Electron Uptake Research Articles

A large π-conjugated tetrakis (4-carboxyphenyl) porphyrin anode enables high specific capacity and superior cycling stability in lithium-ion batteries.

We demonstrated a novel single molecule - tetrakis(4-carboxyphenyl) porphyrin (TCPP) with a large π-conjugated system as a high-performance organic anode of lithium batteries. It was found that this TCPP displayed relatively low solubility (<0.1 mg mL-1) in a 1 M LiDFOB/PC electrolyte, high reversible specific capacity (ca. 1200 mA h g-1 at 358 mA g-1), excellent rate capability (548.4 mA h g-1 at 8 A g-1) and superior cycling performance (capacity retention of 89% after 2500 cycles at 6 A g-1).

Extracellular electron uptake from carbon-based π electron surface-donors: oxidation of graphite sheets by Sulfobacillus thermosulfidooxidans probed by Raman and FTIR spectroscopies.

In this work we report Raman and FTIR evidence for extracellular electron uptake by Sulfobacillus thermosulfidooxidans from the solid phase carbon-based π-electron donor surface of graphite sheets. The primary step in the reaction is the intercalation of water on the surface of graphite followed by the formation of EPS and proceeds to form graphite oxide (GO) with a Raman ID/IG = 0.3 ratio which represents the highest defect content in the carbon lattice reported by bio-oxidation process. We propose and discuss a direct extracellular electron transfer mechanism via outer membrane redox proteins for the electron transfer.

An Acetobacterium strain isolated with metallic iron as electron donor enhances iron corrosion by a similar mechanism as Sporomusa sphaeroides.

Sporomusa sphaeroides related strains are to date the only homoacetogens known to increase metallic iron corrosion. The goal of this work was to isolate additional homoacetogenic bacteria capable of using Fe(0) as electron donor and to explore their extracellular electron transfer mechanism. Enrichments were started from anoxic corrosion products and yielded Acetobacterium as main homoacetogenic genus. Isolations were performed with a new procedure using plates with a Fe(0) powder top layer. An Acetobacterium strain, closely related to A. malicum and A. wieringae, was isolated, in addition to a S. sphaeroides strain. The Acetobacterium isolate significantly increased Fe(0) corrosion ((1.44 ± 0.16)-fold) compared to abiotic controls. The increase of corrosion by type strains ranged from (1.28 ± 0.13)-fold for A. woodii to (2.03 ± 0.22)-fold for S. sphaeroides. Hydrogen mediated the electron uptake from Fe(0) by the acetogenic isolates and tested type strains. Exchange of the medium and SEM imaging suggested that cells were attached to Fe(0). The corrosion enhancement mechanism is for all tested strains likely related to free extracellular components catalyzing hydrogen formation on the Fe(0) surface, or to the maintenance of low hydrogen concentrations on the Fe(0) surface by attached cells thereby thermodynamically favoring hydrogen formation.

Electrode Potential Dependency of Single-Cell Activity Identifies the Energetics of Slow Microbial Electron Uptake Process.

Electrochemical measurements have been widely applied to study microbial extracellular electron transport processes. However, because electrochemistry detects not only microbial electron transport but also other reactions, background signals comparable to or larger than microbial ones hamper the identification of microbial electrochemical properties. This problem is crucial especially for the detection of electron uptake processes by slow-growing microbes in low-energy subsurface sediments, as the environmental samples contain electrochemically active humus and mineral particles. In this study, we report a cell-specific stable isotope analysis to quantify the electrode potential dependency of anabolic activity in individual cells for identifying the electron uptake energetics of slow-growing bacteria. Followed by the incubation of Desulfovibrio ferrophilus IS5 cells with isotopic 15N-ammonium as the sole N source on electrodes poised at potentials of -0.2, -0.3, -0.4, and -0.5 V [vs. standard hydrogen electrode (SHE)], we conducted nanoscale secondary ion mass spectroscopy (NanoSIMS) to quantify 15N assimilation in more than 100 individual cells on the electrodes. We observed significant 15N assimilation at potentials of -0.4 and more 15N assimilation at -0.5 V, which is consistent with the onset potential for electron uptake via outer-membrane cytochromes (OMCs). The activation of cell energy metabolism was further examined by transcriptome analysis. Our results showed a novel methodology to study microbial electron uptake energetics. The results also serve as the first direct evidence that energy acquisition is coupled to the electron uptake process in sulfate-reducing bacteria that are ubiquitous in the subsurface environments, with implications on the electron-fueled subsurface biosphere hypothesis and other microbial processes, such as anaerobic iron corrosion and anaerobic methane oxidation.

