Powering the future: advances and applications of microbial fuel cell-based biosensors.

<i>Harvesting Energy using Biocatalysts</i>

A comprehensive overview on electro-active biofilms, role of exo-electrogens and their microbial niches in microbial fuel cells (MFCs)

Renewable and clean forms of energy are one of the major needs at present. Microbial Fuel Cells (MFC’s) offers unambiguous advantages over other renewable energy conversion methods. Production of energy resources while minimizing waste is one of the best ways for sustainable energy resource management practices. The application of Microbial Fuel Cells (MFCs) may represent a completely new approach to wastewater treatment with the production of sustainable clean energy. The increase in energy demand can be fulfilled by Microbial Fuel Cell (MFC) in the future. In recent years, researchers have shown that MFCs can be used to produce electricity from water containing glucose, acetate, or lactate. Studies on electricity generation using organic matter from wastewater as substrate are in progress. Waste biomass is a cheap and relatively abundant source of electrons for microbes capable of producing electrical current outside the cell. Rapidly developing microbial electrochemical technologies, such as microbial fuel cells, are part of a diverse platform of future sustainable energy and chemical production technologies. In the present investigation to study the two wastewater samples, municipal wastewater from nearby areas of Guntur (A.P.) and Dairy waste from Guntur (A.P.) were used as substrates in Microbial Fuel Cells (MFCs) to generate electricity. Along with electricity generation, the MFCs can successfully help in treating the same sewage samples. The parameters like pH, TS, TSS, TDS, BOD, and COD were analyzed for all two samples. The COD removal efficiency of the MFCs was analyzed using the standard reflux method. All the MFCs were efficient in COD removal. 50%, 75%, and 85% COD removal was observed after 10, 15, and 30 days respectively of operation of MFCs with municipal waste as substrate.

Microbial fuel cell (MFC) is an emerging technology for sustainable energy production. An MFC employs indigenous microorganisms as biocatalysts and can theoretically convert any biodegradable substrate into electricity, making the technology a viable solution for sustainable waste treatment or autonomous power supply. However, the electric energy currently generated from MFCs is not directly usable due to the low voltage and current output. Moreover, the output power can fluctuate significantly according to the operating points, which makes stable harvest of energy difficult. This paper presents an MFC energy harvesting scheme using two layers of DC/DC converters. The proposed energy harvester can capture the energy from multiple MFCs at the most efficient operating point and at the same time form the energy into a usable shape.

Microbial fuel cell (MFC) is an emerging technology for sustainable energy production. An MFC employs indigenous microorganisms as biocatalysts and can theoretically convert any biodegradable substrate into electricity, making the technology a viable solution for sustainable waste treatment or autonomous power supply. However, the electric energy currently generated from MFCs is not directly usable due to the low voltage and current output. Moreover, the output power can fluctuate significantly according to the operating conditions, which makes stable harvest of energy difficult. This paper presents an MFC energy harvesting scheme using a hysteresis controller and two layers of DC/DC converters. The proposed energy harvesting system can capture the energy from multiple MFCs at individually controlled operating point and at the same time form the energy into a usable shape.

Three-dimensional graphitic mesoporous carbon-doped carbon felt bioanodes enables high electric current production in microbial fuel cells

Boosting bioelectricity generation using three-dimensional nitrogen-doped macroporous carbons as freestanding anode

Bio-carbon microtubules in microbial fuel cells for superior performance of 3D free-standing anode derived from Rhus Typhina

Microbial fuel cells (MFCs) have potential in wastewater treatment, biogas production and clean energy generation. MFCs provide an interdisciplinary research approach incorporating engineering and natural sciences. This study explores MFCs’ capabilities to produce electricity and biogas from wastewater and field soil substrates with different compositions. A two-chamber MFC system was operated anaerobically. Household sewage water used as the organic substrate with different soil amounts. Six different process feed compositions, labeled MFC-1–6, were investigated. MFC-1 exhibited the highest biogas generation volume of 245 cm³ and 42 mW/cm² power density. MFC-5 and −6 yielded 100 cm³ and 130 cm³, respectively. Wastewater treatment was effective on day 20, with pH, conductivity, turbidity, and total dissolved solids decreased to 7.3, 2.6 mS, 326 NTUs, and 1114 mg/L, respectively. Since, MFC-1 autonomously generated −800 mV, an external battery supplied an additional 600 mV to meet the methane generation voltage requirements. MFCs’ effectiveness in addressing wastewater treatment and renewable energy production was highlighted.

