Biomining is an increasingly applied biotechnological procedure for processing of ores in the mining industry (biohydrometallurgy). Nowadays the production of copper from low-grade ores is the most important industrial application and a significant part of world copper production already originates from heap or dump/stockpile bioleaching. Conceptual differences exist between the industrial processes of bioleaching and biooxidation. Bioleaching is a conversion of an insoluble valuable metal into a soluble form by means of microorganisms. In biooxidation, on the other hand, gold is predominantly unlocked from refractory ores in large-scale stirred-tank biooxidation arrangements for further processing steps. In addition to copper and gold production, biomining is also used to produce cobalt, nickel, zinc, and uranium. Up to now, biomining has merely been used as a procedure in the processing of sulfide ores and uranium ore, but laboratory and pilot procedures already exist for the processing of silicate and oxide ores (e.g., laterites), for leaching of processing residues or mine waste dumps (mine tailings), as well as for the extraction of metals from industrial residues and waste (recycling). This chapter estimates the world production of copper, gold, and other metals by means of biomining and chemical leaching (bio-/hydrometallurgy) compared with metal production by pyrometallurgical procedures, and describes new developments in biomining. In addition, an overview is given about metal sulfide oxidizing microorganisms, fundamentals of biomining including bioleaching mechanisms and interface processes, as well as anaerobic bioleaching and bioleaching with heterotrophic microorganisms.
A taxonomic study was carried out on a metal-mobilizing, alkaliphilic bacterium from an alkaline slag dump, strain KBS6(T). The strain produced substrate and aerial mycelia. Growth occurred in the pH range 7.0-10.5, with an optimum at pH 8.5. A salt concentration of up to 10% was tolerated, and various organic substrates were used for growth. The results of a 16S rDNA sequence comparison revealed that strain KBS6(T) belongs to the genus Nocardiopsis. DNA-DNA hybridization with the two closest relatives, Nocardiopsis exhalans and Nocardiopsis prasina, gave similarity values of 18.2 and 44.1%, respectively, which indicated that strain KBS6(T) represents a novel species of the genus Nocardiopsis. This is consistent with the morphological, physiological and chemotaxonomic data. Because of the ability of this micro-organism to solubilize metals, the name Nocardiopsis metallicus sp. nov. is proposed for strain KBS6(T) (= DSM 44598(T) = NRRL B-24159(T)), this being the type strain.
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