A Novel Shewanella Isolate Enhances Corrosion by Using Metallic Iron as the Electron Donor with Fumarate as the Electron Acceptor.

The involvement of Shewanella spp. in biocorrosion is often attributed to their Fe(III)-reducing properties, but they could also affect corrosion by using metallic iron as an electron donor. Previously, we isolated Shewanella strain 4t3-1-2LB from an acetogenic community enriched with Fe(0) as the sole electron donor. Here, we investigated its use of Fe(0) as an electron donor with fumarate as an electron acceptor and explored its corrosion-enhancing mechanism. Without Fe(0), strain 4t3-1-2LB fermented fumarate to succinate and CO2, as was shown by the reaction stoichiometry and pH. With Fe(0), strain 4t3-1-2LB completely reduced fumarate to succinate and increased the Fe(0) corrosion rate (7.0 ± 0.6)-fold in comparison to that of abiotic controls (based on the succinate-versus-abiotic hydrogen formation rate). Fumarate reduction by strain 4t3-1-2LB was, at least in part, supported by chemical hydrogen formation on Fe(0). Filter-sterilized spent medium increased the hydrogen generation rate only 1.5-fold, and thus extracellular hydrogenase enzymes appear to be insufficient to explain the enhanced corrosion rate. Electrochemical measurements suggested that strain 4t3-1-2LB did not excrete dissolved redox mediators. Exchanging the medium and scanning electron microscopy (SEM) imaging indicated that cells were attached to Fe(0). It is possible that strain 4t3-1-2LB used a direct mechanism to withdraw electrons from Fe(0) or favored chemical hydrogen formation on Fe(0) through maintaining low hydrogen concentrations. In coculture with an Acetobacterium strain, strain 4t3-1-2LB did not enhance acetogenesis from Fe(0). This work describes a strong corrosion enhancement by a Shewanella strain through its use of Fe(0) as an electron donor and provides insights into its corrosion-enhancing mechanism.IMPORTANCEShewanella spp. are frequently found on corroded metal structures. Their role in microbial influenced corrosion has been attributed mainly to their Fe(III)-reducing properties and, therefore, has been studied with the addition of an electron donor (lactate). Shewanella spp., however, can also use solid electron donors, such as cathodes and potentially Fe(0). In this work, we show that the electron acceptor fumarate supported the use of Fe(0) as the electron donor by Shewanella strain 4t3-1-2LB, which caused a (7.0 ± 0.6)-fold increase of the corrosion rate. The corrosion-enhancing mechanism likely involved cell surface-associated components in direct contact with the Fe(0) surface or maintenance of low hydrogen levels by attached cells, thereby favoring chemical hydrogen formation by Fe(0). This work sheds new light on the role of Shewanella spp. in biocorrosion, while the insights into the corrosion-enhancing mechanism contribute to the understanding of extracellular electron uptake processes.

The Electrochemically Active Arsenic Oxidising Bacterium Ancylobacter sp. TS‐1

AbstractThe study of electrochemically active microorganisms (EAMs) has revealed the metabolic versatility of chemolithoautotrophic microorganisms in bioelectrochemical systems (BESs). However, direct electron uptake from electrodes to support bacterial growth has been suggested only for the iron oxidiser Mariprofundus ferrooxydans, the sulfur oxidiser bacterium Thiobacillus denitrificans and the iron/sulfur oxidiser Acidithiobacillus ferrooxidans. To the best of our knowledge, chemolithoautotrophic arsenite oxidisers (CAOs) have not been reported as biocathodic EAM. This paper studies the electrochemical activity of Ancylobacter sp. TS‐1, a new CAO. The electrochemical capacity of TS‐1 was evidenced by linear sweep voltammetry tests, revealing a peak of cathodic current dependent on biomass concentration at −500 mV (vs. Ag/AgCl, at pH 7.2); and by chronoamperometry, showing an increase in the cathodic current over time. Cathodic currents obtained for TS‐1 (9.5±2.4 μA/cm2) are comparable with values previously reported for A. ferrooxidans (∼27 μA/cm2) and M. ferrooxydans (∼8 μA/cm2). Scanning electron micrographs show TS‐1 cells on electrodes during the chronoamperometry, suggesting biofilm development of strain TS‐1 when using the cathode only as an electron donor. Hence, TS‐1 not only enlarges the list of known biocathodic EAMs, but also paves the way for novel BES applications on arsenic electro‐bioaugmentation and bioremediation.

