Abstract
Integration of electroactive bacteria into electrodes combines strengths of intracellular biochemistry with electrochemistry for energy conversion and chemical synthesis. However, such biohybrid systems are often plagued with suboptimal electrodes, which limits the incorporation and productivity of the bacterial colony. Here, we show that an inverse opal-indium tin oxide electrode hosts a large population of current-producing Geobacter and attains a current density of 3 mA cm-2 stemming from bacterial respiration. Differential gene expression analysis revealed Geobacter's transcriptional regulations to express more electron-relaying proteins when interfaced with electrodes. The electrode also allows coculturing with Shewanella for syntrophic electrogenesis, which grants the system additional flexibility in converting electron donors. The biohybrid electrode containing Geobacter can also catalyze the reduction of soluble fumarate and heterogenous graphene oxide, with electrons from an external power source or an irradiated photoanode. This biohybrid electrode represents a platform to employ live cells for sustainable power generation and biosynthesis.
Highlights
Integration of electroactive bacteria into electrodes combines strengths of intracellular biochemistry with electrochemistry for energy conversion and chemical synthesis
inverse opal-indium tin oxide (IO-ITO) electrodes were prepared by a coassembly method using 10-μm polystyrene beads as the structural template and ITO nanoparticles as the electrode material to suit the dimension of G. sulfurreducens (SI Appendix, Fig. S1 and Fig. 1B) [17, 18]
Bacteria proliferated and progressively colonized the entire electrode, producing an increasing anodic current that plateaued at 3 mA cm−2 after 80 h (Fig. 3A), which corresponds to a volumetric current density of 500 mA cm−3
Summary
Sessile bacteria metabolize acetate to support its growth through the tricarboxylic acid (TCA) cycle, while discharging excess electrons to the electrode via OMCs, which is registered as a continuous anodic current (Fig. 1 D and E). Transcriptome analysis by RNA sequencing revealed that G. sulfurreducens regulates gene expression in order to respire on electrodes. Shewanella loihica PV-4 was introduced together with G. sulfurreducens on the IO-ITO electrode to achieve syntrophic electrogenesis by linking their metabolic pathways (Fig. 1F), which will grant the system additional flexibility in using different electron donors. To outsource the electron supply to a renewable source, the biohybrid electrode was coupled with a photoanode to achieve photoelectrosynthesis without applying an external electrochemical bias
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