Extracellular Electron Transfer Research Articles

Dual-roles of carbon black to accelerate phosphorus recovery as vivianite

Carbon materials have been confirmed to promote phosphorus recovery as vivianite through enhancing dissimilatory iron reduction (DIR), which alleviates phosphorus crisis. Carbon black (CB) exhibits contradictory dual roles of cytotoxicity inducer and electron transfer bridge towards extracellular electron transfer (EET). Herein, the effect of CB on vivianite biosynthesis was investigated with dissimilatory iron reduction bacteria (DIRB) or sewage. With Geobacter sulfurreducens PCA as inoculum, the vivianite recovery efficiency increased accompanied with CB concentrations and enhanced by 39 % with 2000 mg·L−1 CB. G. sulfurreducens PCA activated the adaptation mechanism of secreting extracellular polymeric substance (EPS) to resist cytotoxicity of CB. While in sewage, the highest iron reduction efficiency of 64 % was obtained with 500 mg·L−1 CB, which was appropriate for functional bacterial selectivity like Proteobacteria and bio-transformation from Fe(III)-P to vivianite. The balance of CB's dual roles was regulated by inducing the adaptation of DIRB to gradient CB concentrations. This study provide an innovative perspective of carbon materials with dual roles for vivianite formation enhancement.

Extracellular Electron Transfer of Weak Electricigens in the Presence of a Competing Electron Acceptor

To maximise microbial electroactivity in bioelectrochemical systems, soluble electron acceptors are typically omitted as they compete with the electrode. While practical, this approach provides engineered conditions that do not reflect the natural environment of electroactive microorganisms, which may contain both soluble and insoluble electron acceptors. This study investigates the behaviour of weak electricigens, a relatively understudied category of microorganisms whose members switch between non-electroactive and electroactive states. Enrichments were performed in microbial fuel cells containing both an electrode and the soluble alternative fumarate to probe extracellular electron transfer of weak electricigens. Using fluorescence spectroscopy, chromatography and voltammetry, the electron shuttle riboflavin was not found in these conditions but was found in controls in which only the electrode was available to reduce. Despite this dichotomy in ability to perform riboflavin-based mediated electron transfer, communities of weak electricigens were similarly electroactive in each condition (19.36 ± 0.9 mW m−2 vs 20.25 ± 2.0 mW m−2). 16S rRNA gene sequencing revealed similar communities enriched in each condition, but with differing abundance. Understanding extracellular electron transfer in natural environments is of both fundamental and applied interest, as it can inform the design of real-world bioelectrochemical systems whose influents are likely to contain competing electron acceptors.

Effectively facilitating the degradation of chloramphenicol by the synergism of Shewanella oneidensis MR-1 and the metal-organic framework

Electroactive bacteria (EAB) and metal oxides are capable of synergistically removing chloramphenicol (CAP). However, the effects of redox-active metal-organic frameworks (MOFs) on CAP degradation with EAB are not yet known. This study investigated the synergism of iron-based MOFs (Fe-MIL-101) and Shewanella oneidensis MR-1 on CAP degradation. 0.5 g/L Fe-MIL-101 with more possible active sites led to a three-fold higher CAP removal rate in the synergistic system with MR-1 (initial bacterial concentration of 0.2 at OD600), and showed a superior catalytic effect than exogenously added Fe(III)/Fe(II) or magnetite. Mass spectrometry revealed that CAP was transformed into smaller molecular weight and less toxic metabolites in cultures. Transcriptomic analysis showed that Fe-MIL-101 enhanced the expression of genes related to nitro and chlorinated contaminants degradation. Additionally, genes encoding hydrogenases and c-type cytochromes associated with extracellular electron transfer were significantly upregulated, which may contribute to the simultaneous bioreduction of CAP both intracellularly and extracellularly. These results indicated that Fe-MIL-101 can be used as a catalyst to synergize with EAB to effectively facilitate CAP degradation, which might shed new light on the application in the in situ bioremediation of antibiotic-contaminated environments.

