Microbial Fuel Cell Studies of Iron-Oxidising Bacteria

Abstract

In recent years the bioelectrochemistry of microorganisms has been variously applied to microbial electricity generation,^1,2 biomass assay^3,4 and biosensing.^5,6 Although:these studies have been generally limited to the use of organisms in neutral or near neutral media, the possibilities for exploiting alkalophiles m high pH electrochemical systems was also investigated,⁷ and the present study formed part of a further exploration of the potential uses of microbial fuel cell techniques under extreme conditions. It focussed on acidophilic species which promote bio-oxidation of arsenopryites (FeAsS) mineral concentrates. This reaction is of importance in a novel gold extraction process in which bacterial oxidation of the arsenical pyrites matrix of refractory gold ores enhances the yield of the metal.^8,9 These organisms derivé their energy from the oxidation of reduced sulphur species to sulphate and of Fe(II) to Fe(III), and the latter process was exploited here using a concentration cell in which organisms were placed in the cathode compartment. The electrochemical effects are transmitted by the substrate Fe(II) ions and metabolite Fe(III) ions, which therefore act as mediators. Potentiometric, amperometric and coulometric investigations were conducted as part of a preliminary attempt towards solving one of the problems associated with this technology, namely the assay of bacterial biomass.