title: The influence of acidity on microbial fuel cells containing Shewanella oneidensis.
abstract: Microbial fuel cells (MFCs) traditionally operate at pH values between 6 and 8. However, the effect of pH on the growth and electron transfer abilities of Shewanella oneidensis MR-1 (wild-type) and DSP10 (spontaneous mutant), bacteria commonly used in MFCs, to electrodes has not been examined. Miniature MFCs using bare graphite felt electrodes and nanoporous polycarbonate membranes with MR-1 or DSP10 cultures generated >8W/m(3) and approximately 400muA between pH 6-7. The DSP10 strain significantly outperformed MR-1 at neutral pH but underperformed at pH 5. Higher concentrations of DSP10 were sustained at pH 7 relative to that of MR-1, whereas at pH 5 this trend was reversed indicating that cell count was not solely responsible for the observed differences in current. S. oneidensis MR-1 was determined to be more suitable than DSP10 for MFCs with elevated acidity levels. The concentration of riboflavin in the bacterial cultures was reduced significantly at pH 5 for DSP10, as determined by high performance liquid chromatography (HPLC) of the filter sterilized growth media. In addition, these results suggest that mediator biosynthesis and not solely bacterial concentration plays a significant role in current output from S. oneidensis containing MFCs.
authors.affiliation: Chemistry Division, US Naval Research Laboratory, 4555 Overlook Avenue, SW, Washington, DC 20375, USA.
authors.forename: Justin C
authors.initials: JC
authors.lastname: Biffinger
authors.forename: Jeremy
authors.initials: J
authors.lastname: Pietron
authors.forename: Orianna
authors.initials: O
authors.lastname: Bretschger
authors.forename: Lloyd J
authors.initials: LJ
authors.lastname: Nadeau
authors.forename: Glenn R
authors.initials: GR
authors.lastname: Johnson
authors.forename: Cynthia C
authors.initials: CC
authors.lastname: Williams
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Nealson
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Ringeisen
mesh_terms: D001674:Bioelectric Energy Sources; D019149:Bioreactors / Q000382:microbiology*; D004579:Electron Transport; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006863:Hydrogen-Ion Concentration; D020592:Shewanella / Q000737:chemistry* / Q000502:physiology*