Kha Lil Dinh, Chin‐Tsan Wang, H. Dai et al.

International Journal of Energy Research • 2021

For about 20 years, microbial fuel cells (MFCs) are an emerging technology that has gained attention for its new wastewater treatment and energy generation, especially its ability to convert chemical energy from a broad range of substances into electricity. However, MFC has not been widely commercialized due to low efficiency. Studies have shown that substrate loading is an important factor in scaling up. Therefore, this study investigates the effect of substrate type and concentration on honeycomb MFCs (HCMFCs). The effect of different concentrations ranging from 10 to 40 mM of lactate and acetate (1:1 ratio) substrates was investigated. Power efficiency was analyzed using polarization and power density curves. Results showed that the performance of MFCs and biofilm formation is affected by the substrates. Scanning electron microscopy showed some changes in biofilm formation. Mixing lactate and acetate at 30 mM gave the best performance with a power density of 956.75 mW m−2 and chemical oxygen demand removal of 87.8%. Furthermore, effective substrate degradation, having COD removal of 91.4%, was observed with acetate.

Burak Kilinç, T. Catal

Polish Journal of Environmental Studies • 2023

In this study, a new soil-based microbial fuel cell was developed that can be used for biological remediation in areas with soil pollution. Electricity generation was studied with the developed soil-based microbial fuel cell. Voltage values were measured depending on time and the effects of sodium acetate at different concentrations (20, 40, 60, 80, 100 mM) were investigated. Our results showed that up to 396 mV electricity generation is possible with the new soil-based microbial fuel cell. The voltage values gradually increased with increasing sodium acetate concentration. The half-saturation constant was found to be 75.99 (R 2 = 0.97). In conclusion, the developed soil-based microbial fuel cell has shown that it has biosensor potential and can be used in the detection of various environmental pollutants.

Ludovic Jourdin, Yang Lu, Victoria Flexer et al.

ChemElectroChem • 2016

Abstract Electron‐transfer pathways occurring in biocathodes are still unknown. We demonstrate here that high rates of acetate production by microbial electrosynthesis are mainly driven by an electron flux from the electrode to carbon dioxide, occurring via biologically induced hydrogen, with (99±1) % electron recovery into acetate. Nevertheless, acetate production is shown to occur exclusively within the biofilm. The acetate producers, putatively Acetoanaerobium , showed the remarkable ability to consume a high H 2 flux before it could escape from the biofilm. At zero wastage of H 2 gas, it allows superior production rates and lesser technical bottlenecks over technologies that rely on mass transfer of H 2 to microorganisms suspended in aqueous solution. This study suggests that bacterial modification of the electrode surface (possibly via synthesis of Cu nanoparticles) is directly involved in the significant enhancement of the hydrogen production.

Gowthami Palanisamy, Yeong Min Im, Ajmal P. Muhammed et al.

Membranes • 2023

Developing a hybrid composite polymer membrane with desired functional and intrinsic properties has gained significant consideration in the fabrication of proton exchange membranes for microbial fuel cell applications. Among the different polymers, a naturally derived cellulose biopolymer has excellent benefits over synthetic polymers derived from petrochemical byproducts. However, the inferior physicochemical, thermal, and mechanical properties of biopolymers limit their benefits. In this study, we developed a new hybrid polymer composite of a semi-synthetic cellulose acetate (CA) polymer derivate incorporated with inorganic silica (SiO2) nanoparticles, with or without a sulfonation (–SO3H) functional group (sSiO2). The excellent composite membrane formation was further improved by adding a plasticizer (glycerol (G)) and optimized by varying the SiO2 concentration in the polymer membrane matrix. The composite membrane’s effectively improved physicochemical properties (water uptake, swelling ratio, proton conductivity, and ion exchange capacity) were identified because of the intramolecular bonding between the cellulose acetate, SiO2, and plasticizer. The proton (H+) transfer properties were exhibited in the composite membrane by incorporating sSiO2. The composite CAG–2% sSiO2 membrane exhibited a higher proton conductivity (6.4 mS/cm) than the pristine CA membrane. The homogeneous incorporation of SiO2 inorganic additives in the polymer matrix provided excellent mechanical properties. Due to the enhancement of the physicochemical, thermal, and mechanical properties, CAG–sSiO2 can effectively be considered an eco-friendly, low-cost, and efficient proton exchange membrane for enhancing MFC performance.

P. Arbter, W. Sabra, T. Utesch et al.

Engineering in Life Sciences • 2020

In this contribution, we studied the effect of electro‐fermentation on the butanol production of Clostridium pasteurianum strains by a targeted metabolomics approach. Two strains were examined: an electrocompetent wild type strain (R525) and a mutant strain (dhaB mutant) lacking formation of 1,3‐propanediol (PDO). The dhaB‐negative strain was able to grow on glycerol without formation of PDO, but displayed a high initial intracellular NADH/NAD ratio which was lowered subsequently by upregulation of the butanol production pathway. Both strains showed a 3–5 fold increase of the intracellular NADH/NAD ratio when exposed to cathodic current in a bioelectrochemical system (BES). This drove an activation of the butanol pathway and resulted in a higher molar butanol to PDO ratio for the R525 strain. Nonetheless, macroscopic electron balances suggest that no significant amount of electrons derived from the BES was harvested by the cells. Overall, this work points out that electro‐fermentation can be used to trigger metabolic pathways and improve product formation, even when the used microbe cannot be considered electroactive. Accordingly, further studies are required to unveil the underlying (regulatory) mechanisms.

A. Poladyan, S. Blbulyan, T. Semashko et al.

FEMS Microbiology Letters • 2020

Glycerol is an organic waste material, which can be used for production of microbial biomass and consequently serving valuable biocatalysts promoting generation of electric current in microbial fuel cell (MFC). [NiFe]-Hydrogenases (Hyd) of Escherichia coli and Ralstonia eutropha may be applied as potential anode biocatalysts in MFC. In this study, E. coli K12 whole cells or crude extracts and R. eutropha HF649 synthesizing Strep-tagged membrane-bound Hyd (MBH) were evaluated, as anode enzymes in the bioelectrochemical system. The samples were immobilized on the sensors with polyvinyl acetate support. Mediators like ferrocene and its derivatives (ferrocene-carboxy-aldehyde, ferrocene-carboxylic acid, methyl-ferrocene-methanol) were engaged. The maximal level of bioelectrocatalytic activity of Hyds was demonstrated at 500 mV voltage. Depending on the mediator and biocatalyst current strength varied from 5 μA to 42 μA. Introduction of ferrocene-carboxylic acid enhanced current strength: moreover, the current flow was directly correlated with H2 concentration. The maximal value (up to 150 μA) of current strength was achieved with a two-fold hydrogen supply. It may be inferred that Hyds are efficiently produced by E. coli and R. eutropha grown on glycerol, while ferrocene derivatives act as agents mediating electrochemical activity of Hyds.

