Performance Of Bioelectrochemical Systems Research Articles

Design of an Insulin Tracer Protein-Based Biosensor for Insulin Determination

Aim: The regulation of blood glucose levels is controlled by insulin, which is produced by the pancreatic beta system. Inadequate synthesis of beta insulin, results in elevated glucose levels, a condition known as diabetes, which can lead to various chronic health issues. In recent times, the diagnosis of diabetes, particularly type 1, has shifted towards the direct measurement of insulin levels. To facilitate this, an immunosensor was created to enable rapid and sensitive examination of insulin levels, with the goal of improving the quality for life for diabetic patients. Material and Method: For this purpose, an insulin tracer protein based biosensor was designed for the determination of insulin at all solutions. For determination of insulin, electrobiochemical analyses were performed. Optimisation and characterisation studies were performed using differential pulse voltammetry. The performance of bioelectrochemical system was analysed by Receiver Operating Characteristic method. Results: The insulin biosensor cyclic woltammogram was obtained between -0,1 and 0,6 V potantial. At 0,45 V was found as the anodic peak side for determination the insulin. Optimisation and characterisation studies performed at 0,45 V with differential pulse voltammetry. Conclusion: The study successfully identified stable and easy-to-use insulin concentrations, indicating the potential of the newly developed immunosensor for applications in clinical biochemistry laboratories.

Impact of Condition Variations on Bioelectrochemical System Performance: An Experimental Investigation of Sulfamethoxazole Degradation.

Bioelectrochemical systems (BESs) are an innovative technology for the efficient degradation of antibiotics. Shewanella oneidensis (S. oneidensis) MR-1 plays a pivotal role in degrading sulfamethoxazole (SMX) in BESs. Our study investigated the effect of BES conditions on SMX degradation, focusing on microbial activity. The results revealed that BESs operating with a 0.05 M electrolyte concentration and 2 mA/cm2 current density outperformed electrolysis cells (ECs). Additionally, higher electrolyte concentrations and elevated current density reduced SMX degradation efficiency. The presence of nutrients had minimal effect on the growth of S. oneidensis MR-1 in BESs; it indicates that S. oneidensis MR-1 can degrade SMX without nutrients in a short period of time. We also highlighted the significance of mass transfer between the cathode and anode. Limiting mass transfer at a 10 cm electrode distance enhanced S. oneidensis MR-1 activity and BES performance. In summary, this study reveals the complex interaction of factors affecting the efficiency of BES degradation of antibiotics and provides support for environmental pollution control.

Bioelectrochemical reactor to manage anthropogenic sulfate pollution for freshwater ecosystems: Mathematical modeling and experimental validation

Anthropogenic sulfate loading into otherwise low-sulfate freshwater systems can cause significant ecological consequences as a biogeochemical stressor. To address this challenge, in situ bioremediation technologies have been developed to leverage naturally occurring microorganisms that transform sulfate into sulfide rather than implementing resource-intensive physio-chemical processes. However, bioremediation technologies often require the supply of electron donors to facilitate biological sulfate reduction. Bioelectrochemical systems (BES) can be an alternative approach for supplying molecular hydrogen as an electron donor for sulfate-reducing bacteria through water electrolysis. Although the fundamental mechanisms behind BESs have been studied, limited research has evaluated the design and operational parameters of treatment systems when developing BESs on a scale relevant to environmental systems. This study aimed to develop an application-based mathematical model to evaluate the performance of BESs across a range of reactor configurations and operational modes. The model was based on sulfate transformation by hydrogenotrophic sulfate-reducing bacteria coupled with the recovery of solid iron sulfide species formed by the oxidative dissolution of dissolved ferrous iron from a stainless steel anode. Sulfate removal closely corresponded to the rate of electrolytic hydrogen production and hydraulic residence time but was less sensitive to specific microbial rate constants. The mathematical model results were compared to experimental data from a pilot-scale BES tested with nonacidic mine drainage as a case study. The close agreement between the mathematical model and the pilot-scale BES experiment highlights the efficacy of using a mathematical model as a tool to develop a conceptual design of a scaled-up treatment system.

