fed co-culture MECs, DA (98% abundance) outcompete GS for anode-dependent growth. In contrast, both EAB co-exist (DA: 55 ± 2%; GS: 24 ± 1.1%) in wastewater-fed co-culture MECs despite the advantage of DA over GS based on kinetic parameters alone. The co-existence of efficient acetoclastic EAB with high current density in MECs fed with wastewater is significant in the context of functional redundancy to maintain stable performance. Our findings also provide insight to future studies on bioaugmentation of wastewater-fed MECs with efficient EAB to enhance performance.

Mulat Erkihun, Zelalem Asmare, Kirubel Endalamew et al.

Bacteria • 2024

Biofilms are accumulations of microorganisms in an extracellular polymeric substance matrix which are composed of polysaccharides, proteins, lipids, and nucleic acids. Many bacteria can switch between a planktonic form and a biofilm form. The planktonic bacteria have relatively high cell growth and reproduction rates and have a reduced likelihood of survival but can adapt to occupy new habitats. The biofilm state appears to be a natural and predominant state of bacteria. The need for the formation of bacterial biofilm is that it enhances the tolerance of bacteria to harsh environmental conditions, thereby allowing bacteria to avoid being washed away by water flow or the bloodstream by simply attaching to a surface or tissue, and the EPS matrix protects bacteria cells, in deeper layers, against antimicrobial agents, probably by limiting the diffusion of these agents. Biofilm formation steps are initial contact/attachment to the surface, followed by micro-colony formation, maturation and formation of the architecture of the biofilm, and finally detachment/dispersion of the biofilm. Once formed, biofilm restricts bacterial mobility and increases cell density. Secretions of autoinducers into the environment are critical for cross-signaling between bacteria. This cross-talk is called quorum sensing (QS). Quorum sensing is a cell–cell communication mechanism between bacteria that allows specific processes to be controlled, such as biofilm formation and virulence factor expression. Bacterial quorum sensing signaling mainly consists of acyl-homoserine lactones (produced by Gram-negatives), autoinducing peptides (produced by Gram-positives), and autoinducer-2 (produced by both Gram-negatives and Gram-positives). Therefore, this review is aimed at how bacterial biofilms work and are formed.

Nina Wurzler, Gundula Hidde, Matthias Schenderlein et al.

Engineering Reports • 2021

AbtractThe initial attachment and subsequent biofilm formation of electroactive bacteria Shewanella putrefaciens CN32 was investigated to clarify the influence of organic conditioning layers. A selection of macromolecules and self‐assembled monolayers (SAMs) of different chain lengths and functional groups were prepared and characterized by means of infrared spectroscopy in terms of their chemistry. Surface energy and Zeta (ζ‐) potential of the conditioning layers was determined with contact angle and streaming current measurements. Among the studied surface parameters, a high polar component and a high ratio of polar‐to‐disperse components of the surface energy has emerged as a successful indicator for the inhibition of the initial settlement of S. putrefaciens on stainless steel AISI 304 surfaces. Considering the negative surface charge of planktonic S. putrefaciens cells, and the strong inhibition of cell attachment by positively charged polyethylenimine (PEI) conditioning layers, our results indicate that electrostatic interactions do play a subordinate role in controlling the attachment of this microorganism on stainless steel AISI 304 surfaces. For the biofilm formation, the organization of the SAMs affected the local distribution of the biofilms. The formation of three‐dimensional and patchy biofilm networks was promoted with increasing disorder of the SAMs.

Swee Su Lim, Jean-Marie Fontmorin, Mohd Nur Ikhmal Salehmin et al.

