The role of exopolymers in the bioleaching of a non-ferrous metal sulphide

Exocellular polysaccharides were extracted from Thiobacillus ferrooxidans c ells grown in the presence of iron. Cells without these compounds could not adhere to covellite. The loss of the layer of exocellular polysaccharides also affected the direct mechanism of bioleaching of covellite in a negativ e way. This ability to attach to and leach covellite was restored within a few hours when exopolymeric material was produced again. The addition of ex ocellular compounds to cells stripped of exocellular polymers also restored their ability to the same level as that of untreated cells. Thiobacillus t hiooxidans was not able to attach to and leach covellite even when exocellu lar compounds from Thiobacillus ferrooxidans were added.