Applied and environmental microbiology • 2025

The key limiting factors on energy conversion efficiency in semiconductor-microbe hybrid systems remain inadequately understood. This study investigates the impact of ultrafast electron transfer kinetics at Cd x Zn 1- x S/ Shewanella oneidensis MR-1 interfaces on the overall efficiency of hybrid systems. The reduction efficiency of direct blue 71 dye by Cd x Zn 1- x S/MR-1 is significantly enhanced under light, leveraging the synergy of extracellular photoelectron transfer in various Cd x Zn 1- x S nanoparticles and associated redox pathways in MR-1. Notably, CdS/MR-1 achieved a 98% reduction compared to 31% for ZnS/MR-1 after 1 hour, despite ZnS exhibiting a more favorable conduction band potential of -1.37 V vs normal hydrogen electrode (NHE). Time-resolved spectra and density functional theory calculations reveal that the efficiency advantages of CdS/MR-1 are attributed to its longer photoelectron lifetime (1.14 ± 0.12 ps vs 0.18 ± 0.03 ps for ZnS/MR-1) and higher electron mobility (119.71 cm²/V·s for CdS/MR-1 vs 62.47 cm²/V·s for ZnS/MR-1), providing MR-1 with superior kinetic advantages in utilizing photoelectron energy. Additionally, experiments with exogenous cytochrome c demonstrate its crucial role in modulating extracellular and intracellular electron transfer kinetics at the Cd x Zn 1- x S/MR-1 interface. Transcriptomic analysis reveals similar photoelectron transfer pathways in CdS/MR-1 and ZnS/MR-1, supporting that CdS/MR-1's superior efficiency stems from kinetic advantages at the interface, leading to greater bioavailable photoelectron accumulation. These findings underscore the importance of optimizing photoelectron transfer kinetics to enhance extracellular photoelectron utilization efficiency in semiconductor-microbe hybrid systems.IMPORTANCEThe synergy of light-sensitive semiconductor elements (e.g., natural minerals) and microbes in natural matrices enhances biological functions and opens a wide range of biotechnological possibilities. Given the extremely short lifetimes of photoelectrons and rapid transfer rates at semiconductor-microbe interface, understanding this ultrafast electron transfer process is essential for elucidating the mechanism of extracellular photoelectron utilization and optimizing system efficiency. Our study demonstrates that Shewanella oneidensis MR-1 can benefit from photoelectrons through ultrafast electron transfer pathways, similar to photosynthetic systems. For microbes to efficiently utilize these photoelectrons before charge recombination on an ultrafast timescale, a prolonged photoelectron lifetime is kinetically advantageous. Our findings indicate that the superior efficiency of the CdS/MR-1 hybrid system is driven by kinetic advantages rather than thermodynamic factors. This foundational study is crucial for optimizing the energetics of semiconductor-microbe hybrid systems and expands our understanding of microbial energy metabolism.

Bioelectrochemistry (Amsterdam, Netherlands) • 2025

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a widely recognized conducting polymer, especially in the field of electromicrobiology. Nonetheless, its inherently moderately hydrophobic and smooth surface poses a challenge for bacterial adhesion and biofilm formation, thereby restricting the growth and charge transfer of electroactive bacteria. To overcome these limitations, PEDOT:PSS films were modified with selected salts (FeCl 3 , MgSO 4 , MnCl 2 , CaCl 2 , BaCl 2 ) to improve bacterial attachment, biofilm formation and electrochemical performance, including charge storage capacity and charge transfer efficiency. Among the formed coatings, PEDOT:PSS@Ca demonstrated the highest charge storage capacity of 5.1 ± 1.0 mC/cm 2 in the presence of S. oneidensis MR-1, representing a three orders of magnitude increase when compared with pristine PEDOT:PSS. The improvement in biofilm formation was significant, with PEDOT:PSS@Ca attaining 55.0 ± 1.3 % biofilm formation and 92.8 ± 3.1 % bacterial viability, representing a considerable increase compared to unmodified PEDOT:PSS (4.1 ± 1.2 % biofilm formation and 63.1 ± 7.2 % viability). Calcium modification notably enhanced electron transfer by decreasing the charge transfer resistance, thereby promoting more effective electron exchange at the electrode interface. The findings indicate that functionalization of PEDOT:PSS with metal salts, and particularly CaCl 2 , is an effective approach for enhancing microbial fuel cell performance.

Advanced science (Weinheim, Baden-Wurttemberg, Germany) • 2026

Advancements in bioengineering have unlocked new microbial electrochemical applications in energy, sensing, remediation, and synthesis. Key to realizing these technologies is the engineering of conduits in metabolically versatile microbes like Escherichia coli to enable efficient charge exchange with the electrode. Inspired by mechanisms found in natural exogelectrogens, previous studies have largely focused on introducing conduits based on the metal-reducing (Mtr) pathway in Shewanella oneidensis MR-1. This study explores the concomitant expression of flavin secretion pathways for mediated charge transfer to complement the direct charge transfer from the bioengineered Mtr pathway. The engineered strains show a 3-fold increase in the total secretion of flavin mononucleotide (FMN) and riboflavin compared to a state-of-the-art Mtr-expressing strain lacking flavin overexpression. The concomitant flavin secretion further contributes up to a ≈3.4- and ≈1.5-fold increase in current compared to unmodified cells and the previous Mtr-expressing cells, respectively, with the greatest currents achieved for the strain favoring riboflavin secretion over FMN secretion. The introduction of flavin biosynthesis genes to Mtr-expressing strains thus reveals a distinct, yet complementary, EET mechanism for robust and multi-modal microbial applications.

Bioresource technology • 2026

Algal cathode microbial fuel cells (MFCs) are a promising technology for simultaneous wastewater treatment and bioenergy recovery. However, the fundamental mechanisms of light-mediated 'light-electricity-nitrogen' coupling via photosynthetic metabolites remain unclear, hindering system optimization. This study introduces a novel, simplified model using a defined co-culture of electrogenic Shewanella putrefaciens CN32 and Nannochloropsis oceanica in a dual-chamber MFC to decipher these interactions. Results show that light intensity critically regulates system performance, with an optimal range of 2000-5000 Lux. Within 48 h, this system achieved 49 % total nitrogen removal, a peak current density of 21.05 mA/m 2 , and a minimal charge transfer resistance (4.424 Ω). Mechanistically, photosynthetic oxygen plays a dual role: By enhancing algal nitrogen assimilation and central carbon metabolism, it facilitates the cathodic oxygen reduction through the synergy of biofilm porosity and extracellular polymeric substance-mediated electron shuttling. Furthermore, transcriptomic analysis revealed the molecular basis of this synergy, showing that light exposure upregulates algal genes for nitrogen transport and photosynthetic apparatus maintenance. This work elucidates the light-electricity-nitrogen network, demonstrating how light-regulated metabolites optimize pollutant removal and energy recovery, thereby establishing a theoretical foundation for sustainable algal bioelectrochemical applications.

