Isolation of Cyanide-Degrading Bacteria from Cassava-Processing Effluent

Cyanidation is a widely used process for gold leaching where cyanide-containing solutions are used to extract metals from ores. However, cyanidation produces toxic wastes that must be treated prior to discharge to the environment. In this context, cyanide biodegradation has appeared as an environmental friendly and alternative technology. In this study, cyanide-degrading bacteria was isolated from cassava-processing effluents containing 300 ppm of free cyanide using a selective media with cyanide and glycerol. From the effluent, four isolated strains and one consortium were obtained and were tested to degrade cyanide in alkaline medium containing 150 mg L⁻¹ free cyanide and 0.5 g L⁻¹ scratch for 72 h in orbital agitation. Two strains and the consortium showed the biggest difference from negative control degrading 27–30% of free cyanide in solution proving their potential use in cyanide treatment. Finally, microscopy analysis showed rod-shaped cells in selected samples and classified isolated strains as gram negative and the consortium as gram positive.