Carbon dots internalization enhances electroactive biofilm formation and microbial acetate synthesis

This study investigated how carbon dots (CDs) and N-doped CDs modification of acetogenic bacteria enhanced the extracellular electron transfer (EET) and the formation of electroactive biofilm, which subsequently improved acetate production from CO2 in microbial electrosynthesis (MES). Characteristic fluorescence emission peaks of CDs and N-doped CDs were detected inside and outside of bacterial cells, respectively, suggesting that the CDs were successfully internalized by the cells. The (N-doped) CDs modified acetogens increased current output by 89–95%, and acetate production rate by 57–71%. The highest acetate production rate and electron recovery efficiency reached 2.1 mM d−1 and 91.3%, respectively. Acetoanaerobium and Sporomusa, which are considered to have different EET strategies, dominated the biocathodes modified with CDs and N-doped CDs, respectively. The CDs modification increased biofilm thickness by 86% and reached 41.0 ± 1.3 μm, which could be related to the increased secretion of flavins that enhanced the signal transduction interspecies. With the N-doped CDs modified, the biofilm was occupied with active pyrrolic N/graphitic N (52%), and the expression of functional genes encoding cytochrome (cydB, cybH, CcdA) were enhanced significantly. This study offers insights into the EET mechanisms by acetogens and a viable approach to increase acetate production from CO2.

Doping molybdenum oxides with different non-metal atoms to promote bioelectrocatalysis in microbial fuel cells

The sluggish extracellular electron transfer has been known as one of the bottlenecks to limit the power density of microbial fuel cells (MFCs). Herein, molybdenum oxides (MoOx) are doped with various types of non-metal atoms (N, P, and S) by electrostatic adsorption, followed by high-temperature carbonization. The as-prepared material is further used as MFC anode. Results indicate that all different elements-doped anodes can accelerate the electron transfer rate, and the great enhancement mechanism is attributed to synergistic effect of dopped non-metal atoms and the unique MoOx nanostructure, which offers high proximity and a large reaction surface area to promote microbe colonization. This not only enables efficient direct electron transfer but also enriches the flavin-like mediators for fast extracellular electron transfer. This work renders new insights into doping non-metal atoms onto metal oxides toward the enhancement of electrode kinetics at the anode of MFC.

Mechanism underlying the acceleration of pitting corrosion of B30 copper-nickel alloy by Pseudomonas aeruginosa.

Despite its excellent corrosion resistance, B30 copper-nickel alloy is prone to pitting, particularly when exposed to microorganisms. The mechanism underlying the acceleration of pitting in this alloy is not fully understood. In this study, the acceleration of pitting corrosion in B30 copper-nickel alloy caused by a marine microorganism named Pseudomonas aeruginosa (P. aeruginosa) was investigated using surface analysis and electrochemical techniques. P. aeruginosa significantly accelerated the pitting in B30 copper-nickel alloy, with a maximum pitting depth of 1.9 times that of the abiotic control and a significant increase in pitting density. This can be attributed to extracellular electron transfer and copper-ammonia complex production by P. aeruginosa, accelerating the breakdown of the passivation film.

Efficient hydrogen production from sugarcane bagasse and food waste by thermophilic clostridiales consortium and Fe–Mn impregnated biochars

