Recent advances in microbial mining

Abstract

Microbial mining of copper sulphide ores, has been practiced on an industrial scale since the late 1950s. Since then, advances in microbial mining and the role of microorganisms involved in solubilization of metals have assumed commerical importance. The fact that bioleaching processes save energy, have a minimum pollution potential and are able to yield value-added by-products make these processes invaluable. The metal extraction processes using microorganisms, which are currently in active use, concern copper and uranium bioleaching. Biobeneficiation is also applied at an industrial scale for recovery of gold from arsenopyrites. The developments in these processes during the last 15 years, with particular reference to developing nations, are reviewed. Information gathered on molecular genetics of these microorganisms should lead to a better understanding and control of microbial leaching processes. Areas still needing research to sustain economic expansion of microbial mining techniques are indicated.

Review of Biohydrometallurgical Metals Extraction from Polymetallic Mineral Resources

“…Efficient recovery of metals (75%-80% after 48 h of incubation) was achieved during anaerobic leaching at pH 5-6.5 with glucose as the source of organic carbon and temperatures in a range of 30-45 °C. While not directly comparable with other studies, the leach duration was considerably shorter than those reported for fungal production of organic acids [32,357] or the use of RISC-oxidising autotrophs [335].…”

Bioleaching of uranium from low grade black schists by Acidithiobacillus ferrooxidans

“…In addition, bioleaching is readily adaptable to low grade ores and does not require a complex plant, such that several countries have already adopted bacterial leaching as a new extractive metallurgical process (Agate 1996;Bosecker 1997;Munoz et al 1995c;Rawlings 1998). However, uranium bioleaching plants have not been opened for a couple of decades.…”

“…In contrast to the chemical leaching process, the bioleaching process, which employs microorganisms such as bacteria and fungi as the leaching catalysts, is known to be economical and environmentally acceptable (Agate 1996;Bosecker 1997;Munoz et al 1995c). In addition, bioleaching is readily adaptable to low grade ores and does not require a complex plant, such that several countries have already adopted bacterial leaching as a new extractive metallurgical process (Agate 1996;Bosecker 1997;Munoz et al 1995c;Rawlings 1998).…”

“…This method often creates environmental problems, requires large amounts of energy, and involves a complex operational plant (Agate 1996;Bosecker 1997). It is not, however, economical to extract uranium from lowgrade ores by chemical leaching (Agate 1996;Bosecker 1997;Munoz et al 1995c).…”

“…One of the most widely employed microorganisms in the bioleaching process is A. ferrooxidans (Agate 1996;Bosecker 1997;Krebs et al 1997;Rawlings 1998). A. ferrooxidans is an acidophilic and chemolithotrophic bacterium, which can oxidize reduced iron and sulphur compounds.…”