Effects of NaCl concentration on anode microbes in microbial fuel cells

Abstract

Understanding of how operational parameters affect the composition of exoelectrogenic microbes is an important step in the development of efficient microbial fuel cells (MFCs). In the present study, single-chamber MFCs were inoculated with rice paddy-field soil and continuously supplied with an acetate medium containing different concentrations of NaCl (0–1.8 M). Polarization analyses showed that power output increased as the NaCl concentration increased to 0.1 M, while it was markedly diminished over 0.3 M. The increase in power output was associated with an increased abundance of anode microbes as assessed by protein assays. Notably, the power increase was also accompanied by an increase in the abundance ratio of Geobacter bacteria to total anode bacteria as assessed by pyrosequencing of 16S rRNA gene amplicons and specific quantitative PCR. Although most Geobacter species are known to exhibit high growth rates in freshwater media without NaCl, the present study shows that 0.1 M NaCl facilitates the growth of Geobacter in MFC anode biofilms. This result suggests that the optimum salt concentration in MFC is determined by the balance of two factors, namely, the solution conductivity and salt tolerance of exoelectrogens.

Effect of C/N ratio and salinity on power generation in compost microbial fuel cells

“…Hence, the salt intake should be regulated and sufficient adaptation time might be required to develop a salt tolerant microbial community which is beneficial to MFC performance. Further investigation on MFCs for soils with high salinity may consider a recent finding (Miyahara et al, 2015) on the abundance of a salt-tolerant strain of Geobacter spp. found on the anodes with 0 to 0.1 M (5.84 g/L) NaCl, but decreased significantly above 0.3 M NaCl (17.53 g/L).…”

Alginate‐Encapsulated Bacteria for the Treatment of Hypersaline Solutions in Microbial Fuel Cells

“…The addition of low concentrations of salts in MFCs was reported as beneficial, as performance was improved by reducing the internal resistance of the system (increasing conductivity) . However, the performance could only be improved to a certain threshold of salt concentration, as the microbial catalysis was compromised at higher salt content …”

Poly iron sulfate flocculant as an effective additive for improving the performance of microbial fuel cells

“…MFCs used in the present study were cassette electrode-(CE-) MFCs that were described in our previous study (Miyahara et al, 2015a). The configuration of CE-MFC is presented in Supplementary Fig.…”

“…For analyzing phylogenetic compositions of bacteria in anode microbiomes, 16S rRNA gene fragments were amplified by PCR using tagged bacterial universal primers as described elsewhere (Miyahara et al, 2015a). Amplicons from different samples were mixed at the same concentration (1 ng ll À1 each) and subjected to pyrosequencing using a Genome Sequencer FLX system (Roche Applied Science).…”