In this research, a thermophilic Clostridiales consortium was enriched with pretreated sugarcane bagasse (PSCB). Then the hydrogen production of Clostridiales consortium through dark fermentation had been greatly improved through two-step strengthening. Firstly, food waste was added to optimize C/N ratio of substrate to 10.47. Secondly, Fe–Mn impregnated biochars (Fe·Mn·SB) were supplemented to the co-substrate fermentation system to further improve hydrogen production. Overall, the hydrogen production (1.71 mL H2/mL-culture) and yield (586.19 mL H2/g-carbohydrate) of Clostridiales were increased by 113.75% and 32.48% compared with that of fermentation from single PSCB, respectively. The mechanism of Fe·Mn·SB promoting hydrogen production was further elucidated. Microbial community analysis demonstrated that Fe·Mn·SB could increase the relative abundances of dominant hydrogenogen and stabilize community structure. PICRUSt analysis indicated Fe·Mn·SB boosted substrate degradation and carbon metabolism. Electrochemical analysis implied Fe·Mn·SB promoted reducing power and release of cytochrome c, stimulating extracellular electron transfer (an 18.39% increase in power density). Carbon metabolism analysis indicated that Fe·Mn·SB enhanced hydrogen-producing pathways and suppressed hydrogen-consuming pathways. The present work established a feasible process for hydrogen production by Clostridiales consortium fermentation from co-substrate, deepened the understanding of metal-modified biochars improving hydrogen production, and provided references for future research.

Electro-stimulated anaerobic oxidation of methane with synergistic denitrification by adding AQS: Electron transfer mode and mechanism

Denitrifying anaerobic methane-oxidizing (DAMO) processes, which link anaerobic methane oxidation (AMO) and denitrification, have a promising prospect in anaerobic wastewater treatment. In bioelectrochemical systems (BES), DAMO consortium presented potent metabolic activity. However, the extracellular electron transfer (EET) in BES was poorly understood. This study investigated the EET mechanisms and modes of electron transport in BES dominated by anaerobic methanotrophic bacteria. In the bioreactors with the auxiliary voltage of 0.5 and 1.1 V, named EMN-0.5 and EMN-1.1, respectively, biological voltages of 0.198 and 0.329 V were generated with power densities of 0.6 and 1.20 mW/m2, after removing the voltage. High throughput and metagenome analyses demonstrated that main methanotrophs were DAMO bacteria and Methylocystis sp. The electroactive bacteria detected were Pseudomonas sp., Hypomicrobium sp., Thiobacillus sp, and Rhodococcus sp. The pil, cytochrome c, hdr, and he/fp genes related to EET were present on the electrode surfaces. Carbon 13 isotope tracing and chemicals analysis by GC-MS exhibited that methanol was an intermediate product released to extracellular environment and acted as the electronic carrier to drive the EET in methane oxidation. Extracellular electron transfer was achieved through the collaboration of DAMO bacteria, Methylocystis sp., and Pseudomonas sp. Anthraquinone 2-sulfonic acid ester (AQS) could improve the rate of electron transfer to the extracellular space, especially in the EMN-0.5 reaction system. This study provides a new understanding of AMO consortium metabolism in BES and may provide a scientific basis for developing methane control technology.

Comparative analysis of active networks reveals the changes of key proteins and their interactions under different oxygen levels in Shewanella oneidensis MR-1

PurposeThe extracellular electron transfer (EET) capability enables electroactive microorganisms have a wide range of applications in energy production, wastewater treatment, bioremediation and chemical synthesis. Because the oxygen levels will sharply affect the EET process, we integrated transcriptome changes under different oxygen levels with protein–protein interaction (PPI) network to study the specific changes under these conditions in a typical electroactive microorganism Shewanella oneidensis MR-1 (S. oneidensis MR-1).MethodsFirst, the mRNA expression data of S. oneidensis MR-1 under different oxygen levels were integrated into its PPI network to construct the active protein networks. Then, we studied the changes of key proteins and their interactions by comparative analysis of multiple pairs of active networks.ResultsThe analysis of node centrality and its changes in the active networks under high and low oxygen levels shows that most of the key nodes in the network are ribosomes or proteins closely related to ribosomes. The results of our centrality versus centrality change analysis of nodes show that the two proteins FlgB and PetA are the largest changed proteins. Among these proteins, the FlgB protein is the structural component of flagella, while PetA protein is closely related to cytochrome c. Furthermore, we also analyzed the changes in protein–protein interactions in the active networks under different oxygen levels, identified the key interactions in each pair of active networks, and finally screened out the key interaction Tig-RplX that exists in three pairs of active networks.ConclusionOur results indicate that the translational processes of proteins and the corresponding translation efficiency may play an important role before and after the activation of the EET process of S. oneidensis MR-1. Furthermore, this study can also provide some guidance for identifying key proteins and interactions under different conditions for this species.

