Thiocyanate biodegradation: harnessing microbial metabolism for mine remediation

Thiocyanate (SCN-) forms in the reaction between cyanide (CN-) and reduced sulfur species, e.g. in gold ore processing and coal-coking wastewater streams, where it is present at millimolar (mM) concentrations(1). Thiocyanate is also present naturally at nM to mu M concentrations in uncontaminated aquatic environments(2). Although less toxic than its precursor CN-, SCN- can harm plants and animals at higher concentrations(3), and thus needs to be removed from wastewater streams prior to disposal or reuse. Fortunately, SCN- can be biodegraded by microorganisms as a supply of reduced sulfur and nitrogen for energy sources, in addition to nutrients for growth(4). Research into how we can best harness the ability of microbes to degrade SCN- may offer newer, more cost-effective and environmentally sustainable treatment solutions(5). By studying biodegradation pathways of SCN- in laboratory and field treatment bioreactor systems, we can also gain fundamental insights into connections across the natural biogeochemical cycles of carbon, sulfur and nitrogen(6).