T. Utesch, W. Sabra, Christin Prescher et al.

Biotechnology and Bioengineering • 2019

Microbial electrosynthesis or electro‐fermentation in bioelectrochemical systems (BES) have recently received much attention. Here, we demonstrate with the glycerol metabolism by Clostridium pasteurianum that H 2 from in situ water electrolysis, especially in combination with a redox mediator, provides a simple and flexible way for shifting product selectivity and enhancing product yield in the fermentation process. In particular, we report and quantify for the first time strictly different effects of Neutral Red (NR) and the barely studied redox mediator Brilliant Blue (BB) on the growth and product formation of C. pasteurianum grown on glycerol in a newly developed BES. We were able to switch the product formation pattern of C. pasteurianum with a concentration‐dependent addition of NR and BB under varied iron availability. Interestingly, NR and BB influenced the glycerol metabolism in a strictly opposite manner concerning the formation of the major products 1,3‐propanediol (1,3‐PDO) and n‐butanol (BuOH). Whereas, NR and iron generally enhance the formation of BuOH, BB favors the formation of 1,3‐PDO. In BES the metabolic shifts were enhanced, leading to a further increased yield by as high as 33% for BuOH in NR fermentations and 21% for 1,3‐PDO in BB fermentations compared with the respective controls. For the first time, the electron transfer mediated by these mediators and their recycle (recharge) were unambiguously quantified by excluding the overlapping effect of iron. BB has a higher capacity than NR and iron. The extra electron transfer by BB can account for as high as 30–75% of the total NAD + regeneration under certain conditions, contributing significantly to the product formation.

Jiahao Luo, Qianqian Yuan, Yufeng Mao et al.

Frontiers in Bioengineering and Biotechnology • 2022

Bioelectrochemical systems (BESs) based on Shewanella oneidensis MR-1 offer great promise for sustainable energy/chemical production, but the low rate of electron generation remains a crucial bottleneck preventing their industrial application. Here, we reconstructed a genome-scale metabolic model of MR-1 to provide a strong theoretical basis for novel BES applications. The model iLJ1162, comprising 1,162 genes, 1,818 metabolites and 2,084 reactions, accurately predicted cellular growth using a variety of substrates with 86.9% agreement with experimental results, which is significantly higher than the previously published models iMR1_799 and iSO783. The simulation of microbial fuel cells indicated that expanding the substrate spectrum of MR-1 to highly reduced feedstocks, such as glucose and glycerol, would be beneficial for electron generation. In addition, 31 metabolic engineering targets were predicted to improve electricity production, three of which have been experimentally demonstrated, while the remainder are potential targets for modification. Two potential electron transfer pathways were identified, which could be new engineering targets for increasing the electricity production capacity of MR-1. Finally, the iLJ1162 model was used to simulate the optimal biosynthetic pathways for six platform chemicals based on the MR-1 chassis in microbial electrosynthesis systems. These results offer guidance for rational design of novel BESs.

H. Roume, J. Arends, Camar Ameril et al.

Frontiers in Bioengineering and Biotechnology • 2016

Given the large amount of crude glycerol formed as a by-product in the biodiesel industries and the concomitant decrease in its overall market price, there is a need to add extra value to this biorefinery side stream. Upgrading can be achieved by new biotechnologies dealing with recovery and conversion of glycerol present in wastewaters into value-added products, aiming at a zero-waste policy and developing an economically viable process. In microbial bioelectrochemical systems (BESs), the mixed microbial community growing on the cathode can convert glycerol reductively to 1,3-propanediol (1,3-PDO). However, the product yield is rather limited in BESs compared with classic fermentation processes, and the synthesis of side-products, resulting from oxidation of glycerol, such as organic acids, represents a major burden for recovery of 1,3-PDO. Here, we show that the use of an enriched mixed-microbial community of glycerol degraders and in situ extraction of organic acids positively impacts 1,3-PDO yield and allows additional recovery of propionate from glycerol. We report the highest production yield achieved (0.72 mol1,3-PDO mol−1glycerol) in electricity-driven 1,3-PDO biosynthesis from raw glycerol, which is very close to the 1,3-PDO yield reported thus far for a mixed-microbial culture-based glycerol fermentation process. We also present a combined approach for 1,3-PDO production and propionate extraction in a single three chamber reactor system, which leads to recovery of additional 3-carbon compounds in BESs. This opens up further opportunities for an economical upgrading of biodiesel refinery side or waste streams.

F. Kubannek, Christopher Moß, Katharina J. Huber et al.

Frontiers in Energy Research • 2018

We investigated transformation pathways and determined rate constants in a continuously operated glycerol-fed bioelectrochemical system under chemostatic conditions by applying concentration pulses of various intermediates. Our methodology does not require the interruption of the continuous operation and is thus in principle suitable for elucidating processes in continuously operated bioreactors in industry as well as in laboratory studies. Specifically for the example of glycerol electrooxidation, pulse responses of current density and effluent concentrations reveal that glycerol is first fermented to acetate, which is then oxidized electrochemically by the anode respiring bacteria. Microbial community analysis confirms this division of labour with a bioanode dominated by Geobacter species 92.8 %) and a much more diverse fermenting community in the planktonic phase, containing mainly Desulfovibrio sp. (45.2 %) and Spiroaetales (18.1 %). Desulfovibrio and Geobacter species are identified as promising candidates for tailored communities for glycerol electro-oxidation. From an acetate concentration pulse experiment, growth rates and half saturation rate constants for the biofilm of K_S = 1.4 mol m^-3 and d(q_{max,Ac} X_{bf})/dt = 933 mmol m^-2 d^-2 are obtained. Furthermore, 1,3-propanediol and glycerol concentration pulse experiments show that the reaction from glycerol to 1,3-propanediol is reversed at high 1,3-propanediol concentrations. The presented methodology allows one to study pathways and extract rate constants through simple experiments in a running system without irreversibly altering the microbial community or destroying the biofilm.

Changman Kim, M. Y. Kim, I. Michie et al.

Biotechnology for Biofuels • 2017

Background3-Hydroxypropionic acid (3-HP) is an important platform chemical which can be produced biologically from glycerol. Klebsiella pneumoniae is an ideal biocatalyst for 3-HP because it can grow well on glycerol and naturally synthesize the essential coenzyme B12. On the other hand, if higher yields and titers of 3-HP are to be achieved, the sustained regeneration of NAD+ under anaerobic conditions, where coenzyme B12 is synthesized sustainably, is required.ResultsIn this study, recombinant K. pneumoniae L17 overexpressing aldehyde dehydrogenase (AldH) was developed and cultured in a bioelectrochemical system (BES) with the application of an electrical potential to the anode using a chronoamperometric method (+0.5 V vs. Ag/AgCl). The BES operation resulted in 1.7-fold enhancement of 3-HP production compared to the control without the applied potential. The intracellular NADH/NAD+ ratio was significantly lower when the L17 cells were grown under an electric potential. The interaction between the electrode and overexpressed AldH was enhanced by electron shuttling mediated by HNQ (2-hydroxy-1,4-naphthoquinone).ConclusionsEnhanced 3-HP production by the BES was achieved using recombinant K. pneumoniae L17. The quinone-based electron transference between the electrode and L17 was investigated by respiratory uncoupler experiments. This study provides a novel strategy to control the intracellular redox states to enhance the yield and titer of 3-HP production as well as other bioconversion processes.

