Selective and non-selective bioleaching of manganese from a manganese-containing silver ore

Batch culture experiments showed that manganese could be leached from a manganese-containing silver ore by bacterial strain SSW 22, by a mixed culture derived from unsterilized ore, and by a Penicillium strain isolated from the mixed culture. The extent of leaching was influenced by the kinds of electrolytes and their concentration in the culture medium. The Penicillium strain was the most active. It leached manganese by a nonenzymatic mechanism. Leaching studies with Penicillium in a stirred reactor showed that at low chloride concentration (equivalent to 0.06% NaCl) manganese was leached selectively from the ore, whereas at high chloride concentration (equivalent to 3% NaCl or synthetic seawater) both manganese and silver were readily leached from the ore. Reactor leaching of ore showed the greatest promise for possible commercial exploitation.