[object Object], [object Object], [object Object] et al.

ChemElectroChem • 2025

Lipophilic electron shuttles (ESs), such as phenazine and phenoxazine, can penetrate the outer membrane and enter the periplasmic space, mediating extracellular electron transfer reactions. This study investigates how lipophilic ESs (resazurin, a phenoxazine) regulate carbon metabolic pathways in bioelectrochemical systems using Shewanella oneidensis MR‐1 as a model organism. Through the analysis of acetate yield, CO2 production, coulombic efficiency, and other parameters, it is found that resazurin increases coulombic efficiency (26% vs 17% for anthraquinone‐2,6‐disulfonic acid [AQDS]) and reduces acetate yield (82% vs 90% for AQDS) while slightly increasing CO2 production (13.1% vs 11.8% for AQDS), indicating a shift in carbon metabolism. Transcriptome analysis reveals significant upregulation of genes involved in the NADH‐dependent metabolic pathway (e.g., nuoHIJKLMN) and ATP synthesis (atpABDEFGH) under resazurin conditions. Mutant strains lacking key genes in oxidative phosphorylation (Δatp) or substrate‐level phosphorylation (Δack pta) further confirm the regulatory role of lipophilic shuttles. The study proposes that lipophilic ESs penetrate the periplasm, altering the redox state of inner‐membrane quinones and activating the NADH‐dependent metabolic pathway via the Arc system. This mechanism enhances TCA cycle activity and overall lactate metabolic efficiency. The findings provide insights into microbial carbon metabolic regulation and offer strategies for optimizing bioelectrochemical systems for bioremediation.

[object Object], [object Object]

Frontiers in Chemistry • 2025

Extracellular electron transfer (EET) enables certain microorganisms to respire using soluble and insoluble extracellular electron acceptors by transporting electrons across the cell envelope. Among these, G. sulfurreducens serves as a model organism for understanding direct EET pathways, where multiheme c-type cytochromes mediate electron transport from intracellular redox carriers to extracellular acceptors such as Fe(III) oxides and electrodes. This review focuses on heme-dependent electron transfer in Geobacter sulfurreducens, detailing the roles of inner membrane cytochromes, periplasmic carriers, outer membrane conduits, and recently characterized extracellular nanowires formed by polymerized multiheme c-type cytochromes, including OmcS, OmcE, and OmcZ. We examine the state of understanding of their physiological function, their structural features, expression patterns, and essentiality under various respiratory conditions. These insights advance our understanding of microbial anaerobic respiration and have implications for biogeochemical cycling, bioenergy generation, and bioremediation. The molecular architecture, assembly mechanisms, and secretion pathways of multiheme c-type cytochrome nanowires remain active areas of investigation, offering promising directions for future research and biotechnological innovation in engineered microbial systems.

[object Object], [object Object], [object Object] et al.

Bioscience, Biotechnology, and Biochemistry • 2025

Abstract The metal-reducing bacterium Geobacter sulfurreducens PCA is capable of anaerobic respiration using elemental sulfur as an electron acceptor. Despite 3 decades since its isolation, the molecular mechanisms underlying sulfur respiration remain unclear. In this study, we conducted a transcriptome analysis of G. sulfurreducens PCA cultured with and without sublimed sulfur. In the presence of sulfur, 153 genes were significantly up-regulated, while 599 genes were down-regulated. Notably, genes encoding redox proteins involved in energy conservation, particularly multiheme c-type cytochromes, exhibited altered expression patterns. In addition, elemental sulfur induced the transcription of genes associated with sulfur, selenium, and nitrogen metabolism, as well as protein redox homeostasis, DNA repair, and even cell motility. These transcriptional responses may reflect metabolic adaptation to sulfur respiration, redox state alterations, and sulfur-induced stress. Our findings uncover a complex regulatory landscape governing sulfur respiration and provide critical insights into this long-standing biochemical enigma in G. sulfurreducens PCA.

[object Object], [object Object], [object Object] et al.

Frontiers in Microbiology • 2025

Anaerobic digestion is a key technology for converting organic waste into methane, offering significant potential for renewable energy production and waste management. While the addition of conductive materials has been shown to improve direct interspecies electron transfer (DIET), their application faces challenges like biofouling, environmental risks, and increased operational costs. This study investigated the effects of co-culturing dual Methanosarcina (Methanosarcina barkeri and Methanosarcina acetivorans) and Geobacter metallireducens (DM-G) to enhance DIET and methane production without the addition of exogenous conductive materials. The performance of the DM-G co-culture system was comparable to that of the conductive material-amended single Methanosarcina and G. metallireducens (SM-G) co-culture systems, achieving a maximum methane concentration of 19.5 mM, following the consumption of 15.2 mM ethanol in the 1:1:1 biomass ratio system. This corresponds to a 3.8-fold increase over the SM-G co-culture system with M. barkeri and G. metallireducens, and a 3.0-fold increase over that with M. acetivorans and G. metallireducens. Transcriptomic analysis showed that in the DM-G co-culture system, M. barkeri up-regulated key genes related to methane metabolism and acetate utilization, while the core methanogenic pathway of M. acetivorans was down-regulated, but it could still effectively utilize the electron transfer pathway, indicating metabolic complementarity. These findings propose a novel strategy for enhancing DIET-driven methanogenesis through synergistic microbial consortia, advancing scalable, low-cost bioenergy solutions for organic waste valorization.

[object Object], [object Object], [object Object] et al.

Biofuels, Bioproducts and Biorefining • 2025

Abstract Bioelectrochemical systems (BESs) are emerging as a pivotal technology in waste valorization, with expanding applications in wastewater treatment, resource recovery, and greenhouse gas mitigation. This systematic review explores the diverse applications of BESs and their benefits in renewable energy production, waste management, and environmental protection. Based on biorefinery concepts, BESs are classified into three categories: waste‐to‐power, waste‐to‐fuel, and waste‐to‐chemicals. Key challenges affecting scalability are discussed, including cell design parameters, redox mediators, and electrode architecture. Among BES types, microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) are currently the most developed in terms of deployment and research investment. However, enzymatic electrochemical systems remain underexplored. As global demand grows for sustainable waste management solutions, BESs offer a promising platform that integrates resource recovery with environmental sustainability. Realizing their full potential will require continued innovation and collaboration among researchers, industry stakeholders, and policymakers to facilitate the transition from laboratory‐scale studies to large‐scale, practical applications.