Julia Pereira Narcizo, Lucca Bonjy Kikuti Mancilio, Matheus Pedrino et al.

Catalysts • 2023

The ability of some bacteria to perform Extracellular Electron Transfer (EET) has been explored in bioelectrochemical systems (BES) to obtain energy or chemicals from pure substances or residual substrates. Here, a new pyoverdine-producing Pseudomonas aeruginosa strain was isolated from an MFC biofilm oxidizing glycerol, a by-product of biodiesel production. Strain EL14 was investigated to assess its electrogenic ability and products. In an open circuit system (fermentation system), EL14 was able to consume glycerol and produce 1,3-propanediol, an unusual product from glycerol oxidation in P. aeruginosa. The microbial fuel cell (MFC) EL14 reached a current density of 82.4 mA m−2 during the first feeding cycle, then dropped sharply as the biofilm fell off. Cyclic voltammetry suggests that electron transfer to the anode occurs indirectly, i.e., through a redox substance, with redox peak at 0.22 V (vs Ag/AgCl), and directly probably by membrane redox proteins, with redox peak at 0.05 V (vs Ag/AgCl). EL14 produced added-value bioproducts, acetic and butyric acids, as well as 1,3 propanediol, in both fermentative and anodic conditions. However, the yield of 1,3-PDO from glycerol was enhanced from 0.57 to 0.89 (mol of 1,3-PDO mol−1 of glycerol) under MFC conditions compared to fermentation. This result was unexpected, since successful 1,3-PDO production is not usually associated with P. aeruginosa glycerol metabolism. By comparing EL14 genomic sequences related to the 1,3-PDO biosynthesis with P. aeruginosa reference strains, we observed that strain EL14 has three copies of the dhaT gene (1,3-propanediol dehydrogenase a different arrangement compared to other Pseudomonas isolates). Thus, this work functionally characterizes a bacterium never before associated with 1,3-PDO biosynthesis, indicating its potential for converting a by-product of the biodiesel industry into an emerging chemical product.

Fabian Kubannek, Simone Thiel, Boyke Bunk et al.

ChemElectroChem • 2020

Abstract An effectively operating microbial electrolysis cell requires an inexpensive electron donor in combination with a defined and stable electron‐transferring microbial community. Here, a defined co‐culture of Raoultella electrica and Geobacter sulfurreducens was established to generate current during glycerol oxidation. Maximum current densities of 0.20 mA cm −2 and coulombic efficiencies of 21 % were achieved. Glycerol metabolization into acetate by R. electrica and further acetate utilization by the current‐producing G. sulfurreducens were detected. Based on these observations, a physico‐chemical model was established and used to describe quantitatively the relationships between current density, metabolite concentrations and bacterial growth. The competition for acetate between G. sulfurreducens and R. electrica was identified as the major limitation of the system. This detailed quantitative understanding of the physiological interactions opens the door for target‐oriented genetic engineering of the microbes.

R. Chung, Eunice Y. Kang, Y. Shin et al.

Journal of Sustainable Bioenergy Systems • 2019

Microbial fuel cells (MFCs) are bioelectrochemical systems that convert chemical energy contained in organic matter into electrical energy by using the catalytic (metabolic) activity of living microorganisms. Mediator-less two chamber H-type MFCs were constructed in the current study, using dairy digester microbial population as anode inocula to convert finely ground pine tree (Avicel) at 2% (w/v) to electricity. MFCs were placed at 37°C and after the circuit voltage was stabilized on d9, bovine rumen microorganisms cultured anaerobically for 48 hrs in cellulose broth media were added to treatment group of MFC at 1% v/v dosage. MFC power and current across an external resistor were measured daily for 10 d. At the end of incubation on d19 head space gas and anode chamber liquid solutions were collected and analyzed for total gas volume and composition, and volatile fatty acids, respectively. Addition of enriched rumen microorganisms to anaerobic anode chamber increased cellulose digestibility and increased both CO2 and methane production; however, it decreased the methane to CO2 ratio. Over the experimental period, electricity generation was increased with rumen microorganism addition, and power density normalized to anode surface area was 17.6 to 67.2 mW/m2 with average of 36.0 mW/m2 in treatment, while control group had 3.6 to 21.6 (AVE 12.0) mW/m2. These observations imply that biocatalysis in MFCs requires additional cellulolytic activities to utilize structural biomass in bioenergy production.

M. Kizling, M. Dzwonek, A. Nowak et al.

Nanomaterials • 2020

A significant problem still exists with the low power output and durability of the bioelectrochemical fuel cells. We constructed a fuel cell with an enzymatic cascade at the anode for efficient energy conversion. The construction involved fabrication of the flow-through cell by three-dimensional printing. Gold nanoparticles with covalently bound naphthoquinone moieties deposited on cellulose/polypyrrole (CPPy) paper allowed us to significantly improve the catalysis rate, both at the anode and cathode of the fuel cell. The enzymatic cascade on the anode consisted of invertase, mutarotase, Flavine Adenine Dinucleotide (FAD)-dependent glucose dehydrogenase and fructose dehydrogenase. The multi-substrate anode utilized glucose, fructose, sucrose, or a combination of them, as the anode fuel and molecular oxygen were the oxidant at the laccase-based cathode. Laccase was adsorbed on the same type of naphthoquinone modified gold nanoparticles. Interestingly, the naphthoquinone modified gold nanoparticles acted as the enzyme orienting units and not as mediators since the catalyzed oxygen reduction occurred at the potential where direct electron transfer takes place. Thanks to the good catalytic and capacitive properties of the modified electrodes, the power density of the sucrose/oxygen enzymatic fuel cells (EFC) reached 0.81 mW cm−2, which is beneficial for a cell composed of a single cathode and anode.