Influence of the 3D architecture and surface roughness of SiOC anodes on bioelectrochemical system performance: a comparative study of freeze-cast, 3D-printed, and tape-cast materials with uniform composition

3D-printed anodes for bioelectrochemical systems are increasingly being reported. However, comparisons between 3D-printed anodes and their non-3D-printed counterparts with the same material composition are still lacking. In addition, surface roughness parameters that could be correlated with bioelectrochemical performance are rarely determined. To fill these gaps, slurries with identical composition but different mass fractions were processed into SiOC anodes by tape-casting, freeze-casting, or direct-ink writing. The current generation was investigated using electroactive biofilms enriched with Geobacter spp. Freeze-cast anodes showed more surface pores and the highest surface kurtosis of 5.7 ± 0.5, whereas tape-cast and 3D-printed anodes showed a closed surface porosity. 3D-printing was only possible using slurries 85 wt% of mass fraction. The surface pores of the freeze-cast anodes improved bacterial adhesion and resulted in a high initial (first cycle) maximum current density per geometric surface area of 9.2 ± 2.1 A m−2. The larger surface area of the 3D-printed anodes prevented pore clogging and produced the highest current density per geometric surface area of 12.0 ± 1.2 A m−2. The current density values of all anodes are similar when the current density is normalized over the entire geometric surface as determined by CT-scans. This study highlights the role of geometric surface area in normalizing current generation and the need to use more surface roughness parameters to correlate anode properties, bacterial adhesion, and current generation.

A genetic engineering strategy to enhance outer membrane vesicle-mediated extracellular electron transfer of Geobacter sulfurreducens

Bioelectrochemical systems (BESs) are unique devices that harness the metabolic activity of electroactive microorganisms (EAMs) to convert chemical energy stored in organic substrates into electrical energy. Enhancing electron transfer efficiency between EAMs and electrodes is the key to practical implementation of BESs. Considering the role of outer membrane vesicles (OMVs) in mediating electron transfer of EAMs, a genetic engineering strategy to achieve OMVs overproduction was explored to enhance electron transfer efficiency and the underlying mechanisms were investigated. This study constructed a mutant strain of Geobacter sulfurreducens that lacked the ompA gene encoding an outer membrane protein. Experimental results showed that the mutant strain produced more OMVs and possessed higher electron transfer efficiency in Fe(III) reduction, dye degradation and current generation in BESs than the wild-type strain. More cargoes such as c-type cytochromes, functional proteins, eDNA, polysaccharides and signaling molecules that might be favorable for electron transfer and biofilm formation were found in OMVs produced by ompA-deficient anodic biofilm, which possibly contributed to the improved electron transfer efficiency of ompA-deficient biofilm. The results indicate that overproduction of OMVs in EAMs might be a potential strategy to enhance BESs performance.

Engineering extracellular electron transfer pathways of electroactive microorganisms by synthetic biology for energy and chemicals production.