Diruthenium Complexes of p-Benzoquinone-Imidazole Hybrid Ligands: Innocent or Noninnocent Behavior of the Quinone Moiety.

After double deprotonation, 2,6-diaryl-p-benzoquinonodiimidazoles (aryl=4-tolyl (I) or 2-pyridyl (II)) were shown to bridge two [Ru(bpy)2 ]2+ (bpy=2,2'-bipyridine) complex fragments through the imidazolate N and p-quinone O (I→12+ ) or through the imidazolate N and pyridyl N donor atoms (II→22+ ). Characterization by crystal structure analysis, 1 H/13 C NMR spectroscopy, cyclic and differential pulse voltammetry, and spectroelectrochemistry (UV/Vis/NIR, IR, EPR) in combination with TD-DFT calculations revealed surprisingly different electronic structures for redox systems 1n and 2n . Whereas 12+ is reduced to a radical complex with considerable semiquinone character, the reduction of 22+ with its exclusive N coordination exhibits little spin on the now redox-innocent quinone moiety, compared with the electron uptake by the pyridyl-imidazolate chelating site. The first of two close-lying oxidation processes occurs at the bridging heteroquinone ligand, whereas the second oxidation is partly (14+ ) or predominantly (24+ ) centered on the metal atoms.

Algal biomass derived biochar anode for efficient extracellular electron uptake from Shewanella oneidensis MR-1

The development of cost-effective and highly efficient anode materials for extracellular electron uptake is important to improve the electricity generation of bioelectrochemical systems. An effective approach to mitigate harmful algal bloom (HAB) is mechanical harvesting of algal biomass, thus subsequent processing for the collected algal biomass is desired. In this study, a low-cost biochar derived from algal biomass via pyrolysis was utilized as an anode material for efficient electron uptake. Electrochemical properties of the algal biochar and graphite plate electrodes were characterized in a bioelectrochemical system (BES). Compared with graphite plate electrode, the algal biochar electrode could effectively utilize both indirect and direct electron transfer pathways for current production, and showed stronger electrochemical response and better adsorption of redox mediators. The maximum current density of algal biochar anode was about 4.1 times higher than graphite plate anode in BES. This work provides an application potential for collected HAB to develop a cost-effective anode material for efficient extracellular electron uptake in BES and to achieve waste resource utilization.

Sulfate-Reducing ElectroAutotrophs and Their Applications in Bioelectrochemical Systems

Electroautotrophs are microbes able to perform different biocathodic reactions by using CO2 as sole carbon source and electrochemical reducing power as a sole energy source. Electroautotrophy has been discovered in several groups of microorganisms, including iron-oxidizing bacteria, iron-reducing bacteria, nitrate-reducing bacteria, acetogens, methanogens and sulfate-reducing bacteria. The high diversity of electroautrophs results in a wide range of Bioelectrochemical Systems (BES) applications, ranging from bioproduction to bioremediation. In the last decade, particular research attention has been devoted towards the discovery, characterization and application of acetogenic and methanogenic electroautotrophs. Less attention has been given to autotrophic sulfate-reducing microorganisms, which are extremely interesting biocatalysts for multiple BES technologies, with concomitant CO2 fixation. They can accomplish water sulfate removal, hydrogen production and, in some case, even biochemicals production. This mini-review gives a journey into electroautotrophic ability of sulfate-reducing bacteria and highlights their possible importance for biosustainable applications. More specifically, general metabolic features of autotrophic sulfate reducers are introduced. Recently discovered strains able to perform extracellular electron uptake and possible molecular mechanisms behind this electron transfer capacity are explored. Finally, BES technologies based on sulfate-reducing electroautotrophs are illustrated.

