Self-assembled FeS-Clostridium ljungdahlii biohybrid boost chemicals production in microbial electrosynthesis.

Quantitative analysis of ion crossover in bacterial cellulose membranes separating diffusion behaviour from membrane thickness effects.

Coupling anodic Congo red oxidization with cathodic microbial CO2-reduction for energy-efficient microbial electrosynthesis of acetate

Increased atmospheric carbon dioxide (CO2) emissions in the atmosphere due to excessive usage of fossil fuels, rapid industrial development and human growth have raised a global interest in the greenhouse effect. CO2 conversion is important not just because it is a greenhouse gas that causes a variety of climate consequences, but also because it is the most abundant source of valuable organic chemicals. Upgrading CO2 into valuable chemicals and materials offers a pathway toward net-zero or even carbon-negative production of fuels, pharmaceuticals, alcohols, plastics, etc. However, current CO2 conversion technologies have the problems of high operational costs, high energy consumption, limited to a few-carbon products, and a risk of secondary pollutants. Microbial electrosynthesis (MES) is a novel microbial electrochemical technology that integrates the metabolic activities or genetic behaviour of microorganisms on electrodes to convert CO2 into organics with electrical energy input. Recent developments in electrode and reactor design, synthetic biology-based strain engineering, and genetic engineering have enhanced the production rates and selectivity of MES. This review explores the transformative potential and recent progress of MES with CO2 upgrading strategies, aiming to identify the determinants of the process and its future research directions.It also highlights the current challenges of MES related to upscaling, long-term stability, selecting optimal microbial strains, achieving net-negative carbon emissions, and other operational limitations that need to be addressed for commercial viability.

Coupling microbial electrosynthesis and chain elongation for simultaneous biomethane upgrading and carboxylate recovery: A tunable carbon valorization strategy.

Bioanode-driven microbial electrosynthesis enhances CO2-to-methane conversion rates under galvanostatic operation

Cyclic adenosine monophosphate (cAMP) signaling reprograms extracellular electron transfer of Shewanella oneidensis.

Microbial electrosynthesis is a metabolic process in which extracellular electrons are utilized as the primary energy source for carbon fixation. While microbial electrosynthesis has been proposed as a novel concept for ecological primary production, our understanding of how such microorganisms are distributed in natural environments remains limited. In this study, we constructed a laboratory-scale electrochemical cultivation system that simulates electric discharge conditions in deep-sea hydrothermal fields. Microscopic counts revealed increased cell numbers in the electrochemical culture, and 16S rRNA gene analysis revealed a significant enrichment of a novel Thiomicrorhabdus species. Quantitative PCR confirmed proliferation and enrichment of a metagenome-assembled genome (MAG), named the SREC-4. Electrochemical cultivation with 13C-labeled CO₂ as a substrate indicated significant 13C incorporation specifically in Thiomicrorhabdus cells including MAG SREC-4. The genome of MAG SREC-4 revealed the possession of the putative extracellular electron uptake pathway in addition to the autotrophic sulfur-oxidizing aerobic respiration pathways typically found in Thiomicrorhabdus members. The putative extracellular electron uptake pathway was found in a phylogenetic clade in Thiomicrorhabdus mainly formed by strains derived from hydrothermal fields. These results provide the direct experimental evidence from enrichment cultures derived from hydrothermal fields that an organism inhabiting deep-sea hydrothermal fields can grow electrosynthetically, and suggest that this ability is shared by other Thiomicrorhabdus species, specifically those found in similar environments. This finding suggests electrosynthetic growth may be widely distributed in Thiomicrorhabdus populations dwelling in deep-sea hydrothermal fields, the largest natural electrogenic environment on Earth.

Electroactive bimetallic CoNi and CNT modified carbon felt cathode promotes microbial CO2 electroreduction.

Microbial electrosynthesis (MES) enables a variety of microorganisms, particularly acetogens, to utilize electrical energy in the form of electrons to produce valuable compounds from CO2. In the closely related process of gas fermentation, hydrogen gas (H2) is provided as the energy source, whereas in MES, H2 is produced insitu via water electrolysis. Despite the potential of MES for energy and carbon storage, it still faces major limitations, like low efficiency and low-value products. Here, we identify key limitations of the model MES biocatalyst Clostridium ljungdahlii through comparative transcriptomics, proteomics, and electron microscopy in both processes. We show that cell integrity is severely impaired in MES, consistent with membrane depolarization hampering ATP synthesis. The struggle for ATP is compensated for by activating arginine catabolism to produce ATP, a reaction that is likely fueled by cyanophycin degradation. Diversion of the Wood-Ljungdahl pathway toward the glycine synthase-reductase pathway (GSRP) resulted in a broader spectrum of reduced products, including the two amino compounds ethanolamine and glycine, which appeared exclusively under the electrochemical environment. Additionally, we observed strong induction of bacterial microcompartments, raising questions about their role during MES. This work demonstrates that MES drives C. ljungdahlii into a distinct physiological state that challenges cellular fitness and expands our understanding of MES.

