**2.9. Biodegradation of residual MxCNs**

Unrecoverable (residual) gold-cyanide and silver-cyanide in the solutions after biosorption treatment (in batch studies) were subjected to biodegradation using "live chemoheterotrophic bacterial consortium". The consortium (comprising of three *Pseudomonas* sp. in a proportion of 1:1:1) capable of degrading free cyanide and thiocyanate as the source of nitrogen was isolated by enrichment culture technique (Patil, 2008) and was available in my laboratory. Biodegradation experiment were conducted under aerobic and optimum conditions of pH (7.0), temperature (30°C), inoculum size (107 cells/ml) and glucose concentration (1 mM). The biodegradation process was used as a polishing step to clean the effluent containing traces of cyanide in order to meet the requirements of statutory agencies.
