Bioleaching of Heavy Metals by Sulfur Oxidizing Bacteria: A Review

Bioleaching, a novel biotechnological process, is used to eliminate heavy metals from contaminated sediments by acidification as well as solubilization of heavy metals. Metals from poor-quality ore and mineral compounds are removed by Bioleaching process, which is simple and low cost effective technology. Acidophilic sulfur oxidizing bacteria (Acidithiobacillus ferrooxidans, Acidithiobacillus thioosidans) transforms toxic metal sulphides to less toxic sulphates. Trace elements are processed by using sulfur oxidizing microorganisms (Aspergillus niger). Heap bioleaching of chalcocite ores is widely used as a relatively low cost process option, especially for marginal deposits. Aspergillus niger has good leaching efficiency in the extraction of Fe, Sn and Au. Now these days metal recovery technique is widely practiced for the recovery of copper, gold, iron, manganese and lead. The bacterial species generally used in bioremediation process are known as Thiobacillus. Decomposition and erosion by sulfur oxidizing microorganisms are the preliminary methods for the extraction of toxic metal ions from contaminated environment. Therefore, bioleaching has potential effect on metal retrieval and detoxification of waste products of industry, coal mine, sewage sludge and heavy metal contaminated soil.