The excessive consumption of fossil fuels causes massive emission of CO2, leading to climate deterioration and environmental pollution. The development of substitutes and sustainable energy sources to replace fossil fuels has become a worldwide priority. Bio-electrochemical systems (BESs), employing redox reactions of electroactive microorganisms (EAMs) on electrodes to achieve a meritorious combination of biocatalysis and electrocatalysis, provide a green and sustainable alternative approach for bioremediation, CO2 fixation, and energy and chemicals production. EAMs, including exoelectrogens and electrotrophs, perform extracellular electron transfer (EET) (i.e., outward and inward EET), respectively, to exchange energy with the environment, whose rate determines the efficiency and performance of BESs. Therefore, we review the synthetic biology strategies developed in the last decade for engineering EAMs to enhance the EET rate in cell-electrode interfaces for facilitating the production of electricity energy and value-added chemicals, which include (1) progress in genetic manipulation and editing tools to achieve the efficient regulation of gene expression, knockout, and knockdown of EAMs; (2) synthetic biological engineering strategies to enhance the outward EET of exoelectrogens to anodes for electricity power production and anodic electro-fermentation (AEF) for chemicals production, including (i) broadening and strengthening substrate utilization, (ii) increasing the intracellular releasable reducing equivalents, (iii) optimizing c-type cytochrome (c-Cyts) expression and maturation, (iv) enhancing conductive nanowire biosynthesis and modification, (v) promoting electron shuttle biosynthesis, secretion, and immobilization, (vi) engineering global regulators to promote EET rate, (vii) facilitating biofilm formation, and (viii) constructing cell-material hybrids; (3) the mechanisms of inward EET, CO2 fixation pathway, and engineering strategies for improving the inward EET of electrotrophic cells for CO2 reduction and chemical production, including (i) programming metabolic pathways of electrotrophs, (ii) rewiring bioelectrical circuits for enhancing inward EET, and (iii) constructing microbial (photo)electrosynthesis by cell-material hybridization; (4) perspectives on future challenges and opportunities for engineering EET to develop highly efficient BESs for sustainable energy and chemical production. We expect that this review will provide a theoretical basis for the future development of BESs in energy harvesting, CO2 fixation, and chemical synthesis.

Synchronous hydrogen and electricity production by dual-cathodes in a bioelectrochemical system

Achieving a self-driven microbial electrolysis cell (MEC) to produce hydrogen is important to its applications but remains challenging. Herein, a dual-cathode bioelectrochemical system (BES) was developed, where one cathode produced electricity energy (Power-cathode) and the other cathode produced hydrogen (H2-cathode). When the applied voltage of the H2-cathode was 0.6 V, the maximum voltage generated by the Power-cathode was 0.47 ± 0.03 V, and the hydrogen rate of the H2-cathode was 0.19 ± 0.003 m3/m3/d. The applied voltage of the H2-cathode was ≤0.4 V, which could be supplied entirely with the power generated by the Power-cathode. Geobacter could accumulate in the anodic biofilm through electric potential differences stimulation. The proportion of electroactive bacteria at the bottom of the anode biofilm was higher than that at the top, while denitrifying bacteria were the opposite. A peak-like distribution of electroactive bacteria in the anodic biofilm and denitrifying bacteria formed a valley-like distribution. Those results have demonstrated a new approach based on dual-cathode BES to produce hydrogen and electricity synchronously, and further proposed a bacterial distribution pattern in anode biofilms. This is of great significance for improving the performance of BES in sustainable wastewater treatment and resource recovery.

Enhancing biocathode denitrification performance with nano-Fe3O4 under polarity period reversal

The presence of excessive concentrations of nitrate poses a threat to both the environment and human health, and the bioelectrochemical systems (BESs) are attractive green technologies for nitrate removal. However, the denitrification efficiency in the BESs is still limited by slow biofilm formation and nitrate removal. In this work, we demonstrate the efficacy of novel combination of magnetite nanoparticles (nano-Fe3O4) with the anode-cathode polarity period reversal (PPR-Fe3O4) for improving the performance of BESs. After only two-week cultivation, the highest cathodic current density (7.71 ± 1.01 A m−2) and NO3−-N removal rate (8.19 ± 0.97 g m−2 d−1) reported to date were obtained in the PPR-Fe3O4 process (i.e., polarity period reversal with nano-Fe3O4 added) at applied working voltage of −0.2 and −0.5 V (vs Ag/AgCl) under bioanodic and biocathodic conditions, respectively. Compared with the polarity reversal once only process, the PPR process (i.e., polarity period reversal in the absence of nano-Fe3O4) enhanced bioelectroactivity through increasing biofilm biomass and altering microbial community structure. Nano-Fe3O4 could enhance extracellular electron transfer as a result of promoting the formation of extracellular polymers containing Fe3O4 and reducing charge transfer resistance of bioelectrodes. This work develops a novel biocathode denitrification strategy to achieve efficient nitrate removal after rapid cultivation.