[object Object], [object Object], [object Object] et al.

Sustainability • 2025

The underutilization of fruit waste in agroindustry—particularly star fruit—leads to leachate generation, emissions, and disposal costs, highlighting the need for circular alternatives that treat organic fractions while producing energy. This study evaluated the bioelectrochemical conversion of carambola (Averrhoa carambola) residues in single-chamber microbial fuel cells (MFCs). Three 1000 mL reactors were constructed using carbon anodes and zinc cathodes, operated for 35 days with continuous voltage recording and daily monitoring of pH, conductivity, and ORP. Polarization curves were obtained, and FTIR and SEM analyses were conducted to characterize substrate transformation and anode colonization. The anodic biofilm was also profiled using metagenomics. Measurements were performed using calibrated electrodes and a data logger with one minute intervals. The systems exhibited rapid startup and reached peak performance on day 22, with a voltage of 1.352 V, current of 3.489 mA, conductivity of 177.90 mS/cm, ORP of 202.01 mV, and pH of 4.89. The V–I curve indicated an internal resistance of 16.51 Ω, and the maximum power density reached 0.517 mW/cm2. FTIR revealed a reduction in bands associated with carbohydrates and proteins, consistent with biodegradation, while SEM confirmed extensive biofilm formation and increased anode surface roughness. Metagenomic analysis showed dominance of Acetobacter (59.35%), with Bacteroides (12.93%) and lactobacilli contributing to fermentative and electrogenic synergies. Finally, the series connection of three MFCs generated 2.71 V, sufficient to power an LED, demonstrating the feasibility of low-power applications and the potential for system scalability.

[object Object], [object Object], [object Object] et al.

Journal of Chemical Technology & Biotechnology • 2025

Abstract The globe will continue to confront major issues with environmental sustainability and energy in the years to come. As a result, it is crucial to pursue sustainable development to protect the environment and make the most of renewable energy sources. One promising approach involves using natural microorganisms to generate energy from affordable substrates through Microbial Fuel Cells (MFCs). These bioelectrochemical systems work by harnessing the ability of microbes to break down organic materials. This process releases electrons that travel through an external circuit, producing power. This review explores the basic principles and concepts behind MFCs, while also considering the key factors affecting their performance. The review provides a detailed analysis of MFCs, focusing on the characteristics and functions of exoelectrogens and the optimal conditions necessary for their efficient operation. It also discusses the working principles and mechanisms of MFCs, including recent advancements in the field. The primary focus of the review is on the potential and practical applications of this sustainable energy technology. It details various real‐world uses, including biosensors, electronic devices, desalination, and environmental bioremediation. © 2025 Society of Chemical Industry (SCI).

[object Object], [object Object], [object Object] et al.

ChemElectroChem • 2025

Granular carbon‐based cathodes in carbon dioxide‐reducing bioelectrochemical systems (CO2‐reducing BES) feature high biocompatibility and stability. Wood‐based biochar is gaining popularity in (bio)electrochemical applications due to its sustainability and reduced environmental impact. Yet, previous studies primarily examined lab‐scale biochars. This study investigates how heterogeneity of industrial‐scale granular biochars (GBs) influences their electrocatalytic activity for hydrogen evolution reaction (HER) in the nexus of CO2‐reducing BES. Significant variations are identified in overpotentials for HER at −1 mA cm−2 (η‐1 mA cm−2) among the GB‐based cathodes. Beechwood‐derived GB pyrolyzed at 740 °C shows the lowest η‐1 mA cm−2(223.6 ± 30.0 mV), outperforming birchwood‐derived GB at 700 °C (503.5 ± 4.9 mV) and granular graphite (608.3 ± 19.5 mV). Despite its superior performance, beechwood‐based GB shows high heterogeneity. Such heterogeneity underlies different physicochemical properties, likely due to uneven temperature distribution in industrial pyrolysis. The remarkable performance of beechwood‐based GB pyrolyzed at 740 °C is attributed to its higher electrical conductivity, higher degree of carbonization, favorable H/C ratios, higher disorder in carbonaceous structure, and suitable porosity. The results highlight the influence of the wood type, the importance of systematic GB characterization, and the necessity to optimize industrial‐scale biochar production to achieve homogeneous and high‐performance biochar.

[object Object], [object Object], [object Object] et al.

Molecules • 2025

Bioelectrochemical systems (BESs) are technologies capable of converting chemical energy into electrical energy or producing value-added compounds. These systems typically employ Nafion membranes as proton exchange separators; however, Nafion is costly and prone to fouling. In this study, mixed-matrix membranes (MMMs) based on chitosan and its derivatives, incorporated with Er- and Al-doped ZnO nanoparticles, were synthesized and evaluated. Key properties assessed included antimicrobial activity, antifouling behavior, chemical stability, water retention, and proton conductivity. The results demonstrated that the chitosan-based membranes doped with Er/Al/ZnO outperformed Nafion in terms of antifouling properties, water retention, and a protective effect on the surface of the membrane against Escherichia coli and Staphylococcus aureus, while exhibiting comparable proton conductivity and chemical stability.

[object Object], [object Object], [object Object] et al.

Energies • 2025

This study presents the design and implementation of a crop environmental monitoring system powered by a plant–soil bioelectrochemical energy source. The system integrates a Cu–Zn electrode power unit, a boost converter, a supercapacitor-based energy management module, and a wireless sensing node for real-time monitoring of environmental parameters. Unlike conventional plant microbial fuel cells (PMFCs), the output current originates partly from the galvanic effect of Cu–Zn electrodes and is further regulated by rhizosphere conditions and microbial activity. Under the optimal external load (900 Ω), the system achieved a maximum output power of 0.477 mW, corresponding to a power density of 0.304 mW·cm−2. Stability tests showed that with the boost converter and supercapacitor, the system maintained a stable operating voltage sufficient to power the sensing node. Soil moisture strongly influenced performance, with higher water content increasing power by about 35%. Theoretical calculations indicated that Zn corrosion alone would limit the anode lifetime to ~66 days; however, stable output during the experimental period suggests contributions from plant–microbe interactions. Overall, this work demonstrates a feasible self-powered crop monitoring system and provides new evidence for the potential of plant–soil bioelectrochemical power sources in low-power applications.

