title: Enhanced performance of hexavalent chromium reducing cathodes in the presence of Shewanella oneidensis MR-1 and lactate.
abstract: Biocathodes for the reduction of the highly toxic hexavalent chromium (Cr(VI)) were investigated using Shewanella oneidensis MR-1 (MR-1) as a biocatalyst and performance was assessed in terms of current production and Cr(VI) reduction. Potentiostatically controlled experiments (-500 mV vs Ag/AgCl) showed that a mediatorless MR-1 biocathode started up under aerated conditions in the presence of lactate, received 5.5 and 1.7 times more electrons for Cr(VI) reduction over a 4 h operating period than controls without lactate and with lactate but without MR-1, respectively. Cr(VI) reduction was also enhanced, with a decrease in concentration over the 4 h operating period of 9 mg/L Cr(VI), compared to only 1 and 3 mg/L, respectively, in the controls. Riboflavin, an electron shuttle mediator naturally produced by MR-1, was also found to have a positive impact in potentiostatically controlled cathodes. Additionally, a microbial fuel cell (MFC) with MR-1 and lactate present in both anode and cathode produced a maximum current density of 32.5 mA/m(2) (1000 Ω external load) after receiving a 10 mg/L Cr(VI) addition in the cathode, and cathodic efficiency increased steadily over an 8 day operation period with successive Cr(VI) additions. In conclusion, effective and continuous Cr(VI) reduction with associated current production were achieved when MR-1 and lactate were both present in the biocathodes.
authors.affiliation: Bioenergy and Organic Resources Research Group, Faculty of Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom. nxaf@hotmail.com
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Xafenias
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Banks
mesh_terms: D055162:Biocatalysis; D001674:Bioelectric Energy Sources; D019149:Bioreactors; D002857:Chromium / Q000737:chemistry*; D004566:Electrodes; D019344:Lactic Acid / Q000378:metabolism*; D020592:Shewanella / Q000378:metabolism*
chemical_list: D002857:Chromium; C074702:chromium hexavalent ion; D019344:Lactic Acid