Exploration of bacterial strains with bioremediation potential for mercury and cyanide from mine tailings in "San Carlos de las Minas, Ecuador"

Ecuador is a developing country that relies on mining as a significant source of economic income every year; however, there needs to be more studies on the soil pollution caused by mining over time. Biological remediation as an alternative to the use of physical and chemical methods offers a more cost-effective and environmentally friendly means to counteract the negative impacts that the presence of heavy metals in mining tailings soils can cause. This study focused on soil sampling from the mining tailings of the San Carlos de las Minas sector, in the Zamora Chinchipe province in Ecuador, to find potential bacterial strains that can degrade two specific contaminants, mercury (Hg) and cyanide (CN^-). For this purpose, 68 soil subsamples were collected. pH, electrical conductivity, moisture, and the concentration of the contaminants were analyzed and measured. The initial concentration of CN^- was 0.14 mg/kg, and of Hg was 88.76 mg/kg. From the soil samples, eight bacterial strains were isolated, characterized at macroscopic and microscopic levels, and identified at the molecular level. The bacteria were then subjected to degradability tests for CN^- and Hg, obtaining interesting results. The degradation capacity of CN^- stood out for the strains Micrococcus aloeverae and Pseudomonas alcaliphila, and for the degradation of Hg, the strains Hydrogenophaga laconesensis and Micrococcus aloeverae were highlighted, achieving degradation percentages of up to 98.80%. These results emphasize the discovery of these bacterial species with potential use in cyanide and mercury remediation processes.