An insoluble iron complex coated cathode enhances direct electron uptake by Rhodopseudomonas palustris TIE-1

Microbial electrosynthesis (MES) is a promising bioelectrochemical approach to produce biochemicals. A previous study showed that Rhodopseudomonas palustris TIE-1 can directly use poised electrodes as electron donors for photoautotrophic growth at cathodic potentials that avoid electrolytic H2 production (photoelectroautotrophy). To make TIE-1 an effective biocatalyst for MES, we need to improve its electron uptake ability and growth under photoelectroautotrophic conditions. Because TIE-1 interacts with various forms of iron while using it as a source of electrons for photoautotrophy (photoferroautotrophy), we tested the ability of iron-based redox mediators to enhance direct electron uptake. Our data show that soluble iron cannot act as a redox mediator for electron uptake by TIE-1 from a cathode poised at +100mV vs. Standard Hydrogen electrode. We then tested whether an immobilized iron-based redox mediator Prussian blue (PB) can enhance electron uptake by TIE-1. Chronoamperometry indicates that cathodic current uptake by TIE-1 increased from 1.47±0.04 to 5.6±0.09μA/cm2 (3.8 times). Overall, our data show that immobilized PB can enhance direct electron uptake by TIE-1.

Tracking Electron Uptake from a Cathode into Shewanella Cells: Implications for Energy Acquisition from Solid-Substrate Electron Donors.

ABSTRACTWhile typically investigated as a microorganism capable of extracellular electron transfer to minerals or anodes, Shewanella oneidensis MR-1 can also facilitate electron flow from a cathode to terminal electron acceptors, such as fumarate or oxygen, thereby providing a model system for a process that has significant environmental and technological implications. This work demonstrates that cathodic electrons enter the electron transport chain of S. oneidensis when oxygen is used as the terminal electron acceptor. The effect of electron transport chain inhibitors suggested that a proton gradient is generated during cathode oxidation, consistent with the higher cellular ATP levels measured in cathode-respiring cells than in controls. Cathode oxidation also correlated with an increase in the cellular redox (NADH/FMNH2) pool determined with a bioluminescence assay, a proton uncoupler, and a mutant of proton-pumping NADH oxidase complex I. This work suggested that the generation of NADH/FMNH2 under cathodic conditions was linked to reverse electron flow mediated by complex I. A decrease in cathodic electron uptake was observed in various mutant strains, including those lacking the extracellular electron transfer components necessary for anodic-current generation. While no cell growth was observed under these conditions, here we show that cathode oxidation is linked to cellular energy acquisition, resulting in a quantifiable reduction in the cellular decay rate. This work highlights a potential mechanism for cell survival and/or persistence on cathodes, which might extend to environments where growth and division are severely limited.

Enhanced electrosynthesis performance of Moorella thermoautotrophica by improving cell permeability

Microbial electrosynthesis systems (MES) are promising devices in which microbes obtain electrons from electrodes to produce extracellular multicarbon compounds. This study investigates whether improvement in cell permeability can enhance electrosynthesis performance of Gram-positive Moorella thermoautotrophica in MES. Results showed that when ≤30mg/L penicillin was added, the cell permeability was doubled, and the electron uptake per biomass (including both cathode-associated biomass and suspended biomass) was 1.84 times that of the control, while formate and acetate production rates per biomass were 1.96 and 2.23 times those of the control, respectively. Enhanced cell permeability caused higher redox activities of outmost cytochrome C and increased release of redox electron shuttles, both of which were beneficial to extracellular electron uptake. Coulombic efficiencies increased from 73%±3% to 88%±3% with better cell permeability, demonstrating that higher proportion of electrical energy recovered in the chemical-production reaction. This research demonstrates that making a moderate decrease in peptidoglycan of cell walls to improve cell permeability can enhance electron uptakes and chemical production rates of Gram-positive microbes in MES, which would serve as a base for the future genetic modification study of superior electrosynthesis strains.

Electron transfer mechanism of biocathode in a bioelectrochemical system coupled with chemical absorption for NO removal

A biocathode with the function of Fe(III)EDTA and Fe(II)EDTA-NO reduction was applied in a microbial electrolysis cell coupled with chemical absorption for NO removal from flue gas. As the mediated electron transfer was excluded by the same electrochemical characterizations of the biocathodes before and after a 48 h continuous operation, the profiles of reduction experiments indicated that direct electron transfer was the main mechanism of Fe(III)EDTA reduction, while Fe(III)EDTA-NO was mainly reduced via Fe(II)-assisted autotrophic denitrification. The microscopy of the biocathode confirmed the existence of pili, which was supposed to be bacterial nanowires for electron transfer. The analysis of microbial community revealed that iron-reducing bacteria, including Escherichia coli, had the possibility of electron uptake from electrode via physical contact. These results first time gave us in-depth understanding of the electron transfer in the multifunctional biocathode and mechanism for further enhancement of the bioreduction processes.

