Search Results (56)

We have developed a new bioanode based on a cascade of reactions catalyzed by two enzymes. A glassy carbon electrode is modified with β-glucosidase and glucose oxidase enzymes entrapped within an osmium redox polymer. Cellobiose, the fuel for the anode, is hydrolyzed by β-glucosidase (TxGH116), yielding two molecules of D-glucose. Glucose is then oxidized by glucose oxidase (GOx) into δ-gluconolactone and produces electrons that are transferred to the electrode mediated by osmium redox polymer. We investigated the kinetic parameters of both enzymes at different temperatures. For GOx, the effect of enzyme loading and enzyme/polymer ratio were also optimized. The proposed bioanode is coupled to a biocathode based on horseradish peroxidase (HRP) in which H₂O₂, the oxidant, is reduced. We investigated the performance of the biofuel cell on cellobiose and sugarcane hydrolysates subjected to different pretreatments. Alkaline pretreatments of biomass were found to be more effective than phosphoric acid pretreatment. Adding TxGH116 β-glucosidase further enhanced current generation, even when commercial cellulase was used. Full article

This study explores the use of a pre-acclimated Geobacter-enriched inoculum as a novel strategy to accelerate the start-up of biocathodes. Unlike conventional inoculation with broad-spectrum communities, the proposed inoculum combines a long-term electroactive consortium, previously adapted to anaerobic bioelectrochemical conditions, with digestate produced under controlled laboratory conditions. This prior acclimation ensures the presence of Geobacter strains already conditioned to electrode-associated growth, promoting rapid colonization and early electrochemical activity. Experiments were conducted in a dual-chamber electrochemical cell equipped with a three-electrode setup polarized at −1 V vs. Ag/AgCl. The enriched biocathode reached current densities exceeding 1.4 A/m² within 24 h, whereas the control exhibited significantly lower, less stable, and inconsistent performance. Unlike previously reported approaches based on broad-spectrum co-inoculation, this work presents a tailor-made inoculum in which the electroactive community is not only dominated by Geobacter, but also selectively preconditioned under functional bioelectrochemical conditions. This prior adaptation is a key differentiator that markedly enhances start-up efficiency. The results demonstrate that strategic enrichment with pre-acclimated Geobacter significantly accelerates start-up and improves electrochemical performance, offering a promising pathway toward more efficient and scalable bioelectrochemical systems for wastewater treatment and renewable energy generation. Full article

This study introduces an advanced strategy for improving microbial fuel cell (MFC) performance in hexavalent chromium (Cr(VI)) wastewater treatment. A high-performance nano-iron sulfide (nano-FeS) hybridized biocathode was developed by regulating glucose concentration and applying an external voltage. The combination of a glucose concentration of 1000 mg/L and a 0.2 V applied voltage greatly promoted the in situ biosynthesis of nano-FeS, resulting in smaller particle sizes and increased quantities within the biocathode, leading to enhanced electrochemical performance. The MFC with the hybridized biocathode exhibited the highest power density (43.45 ± 1.69 mW/m²) and Cr(VI) removal rate (3.99 ± 0.09 mg/L·h), outperforming the control by 29% and 71%, respectively. The improvements were attributed to the following processes. (1) Nano-FeS provided additional active sites that enhanced electron transfer and electrocatalytic activity, reducing cathode passivation; (2) it protected microorganisms by reducing Cr(VI) toxicity, promoting redox-active substance enrichment and antioxidant enzyme secretion, which maintained microbial activity; (3) the biocathode selectively enriched electroactive and Cr(VI)-reducing bacteria (such as Brucella), fostering a stable and symbiotic microbial community. This study highlights the promising potential of regulating carbon source and external voltage to boost nano-FeS biosynthesis, offering a sustainable and efficient strategy for MFC-based Cr(VI) wastewater treatment with practical implications. Full article

The expansion of the sugar industry has resulted in large amounts of untreated effluent, necessitating the development of energy-efficient treatment technologies, like microbial desalination cells (MDCs). However, the high cost and potential toxicity of chemical cathode catalysts limit MDC performance, making biocathodes a promising alternative. This study investigates the efficiency of a Scenedesmus obliquus-inoculated photosynthetic microbial desalination cell (PMDC) in the cathode chamber to treat sugar industry effluent, desalinate water, and generate electricity. The performance of the PMDC is compared to that of traditional MDCs. The results showed that the PMDC achieved 21.6% desalination, 73.8% anode COD removal, and a maximum power density of 6.8 mW/m², outperforming MDC by 6.43%, 18.5%, and 112.5%, respectively. These results demonstrate that the PMDC offers an effective, energy-efficient alternative to MDCs with added benefits of nutrient removal and algal biomass production at the cathode, making it a promising solution for water and wastewater treatment. Full article

