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Successful practical implementation of bioelectrochemical systems (BES) requires developing affordable electrode structures that promote efficient electrical communication with microbes. Recent efforts have centered on immobilizing bacteria with organic semiconducting polymers on electrodes via electrochemical methods. This approach creates a fixed biocomposite that takes advantage of the increased electrode's electroactive surface area (EASA). Here, it is demonstrated that a biocomposite comprising the water‐soluble conjugated polyelectrolyte CPE‐K and electrogenic Shewanella oneidensis MR‐1 can self‐assemble with carbon paper electrodes, thereby increasing its biocurrent extraction by ≈6‐fold over control biofilms. A ≈1.5‐fold increment in biocurrent extraction is obtained for the biocomposite on carbon paper relative to the biocurrent extracted from gold‐coated counterparts. Electrochemical characterization revealed that the biocomposite stabilized with the carbon paper more quickly than atop flat gold electrodes. Cross‐sectional images show that the biocomposite infiltrates inhomogeneously into the porous carbon structure. Despite an incomplete penetration, the biocomposite can take advantage of the large EASA of the electrode via long‐range electron transport. These results show that previous success on gold electrode platforms can be improved when using more commercially viable and easily manipulated electrode materials. [ABSTRACT FROM AUTHOR]

Power generation and charge storage devices are commonly uncoupled when it comes to the design of materials relevant for their fabrication. Here, it is demonstrated that the biotic–abiotic composite comprising the self‐doped conjugated polyelectrolyte CPE‐K and electrogenic bacteria Shewanella oneidensis MR‐1 can reversibly switch its function between electrical current generation in chronoamperometry mode (≈150 mA m−2) and electrochemical energy storage as a pseudocapacitor with a specific capacitance of up to 80 F g−1. Interconversion of desirable properties for the different functions is achieved by the simple addition and removal of Mg2+ in the bulk electrolyte. Potentiostatic, galvanostatic, and electrochemical impedance spectroscopy characterization, accompanied by imaging and cell viability tests, indicate that the modulation of properties is a result of reversible changes in CPE‐K macrostructures and in the number of living bacteria within the composite. The results show the possibility to realize an "on‐demand" switch between current generation and charge storage by one integrated "living" material. [ABSTRACT FROM AUTHOR]

Interfacing bacteria as biocatalysts with an electrode provides the basis for emerging bioelectrochemical systems that enable sustainable energy interconversion between electrical and chemical energy. Electron transfer rates at the abiotic‐biotic interface are, however, often limited by poor electrical contacts and the intrinsically insulating cell membranes. Herein, we report the first example of an n‐type redox‐active conjugated oligoelectrolyte, namely COE‐NDI, which spontaneously intercalates into cell membranes and mimics the function of endogenous transmembrane electron transport proteins. The incorporation of COE‐NDI into Shewanella oneidensis MR‐1 cells amplifies current uptake from the electrode by 4‐fold, resulting in the enhanced bio‐electroreduction of fumarate to succinate. Moreover, COE‐NDI can serve as a "protein prosthetic" to rescue current uptake in non‐electrogenic knockout mutants. [ABSTRACT FROM AUTHOR]

Interfacing bacteria as biocatalysts with an electrode provides the basis for emerging bioelectrochemical systems that enable sustainable energy interconversion between electrical and chemical energy. Electron transfer rates at the abiotic‐biotic interface are, however, often limited by poor electrical contacts and the intrinsically insulating cell membranes. Herein, we report the first example of an n‐type redox‐active conjugated oligoelectrolyte, namely COE‐NDI, which spontaneously intercalates into cell membranes and mimics the function of endogenous transmembrane electron transport proteins. The incorporation of COE‐NDI into Shewanella oneidensis MR‐1 cells amplifies current uptake from the electrode by 4‐fold, resulting in the enhanced bio‐electroreduction of fumarate to succinate. Moreover, COE‐NDI can serve as a "protein prosthetic" to rescue current uptake in non‐electrogenic knockout mutants. [ABSTRACT FROM AUTHOR]

We probe anaerobic respiration of bacteria in the presence of conjugated polyelectrolytes (CPEs). Three different CPEs were used to probe how structural variations impact biocurrent generation from Shewanella oneidensis MR-1. For the self-doped anionic CPE only, absorption spectroscopy shows that the addition of S. oneidensis MR-1 leads to the disappearance of the polaron (radical cation) band at >900 nm and an increase in the band at 735 nm due to the neutral species, consistent with electron transfer from microbe to polymer. Microbial three-electrode electrochemical cells (M3Cs) show an increase in the current generated by S. oneidensis MR-1 with addition of the self-doped CPE relative to other CPEs and controls. These experiments combined with in situ cyclic voltammetry suggest that the doped CPE facilitates electron transport to electrodes and reveal structure-function relationships relevant to developing materials for biotic/abiotic interfaces. [ABSTRACT FROM AUTHOR]

We probe anaerobic respiration of bacteria in the presence of conjugated polyelectrolytes (CPEs). Three different CPEs were used to probe how structural variations impact biocurrent generation from Shewanella oneidensis MR-1. For the self-doped anionic CPE only, absorption spectroscopy shows that the addition of S. oneidensis MR-1 leads to the disappearance of the polaron (radical cation) band at >900 nm and an increase in the band at 735 nm due to the neutral species, consistent with electron transfer from microbe to polymer. Microbial three-electrode electrochemical cells (M3Cs) show an increase in the current generated by S. oneidensis MR-1 with addition of the self-doped CPE relative to other CPEs and controls. These experiments combined with in situ cyclic voltammetry suggest that the doped CPE facilitates electron transport to electrodes and reveal structure-function relationships relevant to developing materials for biotic/abiotic interfaces. [ABSTRACT FROM AUTHOR]

