Bacterial community structure of electrogenic biofilm developed on modified graphite anode in microbial fuel cell

Abstract

Abstract Formation of electrogenic microbial biofilm on the electrode is critical for harvesting electrical power from wastewater in microbial biofuel cells (MFCs). Although the knowledge of bacterial community structures in the biofilm is vital for the rational design of MFC electrodes, an in-depth study on the subject is still awaiting. Herein, we attempt to address this issue by creating electrogenic biofilm on modified graphite anodes assembled in an air–cathode MFC. The modification was performed with reduced graphene oxide (rGO), polyaniline (PANI), and carbon nanotube (CNTs) separately. To accelerate the growth of the biofilm, soybean-potato composite (plant) powder was blended with these conductive materials during the fabrication of the anodes. The MFC fabricated with PANI-based anode delivered the current density of 324.2 mA cm −2 , followed by CNTs (248.75 mA cm −2 ), rGO (193 mA cm −2 ), and blank (without coating) (151 mA cm −2 ) graphite electrodes. Likewise, the PANI-based anode supported a robust biofilm growth containing maximum bacterial cell densities with diverse shapes and sizes of the cells and broad metabolic functionality. The alpha diversity of the biofilm developed over the anode coated with PANI was the loftiest operational taxonomic unit (2058 OUT) and Shannon index (7.56), as disclosed from the high-throughput 16S rRNA sequence analysis. Further, within these taxonomic units, exoelectrogenic phyla comprising Proteobacteria , Firmicutes , and Bacteroidetes were maximum with their corresponding level (%) 45.5, 36.2, and 9.8. The relative abundance of Gammaproteobacteria , Clostridia , and Bacilli at the class level, while Pseudomonas , Clostridium , Enterococcus , and Bifidobacterium at the genus level were comparatively higher in the PANI-based anode.

Key findings

• ▸PANI-based anodes delivered the highest current density of 324.2 mA cm⁻²
• ▸CNTs-based anodes delivered a current density of 248.75 mA cm⁻²
• ▸rGO-based anodes delivered a current density of 193 mA cm⁻²
• ▸Blank graphite electrodes delivered a current density of 151 mA cm⁻²
• ▸PANI-based anodes supported the highest bacterial cell densities

Keywords

Identifiers

DOI

10.1038/s41598-023-27795-x

Journal

Scientific Reports

Year

2023