Impact of Ferrous Iron on Microbial Community of the Biofilm in Microbial Fuel Cells

Abstract

The performance of microbial electrochemical cells depends upon microbial community structure and metabolic activity of the electrode biofilms. Iron as a signal affects biofilm development and enrichment of exoelectrogenic bacteria. In this study, the effect of ferrous iron on microbial communities of the electrode biofilms in microbial fuel cells (MFCs) was investigated. Voltage production showed that ferrous iron of 100 μM facilitated MFC start-up compared to 150 μM, 200 μM, and without supplement of ferrous iron. However, higher concentration of ferrous iron had an inhibitive influence on current generation after 30 days of operation. Illumina Hiseq sequencing of 16S rRNA gene amplicons indicated that ferrous iron substantially changed microbial community structures of both anode and cathode biofilms. Principal component analysis showed that the response of microbial communities of the anode biofilms to higher concentration of ferrous iron was more sensitive. The majority of predominant populations of the anode biofilms in MFCs belonged to Geobacter, which was different from the populations of the cathode biofilms. An obvious shift of community structures of the cathode biofilms occurred after ferrous iron addition. This study implied that ferrous iron influenced the power output and microbial community of MFCs.

Keywords: electricity generation; ferrous iron; high throughput sequencing; microbial community; microbial fuel cell.

FIGURE 1

Cyclic voltammetry curves of MFCs supplemented with different concentrations of ferrous iron on 15th day.

FIGURE 2

Voltage curves of MFCs supplemented with ferrous iron of different concentrations.

FIGURE 3

Principal component analysis based on operational taxonomic units of the anode and cathode biofilms of MFCs.

FIGURE 4

Microbial community taxonomic wind-rose plots based on relative abundance of 16S rRNA sequences of the anode and cathode biofilms in MFCs at the phylum (A) and class levels (B).

FIGURE 5

Relative abundance of predominant genera in the anode and cathode biofilms in MFCs supplemented with different concentrations of ferrous iron.

FIGURE 6

Hierarchical cluster analysis of predominant populations in the anode and cathode biofilms in MFCs. The genera with the relative abundance of the top 35 are shown. The species clustering tree is on the left and the sample clustering tree is on the top. Each box of the heatmap represents a Z-score, a positive score indicates a datum above the mean, while a negative score indicates a datum below the mean.