A Microbial Cell Coating Based on a Conjugated Polyelectrolyte with Broad Reduction Potential Increases Inward and Outward Extracellular Electron Transfer

AbstractBioelectrochemical systems hold the promise of enabling sustainable microbial‐mediated energy interconversion between electrical and chemical energy. Herein, it is demonstrated how a single conjugated polymer can be used to enhance bidirectional extracellular electron transfer through forming self‐assembled coatings on individual cells. Specifically, the n‐type conjugated polyelectrolyte p(cNDI‐gT2) exhibits a reduction potential window between −0.1 and −0.8 V (vs Ag/AgCl), thereby driving thermodynamically favored electron transfer in both directions across the abiotic‐biotic interface that involves the outer membrane cytochromes and flavins of Shewanella oneidensis MR‐1. Electrochemical tests show that injection from an external electrode into Shewanella oneidensis MR‐1 is enabled at negative potentials (−0.6 V), while electron extraction is possible at positive potentials (0.2 V). Relative to controls, the biohybrid shows a sixfold increase in biocurrent generation and a 35‐fold increase in current uptake for the bioelectrosynthesis of succinate from fumarate. This demonstrated abiotic‐biotic synergy provides new strategies for designing multifunctional biohybrids.

Synthetic consortium of Ganoderma lucidum and Lactobacillus plantarum for enhanced natural products biosynthesis

Microbial coculture holds immense promise for biomanufacturing. Herein, we designed a synthetic consortium of G. lucidum and L. plantarum for enhanced natural product biosynthesis. The spatio-temporal alignment of the strains revealed an implicit disposition for transient and long-term mutualistic co-existence in the shared environment. The consortium assembly and biomass growth were driven by an intuitive toggle-switching of carbon/nitrogen sources and TOR signaling. Extracellular electron transfer propelled by redox shuttles facilitated the distribution of high-energy electrons and enhanced the consortium's robustness. The ROS-scavenging activity of antioxidant enzymes maintained the cells' viability via intracellular ROS removal. The CAT, GPX, and APX enzymes catalyzed the reduction of H2O2 to H2O and O2, thereby protecting the cells against the toxic effects of ROS. Small-signaling molecules stimulated the biosynthesis of bioactive natural products in the coculture. Over-expression of target genes further enhanced ganoderic acids and exopolysaccharides bioproduction in the coculture system. The study provides insight into the physicochemical and molecular forces that drive cooperative interaction and stimulate natural product biosynthesis in G. lucidum and L. planatarum consortium.

Geobacter sulfurreducens promoted the biosynthesis of reduced graphene oxide and coupled it for nitrobenzene reduction

In order to explore an efficient and green method to deal with nitrobenzene (NB) pollutant, reduced graphene oxide (rGO) as an electron shuttle was applied to enhance the extracellular electron transfer (EET) process of Geobacter sulfurreducens, which was a typical electrochemically active bacteria (EAB). In this study, rGO biosynthesis was achieved via the reduction of graphene oxide (GO) by G. sulfurreducens PCA within 3 days. Also, the rGO-PCA combining system completely reduced 50-200 µmol/L of NB to aniline as end product within one day. SEM characterization revealed that PCA cells were partly wrapped by rGO, and therefore the distance of electron transfer between strain PCA and rGO material was reduced. Beside, the ID/IG of GO, rGO, and rGO-PCA combining system were 0.990, 1.293 and 1.31, respectively. Moreover, highest currents were observed in rGO-PCA-NB as 12.950 µA/-12.560 µA at -408 mV/156 mV, attributing to the faster electron transfer efficiency in EET process. Therefore, the NB reduction was mainly due to: (I) direct EET process from G. sulfurreducens PCA to NB; (II) rGO served as electron shuttle and accelerated electron transfer to NB, which was the main degradation pathway. Overall, the biosynthesis of rGO via GO reduction by Geobacter promoted the NB removal process, which provided a facile strategy to alleviate the problematic nitroaromatic pollution in the environment.

