3. Bioextraction of metals

3.1 Different methods of microbiological extraction of metals from aqueous solutions

Biological concentration comes into play in a number of ways.

• Adsorption to the cell surface

  The negatively charged cell surface, due to the presence of carboxylate, hydryl and phosphate groups in cell wall polymers, captures metal cations. Uncharged groups, such as nitrogen peptides, can act as ligands to complement the metal cation coordination sites.

  Different microorganisms have different charge distributions and geometries, which can selectively retain certain metal cations. Metal retention capacity is also pH-dependent, due to the protonation of these groups.

  Fungi and...