Advances in the Application of Quorum Sensing to Regulate Electrode Biofilms in Bioelectrochemical Systems

Bioelectrochemical systems (BESs) are an emerging technology for wastewater treatment and resource recovery. These systems facilitate electron transfer between microorganisms and electrodes, enabling their application in various fields, such as electricity production, bioremediation, biosensors, and biocatalysis. However, electrode biofilms, which play a critical role in BESs, face several challenges (e.g., a long acclimation period, low attached biomass, high electron transfer resistance, and poor tolerance and stability) that limit the development of this technology. Quorum sensing (QS) is a communication method among microorganisms that can enhance the performance of BESs by regulating electrode biofilms. QS regulation can positively impact electrode biofilms by enhancing extracellular electron transfer (EET), biofilm formation, cellular activity, the secretion of extracellular polymeric substances (EPS), and the construction of microbial community. In this paper, the characteristics of anode electrogenic biofilms and cathode electrotrophic biofilms in BESs, EET mechanisms, and the main factors affecting biofilm formation were summarized. Additionally, QS regulation mechanisms for biofilm formation, strategies for enhancing and inhibiting QS, and the application of QS regulation for electrode biofilms in BESs were systematically reviewed and discussed. This paper provides valuable background information and insights for future research and development of BES platforms based on QS regulation of electrode biofilms.

Electrogenetic control of gene expression in Shewanella oneidensis MR-1 using Arc-dependent transcriptional promoters

Electrochemically active bacteria (EAB) are capable of electrically interacting with electrodes, enabling their application in bioelectrochemical systems (BESs). As the performance of BES is related to the metabolic activities of EAB, the development of methods to control their metabolic activities is important to facilitate BES applications. A recent study found that the EAB Shewanella oneidensis MR-1 uses the Arc system to regulate the expression of catabolic genes in response to electrode potentials, suggesting that a methodology for electrical control of gene expression in EAB, referred to as electrogenetics, can be developed by using electrode potential-responsive, Arc-dependent transcriptional promoters. Here, we explored Arc-dependent promoters in the genomes of S.oneidensis MR-1 and Escherichia coli to identify electrode potential-responsive promoters that are differentially activated in MR-1cells exposed to high- and low-potential electrodes. LacZ reporter assays using electrode-associated cells of MR-1 derivatives revealed that the activities of promoters located upstream of the E.coli feo gene (Pfeo) and the MR-1 nqrA2 (SO_0902) gene (Pnqr2) were significantly increased when S.oneidensis cells were exposed to electrodes poised at+0.7V and-0.4V (versus the standard hydrogen electrode), respectively. Additionally, we developed a microscopic system for in situ monitoring of promoter activity in electrode-associated cells and found that Pnqr2 activity was persistently induced in MR-1cells associated with an electrode poised at-0.4V. Our results indicate that these electrode potential-responsive promoters enable efficient regulation of gene expression in EAB, providing a molecular basis for the development of electrogenetics.

A review on bioelectrochemical systems for emerging pollutants remediation: A computational approaches

A wide range of pollutant compounds are discharged into the environment that they need suitable remediations. For solving the problem, the bioelectrochemical systems (BESs) are green technology suitable for the pollutant treatments. The induced electric current in BESs can stimulate microbes metabolism and increasing electron transfer. It has been reported that the performance of BESs in reducing wastewater emerging pollutants (EPs) reaches more than 90 %. In the BESs, the emerging pollutants as carbon sources plays a significant role between competition and bacterial community and their metabolism. Although some BESs have been presented for the treatment systems, little attention has been paid to the computational approaches and kinetics studies of EPs remediation. Therefore, the current review summarizes the application of BESs for emerging pollutants removal. Moreover, we have provided the predominant microorganisms as well as the microbial metabolism and computational approaches in the biodegradation of EPs. In this review, density functional theory (DFT), molecular dynamics (MD) simulations, computational fluid dynamics (CFD), artificial intelligence or artificial neural networks (ANNs), and quantum mechanics/molecular mechanics (QM/MM) simulations have presented for the BESs. For interpretation of the BESs Michaelis-Menten, First-order kinetic and second order models are suitable kinetic models.

