Isolation and Characterization of<i>Acidithiobacillus ferrooxidans</i>Strain D3-2 Active in Copper Bioleaching from a Copper Mine in Chile

Abstract

Acidithiobacillus ferrooxidans strain D3-2, which has a high copper bioleaching activity, was isolated from a low-grade sulfide ore dump in Chile. The amounts of Cu(2+) solubilized from 1% chalcopyrite (CuFeS(2)) concentrate medium (pH 2.5) by A. ferrooxidans strains D3-2, D3-6, and ATCC 23270 and 33020 were 1360, 1080, 650, and 600 mg x l(-1) x 30 d(-1). The iron oxidase activities of D3-2, D3-6, and ATCC 23270 were 11.7, 13.2, and 27.9 microl O(2) uptake x mg protein(-1) x min(-1). In contrast, the sulfite oxidase activities of strains D3-2, D3-6, and ATCC 23270 were 5.8, 2.9, and 1.0 mul O(2) uptake.mg protein(-1).min(-1). Both of cell growth and Cu-bioleaching activity of strains D3-6 and ATCC 23270, but not, of D3-2, in the chalcopyrite concentrate medium were completely inhibited in the presence of 5 mM sodium bisulfite. The sulfite oxidase of strain D3-2 was much more resistant to sulfite ion than that of strain ATCC 23270. Since sulfite ion is a highly toxic intermediate produced during sulfur oxidation that strongly inhibits iron oxidase activity, these results confirm that strain D3-2, with a unique sulfite resistant-sulfite oxidase, was able to solubilize more copper from chalcopyrite than strain ATCC 23270, with a sulfite-sensitive sulfite oxidase.