Effective thiocyanate biodegradation mediated by bacteria associated to Argentinean mining areas potentially applicable to wastewater biotreatment

Abstract

In San Juan, Argentina, open-pit gold-mining activities use cyanide leaching for metal extraction. This species produces thiocyanate, afecting aquatic organisms at levels of chronic exposure. One of these mines is currently operational fnding anomalous physicochemical parameter values downstream the Jáchal River. The objective of this work was to analyse thiocyanate iodegradation applying isolated native microorganisms. Bacterial tolerance and degradation of thiocyanate were studied, selecting and identifying the strains Pseudomonas mandelii M1 and Pseudomonas veronii M3. The thiocyanate minimal inhibitory concentration for P. mandelii M1 and P. veronii M3 was 109±10 mM and 99±4 mM, respectively. A 4-day degradation study using 25 mM thiocyanate revealed a removal of 94% in 71 h for P. mandelii M1 and 96% for P. veronii M3 at 96 h. These isolates from the mining area were able to reduce SCN− concentrations below discharge guidelines to ensure biota protection. The minimum nutrient requirements, the rapid consumption of thiocyanate achieved and their bioflm development ability constitute the frst tools in the design of biotreatment of thiocyanate-enriched wastewater consequence of cyanide leaching practices.