More than the interface: Synergistic engineering of the interfacial and its subjacent layers followed by self-triggering for high efficient bioelectricity harvesting

The practical application of microbial fuel cell (MFC) is severely impeded by its low output power density stemming from the low bacterial loadings and the sluggish extracellular electron transfer (EET) kinetics. Thus, the current collector designed to greatly enhance the electrocatalytic performance of microbial electrodes ought to possess both high hydrophilicity and high conductivity, which are, however, often mutually incompatible. Herein, to resolve this dilemma, a composite bioelectrode consisting of the poly(ionic liquid) functionalized single-walled carbon nanotube bundles (SWCNT-PIL) layer at the biotic-electrode interface and its subjacent hydrophilic graphene oxides (GO) layer is prepared. Bacterial adhesion is significantly enhanced, resulting from the positive charges of SWCNT-PIL and the hydrophilic GO. After self-reduction of GO by attached electricigens, the as-prepared mrGSP bioelectrode exhibits a maximum output power density of 4.808 W m−2, which is more than one order of magnitude larger than that of conventional carbon-based electrode (0.319 W m−2), because the SWCNT-PIL layer is capable of not only accelerating the flavin-based mediated electron transfer (MET), but also upregulating the membrane protein expression from 14.64% to 18.01% induced by the enhanced electric field, promoting the outer membrane c-type cytochromes-based direct electron transfer (DET). This work provides a new concept of synergistic engineering the interfacial and its subjacent layers to solve the dilemma between high hydrophilicity and high conductivity of the current collector surface for microbial electrocatalysis.

Charging-discharging cycles of geobattery activated carbon enhance iron reduction and vivianite recovery from wastewater

Vivianite as a significant secondary mineral of dissimilatory iron reduction (DIR) exhibits marvelous potential to solve eutrophication as well as phosphorus shortage. Geobattery represents by natural organic matters (NOM) with rich functional groups influences bioreduction of natural iron mineral. Activated carbon (AC) which contains abundant functional groups is expected to serve as geobattery, but there remains insufficient understanding on its geobattery mechanism and how it benefits the vivianite formation. In this study, the charging and discharging cycle of “geobattery” AC enhanced extracellular electron transfer (EET) and vivianite recovery was demonstrated. Feeding with ferric citrate, AC addition increased vivianite formation efficiency by 141 %. The enhancement was attributed to the electron shuttle capacity of storage battery AC, which was contributed by the redox cycle between CO and O–H. Feeding with iron oxides, huge gap of redox potential between AC and Fe(III) minerals broke through the reduction energy barrier. Therefore the iron reduction efficiency of four Fe(III) minerals was accelerated to the same high level around 80 %, and the vivianite formation efficiency were increased by 104 %–256 % in pure culture batches. Except acting as storage battery, AC as a dry cell contributed 80 % to the whole enhancement towards iron reduction, in which O–H groups were the dominant driver. Due to the rechargeable nature and considerable electron exchange capacity, AC served as geobattery playing the role of both storage battery and dry cell on electron storaging and transferring to influence biogeochemical Fe cycle and vivianite recovery.