New insights into the interplay between chain elongation and homoacetogenesis in microbial electrosynthesis: Chloroform-enhanced medium-chain carboxylate production.

Microbial electrosynthesis of methane in an up-scaled zero-gap cell.

Bioelectrochemical systems (BES), including microbial electrosynthesis (MES), represent a sustainable route for carbon recycling through CO2 electroreduction driven by electroactive microorganisms. However, their performance is often limited by sluggish cathodic reactions and the high cost of efficient electrodes. Nitrogen-rich biochar obtained from biomass provides a low-cost, conductive, and porous matrix with abundant active sites, making it suitable for enhancing electron transfer and catalytic activity. In this study, two biomass precursors with distinct nitrogen contents-hazelnut shells (HZS, low N) and urban green waste (UGW, high N)-were screened for biochar electrode production. Physicochemical and electrochemical analyses identified UGW as the most promising feedstock. The pyrolysis and activation processes were optimized by tuning temperature, residence time, and activation strategies (KOH and CO2 flow) to maximize nitrogen retention up to 2.90wt% and porosity in the 450-613 m2g-1 range. The resulting UGW-derived biochar exhibited partially graphitized, nitrogen-enriched structures with high activity for oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and CO2 electroreduction under near-neutral conditions. When used as cathodes in MES cells, these materials promoted enhanced CO2 fixation and supported microbial communities dominated by Clostridiaceae and Eubacteriaceae, achieving average current densities of around 0.20mA cm-2 over 21-day chronoamperometric tests, consistently higher than those of the biochar-free control. These results highlight UGW-derived nitrogen-rich biochars as sustainable cathode materials enabling efficient CO2 electroreduction and MES for circular carbon utilization.

Bridging inner membrane and periplasm in Geobacter sulfurreducens: structural and biochemical insights into CbcA and its redox partners.

Biogenic FeS Reshapes microbial interactions to regulate acetogenesis in CO2-Fed microbial electrosynthesis.

Microbial electro synthesis from CO2 and methanol — methanol-assisted microbial electrosynthesis

Optimizing pH for acetate production in saline photo-assisted microbial electrosynthesis: Roles of EPS and metabolic regulation.

The efficient production of C4 compounds (e.g., butyrate) from CO2 in microbial electrosynthesis (MES) systems faces persistent challenges. This study employed an annular double-chamber MES reactor with ethanol as electron donor to systematically investigate chemicals generation under three controlled currents (50mA, 100mA, and 150mA). The results showed MES with 50mA can produce the highest butyrate concentrations of 8.7g/L with average yield of 0.62g/L/d, and its electron recovery efficiency reached a maximum of 94.4%. In contrast, acetate became the primary product in MES at 100mA and 150mA. The elevated abundance of Clostridium_sensu_stricto_12 correlates with enhanced butyrate synthesis under 50mA. Low current (50mA) combined with minimized electrode spacing in a DC-powered annular double-chamber reactor significantly enhances C4 production efficiency. This study provides a new strategy for generating long carbon chain chemicals in MES.

CO 2 conversion into fuels and chemicals with a Power to X like microbial electrosynthesis reactor (MES) is promising. The overpotential or energy loss in the electron uptake in experimental works with Sporomusa ovata appears high and modelling was attempted to determine theoretical overpotential and kinetics. A key parameter to deduce upfront was the unknown redox potential of the electron uptake system. Both parameters were determined in Nernstian-Tafel inspired modelling. The analysis started with recording an experimental reductive j-E curve incorporating potential loss transforming CO 2 into acetate with Sporomusa ovata by voltammetry. It was combined with an ideal Nernstian j-E curve (free of potential losses). The estimated redox potential of the electron uptake system was developed and found to be E RSys = 0.12 V Ag/AgCl (3 M KCl) indicating a cytochrome b or c (or another compound). The new fitting method was validated by Shewanella oneidenis parametrisation. The difference between the j-E curves led to a theoretical overpotential of η ′ = −0.29 V for acetogenesis with Sporomusa ovata . Tafel parameters were derived with a slope b = 0.186 V/decade ( R = 0.996) indicating a complex reaction, an exchange current j o = 0.065 μA/cm 2 , and a symmetry factor of α = 0.68. Applied CO 2 to acetate transformations were performed in a 50 mL MES reactor for kinetic verification by overpotential switches between η ′ = −0.76 to −0.96 V vs Ag/AgCl (3 M KCl). Global Coulombic efficiencies suffered from non-faradaic losses but peaked up to 84%. The study showed the utility of potential loss modelling when working with an unknown electron uptake system to enhance the kinetic understanding in performance optimisation for microbial electrosynthesis. • Theoretical overpotential determination in microbial electrosynthesis • Redox potential estimation of unknown electron uptake system • Tafel parameters of the kinetics in microbial electrosynthesis • Verification of theoretical kinetic parameters in processing

Rapid enrichment of ternary carbon-fixing microbial consortia from anaerobic sludge via pressurized pre-autotrophic strategy for scalable microbial electrosynthesis.