Periodic step polarization accelerates electron recovery by electroactive biofilms (EABs).

Relatively low rate of electron recovery is one of the factors that limit the advancement of bioelectrochemical systems. Here, new periodic polarizations were investigated with electroactive biofilms(EABs) enriched from activated sludge and Geobacter sulfurreducens biofilms. When representative anode potentials (Ea ) were applied, redox centers with midpoint potentials (Emid ) higher than Ea were identified by localized cyclic voltammetry. The electrons held by these redox centers were accessible when Ea was raised to 0.4 V (vs. Ag/AgCl). New periodic polarizations that discharge at 0.4 V recovered electrons faster than normal periodic and fixed-potential polarizations. The best-performing periodic step polarization accelerated electron recovery by 23%-24% and 12%-76% with EABs and G. sulfurreducens biofilms, respectively, compared to the fixed-potential polarization. Quantitative reverse transcription polymerase chain reactionshowed an increased abundance of omcZ mRNA transcripts from G. sulfurreducens after periodic step polarization. Therefore, both the rate of energy recovery by EABs and the performance of bioelectrochemical systems can be enhanced by improving the polarization schemes.

In-situ fabrication of a three-dimensional nanopalladium network into a biocathode enhances chloramphenicol degradation

Bioelectrochemical systems (BESs) with biocathodes are a promising technology for antibiotic removal, but they are often limited by inefficient electron transfer from the cathode to bacteria due to the low conductivity of biofilms. In this study, a conductive cathodic biofilm was established through in-situ synthesis and immobilization of biogenic palladium nanoparticles (Pd-NPs) for chloramphenicol (CAP) removal. Compared to the control biocathode, the limiting current density of the Pd-fabricated biocathode (Pd-biocathode) was increased by 4.3 times, and the charge transfer resistance was decreased by 673 % due to enhanced extracellular electron transfer. The Pd-biocathode showed accelerated CAP removal, with the removal rate constant (k) increasing by 44 % compared to the control biocathode. In particular, the removal efficiency of the Pd-biocathode increased by 71 % within 4 h. These results might be explained by the decreased charge transfer resistance of the biocathode, the selective enrichment of functional bacteria and the up-expression of genes encoding organic substance metabolism and degrading enzyme activity. In addition, the increased applied voltage negligibly affected the enhancement of CAP removal in the Pd-biocathode BES, but it enhanced CAP removal in the control BES. Additionally, glucose addition markedly improved the CAP removal rates. This work demonstrates the potential of an effective and simple biocathode modification strategy through the in-situ synthesis of conductive NPs that could increase the antibiotic removal rates, but also provides new insight into how microbe-electrode interactions can be improved to enhance BES performance in wastewater treatment.

Enhanced bio-electrochemical performance of microbially catalysed anode and cathode in a microbial electrosynthesis system

Most bio-electrochemical systems (BESs) use biotic/abiotic electrode combinations, with platinum-based abiotic electrodes being the most common. However, the non-renewability, cost, and poisonous nature of such electrode systems based on noble metals are major bottlenecks in BES commercialisation. Microbial electrosynthesis (MES), which is a sustainable energy platform that simultaneously treats wastewater and produces chemical commodities, also faces the same problem. In this study, a dual bio-catalysed MES system with a biotic anode and cathode (MES-D) was tested and compared with a biotic cathode/abiotic anode system (MES-S). Different bio-electrochemical tests revealed improved BES performance in MES-D, with a 3.9-fold improvement in current density compared to that of MES-S. Volatile fatty acid (VFA) generation also increased 3.2-, 4.1-, and 1.8-fold in MES-D compared with that in MES-S for acetate, propionate, and butyrate, respectively. The improved performance of MES-D could be attributed to the microbial metabolism at the bioanode, which generated additional electrons, as well as accumulative VFA production by both the bioanode and biocathode chambers. Microbial community analysis revealed the enrichment of electroactive bacteria such as Proteobacteria (60%), Bacteroidetes (67%), and Firmicutes + Proteobacteria + Bacteroidetes (75%) on the MES-S cathode and MES-D cathode and anode, respectively. These results signify the potential of combined bioanode/biocathode BESs such as MES for application in improving energy and chemical commodity production.