Bimetal-organic framework-derived porous CoFe2O4 nanoparticles as biocompatible anode electrocatalysts for improving the power generation of microbial fuel cells

HypothesisThe relatively lower power density of Microbial fuel cells (MFCs), primarily resulting from weak biofilm habitation and sluggish extracellular electron transfer (EET) at the anode interface, limits their practical implementation on a large scale. To address this challenge, porous CoFe2O4 nanoparticles could be used as anode electrocatalysts based on the following considerations: (i) the introduction of CoFe2O4 nanoparticles endows the anode with a rough surface that facilitates biofilm formation; (ii) the positively charged Co and Fe ions improve the interfacial affinity of anodes, enabling rapid immobilization and colonization of negatively bacteria; (iii) the multi-valent metal states of Co and Fe can function as electron shuttles, mediating EET process between biofilm and anode. ExperimentsCoFe2O4 nanoparticles prepared with a bimetal-organic framework (B-MOF) as precursor, were modified to the surface of carbon cloth as the anode of MFCs. FindingsMFCs equipped with CoFe2O4 anode achieved a maximum power density of 1026.68 mW m−2, which was approximately 3.4 times higher than that of the pristine carbon cloth. Additionally, the biofilm density and viability on the anode were enhanced after CoFe2O4 modification. Considering the facile fabrication process and superior electrocatalytic performance, the CoFe2O4 nanoparticles are promising electrocatalysts for high performance and cost-effective MFCs.

A Biochemical Deconstruction-Based Strategy to Assist the Characterization of Bacterial Electric Conductive Filaments.

Periplasmic nanowires and electric conductive filaments made of the polymeric assembly of c-type cytochromes from Geobacter sulfurreducens bacterium are crucial for electron storage and/or extracellular electron transfer. The elucidation of the redox properties of each heme is fundamental to the understanding of the electron transfer mechanisms in these systems, which first requires the specific assignment of the heme NMR signals. The high number of hemes and the molecular weight of the nanowires dramatically decrease the spectral resolution and make this assignment extremely complex or unattainable. The nanowire cytochrome GSU1996 (~42 kDa) is composed of four domains (A to D) each containing three c-type heme groups. In this work, the individual domains (A to D), bi-domains (AB, CD) and full-length nanowire were separately produced at natural abundance. Sufficient protein expression was obtained for domains C (~11 kDa/three hemes) and D (~10 kDa/three hemes), as well as for bi-domain CD (~21 kDa/six hemes). Using 2D-NMR experiments, the assignment of the heme proton NMR signals for domains C and D was obtained and then used to guide the assignment of the corresponding signals in the hexaheme bi-domain CD. This new biochemical deconstruction-based procedure, using nanowire GSU1996 as a model, establishes a new strategy to functionally characterize large multiheme cytochromes.

Promoting vivianite recovery: Crucial role of tightly-bound extracellular polymeric substances

Vivianite is an important bio-induced product of dissimilated iron reduction (DIR), which exists widely in activated sludge and digested sludge of wastewater treatment plants (WWTPs). Extracellular polymeric substances (EPS) surrounding dissimilatory iron-reducing bacteria (DIRB) were reported to be transient media for microbial extracellular electron transfer (EET) and DIR. However, what happens when a layer of EPS envelops microbial cells during vivianite recovery? This study tried to assess the relationship between iron reduction and electron transfer by stripping EPS layer-by-layer, then clarified the delamination of different EPS layers on the performance of vivianite recovery. After stripping total EPS (PC-EPS batches) of DIRB, the Fe (III) reduction efficiencies (RFe), Fe (III) reduction rate (VFe), and vivianite formation efficiency (RV) decreased by 33%, 37%, and 30%, respectively. Tightly bound-EPS (TB-EPS) was confirmed to play a crucial role in vivianite formation, which contributed 28–51% to vivianite recovery and 34–55% to iron reduction. Electronic shuttle substances were contained in TB-EPS, which enhanced the EET rate and efficiency between cells and Fe (III). The polysaccharide content of TB-EPS was positively related to adhesiveness between cells and mineral, as well as the iron reduction efficiency. Furthermore, redox proteins (PpcA, OmcB) were embedded in EPS, which shortened the distance of electron hopping to across the EPS layer and further accelerated vivianite recovery from wastewater. Long-term operation of anaerobic reactors confirmed that TB-EPS played critical roles in bio-induced vivianite formation.