[object Object], [object Object], [object Object] et al.

Applied Sciences • 2025

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.

[object Object], [object Object], [object Object] et al.

Journal of The Electrochemical Society • 2025

Bioelectrochemical systems (BES) represent a rapidly evolving class of hybrid technologies that merge microbiology, electrochemistry, and materials science to deliver sustainable solutions for energy generation, environmental remediation, and biomedical applications. In this review, we comprehensively explore the working principles of BES, highlighting the critical role of microbial electron transfer mechanisms. Various BES configurations, including microbial fuel cells, microbial electrolysis cells, and microbial desalination cells, are evaluated for their operational features and application potential. Special emphasis is placed on the composition and function of microbial communities at anodic and cathodic interfaces, which govern the efficiency and versatility of these systems. Emerging biomedical applications of BES are examined, spanning biosensing, point-of-care diagnostics, implantable medical devices, and bioelectric stimulation. Additionally, the role of BES in environmental health monitoring, pollutant degradation, and even ruminant health management is discussed. Despite significant advancements, critical challenges persist, particularly in scalability, biocompatibility, and power output. Future research priorities include engineering advanced materials, optimising microbial-electrode interactions, and integrating BES with complementary technologies such as microfluidics, artificial intelligence, and hybrid energy systems. Overall, this review underscores the transformative potential of BES in addressing key global challenges in energy, healthcare, and environmental sustainability, while charting pathways for their broader commercial and clinical deployment.

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International Congress of Geneticists and Breeders of the Republic of Moldova • 2025

The dynamics of potential difference formation in bioelectrochemical systems with different root environment humidity levels from 13% to 60% was studied when growing bok choi cabbage. The highest voltage values reached 320 mV, specific power 0.01 mW/m2 and were typical for samples with higher humidity. A weak correlation (r=0.3) between the root environment humidity indicators and the generated potential difference was obtained. It was suggested that, along with the properties of the root environment, the state of plants and the intensity of metabolic processes also play a significant role in voltage formation.

[object Object], [object Object], [object Object]

Civic Synergy • 2025

Abstract This paper presents the use of novel bioelectrochemical systems (BESs) as sustainable solutions for environmental remediation in smart cities. The potential of BES technology to address urban pollution and waste management is discussed, with a focus on its role in wastewater treatment and soil remediation. The authors examine the integration of BESs into smart city infrastructure and highlight key research directions and case studies to demonstrate their practical applications and effectiveness in the real world.

[object Object], [object Object]

Journal of Innovative Solutions for Eco-Environmental Sustainability • 2025

Hydrogenases (Hyds) are microbial enzymes that reversibly catalyze the oxidation of molecular hydrogen (H₂), playing a critical role in biohydrogen metabolism [1-3]. These include oxygen-resistant biological [NiFe]-hydrogenases, which have attracted great interest for their application in hydrogen fuel cell (H₂-FC) technologies. The results provide insight into the potential of bioelectrochemical-based systems for sustainable energy production. The bioelectrocatalytic efficiency of E. coli bacteria immobilized on the electrode surface in a volume of 3 μl (1.5 mg cell dry weight) was studied under the conditions of 0.2% glucose fermentation in peptone medium at pH-7.5 [4]. In this study, the electrochemical measurements were performed using a two-electrode system equipped with a computer potentiostat, specifically a hydrogen fuel cell voltammetry (HFCV). The wild-type E. coli BW25113, the septuple (BW25113hyaB hybC hycA fdoG ldhA frdC aceE) the F0F1-ATPase-defective, and the Hyd defective hyaB, hybC, hycE, hyfG mutant strains were used in the experiments. Maximal catalytic activity was observed in the hyaB and hyfG mutants, being stimulated ∼2-fold and ∼1.6-fold compared to the wild type, reaching values of ∼1.26 ± 0.02 V and ∼0.98 ± 0.02 V, respectively. The effect of the 10 mM N,N′-dicyclohexylcarbodiimide (DCCD), the F0F1-ATPase inhibitor, on the catalytic activity of Hyd enzymes was observed. It was shown that for all strains, the reading of the voltammeter decreased ~1.5 times, reaching the readings recorded by the F0F1-ATPase-defective strain. Interestingly, in the case of the the septuple mutant strain, DCCD recorded a stimulating rather than a suppressive effect. The results obtained indicate the great potential of bacteria as anodic biocatalysts and demonstrate the need for further studies.

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NEWPORT INTERNATIONAL JOURNAL OF SCIENTIFIC AND EXPERIMENTAL SCIENCES • 2025

Rheumatoid arthritis (RA) is a chronic autoimmune disease marked by joint inflammation, disability, and reduced quality of life. Precision medicine, which tailors treatment to individual molecular profiles, offers promise for improving RA outcomes. While genomic and epigenetic studies have identified biomarkers of susceptibility, progression, and therapeutic response, these insights are largely derived from European and Asian populations. African populations despite their unparalleled genetic diversity remain significantly underrepresented. This gap has critical implications, as African-specific variants, epigenetic modifications, and environmental exposures may influence disease risk and treatment response. The absence of African-focused research restricts the applicability of existing biomarkers and perpetuates disparities in care. To address this, large-scale multi-omics studies, robust biobanking, stronger ethical frameworks, and investment in local research capacity are needed. Identifying population-specific molecular signatures will improve early detection, prognosis, and individualized therapy for African patients. Incorporating African data into RA precision medicine is both a scientific necessity and an ethical imperative, ensuring equitable access to personalized healthcare. Keywords: Rheumatoid arthritis, precision medicine, genomics, epigenetics and biomarkers.

[object Object], [object Object], [object Object] et al.

Fermentation • 2025

As the environmental burden of traditional plastics continues to grow, bioplastics (BPs) have emerged as a promising alternative due to their renewable origins and potential for biodegradability. However, the most popular anaerobic systems (ASs)—anaerobic digestion (AD), acidogenic fermentation (AF), and enzyme hydrolysis (EH)—for BPs degradation still face many challenges, e.g., low degradation efficiency, process instability, etc. As a sustainable clean energy technology, bioelectrochemical systems (BESs) have demonstrated strong potential in the treatment of complex organic waste when integrated with ASs. Nevertheless, research on the synergistic degradation of BPs using BES-ASs remains relatively limited. This review systematically summarizes commonly used anaerobic degradation methods for BPs, along with their advantages and limitations, and highlights the BES-AS as an innovative strategy to enhance BPs degradation efficiency. BESs can accelerate the decomposition of complex polymer structures through the activity of electroactive microorganisms, while also offering benefits such as energy recovery and real-time process monitoring. When coupled with anaerobic digestion, the BES-AS demonstrates significant synergistic effects, improving degradation efficiency and promoting the production of high-value-added products such as volatile fatty acids (VFAs) and biogas, thereby showing great application potential. This review outlines current research progress, identifies key knowledge gaps in mechanism elucidation, system design, source recovery, etc., and proposes future research directions. These include system optimization, microbial community engineering, development of advanced electrode materials, and omics-based mechanistic studies. Advancing multidisciplinary integration is expected to accelerate the practical application of BES-ASs in BP waste management and contribute to achieving the goals of sustainability, efficiency, and circular utilization.