H. Lloyd-Laney, N. Yates, James Stapleton et al.

ECS Meeting Abstracts • 2023

Electron transfer and redox chemistry drives life and Biology can provide inspiration for the design of sustainable fuel catalysts that achieve highly active and selective small molecule transformations. In particular, the Parkin group are interested in hydrogenases,1 biological H2-producing enzymes, and lytic polysaccharide monooxygenases (LPMOs),2, 3 enzymes that breakdown cellulose. We seek to understand how the rate and energetics of electron transfer controls catalysis in such enzymes;4 to do this we collaborate with the Gavaghan and Bond groups to develop more powerful bioelectrochemical methodologies.5 This talk will describe our most recent efforts to integrate sinusoidal voltammetry into our enzyme-electrochemistry toolkit.6, 7 The technique offers advantages in terms of simulation speed, which in turn enables the powerful application of Bayesian statistical analysis to visualise the uncertainty in the modelling approach. However, we still rely on large amplitude Fourier transform voltammetry and direct current methodologies to visualise the Faradaic current and readily define redox reaction parameter bounds. References: [1] H. Adamson, M. Robinson, J. J. Wright, L. A. Flanagan, J. Walton, D. Elton, D. J. Gavaghan, A. M. Bond, M. M. Roessler and A. Parkin, J. Am. Chem. Soc., 2017, 139, 10677-10686. [2] P. J. Lindley, A. Parkin, G. J. Davies and P. H. Walton, Faraday Discuss., 2022, 234, 336-348. [3] J. Branch, B. S. Rajagopal, A. Paradisi, N. Yates, P. J. Lindley, J. Smith, K. Hollingsworth, W. B. Turnbull, B. Henrissat, A. Parkin, A. Berry and G. R. Hemsworth, Biochem. J., 2021, 478, 2927-2944. [4] A. R. Dale-Evans, M. J. Robinson, H. O. Lloyd-Laney, D. J. Gavaghan, A. M. Bond and A. Parkin, Front. Chemistry, 2021, 9. [5] H. Adamson, A. M. Bond and A. Parkin, Chem. Comm., 2017, 53, 9519-9533. [6] H. O. Lloyd-Laney, N. D. J. Yates, M. J. Robinson, A. R. Hewson, J. D. Firth, D. M. Elton, J. Zhang, A. M. Bond, A. Parkin and D. J. Gavaghan, Anal. Chem., 2021, 93, 2062-2071. [7] H. O. Lloyd-Laney, N. D. J. Yates, M. J. Robinson, A. R. Hewson, J. Branch, G. R. Hemsworth, A. M. Bond, A. Parkin and D. J. Gavaghan, Journal of Electroanalytical Chemistry, 2023, 935, 117264.

Jiao Li, Xiyun Feng, Yi Jia et al.

Journal of Materials Chemistry A • 2017

Photosystem II (PSII), as the only enzyme to catalyze the light-induced water oxidation reaction in the natural photosynthesis system, is introduced to fabricate artificial solar conversion systems with an intensive photo-to-current efficiency to convert solar energy into electrical power. In this research, we report a hybrid photo-bioelectrochemical system consisting of PSII isolated from spinach leaves that is co-assembled in nanotubular indium–tin oxide (ITO) multilayer films pasted on the commercial ITO substrate as a photoanode, which presents enhanced photocurrent responses as high as 2.4 μA cm−2 (mediator-free) and 39 μA cm−2 (with mediator) under white light irradiation (λ < 800 nm) using a xenon lamp as the light source. In this photoanode system, the three-dimensional (3D) hierarchical porous nanotubular ITO film was synthesized through a layer-by-layer (LBL) self-assembly process using a natural cellulose substance (e.g., filter paper) as a template. The specific structure, and good optical and electrical properties of the hierarchical nanotubular ITO allow for an increased protein loading as high as 166 pmol PSII cm−2 and an enhanced photocurrent by about 78 times compared with the bare PSII photoanode. This biomimetic template fabrication method of ITO materials with unique morphologies and desirable properties provides an effective assembly strategy for PSII-based hybrid photoanode systems for solar energy conversion.

Jiao Li, Xiyun Feng, J. Fei et al.

Journal of Materials Chemistry A • 2016

The fabrication of artificial photosynthetic systems to convert solar energy into electrical power is of great importance to meet human needs for energy; photosystem II (PSII), the core enzyme for water splitting in natural solar energy conversion processes can be introduced for this purpose. However, there remain significant challenges in the facile preparation of such semi-artificial photoanode systems with enhanced photocurrent responses. Herein we report a hybrid photoanode system consisting of PSII from spinach integrated into an indium-tin oxide electrode modified with nanotubular titania that is synthesized by using cellulose paper as a scaffold. This electrode provides a well-defined hierarchical nanostructure for protein loading, and the fine titania nanocrystals facilitate electron transfer from PSII to the electrode. The resulting semiconductor–protein hybrid photo-bioelectrochemical system enhances direct electron transfer (1.3 μA cm−2) and mediated electron transfer (10.6 μA cm−2) photocurrents.

R. Latonen, J. Cabrera, S. Lund et al.

ACS Applied Bio Materials • 2020

Electrically conductive composite nanofibers were fabricated using poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT-PSS) and cellulose nanofibrils (CNFs) via the electrospinning technique. Poly(ethylene oxide) (PEO) was used to assist the electrospinning process, and poly(ethylene glycol) diglycidyl ether was used to induce chemical cross-linking, enabling stability of the formed fibrous mats in water. The experimental parameters regarding the electrospinning polymer dispersion and electrospinning process were carefully studied to achieve a reproducible method to obtain bead-free nanofibrous mats with high stability after water contact, with an electrical conductivity of 13 ± 5 S m-1, thus making them suitable for bioelectrochemical applications. The morphology of the electrospun nanofibers was characterized by scanning electron microscopy, and the C/S ratio was determined with energy dispersive X-ray analysis. Cyclic voltammetric studies showed that the PEDOT-PSS/CNF/PEO composite fibers exhibited high electroactivity and high stability in water for at least two months. By infrared spectroscopy, the slightly modified fiber morphology after water contact was demonstrated to be due to dissolution of some part of the PEO in the fiber structure. The biocompatibility of the PEDOT-PSS/CNF/PEO composite fibers when used as an electroconductive substrate to immobilize microalgae and cyanobacteria in a photosynthetic bioelectrochemical cell was also demonstrated.

A. A. Yaqoob, Mohamad Nasir Mohamad Ibrahim, K. Umar et al.

Polymers • 2020

Benthic microbial fuel cells (BMFCs) are considered to be one of the eco-friendly bioelectrochemical cell approaches nowadays. The utilization of waste materials in BMFCs is to generate energy and concurrently bioremediate the toxic metals from synthetic wastewater, which is an ideal approach. The use of novel electrode material and natural organic waste material as substrates can minimize the present challenges of the BMFCs. The present study is focused on cellulosic derived graphene-polyaniline (GO-PANI) composite anode fabrication in order to improve the electron transfer rate. Several electrochemical and physicochemical techniques are used to characterize the performance of anodes in BMFCs. The maximum current density during polarization behavior was found to be 87.71 mA/m2 in the presence of the GO-PANI anode with sweet potato as an organic substrate in BMFCs, while the GO-PANI offered 15.13 mA/m2 current density under the close circuit conditions in the presence of 1000 Ω external resistance. The modified graphene anode showed four times higher performance than the unmodified anode. Similarly, the remediation efficiency of GO-PANI was 65.51% for Cd (II) and 60.33% for Pb (II), which is also higher than the unmodified graphene anode. Furthermore, multiple parameters (pH, temperature, organic substrate) were optimized to validate the efficiency of the fabricated anode in different environmental atmospheres via BMFCs. In order to ensure the practice of BMFCs at industrial level, some present challenges and future perspectives are also considered briefly.

Anjana Ratheesh, B. R. Sreelekshmy, Anil Kumar T R et al.

