Conductive Polymer–Exoelectrogen Hybrid Bioelectrode with Improved Biofilm Formation and Extracellular Electron Transport

Abstract

generation and wastewater treatment. [1][2][3] MFCs generate power by harvesting electrons from the exoelectrogen through oxidizing organic substrates, [4] and BPVs produce current by acquiring electrons from photosynthetic organisms through photochemical and respiratory activities. [5] Although great progresses have been achieved during recent years, low biocompatibility and organisms loading capacity at the surface of electrode and inefficient extracellular electron transport (EET), the ability of microorganisms transferring electrons to electrode, are still bottlenecks that limit the practical applications of BESs. [6][7][8] To address these issues, extensive studies have been devoted to enhance the biocompatibility of anode and improve the EET efficiency. The first strategy is to add exogenous mediators in order to increase the EET, such as riboflavin, [9] quinone, [10] neutral red, [11] and thionin. [12] But the toxicity, solubility, and requirement of continuous exogenous addition limit their application. [13,14] The second strategy is the modification of the anode with materials to provide large surface area for bacteria adhesion in the electrode interior, including inorganic nanoparticles, [15] conducting polymer nanoparticles, [16,17] and porous carbon materials. [18,19] However, the complexity and rigor of the preparation for these nanoparticles lead to poor reproducibility and the hydrophobicity of carbon materials would hinder the attachment of organisms. [20] The third way is the employment of conductive nanomaterial-coated organisms. [21,22] By coating bacteria with polypyrrole through in situ polymerization, enhanced electrical conductivity, and power output in MFC are achieved by improving the direct contact-based EET and the viability of bacteria. [23] However, the encapsulation of individual bacteria with in situ generated conductive polypyrrole needs tedious and time-consuming procedure, and the enhancement is restricted only to direct EET. Therefore, it is highly desirable to develop simple and new strategies to simultaneously satisfy the need of increased organisms loading capacity, enhanced viability of organisms on anode, and improved EET efficiency.Conductive polymers (CPs) have an electronically delocalized structure that allows electron transfer along the whole backbone. Thus, they have long been used as semiconductor and Low organism loading capacity and inefficient extracellular electron transport (EET) are still the bottlenecks hindering the development of bioelectrochemical systems (BESs). It is shown that cationic polythiophene derivative (PMNT) has the ability to simultaneously enhance bacteria biofilm formation, improve the bacteria viability, decrease the resistance value, and accelerate the EET process between exoelectrogen and the electrode. Shewanella oneidensis can form a robust and thick biofilm on the electrode surface in the presence of PMNT. Mediated by electron-transporting PMNT, even bacteria far away from the electrode can transfer electrons to it. This bioelectrode is...

Solar‐Powered Organic Semiconductor–Bacteria Biohybrids for CO2 Reduction into Acetic Acid

“…Very recently, the conjugated polymers have been found to exhibit the ability to accelerate electron transfer to thylakoid, leading to the enhancement of the photosynthesis of chloroplasts . More importantly, cationic conjugated polymers can greatly enhance extracellular electron transport exoelectrogen to the electrode by intercalating into the membrane of bacteria through electrostatic interactions and hydrophobic interactions . Thus, it can be seen that organic conjugated semiconductors could provide an excellent opportunity to develop efficient solar‐to‐chemical conversion biohybrid systems.…”

“…[20,21] More importantly, cationic conjugated polymers can greatly enhance extracellular electron transport exoelectrogen to the electrode by intercalating into the membrane of bacteria through electrostatic interactions and hydrophobic interactions. [22] Thus, it can be seen that organic conjugated semiconductors could provide an excellent opportunity to develop efficient solar-to-chemical conversion biohybrid systems. To the best of our knowledge, an organic semiconductorbacteria biohybrid photosynthetic system has not been explored up to date.…”

Bacterial Materials: Applications of Natural and Modified Biofilms

“…[ 79,148–152 ] In a recent study, Zhang et al. [ 153 ] mixed a bacterial culture of S. oneidensis with the conductive polymer PMNT (poly(3‐(3′‐ N , N , N ‐triethyloamino‐1′‐propyloxy)‐4methyl2,5‐thiophene hydrochloride)). There, a combination of electrostatic and hydrophobic interactions between PMNT and S. oneidensis cells was suggested to help the bacteria transfer electrons between each other and to the electrodes.…”

Biohybrid Conjugated Polymer Materials for Augmenting Energy Conversion of Bioelectrochemical Systems

“…oneidensis hybrid bioelectrode and assembled it into MFC, where PMNT successfully improved operating life ande nergy output. [41] With alkyl quaternary ammonium moiety in the side chain, PMNT could be bound to the surface of S. oneidensis by synergistic electrostatic and hydrophobic interactions to form PMNT-bacteria aggregates. The formation of the aggregation is conducive to the adhesion of S. oneidensis on the surface of carbon paper electrode, thus promoting the formation of biofilm (Figure 5a).…”

“…Besides, the nanostructured polyaniline and polypyrrole have also been shown to contribute to the current output of MFCs [40] . In this way, Wang and co‐workers constructed polythiophene derivatives PMNT/ S. oneidensis hybrid bioelectrode and assembled it into MFC, where PMNT successfully improved operating life and energy output [41] . With alkyl quaternary ammonium moiety in the side chain, PMNT could be bound to the surface of S. oneidensis by synergistic electrostatic and hydrophobic interactions to form PMNT–bacteria aggregates.…”