[object Object], [object Object], [object Object] et al.

BioTech • 2025

Carbon capture and power-to-X are becoming increasingly relevant in the context of decarbonization and supply security. Actinobacillus succinogenes is capable of transforming CO2 into succinate, whereby product formation is significantly limited by the availability of NADH. The aim of this work was to further develop a bioelectrochemical system (BES) in order to provide additional reduction equivalents and thus increase yield and titer. To this end, a new BES configuration was established. A conventional stirred tank reactor (STR) is coupled via a bypass to an H-cell, in which the redox mediator neutral red (NR) is electrochemically reduced and then returned back to the bioreactor. The indirect electron transfer decouples the electrochemical reduction from the biology and results in increased intracellular availability of NADH. The present approach resulted in an increase in yield from 0.64 g·g−1 to 0.76 g·g−1, corresponding to an increase of 18%. At the same time, a titer of 16.48 ± 0.19 g·L−1 was achieved in the BES, compared to 12.05 ± 0.18 g·L−1 in the control. The results show that the mediator-assisted, partially decoupled BES architecture significantly improves CO2-based succinate production and opens up a scalable path to the use of renewable electricity as a reduction source in power-to-X processes.

[object Object], [object Object], [object Object] et al.

REVISTA TERRA LATINOAMERICANA • 2025

Bioelectrochemical systems (BES) remove high concentrations of organic and inorganic contaminants and generate energy. It has been proven that they are more ef ficient when working with small-volume modules (such as stacks or cascades) than with a large reactor volume. In this work, the ef fect of hydraulic retention time (HRT) on the removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total solids (TS), total suspended solids (TSS), total coliforms (TC), fecal coliforms (FC), helminth eggs (HE), and power generation of a modular bioelectrochemical system consisting of ten dual-compartment microbial fuel cells (MFC) of 2000 mL each during the treatment of municipal wastewater (MWW) was assessed. The increase in HRT had a positive impact. In a 5-h HRT, the removal ef ficiency percentages of COD, BOD5, TS, TSS, TC, FC, and HE were 66.46, 34.18, 36.76, 53.84, 99.99, 99.99, and 91.88%, respectively. Likewise, at this same HRT (5 h), the highest maximum power density of 5.709 mW m-3 and the coulombic ef ficiency of 0.0056% were obtained. Results showed that the modular BES increases energy generation and contaminant removal, especially pathogens (TC, FC, and HE).

[object Object], [object Object], [object Object]

Membranes • 2025

Biofouling remains a critical challenge in bioelectrochemical cells (BECs), hindering their efficiency and performance. This research article reviews advances in biofouling mitigation techniques within BEC systems during the period from 2019 to 2025, focusing on membrane modifications and electro-assisted membrane technologies. Through comprehensive analysis, it is revealed that Nafion alternatives, including ceramic membranes and recycled nonwoven fabrics like polypropylene, have emerged as significant contenders due to their combination of low cost and high performance. Additionally, the incorporation of silver, zeolite, and graphene oxide onto membranes has demonstrated efficacy in mitigating biofouling under laboratory conditions. Furthermore, the application of direct current electric fields has shown potential as a chemical-free preventative measure against biofouling in BECs. However, challenges related to long-term stability, scalability, and cost-effectiveness must be addressed for widespread adoption.

[object Object], [object Object], [object Object] et al.

Small • 2025

Abstract Extracellular electron transfer (EET) at the microbe‐anode interface remains a critical bottleneck in microbial fuel cells (MFCs). While high‐entropy oxides (HEOs) show promise for enhancing anode kinetics, conventional synthesis methods yield poor interfacial integration and fail to elucidate entropy‐driven EET mechanisms. Herein, an entropy‐engineered bioanode fabricated via ultrafast flash Joule heating (FJH) is reported, which uniformly anchors HEO nanoparticles (Fe─Co─Ni─Cr─Mn─O) onto vertically aligned Fe, N‐doped carbon nanotubes grown on carbon cloth (HEO/Fe, N‐CNTs/CC). This design synergizes CNT conductivity with HEO pseudocapacitance, achieving a record power density of 3.76 W m −2 , surpassing the state‐of‐the‐art HEO anode by 9.6% and bare carbon cloth by 2.2‐fold. The entropy‐broadened conduction bands and strengthened cytochrome adsorption (ΔE ads = −3.20 eV) reduce the electron tunneling distance to 2.47 Å, as revealed by DFT calculations. Furthermore, the anode promotes Geobacter enrichment (71% biofilm abundance) and riboflavin secretion, facilitating dual direct and mediated EET pathways. This work establishes entropy modulation as a universal strategy for high‐performance bioelectrochemical systems, opening avenues for sustainable energy harvesting and environmental sensing.

[object Object], [object Object], [object Object] et al.

Water • 2025

This study evaluates the energy efficiency and trade-offs of a sidestream bioelectrochemical anaerobic digestion (SBEAD) system compared to conventional anaerobic digestion (AD). Both reactors were operated in sequencing batch mode under mesophilic conditions, with a low voltage of 0.4 V applied to SBEAD. Experiments were conducted across four organic loading rates (OLRs): 2, 3, 4, and 6 kg-COD/m3/day. At OLRs of 3 kg-COD/m3/day or lower, methane production and energy efficiency were comparable between AD and SBEAD. However, at higher OLRs, SBEAD demonstrated superior methane production and overall energy recovery, while AD performance deteriorated due to acidification. Specifically, at 6 kg-COD/m3/day, SBEAD achieved an energy efficiency of 63.8 ± 3.5%, compared to 23.1 ± 12.4% for AD. A novel metric, the Methane Gain Index (MGI), was analyzed, with SBEAD achieving MGI values exceeding 50 kJ/kJ at low OLRs and reaching 585.3 kJ/kJ at high OLRs. Additionally, microbial community analysis indicated that SBEAD favored the abundance of species that enhance substrate degradation and methane production. These findings suggest that SBEAD is a scalable strategy for treating high-strength organic waste in waste-to-energy systems.