ACS Applied Bio Materials • 2025

Lignocellulose recalcitrance remains a significant economic challenge in modern biomass conversion processes. Microbial strategies offer considerable promise for ecofriendly bioenergy generation. This study presents an advanced integrated approach that combines bacterial treatment with a bioelectrochemical system (BES) to enhance the conversion efficiency of lignocellulosic biomass. Unlike integrated or sequential approaches, a comparative evaluation of two distinct pretreatment strategies, alkaline delignification and biological treatment, was conducted independently to assess their individual effectiveness in sugar cane bagasse (SCB) degradation and their performance in a microbial fuel cell (MFC). Biological treatment with B. subtilis alone yielded superior outcomes in terms of saccharification efficiency, microbial growth, and bioelectricity generation, as evidenced by higher open-circuit potentials in MFC half-cell studies in comparison with alkali delignified SCB. Notably, B. subtilis treatment increased cellulose content by 72% and reduced hemicellulose and lignin by approximately 0.84-fold, indicating effective enzymatic action. Metabolomic profiling identified 2846 metabolites that significantly diverged between the experimental groups. Notably, lignin-derived compounds such as ferulic acid, syringic acid, and p-coumaric acid were detected at elevated levels, confirming enhanced ligninase activity in pretreated SCB. Additionally, the presence of organic acids (e.g., acetic acid), amino acids, and their derivatives, resulting from the breakdown of cellulose, hemicellulose, and lignin, provided essential bioenergy substrates for exoelectrogenic organisms in BESs. This integration led to a maximum power density of 353 ± 5 mW/m2 and a current density of 200 ± 3 mA/m2, demonstrating significant enhancement in performance of MFC. Furthermore, the biotransformation of SCB facilitated the channeling of metabolites into value-added products, increasing the overall efficiency of the biomass valorization. Thus, the rational utilization of SCB underscores its potential for scalable biorefinery applications and its broader implications for sustainable bioenergy production.

Euntae Yang, Kyoung-Yeol Kim, K. Chae et al.

Desalination and Water Treatment • 2016

AbstractRecent forward osmosis–bioelectrochemical hybrid systems (FO-BESs) have been designed to simultaneously produce bio-energy and clean water from wastewater. Asymmetric forward osmosis (FO) membranes are a crucial component for determining FO-BES performance, but only cellulose triacetate (CTA NW) membranes in the same orientation have been applied to FO-BESs. In this work, both CTA NW and polyamide (PA) membranes were tested in two membrane orientations (active layer facing feed solution or anolyte and support layer facing feed solution). For an in-depth understanding of the FO membranes, properties were investigated using scanning electron microscopy, contact angle, impedance spectroscopy, and proton transport analyses. The electricity generation and water extraction in FO-BESs having these two FO membranes in different orientations were then evaluated. Based on membrane characterization, PA seemed to be a proper membrane for the FO-BES because of higher hydrophilicity, lower membrane thickness, l...

Stanisław Ledakowicz

Energies • 2025

After a brief characterisation of lignocellulosic biomass (LCB) in terms of its biochemical structure and the pretreatment techniques used to disrupt lignin structure and decrystallise and depolymerise cellulose, this review considers five main pathways for biochemical biomass conversion: starting with anaerobic digestion to convert various LCB feedstocks into bioproducts; considering the integration of biochemical and thermochemical processes, syngas fermentation, which has been recently developed for biofuel and chemical production, is reviewed; the production of 2G bioethanol and biobutanol from LCB waste is discussed; the literature on biohydrogen production by dark fermentation, photofermentation, and bioelectrochemical processes using microbial electrolysis cells as well as hybrid biological processes is reviewed. The conclusions and future prospects of integrating biochemical and thermochemical conversion processes of biomass are discussed and emphasised.

Dan Sun, Xinyuan Wan, Wenzong Liu et al.

RSC Advances • 2019

Geobacter anodireducens is unique in that it can generate high current densities in bioelectrochemical systems (BES) operating under high salt conditions.

Fei Zhao, Elizabeth S. Heidrich, Thomas P. Curtis et al.

Applied Microbiology and Biotechnology • 2020

Abstract Anode potential can affect the degradation pathway of complex substrates in bioelectrochemical systems (BESs), thereby influencing current production and coulombic efficiency. However, the intricacies behind this interplay are poorly understood. This study used glucose as a model substrate to comprehensively investigate the effect of different anode potentials (− 150 mV, 0 mV and + 200 mV) on the relationship between current production, the electrogenic pathway and the abundance of the electrogenic microorganisms involved in batch mode fed BESs. Current production in glucose-acclimatized reactors was a function of the abundance of Geobacteraceae and of the availability of acetate and formate produced by glucose degradation. Current production was increased by high anode potentials during acclimation (0 mV and + 200 mV), likely due to more Geobacteraceae developing. However, this effect was much weaker than a stimulus from an artificial high acetate supply: acetate was the rate-limiting intermediate in these systems. The supply of acetate could not be influenced by anode potential; altering the flow regime, batch time and management of the upstream fermentation processes may be a greater engineering tool in BES. However, these findings suggest that if high current production is the focus, it will be extremely difficult to achieve success with complex waste streams such as domestic wastewater.

Deng Wang, Ying Wang, Jing Yang et al.

Polymers • 2020

The flavin-based indirect electron transfer process between electroactive bacteria and solid electrode is crucial for microbial fuel cells (MFCs). Here, a cellulose-NaOH-urea mixture aerogel derived hierarchical porous carbon (CPC) is developed to promote the flavin based interfacial electron transfer. The porous structure of the CPC can be tailored via adjusting the ratio of urea in the cellulose aerogel precursor to obtain CPCs with different type of dominant pores. According to the electrocatalytic performance of different CPC electrodes, the CPCs with higher meso- and macropore area exhibit greatly improved flavin redox reaction. While, the CPC-9 with appropriate porous structure achieves highest power density in Shewanella putrefaciens CN32 MFC due to larger active surface for flavin mediated interfacial electron transfer and higher biofilm loading. Considering that the CPC is just obtained from the pyrolysis of the cellulose-NaOH-urea aerogel, this work also provides a facile approach for porous carbon preparation.

Mehran Abbaszadeh Amirdehi, Sokunthearath Saem, Mir Pouyan Zarabadi et al.

Advanced Materials Interfaces • 2018

Abstract A method for producing hierarchical wrinkled gold surfaces is used to continuously change characteristic microstructure dimensions of a bioanode in a microbial fuel cell, while conserving the total electroactive surface area and material chemistry. Using this approach, the effect of anode topography on power outputs from direct electron transfer from Geobacter sulfurreducens biofilms can be isolated and studied without the competing effects associated with additive manufacturing. Despite having the same electroactive surface area for all structured anodes, tall and well‐spaced features perform best. Anodes with the shortest, most closely packed structures, on the other hand, do not perform any better than planar surfaces with the same footprint and lower electroactive surface area. It is postulated that large interfold spacing provides better electrical contact between the biofilm and the electrode via improved bacterial packing density at the electrode surface. Rigorous attention to structural dimensions rather than total electroactive surface area is proposed as an important direction for future bioanode optimization in microbial fuel cells containing direct electron transfer electroactive biofilms.