The reverse polarity biocathode culture (RPBC) is a technology for the rapid preparation of biocathodes, which quickly enrich electroactive bacteria (EAB) in the microbial fuel cell (MFC) anode and then transform the electrode function from bioanode to biocathode by reversing bioelectrode polarity. However, the mechanism of RPBC is still unclear, and methods to regulate performance and ensure the long-term stability of cultured biocathodes have not been established. This study investigated the correlation between electrogenic bacteria and the target reducing EAB, from two aspects: energy supply and the formation of a composite biofilm. The results showed that electrogenic bacteria provided energy for the reducing EAB through interspecies electron transfer. This process could be regulated by changing the electrode potential and substrate concentration to obtain an optimized biocathode. In addition, the RPBC forms a composite biofilm of electrogenic bacteria and reducing EAB, which significantly improves the enrichment efficiency and the amount of reducing EAB (compared with a direct biocathode culture, respectively, shortening the enrichment time by 80%, increasing the electroactivity by 12.4 times, and increasing the nitrate degradation rate by 4.85 times). This study provides insights into regulating the performance and maintaining the long-term stability of RPBC-cultured biocathodes. Full article

This study explores the efficient decolorization and complete mineralization of the diazo dye Evans blue, using an integrated aerobic bioreactor system coupled with a double-chamber microbial fuel cell (DCMFC) including a bio-cathode and acetate as a cosubstrate. The research addresses the environmental challenges posed by dye-laden industrial effluents, focusing on achieving high decolorization efficiency and understanding the microbial communities involved. The study utilized mixed strains of actinomycetes, isolated from garden compost, to treat initial dye concentrations of 100 mg/L and 200 mg/L. Decolorization efficiency and microbial community composition were evaluated using 16S rRNA sequencing, and electrochemical impedance spectroscopy (EIS) was used to assess anode and DCMFC resistance. The results demonstrated decolorization efficiencies ranging from 90 ± 2% to 98 ± 1.9% for 100 mg/L and from 79 ± 2% to 87% ± 1% for 200 mg/L. An anode resistance of 12.48 Ω indicated a well-developed biofilm and enhanced electron transfer. The microbial community analysis revealed a significant presence of Pseudomonadota (45.5% in dye-acclimated cultures and 32% in inoculum cultures), with key genera including Actinomarinicola (13.75%), Thermochromatium (4.82%), and Geobacter (4.52%). This study highlights the potential of the integrated DCMFC–aerobic system, utilizing mixed actinomycetes strains, for the effective treatment of industrial dye effluents, offering both environmental and bioenergy benefits. Full article

This paper describes the study of an amperometric glucose biosensor based on an enzymatic biofuel cell consisting of a bioanode and a biocathode modified with the same enzyme—glucose oxidase (GOx). A graphite rod electrode (GRE) was electrochemically modified with a layer of Prussian blue (PB) nanoparticles embedded in a poly(pyrrole-2-carboxylic acid) (PPCA) shell, and an additional layer of PPCA and was used as the cathode. A GRE modified with a nanocomposite composed of poly(1,10-phenanthroline-5,6-dione) (PPD) and gold nanoparticles (AuNPs) entrapped in a PPCA shell was used as an anode. Both electrodes were modified with GOx by covalently bonding the enzyme to the carboxyl groups of PPCA. The developed biosensor exhibited a wide linear range of 0.15–124.00 mM with an R² of 0.9998 and a sensitivity of 0.16 μA/mM. The limit of detection (LOD) and quantification (LOQ) were found to be 0.07 and 0.23 mM, respectively. The biosensor demonstrated exceptional selectivity to glucose and operational stability throughout 35 days, as well as good reproducibility, repeatability, and anti-interference ability towards common interfering substances. The studies on human serum demonstrate the ability of the newly designed biosensor to determine glucose in complex real samples at clinically relevant concentrations. Full article

Acetate can be produced from carbon dioxide (CO₂) and electricity using bacteria at the cathode of microbial electrosynthesis (MES). This process relies on electrolytically-produced hydrogen (H₂). However, the low solubility of H₂ can limit the process. Using metal cathodes to generate H₂ at a high rate can improve MES. Immobilizing bacteria on the metal cathode can further proliferate the H₂ availability to the bacteria. In this study, we investigated the performances of 3D bioprinting of Sporomusa ovata on three metal meshes—copper (Cu), stainless steel (SS), and titanium (Ti), when used individually as a cathode in MES. Bacterial cells were immobilized on the metal using a 3D bioprinter with alginate hydrogel ink. The bioprinted Ti mesh exhibited higher acetate production (53 ± 19 g/m²/d) at −0.8 V vs. Ag/AgCl as compared to other metal cathodes. More than 9 g/L of acetate was achieved with bioprinted Ti, and the least amount was obtained with bioprinted Cu. Although all three metals are known for catalyzing H₂ evolution, the lower biocompatibility and chemical stability of Cu hampered its performance. Stable and biocompatible Ti supported the bioprinted S. ovata effectively. Bioprinting of synthetic biofilm on H₂-evolving metal cathodes can provide high-performing and robust biocathodes for further application of MES. Full article