[object Object], [object Object], [object Object] et al.

Processes • 2025

This study addresses the critical issue of fossil fuel dependence and its environmental impacts by examining bioelectrochemical systems (BES) for converting CO2 into sustainable biofuels. A bibliometric analysis was conducted on 87 Scopus documents (2010–2025) using RStudio (Bibliometrix) and VOSviewer to map co-authorship, co-citation, and keyword networks. Results show exponential growth since 2017, dominated by Environmental Science, Chemical Engineering, and Energy. China leads in publication volume, while Belgium excels in international collaboration and impact per article. Research networks are concentrated in Europe and Asia, with significant underrepresentation of Latin America and Africa. Thematic clusters center on CO2, microbial fuel cells, and bioenergy, indicating a shift toward material and process optimization. Influential authors such as Bajracharya S. focus on microbial electrosynthesis. However, key research gaps persist: limited integration of direct carbon capture technologies, inadequate biofilm characterization, and a scarcity of industrial-scale studies. Moreover, fewer than 10% of studies include comprehensive life cycle assessments (LCA) to evaluate the environmental footprint of BES. We propose a standardized LCA framework integrating techno-economic and circular economy metrics to advance BES from lab-scale proofs-of-concept to industrially viable, net-negative carbon technologies. The analysis also underscores a critical gap in policy and regulatory research, which is essential to create enabling conditions for the demonstration and scaling of BES technologies.

[object Object], [object Object], [object Object] et al.

Preprints.org • 2025

Electroactive biofilms (EABs) are essential for the performance of bioelectrochemical systems (BESs), but their formation in Geobacter critically on conductive pili and exopolysaccharides, limiting applications under conditions where these components are deficient. Herein, we investigated the restorative effects of exogenous flavin mononucleotide (FMN) on EAB formation and extracellular electron transfer (EET) in two defective mutants of G. sulfurreducens: the pili-deficient PCA△1496 and exopolysaccharides-deficient PCA△1501. Results show that FMN significantly promoted biofilm thickness in PCAΔ1496 (250%) and PCAΔ1501 (33%), while boosting maximum current outputs by 175-fold and 317.7%, respectively. Spectroscopic and electrochemical analyses revealed that FMN incorporates into biofilms, binds to outer membrane c-type cytochromes (c-Cyts), and enhances electron exchange capacity. Differential pulse voltammetry further confirmed that FMN did not exist independently in the biofilm but bound to outer membrane c-Cyts as a cofactor. Collectively, exogenous FMN plays dual roles (electron shuttle and cytochrome-bound cofactor) in defective Geobacter EABs, effectively restoring biofilm formation and enhancing EET efficiency. This study expands the understanding of the mechanism of Geobacter EABs formation and provides a novel strategy for optimizing BES performance.

[object Object], [object Object], [object Object] et al.

Bioengineering • 2025

This study investigated methane (CH4) production in a bioelectrochemically enhanced anaerobic digester (BEAD) equipped with a pair of 3-dimensional flow-through electrodes made of conductive polypropylene biorings. The performance of the BEAD reactor was compared to that of a similarly sized Anaerobic Upflow Sludge Bed (UASB) reactor. The reactors were operated at a temperature of 22 ± 1 °C using food waste (FW) leachate fed at organic loading rates of 3–8 g (LR d)−1 or at a temperature of 35 ± 1 °C using the liquid fraction of FW separated using a screw press. With both tested feedstocks, the BEAD reactor demonstrated up to 30% higher CH4 yield, reaching 0.35–0.38 L g−1 (COD consumed), compared to the UASB reactor. Additionally, reactor stability under organic overload conditions improved, with the difference more pronounced at organic loads above 6 g (LR d)−1. Energy consumption for bioelectrochemical CH4 production was estimated at 5.1–12.4 Wh L−1 (of CH4 produced), which is significantly below the energy consumption for electrochemical H2-based methanation. Overall, BEAD increases methane production and improves process stability, offering a novel sustainable solution for waste management.

[object Object], [object Object], [object Object] et al.

Microbial Cell Factories • 2025

Abstract Background Used motor oil (UMO) is a dangerous environmental pollutant that needs to be treated effectively. This work introduces a novel approach for producing bioelectricity and UMO biodegradation simultaneously in a single-chamber microbial fuel cell (SCMFC) using native mixed bacterial cultures. Results Under certain conditions (2% oil, 1% peptone, 4% inoculum, 21 days), the optimized bacterial culture degraded UMO by about 80%. Through bioelectrochemical studies, a maximum voltage of 257 mV and a power density of 36.6 mW/m² were demonstrated, showing a strong correlation between UMO removal and electricity generation. Moreover, metagenomic data showed that Firmicutes, particularly Bacillus , dominated the biofilm at roughly 65%. Fourier Transform Infrared (FTIR) and Gas Chromatography-Mass Spectroscopy (GC-MS) verified the breakdown of complex hydrocarbon molecules, highlighting their crucial role in UMO biodegradation and bioenergy production. The effective elimination of UMOs and simultaneous power generation, supported by metagenomic and biochemical tests, showed the microbial activity and hydrocarbon breakdown. Conclusions The results suggest SCMFC technology as a sustainable solution for managing petroleum waste while producing renewable energy.

[object Object], [object Object], [object Object] et al.

Environmental Science: Nano • 2026

The introduction of green nanoparticles to expedite the (bio)electrochemical reactions has proven to be a promising technique for wastewater treatment to meet the universal and equitable accessibility to clean water, which is in line with the clean water and sanitation goal (SDG 6).

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Environmental Science: Water Research & Technology • 2026

This study validated a 1 L-capacity sulfate-reducing bacteria-based bioelectrochemical system (SRB-BES) for treating sewage wastewater in continuous mode over ∼66 days.

[object Object], [object Object], [object Object] et al.