Shaofeng Zhou, Da Song, Ji-Dong Gu et al.

Frontiers in Microbiology • 2022

The overlap of microbiology and electrochemistry provides plenty of opportunities for a deeper understanding of the redox biogeochemical cycle of natural-abundant elements (like iron, nitrogen, and sulfur) on Earth. The electroactive microorganisms (EAMs) mediate electron flows outward the cytomembrane via diverse pathways like multiheme cytochromes, bridging an electronic connection between abiotic and biotic reactions. On an environmental level, decades of research on EAMs and the derived subject termed “ electromicrobiology ” provide a rich collection of multidisciplinary knowledge and establish various bioelectrochemical designs for the development of environmental biotechnology. Recent advances suggest that EAMs actually make greater differences on a larger scale, and the metabolism of microbial community and ecological interactions between microbes play a great role in bioremediation processes. In this perspective, we propose the concept of microbial electron transfer network (METN) that demonstrates the “species-to-species” interactions further and discuss several key questions ranging from cellular modification to microbiome construction. Future research directions including metabolic flux regulation and microbes–materials interactions are also highlighted to advance understanding of METN for the development of next-generation environmental biotechnology.

Joseph Oram, Lars J. C. Jeuken

ChemElectroChem • 2016

Abstract Exoelectrogenic bacteria can couple their metabolism to extracellular electron acceptors, including macroscopic electrodes, and this has applications in energy production, bioremediation and biosensing. Optimisation of these technologies relies on a detailed molecular understanding of extracellular electron‐transfer (EET) mechanisms, and Shewanella oneidensis MR‐1 (MR‐1) has become a model organism for such fundamental studies. Here, cyclic voltammetry was used to determine the relationship between the surface chemistry of electrodes (modified gold, ITO and carbon electrodes) and the EET mechanism. On ultra‐smooth gold electrodes modified with self‐assembled monolayers containing carboxylic‐acid‐terminated thiols, an EET pathway dominates with an oxidative catalytic onset at 0.1 V versus SHE. Addition of iron(II)chloride enhances the catalytic current, whereas the siderophore deferoxamine abolishes this signal, leading us to conclude that this pathway proceeds via an iron mediated electron transfer mechanism. The same EET pathway is observed at other electrodes, but the onset potential is dependent on the electrolyte composition and electrode surface chemistry. EET pathways with onset potentials above −0.1 V versus SHE have previously been ascribed to direct electron‐transfer (DET) mechanisms through the surface exposed decaheme cytochromes (MtrC/OmcA) of MR‐1. In light of the results reported here, we propose that the previously identified DET mechanism of MR‐1 needs to be re‐evaluated.

Aiichiro Fujinaga, Kamin Tei, H. Ozaki et al.

Journal of Water and Environment Technology • 2016

The graphite powder was added to a microbial fuel cell (MFC) that uses soil to decrease the internal resistance and increase the electric power and electric charge (ampere hour: Ah). The effect of adding the graphite powder to soil MFC is evaluated by experiment and simulation using mathematical models. In this experiment, the total weight of the reddish granular soil and the graphite powder was 1000 g, and ratios of the graphite were set to five values between 0% and 20% by weight. The grain size of the soil was between 3 and 8 mm. The diameter of electrode was 9 cm. The initial chemical oxygen demand (COD) of synthetic wastewater was 1400 mg/L. As a result, the amount of Ah was maximized when 10% of the graphite was mixed. When the amount of the graphite increased, the internal resistance decreased; however, consumption of COD decreased and the microbial reaction decreased. This might be because the graphite covers the surface of the soil, and it disturbs the adsorption of the soil and decreases the biofilms. Therefore, a suitable proportion of the graphite exists, and it was approximately 10% in this experiment.

Ting Liu, Yangyang Yu, Dongzhe Li et al.

RSC Advances • 2016

External resistance is one of the important factors that affect the performance of microbial fuel cells (MFCs). In this study, bioelectrochemical and biofilm characterization was conducted for Shewanella oneidensis MR-1 inoculated MFCs with 250 Ω, 500 Ω, 2 kΩ, 6 kΩ and 22 kΩ resistors. Overall, a smaller external resistance resulted in a higher maximum power density and more riboflavin secretion. A maximum power density of 136.8 ± 3.1 mW m−2 was achieved when MFCs were operated with a 500 Ω resistor, which was 3.7 times that with a 22 kΩ resistor. Electrochemical impedance spectra (EIS) analysis verified an increased internal resistance with a higher external resistance. Meanwhile, more biofilm mass and extracellular polymer substances (EPS) were confirmed on the MFC anode with a higher external resistance.

Luisa Alvarez-Benítez, S. Silva-Martínez, Alfredo Hernandez-Perez et al.

Catalysts • 2022

Anaerobic biodegradation of petroleum-contaminated sediments can be accomplished by a sediment microbial fuel cell (SMFC), but the recovered energy is very low (~4 mW m−2). This is due to a high internal resistance (Ri) that develops in the SMFC. The evaluation of the main experimental parameters that contribute to Ri is essential for developing a feasible SMFC design and this task is normally performed by electrochemical impedance spectroscopy (EIS). A faster and easier alternative procedure to EIS is to fit the SMFC polarization curve to an electrochemical model. From there, the main resistance contributions to Ri are partitioned. This enables the development of a useful procedure for attaining a low SMFC Ri while improving its power output. In this study, the carbon-anode surface was increased, the biodegradation activity of the indigenous populations was improved (by the biostimulation method, i.e., the addition of kerosene), the oxygen reduction reaction was catalyzed, and a 0.8 M Na2SO4 solution was used as a catholyte at pH 2. As a result, the initial SMFC Ri was minimized 20 times, and its power output was boosted 47 times. For a given microbial fuel cell (MFC), the main resistance contributions to Ri, evaluated by the electrochemical model, were compared with their corresponding experimental results obtained by the EIS technique. Such a validation is also discussed herein.

Xiaojun Jin, Nuan Yang, Dake Xu et al.

Frontiers in Bioengineering and Biotechnology • 2024

Bioelectrochemical systems are sustainable and potential technology systems in wastewater treatment for nitrogen removal. The present study fabricated an air-cathode denitrifying microbial fuel cell (DNMFC) with a revisable modular design and investigated metabolic processes using nutrients together with the spatiotemporal distribution characteristics of dominated microorganisms. Based on the detection of organics and solvable nitrogen concentrations as well as electron generations in DNMFCs under different conditions, the distribution pattern of nutrients could be quantified. By calculation, it was found that heterotrophic denitrification performed in DNMFCs using 56.6% COD decreased the Coulombic efficiency from 38.0% to 16.5% at a COD/NO3 −-N ratio of 7. Furthermore, biological denitrification removed 92.3% of the nitrate, while the residual was reduced via electrochemical denitrification in the cathode. Correspondingly, nitrate as the electron acceptor consumed 16.7% of all the generated electrons, and the residual electrons were accepted by oxygen. Microbial community analysis revealed that bifunctional bacteria of electroactive denitrifying bacteria distributed all over the reactor determined the DNMFC performance; meanwhile, electroactive bacteria were mainly distributed in the anode biofilm, anaerobic denitrifying bacteria adhered to the wall, and facultative anaerobic denitrifying bacteria were distributed in the wall and cathode. Characterizing the contribution of specific microorganisms in DNMFCs comprehensively revealed the significant role of electroactive denitrifying bacteria and their cooperative relationship with other functional bacteria.