For traditional heterotrophic denitrification technology, organics are usually added as the electron donor for nitrate removal, which increases the operation cost for wastewater treatment. Solar panel production wastewater contains a large amount of nitrate. To decrease the operation cost and reduce CO₂ emissions, an iron anode microbial fuel cell (Fe-MFC) was constructed to treat solar panel production wastewater by sequencing batch operation. The results showed that the maximum nitrate removal efficiency reached 99.98% and the maximum removal rate was 0.049 kg·m⁻³·d⁻¹. The output voltages rose rapidly to 560 ± 10 mV within 2 h and then stabilized at 520 ± 50 mV for about 40 h. Combining the detection of coulombic efficiency, CV curve, q* value and internal resistance; the decrease in denitrification efficiency and electricity generation efficiency probably resulted from the passivation of iron anode and the aging of the cathode biofilm resulted in the efficiency decrease. From the microbial analysis, Chryseobacterium, Thermomonas and Thauera predominated at the end of Fe-MFC operation. Microorganisms that cannot adapt to the autotrophic environment in Fe-MFC died out finally. Periodic replacement of the iron anode and domestication of the bio-cathode were essential to maintain the Fe-MFC efficiency. The Fe-MFC technology was feasible to be used to remove nitrate and generate electricity from solar panel production wastewater. Without organics addition, the Fe-MFC technology was cost-efficient and environmentally friendly, endowing itself with a broad prospect of application. Full article

Electron shuttling molecules (ESMs) have been proven to accelerate the electron transfer from the electrode to the electroactive microorganism in microbial electrosynthesis (MES) for higher CO₂ reduction or chemical production rate. However, the microbial electron acceptors of electroactive microorganisms and their responses to different electron shuttling molecules in MES were still unknown. In this study, three kinds of ESMs, e.g., riboflavin (B2), methyl viologen (MV) and neutral red (NR) were applied in the MES for acetate production to explore the mechanism of different ESMs on microbial interactions. The acetate concentrations were 41% and 51% higher than that of the control in B2 and NR addition. The acetogens relative abundances of control, B2, MV and NR were 0.29%, 5.68%, 22.78% and 42.89%, respectively. The microbial function profile of the microbial community on the biocathodes indicated that the performance of acetate production was more closely related to the expression of electron transport. The B2 was coupled with the NADH complex and hydrogenase, while MV and NR were coupled with the Rnf complex to support electron transfer and energy conversion via various electron transfer pathways. The study revealed that the ESMs coupled with different electron transport complexes of microorganisms to achieve electron transfer, resulting in product changes. Full article

The increased demand for alternative sustainable energy sources has boosted research in the field of fuel cells (FC). Among these, microbial fuel cells (MFC), based on microbial anodes and different types of cathodes, have been the subject of renewed interest due to their ability to simultaneously perform wastewater treatment and bioelectricity generation. Several different MFCs have been proposed in this work using different conditions and configurations, namely cathode materials, membranes, external resistances, and microbial composition, among other factors. This work reports the design and optimization of MFC performance and evaluates a hydrogel (Ion Jelly^®) modified air-breathing cathode, with and without an immobilized laccase enzyme. This MFC configuration was also compared with other MFC configuration performances, namely abiotic and biocathodes, concerning wastewater treatment and electricity generation. Similar efficiencies in COD reduction, voltage (375 mV), PD (48 mW/m²), CD (130 mA/m²), and OCP (534 mV) were obtained. The results point out the important role of Ion Jelly^® in improving the MFC air-breathing cathode performance as it has the advantage that its electroconductivity properties can be designed before modifying the cathode electrodes. The biofilm on MFC anodic electrodes presented a lower microbial diversity than the wastewater treatment effluent used as inocula, and inclusively Geobacteracea was also identified due to the high microbial selective niches constituted by MFC systems. Full article

Biofuel cells (BFCs) with enzymatic electrocatalysts have attracted significant attention, especially as power sources for wearable and implantable devices; however, the applications of BFCs are limited owing to the limited O₂ supply. This can be addressed by using air-diffusion-type bilirubin oxidase (BOD) cathodes, and thus the further development of the hierarchical structure of porous electrodes with highly effective specific surface areas is critical. In this study, a porous layer of gold is deposited over magnesium-oxide-templated carbon (MgOC) to form BOD-based biocathodes for the oxygen reduction reaction (ORR). Porous gold structures are constructed via electrochemical deposition of gold via dynamic hydrogen bubble templating (DHBT). Hydrogen bubbles used as a template and controlled by the Coulomb number yield a porous gold structure during the electrochemical deposition process. The current density of the ORR catalyzed by BOD without a redox mediator on the gold-modified MgOC electrode was 1.3 times higher than that of the ORR on the MgOC electrode. Furthermore, the gold-deposited electrodes were modified with aromatic thiols containing negatively charged functional groups to improve the orientation of BOD on the electrode surface to facilitate efficient electron transfer at the heterogeneous surface, thereby achieving an ORR current of 12 mA cm⁻² at pH 5 and 25 °C. These results suggest that DHBT is an efficient method for the fabrication of nanostructured electrodes that promote direct electron transfer with oxidoreductase enzymes. Full article