Mediator-free enzymatic electrosynthesis of formate by the Methanococcus maripaludis heterodisulfide reductase supercomplex

Electrosynthesis of formate is a promising technology to convert CO2 and electricity from renewable sources into a biocompatible, soluble, non-flammable, and easily storable compound. In the model methanogen Methanococcus maripaludis, uptake of cathodic electrons was shown to proceed indirectly via formation of formate or H2 by undefined, cell-derived enzymes. Here, we identified that the multi-enzyme heterodisulfide reductase supercomplex (Hdr-SC) of M. maripaludis is capable of direct electron uptake and catalyzes rapid H2 and formate formation in electrochemical reactors (−800 mV vs Ag/AgCl) and in Fe(0) corrosion assays. In Fe(0) corrosion assays and electrochemical reactors, purified Hdr-SC primarily catalyzed CO2 reduction to formate with a coulombic efficiency of 90% in the electrochemical cells for 5 days. Thus, this report identified the first enzyme that stably catalyzes the mediator-free electrochemical reduction of CO2 to formate, which can serve as the basis of an enzyme electrode for sustained electrochemical production of formate.

Appending Diverse π-Extended Acceptors with Tetrathiafulvalene/Dithiafulvalene Donors: Multistate Redox Properties, Radical Ion Generation, and Mid-IR-Absorbing Mixed-Valence States.

Three classes of donor-acceptor (D-A) π-extended chromophores (1-12) were synthesized through a phosphite-mediated cross-coupling reaction, in which the anhydride- or imide-based π-As and number of tetrathiafulvalene (TTF)/dithiafulvalene (DTF) Ds were systematically changed. Large π rings, such as benzoperylene and coronene, were integrated into the TTF/DTF unit, for the first time, to overcome their high insolubility. The anhydride and imide groups in the π acceptors can significantly alter the frontier orbitals and influence the optoelectronic properties. The D moieties allow the formation of radical cations (D.+ ) and the π-extended A moieties aid the formation of radical anions (A.- ) by oxidation/reduction under ambient conditions. The molecules revealed UV/Vis/near-IR absorption, fluorescence extending into the near-IR region, and amphoteric electrochemical properties. Chromophores 10 and 12 show solvatochromism in a wide range of solvents. The π-As with anhydride functionality allow easier electron uptake, relative to the imide groups, whereas the increasing number of D TTF/DTF units make them easy to oxidize. Interestingly, the trans-TTF-fused molecules (1, 6, and 11) exhibited a mixed-valence state in the mid-IR region (ν˜ =5130-4000 cm-1 ). Moderate electron coupling between the redox centers is inferred to the compounds being of Robin-Day class II. The multistate redox activity along with panchromism and near-/mid-IR optical absorption of these systems can be attractive towards advanced switchable materials.

Nitrogen-doped carbon black supported NiCo2S4 catalyst for hydrogenation of nitrophenols under mild conditions

Catalytic hydrogenation of nitrophenols to aminophenols was considered as the most efficient way to solve their contamination together with huge economic benefit. NiCo2S4 can be used not only as supercapacitor materials, but also competitive catalytic materials in hydrogenation reactions. In this work, a nitrogen-doped carbon black (NCB) supported NiCo2S4 catalyst is successfully prepared by a facile one-pot solvothermal approach. TEM results show that the ultrafine NiCo2S4 particles are uniformly dispersed on the surface of NCB at a low NiCo2S4 loading, while aggregation may occur in NiCo2S4/NCB catalysts with an excessive NiCo2S4 content. The NiCo2S4-30/NCB catalyst with a BET surface area of 47.20 m2 g−1 exhibits the most excellent catalytic activity and durability for heterogeneous catalytic hydrogenation of nitrophenols using NaBH4 as the reducing agent at 30 °C in the aqueous solution. The kinetic constant of hydrogenation of p-nitrophenol catalyzed by NiCo2S4-30/NCB is almost five times higher than the reaction catalyzed by pristine NiCo2S4. The outstanding performance of NiCo2S4-30/NCB is ascribed to the unique nanostructure of the catalyst and the combined effect between the NiCo2S4 and NCB, including abundant surface functional groups of NCB for anchoring and dispersing NiCo2S4, strong adsorption ability for nitrophenol molecules facilitated by π–π stacking interaction, as well as fast electron transfer from NCB to NiCo2S4, resulting in higher local electron densities and thus facilitating the uptake of electrons by nitrophenols.