I. R. Garduño‐Ibarra, Shruti Tanga, Alexandra Tsitouras et al.

Journal of Chemical Technology &amp; Biotechnology • 2024

This study focuses on the treatment of brewery waste slurries (BWS) with high chemical oxygen demand (COD) using a single‐chamber microbial fuel cell (MFC) inoculated with heat‐treated anaerobic seed sludge. A co‐substrate of 5 g L−1 glycerol was added, and carbon felt (CF) was employed as the anode material, enhanced through in situ polymerization of aniline (PANI/CF). Additionally, the adsorption of ruthenium dioxide nanoparticles onto the modified CF was assessed (PANI‐RO/CF).Tests conducted at room temperature (19 °C to 22 °C) achieved an average COD reduction of 36%. The PANI‐RO/CF electrode accumulated 24% more charge, resulting in the highest coulombic efficiency of 75.1%, significantly exceeding similar studies. However, the PANI‐modified anode generated more energy, exceeding that of the bare CF by more than double, reaching 57.1 mW m−2. An optimized working volume was identified in relation to other reported works. Microbial population analysis revealed an interaction between Staphylococcus epidermidis and a rarely reported psychrophilic Bacillus species. After 30 h, lactic acid emerged as the main by‐product, with a concentration of 7.5 ± 0.6 g L−1.These findings highlight an optimization approach based on cell configuration and inoculum selection, as well as a significant valorization pathway that is frequently overlooked in the existing literature on brewery wastewater treatment using MFCs, particularly regarding the attractiveness of lactic acid production. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Matthew Kwofie, Bright Amanful, Samuel Gamor et al.

International Journal of Energy Research • 2024

This paper reviews the current state of microbial fuel cell (MFC) technology for energy generation. It begins by exploring clean energy alternatives, focusing on waste‐to‐energy solutions, and introduces the concept, applications, and advantages of MFCs. The biochemical processes within MFCs are explained, highlighting how microorganisms metabolize substrates through glycolysis, the Krebs cycle, and the electron transport chain to generate electrons. These electrons flow through an external circuit and combine with protons and oxygen at the cathode to produce water or reduced forms of nitrogen and sulfur. This paper also analyzes 10 key parameters affecting MFC performance: coulombic efficiency, pH, temperature, substrates, organic loading rate, electrode potential, open circuit voltage, treatment efficiency, organic removal rate, and hydraulic retention time. Recent advancements in MFC technology are also discussed, including innovations in reactor configuration and scaling, the development of new membrane materials like earthen and ceramic, and improvements in wastewater treatment methods. The advancements also extend to genetic engineering techniques to enhance microbial efficiency and component modifications, such as the use of carbon‐based nanomaterials and metal catalysts for improved performance, innovations in proton transfer membranes, and mediator‐less MFCs utilizing metal‐reducing bacteria. Challenges facing MFC technology, such as cost, scalability, and environmental sensitivity, are mentioned. The paper concludes with future directions, including the use of advanced materials, integration with wastewater treatment infrastructure, and the potential for nutrient recovery and chemical synthesis. This comprehensive review aims to provide knowledge into optimizing MFCs for sustainable energy generation and environmental benefits.

Xiaoou Wang, Ming Xue, Zhaoyu Wang et al.

Water • 2024

This study designed integrated constructed wetland–microbial fuel cell (CW–MFC) systems using activated carbon (AC) as both CW substrates and MFC anodes and investigated the structure-activity relationship of six kinds of commercial columnar AC, as well as the organics and nitrogen removal, microbial activity and diversity of CW–MFCs. Results showed that the nitrogen adsorption by AC tended to be a linear process in which physical adsorption played a leading role and micropores made great contributions. A higher specific surface area, developed mesopores, and oxygen functionalities were conducive to the capacitance properties of AC, while a higher specific surface area and developed micropores were conducive to reduce material resistance and improve ion permeability. Coconut-shell-based AC had both excellent nitrogen adsorption capacity and electrochemical properties, making it ideal as both CW substrates and MFC anodes for CW–MFCs. The electricity generation, coulombic efficiency, internal resistance, and organics and nitrogen removal of CW–MFCs were positively correlated with the total depth of AC anodes. The total depth of AC anodes can be determined based on the influent organics/nitrogen loadings and organics/nitrogen removal load of AC, and a relatively smaller depth of a single AC anode (5 cm) was recommended. The MFC effectively improved the enzymatic activity (by 10.33% dehydrogenase, 8.72% catalase, and 7.35% ammonia monooxygenase), nitrification/denitrification intensity (by 9.53%/6.68%), and microbial diversity (by 1.64–4.07%) of AC (MFC anodes) in CW–MFCs, while the depth of a single AC anode barely influenced the microbial activity and diversity. MFCs increased COD and NH3-N removal in CW–MFCs by 11.60% and 3.4%, respectively. The increased total adsorption capacity of AC with the increase of its total depth narrowed the difference in COD removal resulting from the promotion of MFCs on organics degradation. MFCs increased TN removal in CW–MFCs by 5.29% through promoting denitrification in cathodes and enhancing NH3-N assimilation in anodes. The phyla of EAB (Proteobacteria, Bacteroidetes, Firmicutes, and Acidobacteria) and genera of EAB (Citrobacter, Geobacter, and Pseudomonas) accounted for 85–86% and 15.58–16.64% of the microbial community on AC anodes in CW–MFCs, respectively.

Liangyue Cheng, Limin Jiang, Xiaowen Yang et al.

AMB Express • 2024

Microbial fuel cells (MFCs) have the functions of wastewater treatment and power generation. The incorporation of modified anodes enhances the sustainable power generation performance of MFCs. In this study, to evaluate the feasibility of sodium alginate (SA) as a biocompatible binder, hydrogel mixed with super activated carbon (SAC) and SA was modified the carbon cloth anode of MFC. The results showed that the maximum output voltage in the SAC/SA hydrogel modified anode MFC was 0.028 V, which was increased by 115%, compared with the blank carbon cloth anode. The internal resistance of MFC was 9429 Ω, which was 18% lower than that of control (11560 Ω). The maximum power density was 6.14 mW/m^2, which was increased by 365% compared to the control. After modification of SAC/SA hydrogel, the chemical oxygen demand (COD) removal efficiency reached to 56.36% and was 12.72% higher than the control. Coulombic efficiency with modified anode MFC reached 17.65%, which was increased by 104%, compared with the control. Our findings demonstrate the feasibility of utilizing SA as a biocompatible binder for anode modification, thereby imparting sustainable and enhanced power generation performance to MFCs. This study presented a new selectivity for harnessing algal bioresources and improving anode binders in future MFC applications.