Microorganisms • 2026

Electroactive biofilms (EABs) are essential for the performance of bioelectrochemical systems (BESs), but their formation in Geobacter, critically on conductive pili and exopolysaccharides, limits application under conditions where these components are deficient. Herein, we investigated the restorative effects of exogenous flavin mononucleotide (FMN) on EAB formation and extracellular electron transfer (EET) in two defective mutants of Geobacter sulfurreducens: the pili-deficient PCAΔ1496 and exopolysaccharides-deficient PCAΔ1501. Results show that FMN significantly promoted biofilm thickness in PCAΔ1496 (250%) and PCAΔ1501 (33%), while boosting maximum current outputs by 175-fold and 317.7%, respectively. Spectroscopic and electrochemical analyses revealed that FMN incorporates into biofilms, binds to outer membrane c-type cytochromes (c-Cyts), and enhances electron exchange capacity. Differential pulse voltammetry further confirmed that FMN did not exist independently in the biofilm but bound to outer membrane c-Cyts as a cofactor. Collectively, exogenous FMN plays dual roles (electron shuttle and cytochrome-bound cofactor) in defective Geobacter EABs, effectively restoring biofilm formation and enhancing EET efficiency. This study expands the understanding of the formation mechanism of Geobacter EABs and provides a novel strategy for optimizing BES performance.

[object Object], [object Object], [object Object] et al.

Frontiers in Microbiology • 2026

Mercury (Hg) is a global environmental concern due to its microbial conversion to methylmercury (MeHg), a potent neurotoxin that bioaccumulates in food webs and poses risks to ecosystems and human health. Thiol functional groups (RSH) play an important role in controlling Hg(II) speciation and bio-uptake in methylating bacteria, yet the spatial distribution and density of these thiols within cells remain largely unknown. We isolated subcellular fractions of the Hg methylating bacterium Geobacter sulfurreducens in the exponential growth phase, and used Hg L III -edge EXAFS (Extended X-ray Absorption Fine Structure) to quantify thiols in the extracellular medium, inner and outer membranes, periplasm and cytoplasm. The whole-cell thiol content was determined to be 1.3 × 10 −10 μmol cell −1 . The inner membrane contributed 7.1 × 10 −11 (53%), the outer membrane 1.2 × 10 −11 (9%), the periplasm 3.6 × 10 −11 (27%) and the cytoplasm 1.5 × 10 −11 μmol cell −1 (11%). The extracellular fraction contributed an additional 5.7 × 10 −11 μmol cell −1 , corresponding to 30% of the thiols of the cell culture. Local thiol density (thiols normalized to TOC in individual compartment, RSH/TOC, μmol g −1 C) was 36, 450, 140, 600 and 29 μmol g −1 C in the cytoplasm, inner membrane, periplasm, outer membrane and extracellular fractions, respectively. EXAFS analyses demonstrate Hg-thiolate coordination across all compartments, with Hg-O/N bonding and elemental Hg 0 formed at higher Hg loadings. In the periplasm, Hg-disulfide and traces of β -HgS were detected. The high thiol density at the membranes, relative to other compartments, may imply they have an important role in the retention and internalization of Hg(II). Periplasmic thiols may modulate Hg(II) transfer between membranes, and cytoplasmic thiols may regulate the intracellular availability of Hg(II) for methylation. This work provides the first compartment-resolved quantification of thiol abundances and densities in a model Hg-methylating bacterium at subcellular level, offering a mechanistic framework for understanding the speciation, bioavailability, and subcellular transformation of Hg(II) with relevance for other soft metals (e.g., Cd, Pb, Zn, Ag, and Cu).

[object Object], [object Object], [object Object] et al.

Journal of Chemical Technology & Biotechnology • 2026

Abstract BACKGROUND Chlorinated aliphatic hydrocarbons such as trichloroethylene ( TCE ) are persistent groundwater contaminants due to improper disposal and low biodegradability. This work presents an innovative bioelectrochemical system for the integrated reductive/oxidative removal of TCE from contaminated water, implemented in a single tubular reactor. Unlike previous approaches relying on sequential reactor configurations, this study optimizes a three‐electrode setup that enables both anaerobic and aerobic dechlorination processes to occur simultaneously within the same unit. The system features a mixed metal oxide ( MMO ) anode that facilitates oxygen evolution and supports oxidative degradation, and a graphite cathode for TCE reduction under anaerobic conditions. The reactor's configuration promotes the coexistence of both anaerobic and aerobic microbial communities, enabling complete dechlorination of TCE and minimization of toxic by‐products RESULTS After characterizing the system from a fluid‐dynamic point of view, continuous‐flow galvanostatic runs at +15, +30, and +20 mA achieved removal efficiencies above 97%. By‐product profiles confirmed the progression toward full mineralization. The most effective performance was obtained at +30 mA, with a removal rate of 38.6 μmol/L d −1 . Coulombic efficiency and energy consumption were also evaluated, highlighting the feasibility of low‐energy operation. CONCLUSION This single‐reactor strategy represents a significant advancement in the design of compact and efficient systems for in situ groundwater remediation, reducing operational complexity while enhancing treatment performance. © 2026 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley Sons Ltd on behalf of Society of Chemical Industry (SCI).

[object Object], [object Object], [object Object] et al.

bioRxiv (Cold Spring Harbor Laboratory) • 2026

ABSTRACT The accumulation of propionate is a challenge in numerous fermentative industrial processes because its degradation is energetically unfavorable and limited to few microbial species. Here, we report for the first time the oxidation of propionate by the extracellular electron transfer (EET)-capable bacterium Geobacter sulfurreducens in axenic cultures. G. sulfurreducens was capable of utilizing propionate both as electron donor (ED) and source of carbon with fumarate as electron acceptor (EA). In contrast, propionate was metabolized only in the presence of acetate with soluble Fe(III) citrate, and was not oxidized when insoluble iron oxides or glassy carbon electrodes poised at +0.1 V vs. SHE were the EAs. Biomass yield (per mole of electrons available) was lower with propionate alone than with propionate and acetate together, and acetate was preferentially consumed when both were present. Transcriptomic analysis of cultures grown with either propionate or acetate (with fumarate as EA) showed significant gene expression shifts strongly suggesting the methylmalonyl-CoA pathway as the main route for propionate degradation. Furthermore, propionate-consuming cultures exhibited an upregulation of branched chain amino acids (BCAAs) biosynthesis, as well as sulfur, nitrogen, and 2-oxocarboxylic acids metabolism. IMPORTANCE The accumulation of propionate is a challenge in anaerobic and fermentative processes because it inhibits methanogenesis, and few microbial species within such systems can degrade it. G. sulfurreducens is a model electroactive bacterium widely used in bioelectrochemical systems and is increasingly studied in wastewater treatment and anaerobic digestion because of its ability to enhance syntrophic metabolism via direct interspecies electron transfer. We show for the first time that G. sulfurreducens can oxidize propionate, expanding its known metabolic repertoire, and that this capability is controlled by the nature of the terminal electron acceptor. Transcriptomic analyses strongly suggest that the methylmalonyl-CoA pathway is the main pathway for propionate degradation and reveal additional associated transcriptional changes. These findings, together with insights into propionate degradation kinetics, could inform future strategies aimed at using this bacterium to mitigate propionate buildup and improve the stability of anaerobic treatment systems.

