Surface Modification of a Graphite Felt Cathode with Amide-Coupling Enhances the Electron Uptake of Rhodobacter sphaeroides

Hana Nur Fitriana,Sangmin Lee,Jiye Lee,Yu Rim Lee,Soo Youn Lee,Jinju Song,Jin-Suk Lee,You-Kwan Oh,Myounghoon Moon,Myeonghwa Park

doi:10.3390/app11167585

Abstract

Microbial electrosynthesis (MES) is a promising technology platform for the production of chemicals and fuels from CO2 and external conducting materials (i.e., electrodes). In this system, electroactive microorganisms, called electrotrophs, serve as biocatalysts for cathodic reaction. While several CO2-fixing microorganisms can reduce CO2 to a variety of organic compounds by utilizing electricity as reducing energy, direct extracellular electron uptake is indispensable to achieve highly energy-efficient reaction. In the work reported here, Rhodobacter sphaeroides, a CO2-fixing chemoautotroph and a potential electroactive bacterium, was adopted to perform a cathodic CO2 reduction reaction via MES. To promote direct electron uptake, the graphite felt cathode was modified with a combination of chitosan and carbodiimide compound. Robust biofilm formation promoted by amide functionality between R. sphaeroides and a graphite felt cathode showed significantly higher faradaic efficiency (98.0%) for coulomb to biomass and succinic acid production than those of the bare (34%) and chitosan-modified graphite cathode (77.8%), respectively. The results suggest that cathode modification using a chitosan/carbodiimide composite may facilitate electron utilization by improving direct contact between an electrode and R. sphaeroides.

Highlights

Microbial electrosynthesis (MES) is an economically emerging bio-electrochemical technology for transforming CO2 and renewable electrical energy into chemicals and fuels [1,2]
In an MES reaction, the electroactive microorganisms can utilize electrons (e− ) from external conducting materials as reducing energy to catalyze the conversion of CO2 [4]
The results presented in this paper illustrate that amide-coupling between a cathode

Summary

Introduction

Microbial electrosynthesis (MES) is an economically emerging bio-electrochemical technology for transforming CO2 and renewable electrical energy into chemicals and fuels [1,2]. In an MES reaction, the electroactive microorganisms (called electrotrophs) can utilize electrons (e− ) from external conducting materials (i.e., electrodes) as reducing energy to catalyze the conversion of CO2 [4]. These electrotrophs achieve CO2 conversion through several carbon-fixation pathways including the reductive pentose phosphate cycle (e.g., photo- or chemoautotrophs), reductive tricarboxylic acid cycle (e.g., Clostridium thiosulfatophilum), and reductive acetyl-CoA pathway (e.g., Clostridium ljungdahlii) [1,5]. MES-driven CO2 uptake and H2 production in R. sphaeroides were found to occur simultaneously without additional organic carbon substrates [7]

Methods

Results

Conclusion