Sarah M. Glaven

Microbial Biotechnology • 2019

Microbial electrochemical technologies (METs) are applications or processes that utilize the electrochemical interaction of microbes and electrodes (Schroder et al., 2015). It has been known for over 100 years (Potter, 1911) that microorganisms can form electrical connections to devices, but only recently (approximately 20 years) has this concept been put to technological use. Microbial electrochemistry and electromicrobiology have grown as disciplines due to an intense interest in the possibility of using MET for alternative energy, wastewater treatment and biofuels production. METs have the potential to contribute to a circular economy, where carbon is cycled back into products or electricity from renewable sources. For these reasons, MET represent a significant and attractive source of new enterprise and employment creation. The natural physiological activity of electroactive bacteria, those capable of extracellular electron transfer (EET), has been studied intensely over the past two decades in order to improve efficiency and productivity of METs. A diverse group of scientists has contributed to this knowledge base including microbiologists, electrochemists, physicists, biochemists and molecular biologists. Genetic engineering has been used to determine the molecular underpinnings responsible for carrying charge between cells and the electrode of the two model EET organisms, Geobacter sulfurreducens and Shewanella oneidensis. New electroactive organisms have been discovered using genomics (Eddie et al., 2016), and new ways to transform electrode-associated microbial communities are being developed. Electrochemistry, advanced imaging techniques and modelling have all been employed to track the movement of electrons through biofilms and purified proteins. New lexicons have been created to allow interdisciplinary discussions of extracellular electron transfer, and an entire Center for Electromicrobiology has been funded at Aarhus University in Denmark. Our growing knowledge of the principles of EET is now poised to intersect with the nascent field of synthetic biology to bring about the next generation of MET for power and energy, microbial electrosynthesis and microbial bioelectronics. Synthetic biology is an emerging field that has grown out of the principles of biology and engineering disciplines, devoted to the rational design and engineering of organisms and their components (Church et al., 2014). It is now possible to both engineer specific functions into living systems and construct entirely new ones (Liu et al., 2018a,2018b). Microorganisms are viewed as tiny supercomputers that can be programmed as such by reading, writing and editing the cell’s DNA. Genetic circuits can be designed computationally to wire cells for on-demand functionality (Nielsen et al., 2016), and these circuits can be printed and shipped to a scientist at the bench to deploy in the organism of their choice (Libby and Silver, 2019). Growth of the field of synthetic biology has resulted in the development of new tools and approaches in molecular genetics to advance biotechnology across a wide application space. For example, it is now possible to precisely tune gene expression from 12 independent small-molecule sensors engineered into the genome of E. coli (Meyer et al., 2018) or confer the ability of a bacterial cell to ‘see’ different wavelengths of light and respond in a pre-programmed manner (Fernandez-Rodriguez et al., 2017). Synthetic biology has the potential to advance microbial electrochemical technologies (MET) by bringing new design platforms to engineer EET pathways in organisms that do not naturally have them, modify microbial metabolism to improve EET rates and increase the diversity of products from microbial electrosynthesis. Two examples are given below: (i) enhanced power output from microbial fuel cells and (ii) the potential for microbial electrosynthesis to be a viable approach for fuels or molecules production.

Aishwarya Rani, Suraj Negi, Yu-Ning Chen et al.

GCB Bioenergy • 2025

Biogas, a renewable energy source produced from the anaerobic digestion of biomass and/or organic residues, contains a mixture of methane (CH4) and carbon dioxide (CO2). To be used as a fuel, biogas must be upgraded to increase its CH4 content to over 90%. Traditional upgrading methods, such as amine scrubbing and membrane separation, are energy‐intensive, costly, and environmentally burdensome. This study explores the potential of electrochemical technologies as sustainable alternatives for biogas upgrading from the aspects of energy, environment, economics, and engineering. Recent advances in promising electrochemical approaches including pretreatment, microbial conversion enhancement, CO2 capture, CO2 reduction reactions, and methanation are first reviewed. The performance of these approaches is then systematically compared based on operational characteristics and efficiency metrics. Our findings indicate that microbial and bioelectrochemical systems can achieve CH4 purities over 92%. Also, electrochemical technologies offer > 99.9% hydrogen sulfide removal (desulfurization). State‐of‐the‐art electrochemical CO2 reduction technologies demonstrate Faradaic efficiencies generally 50%–80%, with the selectivity of CH4 up to 99.7%. From the environmental aspect, integrating renewable electricity into microbial, electrochemical (or ‐based), and bioelectrochemical upgrading systems yields roughly 10%–74% life‐cycle GHG reductions relative to conventional fossil‐energy pathways, with certain renewable power‐to‐methane configurations achieving net‐negative emissions. Lastly, this study identifies several priority research directions, such as (1) advanced catalyst and electrode development, (2) system integrations with air pollutant control facilities, (3) life‐cycle environmental and techno‐economic assessment, and (4) digestate valorization for multiple product ecosystems. Electrochemical approaches offer a promising path toward clean, efficient, and decentralized biogas utilization, contributing to global decarbonization and energy transition goals toward a circular bioeconomy.

Anuj Sharma, Aman Grewal, Shubham Kumar Patial et al.

Current Natural Sciences and Engineering • 2025

Bioelectrochemical systems (BES) utilize microbes for energy generation, which means microbes that are known to be harmful can still be non-harmful for their capability to produce alternate energy sources, thus giving dual benefits: waste reduction with simultaneous energy generation. However, the performance of these systems depends on the electrode material, which controls the electrode’s extracellular electron transfer and electron retrieval mechanism. Different materials have been tested as electrode materials to maximize energy efficiency. Recently, carbon-based nanomaterials like graphene sheets, carbon nano-tubes/wires, and quantum dots have been employed successfully as cathode and anode electrodes. These nanomaterials are environment-friendly, non-toxic, and have high physical/chemical stability. This review is an attempt to provide a comprehensive summary of different carbon-based nanomaterials used as electrode modifier materials for BES systems covering the dimensionality of the functional materials (0-D, 1-D, and 2-D), synthesis of materials, carbon composite materials, and (iv) their application in microbial/bio photovoltaic fuel cells (electro/photocatalysis). This review article will also discuss various electrode materials generally used in BESs. There is a surge in the use of carbon-based materials and the opting for low-cost optimised electrodes over expensive, efficient ones. After that, a discussion will be made on the researched nanomaterial approach, their use as advanced working electrode material, with respect to their dimensionality, and the reported power generated by incorporating these materials as electrodes. Then, a detailed discussion will be made on the composite structures that have been reported as more efficient electrode materials than conventional and metal-based electrodes. The coming section briefly explains the design and working principle of MFCs.