Microbial Fuel Cell (MFC) technology has been heralded as a tool for energy conservation, resource recovery and valuable compound synthesis, amongst others. The MFC concept is possible due to the ability of electrochemically active bacteria (EcAB) to transfer the electrons produced from substrate degradation, out of the bacterial cell and onto the electrode surface via different mechanisms; a process called exocellular electron transfer (EET). However, despite advances and extensive studies on EET mechanisms and EcAB, like the Fe(III)-reducing Geobacter sulfurreducens PCA, the technology has not reached yet the stage of broad applicability. This thesis investigates characteristics and performance of EcAB in the anodic compartment of pure- and mixed-culture MFCs in an effort to shed light to processes important to MFC performance and efficiency. In order to reliably study EcAB in a microbial fuel cell environment, a gas-tight, sterile MFC setup was developed and optimized for electrochemical and microbiological studies of the anodic bacteria and consequently the electrochemically active biofilm/bioanode. In addition, a method for Geobacter species quantification with quantitative PCR (qPCR) was developed. Furthermore, a multiple-unit MFC setup was designed for convenient and simultaneous operation of identical MFCs ‘in-parallel’. A design for a new compact, multi-array MFC to be used as a small-scale culturing platform of EcAB based solely on their electrochemical properties is also introduced. Our research with different titanium (Ti) electrodes in the same MFC setup, suggests that the MFC electrode surface is critical as it determines attachment of EcAB and bioanode formation that leads ultimately to efficient electrochemical activity. Pt- and Ta- coated Ti electrodes performed the best while uncoated Ti with either smooth or rough surfaces performed the worst. Future MFC research could benefit greatly from enhancing the electrode interface for optimum bioanode formation and electron transfer. Our studies with flat-plate, graphite-electrode, mixed-culture microbial fuel cells (Pmax ≈ 1 W/m2) operated for several months with external load (Rext), indicated stable and reproducible characteristics including Coulombic efficiencies, average values of cell voltage, anode potentials, and current densities as well as main microbial populations of both the anolyte and the bioanode. However, transient testing of power maxima values (Pmax) that required lower Rext, or applied potential showed result variability, that might be linked to differences in electrochemical impedance factors, redox-active centers and electron-producing states of the bioanodes. Differences in the quantities of the bioanode microbial species did not seem to correlate with this variability. Since energy-conserving applications like waste-water treatment MFCs would ideally be operated with an Rext rather than applied voltage, addressing interface impedance factors, such as charge transfer resistance and electrical double layer capacitance, is important especially when MFCs are operated at lower Rext. Furthermore, mixed-culture MFCs were shown to be selective for certain bacterial consortia, including Geobacter- and Pseudomonas- related species. Geobacter-related species were dominant on the surface of different electrodes suggesting a pivotal role of the species in electrochemical activity and EET. This was not surprising as the original mixed-culture inoculum - used for starting up several bioelectrochemical systems at our research facilities - was amended with pure cultures of G. sulfurreducens PCA. However, the strain specifically selected for and present in most bioanodes was a novel Geobacter, strain T33 that was phylogenetically closely related (99% by 16S rRNA sequence similarity) to several strains detected in a variety of MFCs operated by other research groups under various conditions and anodic substrates. These strains formed a new phylogenetic Geobacter cluster, distinct from G. sulfurreducens. This observation suggested that strain T33 might have an ecological advantage in MFCs over G. sulfurreducens PCA. In-depth characterization of strain T33 in pure-culture experiments showed that strain T33 forms efficient bioanodes with high Pmax similar to strain PCA, but exhibits different redox-centers than strain T33. Furthermore, strain T33 has a more limited electron acceptor range, but a wider electron donor range than strain PCA, including glucose and succinate. Phylogenetic analysis indicated that strain T33 and recently described electrochemically active strains G. soli GSS01 and G. anodireducens SD-1 are closely related (99% by 16S rRNA) and form a new phylogenetic cluster within the Geobacters, 98% by 16S rRNA similar to G. sulfurreducens strains PCA and KN400. Genome-based analyses indicates that even though the two clusters share common metabolic properties, some differences exist with respect to electron donor utilization, attachment and conductive cell surface components (e-pili) production and genome rearrangement and gene acquisition. It is not sufficiently clear how the differences in the genome of strain T33 are relevant to persistence of the strain in MFCs, biofilm formation and EET, our studies overall suggest that strain T33 even though producing similar power densities as G. sulfurreducens PCA, might be more stable and versatile in MFCs, and therefore a better candidate for waste-water treatment if it can couple the oxidation of several organic substrates, as observed with Fe(III)-respiration, also to electrode-respiration.