Endogenous electric field accelerates phenol degradation in bioelectrochemical systems with reduced electrode spacing.

Reducing the electrode spacing in bioelectrochemical systems (BESs) are widely reported to improve power output, which was mainly attributed to the decrease of ohmic resistance (Rohm) for a long time. Here we found the change of endogenous electric field (EF) intensity was the key to improve electroactivity in response to a reduced electrode spacing, which also accelerated phenol biodegradation. Correlation and principal components analysis revealed that the microbial community of electroactive biofilm (EAB) was independent of Rohm, while the EF intensity was found closely related to most of predominant genera. A strong EF selectively enriched phenol-degrading bacteria Comamonas in suspension and Geobacter in EAB, contributed to the improvement of degradation efficiency. EF also induced the secretion of extracellular polymeric substances, protected EAB from being inactivated by phenol. Our findings highlighted the importance of EF intensity on BESs performance, providing new insights into the design and application of BESs in wastewater treatment.

Bioelectrochemical Remediation for the Removal of Petroleum Hydrocarbon Contaminants in Soil

Consistent accumulation of petroleum hydrocarbon (PH) in soil and sediments is a big concern and, thus, warrants a static technology to continuously remediate PH-contaminated soil. Bioelectrochemical systems (BESs) can offer the desired solution using the inimitable metabolic response of electroactive microbes without involving a physiochemical process. To date, a wide range of BES-based applications for PH bioremediations under different environmental conditions is readily available in the literature. Here, the latest development trend in BESs for PH bioremediation is critically analyzed and discussed. The reactor design and operational factors that affect the performance of BESs and their strategic manipulations such as designing novel reactors to improve anodic reactions, enhancing soil physiology (electrical conductivity, mass diffusion, hydraulic conductivity), electrode modifications, operational conditions, microbial communities, etc., are elaborated to fortify the understanding of this technology for future research. Most of the literature noticed that a low mass diffusion condition in soil restricts the microbes from interacting with the contaminant farther to the electrodes. Therefore, more research efforts are warranted, mainly to optimize soil parameters by specific amendments, electrode modifications, optimizing experimental parameters, integrating different technologies, and conducting life cycle and life cycle cost analysis to make this technology viable for field-scale applications.

Ferrous iron oxidation microflora from rust deposits improve the performance of bioelectrochemical system

Ferric iron (Fe(III)) ions are efficient electron acceptor in bioelectrochemical systems (BESs). For the first time, this study applied the enriched Fe(II)-oxidizing microflora individually from rust deposits, aerobic sludge, or topsoil to catholyte to regenerate Fe(III) ions to boost BES operation. Among three microflora, the rust-microflora had the highest Fe2+ oxidation rate and the lowest Fe ion loss rate since Acidithiobacillus sp., Ferrovum sp., Rhodobacter sp., Sphingomonas sp., and others enriched it. The rust-seeded BES generated the maximum power density of 77.15 ± 1.62 Wm−3 at 15 ℃, 38.9 %, and 31.4 % higher than those in sludge and topsoil-seeded BES, respectively. The rust-microflora with enriched Fe(II)-oxidizing bacteria could enhance the performance of BES, reaching coulombic efficiencies of 98.2 ± 2.6 at reduced internal resistance (5.14 Ω), with 1.59 Ω by activation resistance and 0.77 Ω by diffusion resistance.

