Abstract
Cyanide compunds, both organic and inorganic, are widely present in natural and industrial environments, especially in effluents from mining and metallurgical processes. Their high toxicity, particularly in the form of free cyanides and hydrogen cyanide, poses severe risks to ecosystems and public health by disrupting cellular respiration via inhibition of cytochrome c oxidase. Conventional chemical treatments such as alkaline chlorination are effective but can be costly, energy-intensive, and generate secondary pollutants. In contrast, microbial bioremediation has emerged as a potentially more sustainable and cost-effective alternative, particularly for on-site treatment of cyanide-laden wastewater from massive tailings dams. Microorganisms including cyanotrophs utilize cyanide as a nitrogen or carbon sources, transforming it into less toxic compounds such as ammonia and carbon dioxide through enzymatic systems like cyanide hydratase, nitrilase, and rhodanese. While bioremediation may operate more slowly than chemical methods, its advantages lie in lower energy consumption, reduced material input, simpler maintenance, and minimized toxic by-products. This review synthesizes current understanding of cyanide’s chemical nature, toxicity, and environmental impact, and explores microbial cyanide degradation mechanisms. It further highlights how advances in metagenomics and synthetic biology (“cyanomics”) are enabling the design of more robust biocatalytic systems. Integrating these biological approaches into environmental management frameworks could reduce long-term operational costs and improve sustainability across cyanide-intensive inustries.