Interfacial mass storage in nanocomposites

The most significant electrochemical storage systems are insertion batteries in which the electrode function relies on the uptake of lithium (or sodium) ions and electrons by the electroactive phase. This short review considers the case of interfacial storage and focuses on abrupt junctions. The materials space may be substantially extended and the rate performance substantially enhanced by using job-sharing composites in which the Li+ (or Na+) are stored in one and the e− in the other phase. Literature examples relying on such a mode are reviewed. Thermodynamics and kinetics of such space charge storage are discussed and the discussion embedded in the more general context of storage in mixed conductors which includes both bulk and space charge zones. In this way a deeper understanding of storage in nanosystems, the behavior of passivation layers as well as transfer and transport kinetics of battery systems is achieved.

Impact of Antibiotics Pretreatment on Bioelectrochemical CH4 Production

Methane (CH4)-producing bioelectrochemical systems (BES) are an attractive way to store excess renewable electricity and captured CO2. Studies have suggested that methanogenesis via direct electron uptake from a biocathode is more energetically efficient than hydrogenotrophic methanogenesis. However, mechanisms and key microorganisms involved in direct electron uptake remain unclear, primarily because of H2 produced by bacteria or extracellular hydrogenases in the system. In an attempt to minimize biological H2 production and enrich for methanogens that could efficiently convert electrons from the cathode surface to CH4, cathode chambers were pretreated with antibiotics targeting bacteria. We found that antibiotics pretreatment effectively reduced the proportion of H2-producing bacteria and H2-utilizing methanogens associated with the biocathode biofilm, and significantly promoted growth of acetoclastic methanogens from the genera Methanosarcina and Methanosaeta, several of which are known to participate ...

Thermophilic Moorella thermoautotrophica-immobilized cathode enhanced microbial electrosynthesis of acetate and formate from CO2

Microbial electrosynthesis (MES) is a promising technique that converts electricity and CO2 to biofuels using microbes as the catalysts. However, most of previous MES are conducted at mesophilic temperatures and challenged by low performances. Here we report a significant electrosynthesis performance enhancement via immobilization of a thermophilic microbe to cathodes. A temperature-dependent electron uptake rate of Moorella thermoautotrophica was observed at a cathode potential of −0.4V (vs. SHE), with a maximum current density of 63.47mAm−2 at 55°C. Moreover, electrosynthesis rates of formate and acetate at 55°C were accelerated by 23.2 and 2.8 fold than those of 25°C, respectively. Compared with natural biofilms, immobilization of M. thermoautotrophica with carbon nanoparticles to electrodes further enhanced acetate and formate production rates (by 14 and 7.9 fold), reaching 58.2 and 63.2mmolm−2day−1 at a coulombic efficiency of 65%, respectively. To our best knowledge, these are the highest electrosynthesis rates obtained thus far for pure cultures under the conditions of −0.4V (vs. SHE) and 55°C. This study, for the first time, demonstrates that embedding microbes to electrodes by carbon nanoparticles is a facile and efficient method of improving MES performance.

Cooperative growth of Geobacter sulfurreducens and Clostridium pasteurianum with subsequent metabolic shift in glycerol fermentation

Interspecies electron transfer is a common way to couple metabolic energy balances between different species in mixed culture consortia. Direct interspecies electron transfer (DIET) mechanism has been recently characterised with Geobacter species which couple the electron balance with other species through physical contacts. Using this mechanism could be an efficient and cost-effective way to directly control redox balances in co-culture fermentation. The present study deals with a co-culture of Geobacter sulfurreducens and Clostridium pasteurianum during glycerol fermentation. As a result, it was shown that Geobacter sulfurreducens was able to grow using Clostridium pasteurianum as sole electron acceptor. C. pasteurianum metabolic pattern was significantly altered towards improved 1,3-propanediol and butyrate production (+37% and +38% resp.) at the expense of butanol and ethanol production (−16% and −20% resp.). This metabolic shift was clearly induced by a small electron uptake that represented less than 0.6% of the electrons consumed by C. pasteurianum. A non-linear relationship was found between G. sulfurreducens growth (i.e the electrons transferred between the two species) and the changes in C. pasteurianum metabolite distribution. This study opens up new possibilities for controlling and increasing specificity in mixed culture fermentation.