Chemosphere • 2021

A microbial electrolysis cell (MEC) fully catalysed by microorganisms is an attractive technology because it incorporates the state-of-the-art concept of converting organic waste to hydrogen with less external energy input than conventional electrolysers. In this work, the impact of the anode feed mode on the production of hydrogen by the biocathode was studied. In the first part, three feed modes and MEC performance in terms of hydrogen production were evaluated. The results showed the highest hydrogen production under the continuous mode (14.6&#xa0;&#xb1;&#xa0;0.4), followed by the fed-batch (12.7&#xa0;&#xb1;&#xa0;0.4) and batch (0&#xa0;L&#xa0;m-2 cathode day-1) modes. On one hand, the continuous mode only increased by 15% even though the hydraulic retention time (HRT) (2.78&#xa0;h) was lower than the fed-batch mode (HRT 5&#xa0;h). A total replacement (fed-batch) rather than a constant mix of existing anolyte and fresh medium (continuous) was preferable. On the other hand, no hydrogen was produced in batch mode due to the extensive HRT (24&#xa0;h) and bioanode starvation. In the second part, the fed-batch mode was further evaluated using a chronoamperometry method under a range of applied cell voltages of 0.3-1.6&#xa0;V. Based on the potential evolution at the electrodes, three main regions were identified depending on the applied cell voltages: the cathode activation (<0.8&#xa0;V), transition (0.8-1.1&#xa0;V), and anode limitation (>1.1&#xa0;V) regions. The maximum hydrogen production recorded was 12.1&#xa0;&#xb1;&#xa0;2.1&#xa0;L&#xa0;m-2 cathode day-1&#xa0;at 1.0&#xa0;V applied voltage when the oxidation and reduction reactions at the anode and cathode were optimal (2.38&#xa0;&#xb1;&#xa0;0.61 A m-2). Microbial community analysis of the biocathode revealed that Alpha-, and Deltaproteobacteria were dominant in the samples with >70% abundance. At the genus level, Desulfovibrio sp. was the most abundant in the samples, showing that these microbes may be responsible for hydrogen evolution.

Jinyue Jiang, Lin Du, Buchun Si et al.

Water research • 2024

The global shift toward net-zero emissions necessitates resource recovery from wet waste. In this study, we demonstrate the first feasibility of combining pilot-scale microbial electrolytic cells (MECs) with hydrothermal liquefaction (HTL) for simultaneous post-hydrothermal liquefaction wastewater (PHW) treatment and efficient hydrogen (H&#x2082;) production to meet biocrude upgrading requirements. Long-term single reactor operation revealed that fixed anode potential enabled rapid startup, and low catholyte pH and high salinity were effective in suppression of cathodic methanogenesis and acetogenesis - resulting in high current density of 16.6 A m-2 and 9.3 A m-2 when feeding synthetic wastewater and PHW respectively. Additionally, the anode biofilm exhibited spatial variations in response to local environmental conditions. Onsite parallel or serial operations of multiple MECs showed good performance using actual PHW with a record-high H2 production rate of 0.5 L LR day-1 for MEC over 10 liters scale, and the optimal chemical oxygen demand (COD)-to-H2 yield reached 0.127 kg-H2 per kg-COD, supporting a self-sufficient, closed-loop upgrade to jet fuel.

Luguang Wang, Fei Long, Dawei Liang et al.

Bioresource technology • 2020

Hydrogen production from renewable resources via microbial electrolysis cells (MECs) is a promising approach for sustainable energy production. Yet high hydrogen yield from real feedstocks has not been demonstrated in up-scaled MECs. In this study, a 10-L single chamber MEC with a high electrode surface area to volume ratio (66&#xa0;m2/m3) was constructed and electroactive cathodic biofilms were enriched for hydrogen evolution reaction. A high hydrogen yield of 91% was achieved using lignocellulosic hydrolysate with a hydrogen production rate of 0.71 L/L/D at an organic loading rate of 0.4&#xa0;g/D. The anodic and cathodic microbial communities, with Enterococcus spp. as the known electroactive bacteria, were capable of achieving current densities of 13.7&#xa0;A/m2 and 16.5&#xa0;A/m2, respectively. A machine learning algorithm was used to investigate the correlation between community data and electrochemical performance, and the critical genera on determining current density were identified.

Swee Su Lim, Byung Hong Kim, Da Li et al.