The treatment of wastewater is an expensive and energy-extensive practice that not only ensures the power generation requirements to sustain the current energy demands of an increasing human population but also aids in the subsequent removal of enormous quantities of wastewater that need to be treated within the environment. Thus, renewable energy source-based wastewater treatment is one of the recently developing techniques to overcome power generation and environmental contamination issues. In wastewater treatment, microbial fuel cell (MFC) technology has demonstrated a promising potential to evolve as a sustainable approach, with the simultaneous recovery of energy and nutrients to produce bioelectricity that harnesses the ability of electrogenic microbes to oxidize organic contaminants present in wastewater. Since traditional wastewater treatment has various limitations, sustainable implementations of MFCs might be a feasible option in wastewater treatment, green electricity production, biohydrogen synthesis, carbon sequestration, and environmentally sustainable sewage treatment. In MFCs, the electrochemical treatment mechanism is based on anodic oxidation and cathodic reduction reactions, which have been considerably improved by the last few decades of study. However, electricity production by MFCs remains a substantial problem for practical implementations owing to the difficulty in balancing yield with overall system upscaling. This review discusses the developments in MFC technologies, including improvements to their structural architecture, integration with different novel biocatalysts and biocathode, anode, and cathode materials, various microbial community interactions and substrates to be used, and the removal of contaminants. Furthermore, it focuses on providing critical insights and analyzing various types, processes, applications, challenges, and futuristic aspects of wastewater treatment-related MFCs and thus sustainable resource recovery. With appropriate planning and further studies, we look forward to the industrialization of MFCs in the near future, with the idea that this will lead to greener fuels and a cleaner environment for all of mankind. Full article

Nitrate (NO₃⁻-N) and nitrites (NO₂⁻-N) are common pollutants in various water bodies causing serious threats not only to aquatic, but also to animals and human beings. In this study, we developed a strategy for efficiently reducing nitrates in microbial fuel cells (MFCs) powered by a granular activated carbon (GAC)-biocathode. GAC was developed by acclimatizing and enriching denitrifying bacteria under a redox potential (0.3 V) generated from MFCs. Thus, using the formed GAC-biocathode we continued to study their effect on denitrification with different cathode materials and circulation speeds in MFCs. The GAC-biocathode with its excellent capacitive property can actively reduce nitrate for over thirty days irrespective of the cathode material used. The stirring speed of GAC in the cathode showed a steady growth in potential generation from 0.25 V to 0.33 V. A rapid lag phase was observed when a new carbon cathode was used with enriched GAC. While a slow lag phase was seen when a stainless-steel cathode was replaced. These observations showed that effective storage and supply of electrons to the GAC plays a crucial role in the reduction process in MFCs. Electrochemical analysis of the GAC properties studied using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and zeta potential showed distinct properties with different abiotic and biocathode conditions. We found that the enrichment of electrotrophic bacteria on GAC facilitates the direct electron transfer in the cathode chamber for reducing NO₃⁻-N in MFCs as observed by scanning electron microscopy. Full article

Microbial electrochemical technologies now enable microbial electrosynthesis (MES) of organic compounds using microbial electrolysis cells handling waste organic materials. An electrolytic cell with an MES cathode may generate soluble organic molecules at a higher market price than biomethane, thereby satisfying both economic and environmental goals. However, the long-term viability of bioanode activity might become a major concern. In this work, a 15-L MES reactor was designed with specific electrode configurations. An electrochemical model was established to assess the feasibility and possible performance of the design, considering the aging of the bioanode. The reactor was then constructed and tested for performance as well as a bioanode regeneration assay. Biowaste from an industrial deconditioning platform was used as a substrate for bioanode. The chemical oxygen demand (COD) removal rate in the anodic chamber reached 0.83 g day⁻¹ L⁻¹ of anolyte. Acetate was produced with a rate of 0.53 g day⁻¹ L⁻¹ of catholyte, reaching a maximum concentration of 8.3 g L⁻¹. A potential difference (from 0.6 to 1.2 V) was applied between the bioanode and biocathode independent of reference electrodes. The active biocathode was dominated by members of the genus Pseudomonas, rarely reported so far for MES activity. Full article