The mechanism of copper leaching by intact cells of thiohacillus ferrooxidans

Under aerobic conditions, washed intact cells of Thiobacillus ferrooxidans AP19-3 solubilized copper enzymatically from a copper concentrate containing Cu(20.48%), Fe(31.61%), S(38.22%), Pb(3.84%), and Zn(4.22%). The optimum pH of copper solnbilization from copper concentrate was at pH 3.0. In contrast, under anaerobic conditions or under aerobic conditions in the presence of sodium cyanide, inhibitor of iron oxidase, the amount of copper solubilized enzymatically from the ore markedly decreased, indicating that iron oxidase is involved in the copper solubilization. Under the conditions under which iron oxidase of the cells cannot operate, Fe²⁺ and Cu⁺ ions were produced enzymatically, suggesting that a hydrogen snlfide: ferric ion oxidoreductase (SFORase) was involved in this copper solubilization from the ore. A short treatment of the strain with 0.5% phenol completely destroyed the SFORase. However, this treatment did not affect the iron oxidase of the cells. A concomitant loss of the activity of copper solnbilization from the ore was observed in 0.5% phenol-treated cells. The results strongly suggest that both iron oxidase and SFO Rase are crucial in copper ore leaching by T. ferrooxidans AP19-3.