[object Object], [object Object], [object Object] et al.

Molecules • 2026

The global energy crisis driven by an 80% reliance on fossil fuels and the urgent need to reduce greenhouse gas emissions demands the exploration of sustainable biotechnological alternatives. This study addresses a critical knowledge gap regarding the integration of fungal secondary metabolites into bioelectrochemical energy systems, as these compounds have traditionally been investigated for pharmacological purposes. The methodology involved a documentary analysis using the Scopus database (2000–2025), applying a search equation that combined terms such as “secondary metabolite”, “fungi”, and “bioenergy”. Data processing was conducted using R Studio (R 3.6.0+), VOSviewer (1.6.20) for collaboration networks, and Plotly Studio (v6.5.0) for interactive visualizations. Key findings revealed that redox mediators such as quinones and organic acids derived from Aspergillus niger enhanced electron transfer efficiency by 35%, achieving power densities of 1.2 W/m2. Meanwhile, Penicillium chrysogenum reduced internal electrode resistance by 40%. Additionally, the “xeno-fungosphere” system achieved 97.9% herbicide removal and generated 9.3 µW/cm2. Notably, biosynthesized bis-quinones were successfully applied in redox flow batteries, reaching a capacity of 1.58 Ah/L. In conclusion, the study identified a scientific shift from pharmacological applications toward energy metabolism and sustainability, positioning fungi as critical components for the future efficiency of bioelectrical technologies.

Environmental science and pollution research international • 2025

Geobacter sulfurreducens DL1 is a metal-reducing dissimilatory bacterium frequently used to produce electricity in bioelectrochemical systems (BES). The biofilm formed on electrodes is one of the most important factors for efficient electron transfer; this is possible due to the production of type IV pili and c-type cytochromes that allow it to carry out extracellular electron transfer (EET) to final acceptors. In this study, we analyzed the biofilm formed on different support materials (glass, hematite (Fe 2 O 3 ) on glass, fluorine-doped tin oxide (FTO) semiconductor glass, Fe 2 O 3 on FTO, graphite, and stainless steel) by G. sulfurreducens DL1 (WT) and GSU1771-deficient strain mutant (Δgsu1771). GSU1771 is a transcriptional regulator that controls the expression of several genes involved in electron transfer. Different approaches and experimental tests were carried out with the biofilms grown on the different support materials including structure analysis by confocal laser scanning microscopy (CLSM), characterization of electrochemical activity, and quantification of relative gene expression by RT-qPCR. The gene expression of selected genes involved in EET was analyzed, observing an overexpression of pgcA, omcS, omcM, and omcF from Δgsu1771 biofilms compared to those from WT, also the overexpression of the epsH gene, which is involved in exopolysaccharide synthesis. Although we observed that for the Δgsu1771 mutant strain, the associated redox processes are similar to the WT strain, and more current is produced, we think that this could be associated with a higher relative expression of certain genes involved in EET and in the production of exopolysaccharides despite the chemical environment where the biofilm develops. This study supports that G. sulfurreducens is capable of adapting to the electrochemical environment where it grows.

Water research • 2025

Bioelectrochemical systems (BES) is a promising strategy for azo dyes decolorization enhancement in carbon-limited condition, but decolorization products need further aerobic mineralization. Here, a counter-diffusion biofilm-supported BES (E-MABR) was designed to achieve the decolorization, mineralization and denitrogenation of Alizarin Yellow R (AYR) in electron-deficient wastewater. The introduction of electrodes facilitated the secretion of extracellular polymeric substances (EPS), particularly proteins (PN), whose content in the cathodic biofilm was 2.5 ± 0.2 times higher than that in the MABR. Additionally, electrical stimulation enriched electroactivity bacteria (e.g. Geobacter) and azo dyes metabolism contributor (e.g., Thauera and Dechloromonas), and significantly upregulated the expression of decolorization-related genes, particularly azoR (1.2 log 2 ) in the cathodic biofilm. The increased β-sheet proportions of protein structures in the anode (22.2 ± 1.5 %) and cathode (20.1 ± 1.7 %) promoted the exposure of hydrophobic groups in amino acid; consequently, more hydrogen bonds formed, leading to stronger hydrophobic interactions in molecular dynamic simulations. Under the electric field stress, the total binding free energy between azoR and AYR declined to -32.6 kJ·mol⁻¹, enhancing the stability of the complex and creating a favourable environment for AYR degradation. Finally, under carbon-limiting conditions, E-MABR significantly promoted AYR decolorization efficiency, mineralization efficiency, and total nitrogen removal by 32.4 ± 2.3 %, 29.4 ± 3.6 %, and 18.4 ± 2.0 %, respectively, compared to MABR.

Bioelectrochemistry (Amsterdam, Netherlands) • 2025

Mature Geobacter sulfurreducens biofilms cultivated at two distinct anode potentials, representing unlimited and limited electron acceptor availability, were subjected to different acetate concentrations in a continuous reactor system. The Nernst-Michaelis-Menten equation, being modified to consider the conditions of a continuous stirred-tank reactor, was applied to analyze the acetate uptake kinetics. For the first time, the kinetics of pure G. sulfurreducens biofilms based on quantification of the acetate consumption were determined. Acetate uptake parameters (K M,Ac = 1.41 ± 0.42 mM, v max,Ac = 1.10 ± 0.12 mmolAc - h -1 g DW -1 , n = 4) obtained from cultivation at 0.4 V (vs. SHE), showed significant differences compared to an approach that derived acetate uptake parameters from the current production. This deviation is likely related to the coulombic efficiency, which exhibited a dependence on the acetate concentration. The coulombic efficiency was 30-50 % for acetate concentrations <1 mM, and saturated at 78.6 ± 4.0 % for more than 2 mM acetate. Despite the Nernst-Michaelis-Menten equation being developed to cover limiting terminal electron acceptor conditions, its application to biofilms cultivated at -0.1 V yielded contradictory results indicating application limits. Considering the complexity and plasticity of acetate uptake kinetics together with the complex extracellular electron transfer machinery, Geobacter sulfurreducens biofilms are a model system that is shown to provide unexpected challenges and demanding highly controlled experimental conditions.