Enhanced microbial reduction of Cr(VI) in soil with biochar acting as an electron shuttle: Crucial role of redox-active moieties

Biochar has been proven to participate in the biotic reduction of hexavalent chromium (Cr(VI)) in environment since its involvement may accelerate the extracellular electron transfer (EET). However, roles of the redox-active moieties and the conjugated carbon structure of biochar in this EET process remain unclear. In this study, 350 °C and 700 °C were selected to produce biochar with more O-containing moieties (BC350) or more developed conjugated structures (BC700), and their performances in the microbial reduction of soil Cr(VI) were investigated. Our results showed that BC350 presented a 241% increase of Cr(VI) microbial reduction after 7-day incubation, much higher than that of BC700 (39%), suggesting that O-containing moieties might play more important roles in accelerating the EET process. Biochar, especially BC350 could serve as an electron donor for microbial anaerobic respiration, but its contribution (73.2%) as an electron shuttle for EET was dominant to the enhanced Cr(VI) reduction. The positive correlation between electron exchange capacities (EECs) of pristine and modified biochars and the corresponding maximum reduction rates of Cr(VI) evidenced the crucial role of redox-active moieties in electron shuttling. Moreover, EPR analysis suggested the nonnegligible contribution of semiquinone radicals in biochars to the accelerated EET process. This study demonstrates the crucial role of redox-active moieties, i.e., O-containing moieties in mediating the EET process during the microbial reduction of Cr(VI) in soil. Findings obtained will advance the current understanding of biochar as an electron shuttle participating in the biogeochemical processes of Cr(VI).

The degradation of high emulsified oil wastewater in an intermittently-aerated MBBR packed with magnetic polystyrene particles

This work aims to explore the effects of the magnetic polystyrene particles (MPS) on contaminants removal of the high emulsified oil wastewater. 26 days intermittently-aerated progress illustrated that COD removal efficiency and the resistance to the shock loading was promoted in the presence of MPS. Gas chromatography (GC) results also indicated that MPS enhanced the number of organic species reduced. According to the cyclic voltammetry test, conductive MPS appeared special redox performance which was considered could to facilitate the extracellular electron transfer. Furthermore, MPS dosing accelerated the electron-transporting system (ETS) activity by 24.91% compared the control. Based on the superior performance above, the conductivity of MPS is considered to be responsible for the enhanced organic removal efficiency. Moreover, the high-throughput sequencing displayed that electroactive Cloacibacterium and Acinetobacter accounted for a higher proportion in the MPS reactor. Additionally, Porphyrobacter and Dysgonomonas which were capable of degrading organics were also enriched more by MPS. To sum up, MPS is a promising additive to enhance the organic substances removal for the high emulsified oil wastewater.

Polypyrrole Electrodes Show Strain‐Specific Enhancement of Photocurrent from Cyanobacteria

AbstractThe discovery of extracellular electron conduits has spurred new applications in microbial electronics. Except for a limited number of exoelectrogens, most microbes are surrounded by insulating membranes that impair extracellular electron transfer. This study focuses on the fabrication of a conductive polypyrrole (PPy) coating for enhancing microbial charge extraction. The polymer deposition is characterized and optimized using a combination of potentiodynamic and potentiostatic measurements as well as scanning electron microscopy (SEM), energy dispersive X‐Ray (EDX) analysis, and Raman spectroscopy. The electrodes are used to extract photosynthetic electrons from the cyanobacteria Synechocystis sp. PCC6803 (Synechocystis) and Synechococcus Elongatus PCC7942 (Elongatus). The PPy electrode shows a sixfold increase in extracted photocurrent for Synechocystis under unmediated conditions compared to bare graphite electrodes. This enhancement is attributed to the decreased resistance and increased electroactive surface area of the PPy electrode. By contrast, Elongatus shows no substantial difference in photocurrent between the PPy and bare electrodes. Compared to Synechocystis cells, the Elongatus cells show limited electrode adherence with weaker charge interactions. These findings lay the framework for designing customized polymer electrodes for strain‐specific charge extraction.