LAUSR

Abstract In this work is evaluated the bioleaching capacity of a bacterium isolated from a mine in Guanajuato, Mexico, namely LR-1. The bacterium oxidized Fe2+ and S2O32− at acidic pH for its energy metabolism. This oxidant activity provided Fe3+ and/or protons that provoke sulfide ore dissolution. Five sulfide ore samples were obtained from different Mexican mines: Remedios, Guerrero, Bolanitos, Aldama, and Ocampo. The Ag, Cr, Cu, Fe, Pb, and Zn contents in the ores was analyzed by atomic absorption. Other physicochemical properties, including pH, electrical conductivity, and oxide-reducing potential, were also measured. Bioleaching was evaluated by metal concentration in the medium due to bacterial growth developed in basal salt medium with 2% (w/v) mineral in acidic conditions at 37 °C. There was an Increase in the percentage release of Ag (18.66% to 29.85%), Cu (60.90% to 73.66%), and Cr (11.71% to 15.04%), with respect to chemical leaching, mainly from the Remedios ore. A phylogenetic analysis of the 16S rRNA gene sequences revealed that bacterium LR-1 belongs to the genus Brevibacillus. There are no known species from this genus related with the leaching processes. This is the first report of an acidophile chemolithoautotrophic iron oxidizing bacterium from the genus Brevibacillus in the metal bioleaching. Therefore, these data contribute to the knowledge of the hydrometallurgical microbiology.