Abstract
Mining of copper ores affects soils, as well as surface and groundwater on and adjacent to mine sites. Increasingly stringent environmental regulations, corporate sustainability goals and diminishing high-grade ore bodies are driving the mining industry to seek innovative, cost-effective technologies not only for effluent quality improvement, but also to recover values from wastes. These innovations include the development of new biotechnology processes that can be used to recover metal values due to the specificity of specialized microorganisms for particular metals through adsorption or precipitation as part of their metabolism or toxicity response. A large metagenomic database has been established, called M-MAP, the mining microbiome analytics platform, with the goal of identifying candidate native microorganisms present on mine sites with metabolic potentials for mineral, metal, and metalloid transformations. As part of this project, the objective of this study was to discover microorganisms native to copper mine waste environments with the capability for removal of copper from solution. Such organisms can be used in biotechnologies for recovery of copper from mine impacted water.
Samples were collected from mine tailings at a copper mine where copper concentrations were between 100 and 3000 mg/kg. These samples were enriched in growth medium designed for aerobic heterotrophic bacteria that was supplemented with copper (Cu2+) over a range of concentrations from 0 to 400 mg/L. An isolate was obtained that grew in the presence of 100 mg/L Cu2+. This was identified, using whole genome sequencing, as a strain of Stenotrophomonas maltophilia. The strain’s tolerance to copper was tested at concentrations up to 1000 mg/L, and it grew in 200 mg/L copper, but not when the copper concentration was 400 mg/L and above. The S. Maltophilia isolate removed 18% of copper from a 200 mg/L Cu2+ solution after 24 hours of growth. It was observed that S. maltophilia increased the pH of the medium from an initial pH of 5 to pH 8 throughout its exponential growth period. Using scanning electron microscopy, biopolymers were observed interconnecting the microorganism cells when copper was present in the growth medium. Preliminary results suggest that this Stenotrophomonas Maltophilia strain has the potential for use in bioremediation and recovery of copper from mine impacted water.