Microbial electrochemical bioremediation of petroleum hydrocarbons (PHCs) pollution: Recent advances and outlook

Soil contamination by petroleum hydrocarbons (PHCs) causes various acute problems such as crop growth, yield, and grain quality. Many Physico-chemical and biological approaches are employed to remove the PHCs from polluted soil. However, some of these approaches are too slow, or ineffective, and/or environmentally unfriendly. Indeed, bioelectrochemical systems (BES) combine biological methods and electrochemistry in the context of a redox reaction. BES is gaining attention from scientists and policymakers as a promising technology for the remediation of soil contaminated with PHCs. This review discusses BES working principles, mechanisms, design configuration, operational parameters, and advances in BES applications to remediate PHCs from contaminated soil efficiently. The role of biosurfactants and biochar in enhancing PHC degradation in soil using BES mediating extracellular electron transfer (EET) and biofilm formation is highlighted. Furthermore, recent innovations in this field, technical and economic challenges and limitations in scaling-up BES, and future perspectives are discussed. This review suggests that biochar-based single-chamber air-cathode reactors are preferred because of their lower cost compared to the other classic configurations. Additional efforts are needed in the design of BES reactors, soil characteristics, and seasonal variations in BES performance over a long period of operation to improve the efficiency of soil remediation and power production as well as to apply it on a large scale.

Boosting wastewater bioelectricity recovery via solvent mediation and zinc fencing: Dual regulation for catalyst spatial structure and active sites

Bioelectrochemical systems (BESs) are promising in self-sustaining energy recovery of wastewater. Cathode catalysts are crucial to enhancing the oxygen reduction reaction (ORR) process in BESs. In this study, a dual regulation strategy including solvent mediation and zinc fencing was proposed for regulation of catalyst spatial structure and active sites. The particle size of catalysts derived from bimetallic zeolitic imidazolate frameworks (ZIFs) was tuned over a wide range via solvent mediation while the dispersion of cobalt active sites was achieved via zinc fencing. As-optimized cobalt active sites embedded nitrogen-doped porous carbon with a Co/Zn molar ratio of 1/20 (Co1/20@NPC) directed a four-electron transfer pathway in ORR process. The BES employing Co1/20@NPC as cathode catalyst produced a maximum power density of 2057 ± 21 mW m−2, 40% higher than the BES using Pt/C as cathode catalyst. Co1/20@NPC BES displayed fast organic elimination and efficient energy recovery with a coulombic efficiency of 73 ± 1% and a normalized energy recovery of 0.361 ± 0.006 kWh m−3. The outstanding ORR activity, high bioelectricity generation and operation stability made Co1/20@NPC a prospective cathode catalyst. This dual regulation strategy provides implications for controllable synthesis of ZIF-derived catalysts with tailored structures and characteristics, and demonstrates potential in improving wastewater energy recovery performance in BESs.

Performance of bioelectrochemical systems in treating exhaust gas with power generation: Effects of shock-load, shut-down episodes and microbial community

A diffusive packed anode-bioelectrochemical (Dpa-Bes) system was constructed by feeding waste gas from the cathode to the anode tank in DPa-Bes through a proton exchange membrane (PEM). The high removal of oxygen by the PEM and the effective combination of the two packing materials reduced the electron loss and enhanced the proton transfer capacity, promoting the removal of acetone from the exhaust gas and increasing the output power. The maximum acetone removal efficiency of the modified Dpa-Bes reached ∼99 % after seven days of closed-circuit operation, with a 3.2-fold increase in maximum power density and a 2.27-fold increase in closed-circuit voltage relative to those of the unmodified Dpa-Bes. When the acetone concentration was 2400 ppm, the removal efficiency was 73.22 % and the elimination capacity was at its highest value of 290.21 g/m3/h. Microbial analysis revealed that the conductive filter contained abundant facultative and anaerobic bacteria, whereas the non-conductive filter was rich in aerobic bacteria. The abundance of anaerobic and facultative microorganisms in Dpa-Bes was much higher than in the unmodified Dpa-Bes, and the dominant bacteria were Flavobacterium and Ferruginibacter.