Microbial fuel cells (MFCs) are environmentally friendly energy converters that use electrochemically active bacteria (EAB) as catalysts to break down organic matter while producing bioelectricity. Traditionally, MFC research has relied on simple organic substrates, such as acetate, glucose, sucrose, butyrate, and glutamate, the production of which involves energy-intensive, CO2-dependent processes and chemically aggressive methods. In contrast, nonconventional waste streams offer a more sustainable alternative as feedstocks, aligning with zero-waste and regenerative agricultural principles. This review highlights the potential of nonconventional organic wastes, such as fruit and vegetable wastes, raw human and livestock urine, and farm manure, as globally available and low-cost substrates for MFCs, particularly in household and farming applications at small-scale waste levels. Furthermore, complex waste sources, including hydrocarbon-contaminated effluents and lignin-rich industrial wood waste, which present unique challenges and opportunities for their integration into MFC systems, were examined in depth. The findings of this review reveal that MFCs utilizing nonconventional substrates can achieve power outputs comparable to traditional substrates (e.g., 8314 mW m−2–25,195 mW m−2 for crude sugarcane effluent and raw distillery effluent, respectively) and even superior to them, reaching up to 88,990 mW m−2 in MFCs utilizing vegetable waste. Additionally, MFCs utilizing hydrocarbon-containing petroleum sediment achieved one of the highest reported maximum power densities of 50,570 mW m−2. By integrating diverse organic waste streams, MFCs can contribute to carbon-neutral energy generation and sustainable waste management practices.

Microbes to Generate Electricity

Agri‐food waste valorisation

Recently microbial fuel cells (MFCs) have been considered as an alternative power generation technique by utilizing organic wastes. In this study, an experiment was carried out to generate bioelectricity from co-digestion of organic waste (kitchen waste) and sewage sludge as a waste management option using microbial fuel cell (MFC) in anaerobic process. A total of five samples with different sludge-waste ratio were used with zinc (Zn) and cupper (Cu) as cell electrodes for the test. The trends of voltage generation were different for each sample in cells such as 350 mV, 263 mV, 416 mV maximum voltage were measured from sample I, II and III respectively. It was observed that the MFC with sewage sludge showed the higher values (around 960 mV) of voltages with time whereas 918 mV obtained with organic waste. Precisely comparing cases with varying the organic waste and sewage sludge ratio helps to find the best bioelectricity generation option. Using MFCs can be appeared as the solution of electricity scarcity along the world as an efficient and eco-friendly manner as well as organic solid waste and sewage sludge management.

Microbial fuel cells (MFCs) have emerged as a promising technology to convert biomass and organic waste into electricity, offering an eco-friendly and sustainable alternative to fossil fuels. Recent innovations in nanotechnology have significantly enhanced the performance and efficiency of MFCs by improving electron transfer rates, expanding surface areas, and optimizing the properties of anode and cathode materials. This review provides a detailed assessment of the fundamental and functional components of MFCs. These components include the anode, which facilitates the oxidation of organic matter, and the cathode, where the reduction of oxygen or other electron acceptors occurs. Another critical component is the proton exchange membrane (PEM), which allows the transfer of protons from the anode to the cathode while preventing oxygen from diffusing into the anode chamber. In addition to discussing these key elements, the article explores the role of various microorganisms involved in MFCs. These microorganisms, which include both naturally occurring species and genetically engineered strains, play a vital role in facilitating extracellular electron transfer (EET), a process that enables the conversion of chemical energy stored in organic compounds into electrical energy. We analyze different biomass pretreatment strategies, such as physical, chemical, and biological approaches, that enhance the breakdown of lignocellulosic biomass to improve energy output. Furthermore, the review highlights optimization techniques for improving biomass-powered MFC performance, such as electrode modification, pH control, and organic loading rate management. The application potential of MFCs is extensively discussed, covering bioremediation, wastewater treatment, biosensors, and power generation, with a particular focus on MFC-based biosensors for environmental monitoring and medical diagnostics. Despite their immense potential, challenges such as low power output, biofouling, and high operational costs hinder large-scale commercialization. To address these issues, we propose innovative strategies, including the integration of nanomaterials, electroactive microorganisms, and advanced membrane designs, to enhance the efficiency and reliability of MFCs. We conclude that nanotechnology-enabled MFCs, combined with engineered microbes and optimized system designs, hold immense potential for revolutionizing sustainable energy generation and biosensing applications, paving the way for a cleaner and more efficient future.