Frontiers in chemistry • 2017

Understanding the mechanism of electron transfer between the cathode and microorganisms in cathode biofilms in microbial electrolysis cells (MECs) for hydrogen production is important. In this study, biocathodes of MECs were successfully re-enriched and subjected to different operating parameters: applied potential, sulfate use and inorganic carbon consumption. It was hypothesized that biocathode catalytic activity would be affected by the applied potentials that initiate electron transfer. While inorganic carbon, in the form of bicarbonate, could be a main carbon source for biocathode growth, sulfate could be a terminal electron acceptor and thus reduced to elemental sulfurs. It was found that potentials more negative than -0.8 V (vs. standard hydrogen electrode) were required for hydrogen production by the biocathode. In additional, a maximum hydrogen production was observed at sulfate and bicarbonate concentrations of 288 and 610 mg/L respectively. Organic carbons were found in the cathode effluents, suggesting that microbial interactions probably happen between acetogens and sulfate reducing bacteria (SRB). The hydrogen-producing biocathode was sulfate-dependent and hydrogen production could be inhibited by excessive sulfate because more energy was directed to reduce sulfate (E&#xb0; SO42- /H2S = -0.35 V) than proton (E&#xb0; H+/H2 = -0.41 V). This resulted in a restriction to the hydrogen production when sulfate concentration was high. Domestic wastewaters contain low amounts of organic compounds and sulfate would be a better medium to enrich and maintain a hydrogen-producing biocathode dominated by SRB. Besides the risks of limited mass transport and precipitation caused by low potential, methane contamination in the hydrogen-rich environment was inevitable in the biocathode after long term operation due to methanogenic activities.

Md Tabish Noori, Ruggero Rossi, Bruce E Logan et al.

Trends in biotechnology • 2023

Electroautotrophic microbes at biocathodes in microbial electrolysis cells (MECs) can catalyze the hydrogen evolution reaction with low energy demand, facilitating long-term stable performance through specific and renewable biocatalysts. However, MECs have not yet reached commercialization due to a lack of understanding of the optimal microbial strains and reactor configurations for achieving high performance. Here, we critically analyze the criteria for the inocula selection, with a focus on the effect of hydrogenase activity and microbe-electrode interactions. We also evaluate the impact of the reactor design and key parameters, such as membrane type, composition, and electrode surface area on internal resistance, mass transport, and pH imbalances within MECs. This analysis paves the way for advancements that could propel biocathode-assisted MECs toward scalable hydrogen gas production.

Burak Kilinc, Dilan Akagunduz, Murat Ozdemir et al.

3 Biotech • 2022

In this study, the effects of cocaine metabolite, benzoylecgonine, commonly found in wastewater on hydrogen production were investigated using microbial electrolysis cells. Benzoylecgonine dissolved in synthetic urine and human urine containing benzoylecgonine were inoculated to evaluate hydrogen production performance in microbial electrolysis cells. Microbial electrolysis cells were inoculated with synthetic urine and human urine containing the cocaine metabolite benzoylecgonine for hydrogen gas production performance. Gas production was observed and measured daily by gas chromatography. GC-MS was used to analyze the compounds found in human urine before and after operation in microbial electrolysis cells. The metabolite's pH values and optical density in microbial electrolysis cells were analyzed spectrophotometrically. Hydrogen gas was successfully produced in microbial electrolysis cells (~&#x2009;5.5&#xa0;mL) at the end of the 24th day in the presence of benzoylecgonine in synthetic urine. Human urine containing benzoylecgonine also generated hydrogen in microbial electrolysis cells. In conclusion, microbial electrolysis cells can be used to remove cocaine metabolites from contaminated wastewater generating hydrogen gas.

Junxi Dai, Zhongyi Huang, Hongguo Zhang et al.

The Science of the total environment • 2023

Bio-cathode Microbial electrolysis cell (MEC) has been widely discovered for heavy metals removal and hydrogen production. However, low electron transfer efficiency and heavy metal toxicity limit MEC treatment efficiency. In this study, ZIF-67 was introduced to modify Sulfate-reducing bacteria (SRB) bio-cathode to enhance the bioreduction of sulfate and Antimony (Sb) with hydrogen production in the MEC. ZIF-67 modified bio-cathode was developed from a bio-anode microbial fuel cell (MFC) by operating with an applied voltage of 0.8 V to reverse the polarity. Cyclic voltammetry, linear sweep voltammetry and electrochemical impedance were done to confirm the performance of the ZIF-67 modified SRB bio-cathode. The synergy reduction of sulfate and Sb was accomplished by sulfide metal precipitation reaction from SRB itself. Maximum sulfate reduction rate approached 93.37 % and Sb removal efficiency could reach 92 %, which relies on the amount of sulfide concentration generated by sulfate reduction reaction, with 0.923 &#xb1; 0.04 m3 H2/m3 of hydrogen before adding Sb and 0.857 m3 H2/m3 of hydrogen after adding Sb. The hydrogen was mainly produced in this system and the result of gas chromatography (GC) indicated that 73.27 % of hydrogen was produced. Meanwhile the precipitates were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy to confirm Sb2S3 was generated from Sb (V).