Biodegradation Of Thiocyanate Using Microbial Consortia Cultured From Gold Mine Tailings

Abstract:

Some bacteria possess the capability to degrade SCN^-; therefore, harnessing this metabolic trait offers a biotechnological remediation strategy for SCN^- produced in gold ore processing. A tailings storage facility (TSF) at a gold mine in Victoria, Australia holds large quantities of thiocyanate (SCN^-) contaminated mine waste. The surface water in the TSF typically contains SCN^- concentrations of >800 mg L^-1, and seepage from the facility has contaminated the groundwater at the site. This study aimed to culture SCN^-degrading microbes from the TSF, characterize the microbial consortia and test its operational parameters for use in a thiocyanate-degrading bioreactor.

Surface samples were obtained from several locations around the TSF facility and used to inoculate medium reflective of the moderately saline and alkaline tailings water at the TSF, in the absence of organic carbon but subject to additions of phosphate and trace metals. Four microbial consortia capable of rapid SCN^- degradation were successfully cultured. Sequencing of 16S rRNA genes found that the consortia were dominated by Thiobacillus species, a genus of known SCN^- degraders. Lower abundances of other SCN^- degraders; Sphingopyxis and Rhodobacter, were also identified. The impact of a number of geochemical conditions, including pH, temperature and SCN^- concentration, upon the growth and SCN^- degrading capacity of these consortia was determined. These results informed the optimization of a lab-scale thiocyanate degrading bioreactor.

In summary, the cultured bacterial consortia proved effective towards SCN^- degradation at the prevailing geochemical conditions of the TSF, requiring minimal nutrient additions. These consortia were dominated by genera of known autotrophic SCN^- degraders. The comprehensive characterisation of these SCN^- degrading consortia will provide the fundamental operational parameters required for deployment of this technique at the field scale.