The high electrical conductivity and low dimensionality of graphene is essential for the development of novel lightweight bioanodes for new-generation energy technologies. However, the integration of graphene in biointerfaces presents a formidable challenge, especially because the surface energy of graphene is not compatible with living matter. Here we propose a sustainable chemical control method to reach the demanded surface hydrophilicity and conductivity of graphene nanowalls to form a lightweight, graphene-based, sponge bioanode. The few-nanometer–thick conductive graphene nanowalls create biocompatible hydrophilic microconfinements to harvest the biomass density of electrogenic Shewanella Oneidensis MR-1. The graphene-based bioanode shows a stable and rapid response with a steady-state biocurrent density of 135.35 mA m−2 realized within a few hours. Our novel and sustainable graphene-based material provides a revolutionary energy opportunity for the establishment of new energy-related graphene industries as well as facilitates many startups. A facile and chemical-free method was leveraged to produce the graphene-based bioanode. Balancing the hydrophilicity and conductivity of the graphene nanowalls was achieved by simply tuning its reduction temperature and was the first time, revealed to play an important role in the performance of the microbial electrode. A steady-state bio-current density of 135.35 mA m−2 was realized within a few hours and with long-term duration. [Display omitted] [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems (BESs) are emerging as a platform technology with great application potentials such as wastewater remediation and power generation. Materials for electrode/microorganism modification are being examined in order to improve the current production in BESs. Herein, we report that the current production increased almost one fold in single-chamber BES reactors, by adding a conjugated polyelectrolyte (CPE-K) in the growth medium to co-form the anodic biofilm with Geobacter sulfurreducens cells. The CPE-K treated BESs had a maximum current density as high as 12.3 ± 0.5 A/m2, with that of the controls being 6.2 ± 0.7 A/m2. Improved current production was sustained even after CPE-K was no longer added to the medium. It was demonstrated that increased current resulted from improvement of certain biofilm properties. Analysis using electrochemical impedance spectroscopy (EIS) showed that CPE-K addition decreased the charge transfer resistance at the cell/electrode interface and the diffusion resistance through the biofilm. Protein quantification showed increased biomass growth on the electrode surface, and confocal scanning microscopy images revealed enhanced biofilm permeability. These results demonstrated for the first time that conjugated polyelectrolytes could be used for G. sulfurreducens biofilm augmentation to achieve high electricity production through tuning the anodic biofilm in BESs. • Adding CPE-K increased maximum current densities of G. sulfurreducens by one-fold. • The increased current sustained even with no further addition of CPE-K. • The improved performance resulted from increased biomass growth. • Adding CPE-K decreased charge transfer resistance at the cell/electrode interface. • Addition of CPE-K lead to more permeable G. sulfurreducens biofilm structure. [ABSTRACT FROM AUTHOR]

Back Cover: An n-Type Conjugated Oligoelectrolyte Mimics Transmembrane Electron Transport Proteins for Enhanced Microbial Electrosynthesis (Angew. Keywords: Biocatalysis; Biohybrid; Conjugated Oligoelectrolyte; Energy Conversion; Microbial Electrosynthesis EN Biocatalysis Biohybrid Conjugated Oligoelectrolyte Energy Conversion Microbial Electrosynthesis 1 1 1 08/10/23 20230814 NES 230814 B Microbial electrosynthesis b is a sustainable strategy for electricity-driven chemical production. Biocatalysis, Biohybrid, Conjugated Oligoelectrolyte, Energy Conversion, Microbial Electrosynthesis. [Extracted from the article]

In their Communication (e202305189), Guillermo C. Bazan et al. designed an n-type redox-active conjugated oligoelectrolyte (COE) that intercalates into cell membranes and mimics the function of endogenous transmembrane electron transport proteins. Biocatalysis, Biohybrid, Conjugated Oligoelectrolyte, Energy Conversion, Microbial Electrosynthesis Keywords: Biocatalysis; Biohybrid; Conjugated Oligoelectrolyte; Energy Conversion; Microbial Electrosynthesis EN Biocatalysis Biohybrid Conjugated Oligoelectrolyte Energy Conversion Microbial Electrosynthesis 1 1 1 08/09/23 20230814 NES 230814 B Microbial electrosynthesis b is a sustainable strategy for electricity-driven chemical production. [Extracted from the article]

A conjugated polyelectrolyte (poly[2,6-(4,4-bis-potassium butanylsulfonate-4H-cyclopenta-[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)], PCPDTBT-SO3K) assembles into a novel, hierarchical hydrogel structure with all structural evidence indicating dominant electrostatic rather than aromatic or mesogen interactions. PCPDTBT-SO3K forms an entangled polymer mesh, where polymer chains are tied together by ionic cross-links, comprising microgel clusters that percolate to form a macroscopic three-dimensional network. With increasing temperature, ions gain mobility to move toward the exterior of the microgel clusters, dissolving the ionic cross-links and inhibiting network percolation through electrostatic repulsion. While π-π stacking interactions may be present in a disorganized fashion, no long-range π-π stacking is evident in X-ray scattering. Soft materials based on PCPDTBT-SO3K remain semiconducting and exhibit elevated ionic conductivity at the structural reorganization temperature. [ABSTRACT FROM AUTHOR]