Microbial communities of acidic post-mining environments and their use in laterite bioreduction

Abstract

The biogeochemistry of post-mining areas is important because of their impact on the environment and the possibility of remediating such areas. Such a hostile environment is also a source of acidophilic microorganisms that can dissolve minerals that might be applied in the extractive metallurgy of low-grade oxide ores. Therefore, the study used autochthonic microorganisms isolated from water and sediment samples taken from places affected by acid mine drainage. The acidophiles were isolated under aerobic and anaerobic conditions. Genomic analysis revealed low prokaryotic diversity. The genera with a relative abundance greater than 1% were Acidithiobacillus (39.8-84.2%), Ferrimicrobium (26.4-34.4%), Acidiphilium (8.31-28.8%), and Leptospirillum (9.6-32.1%). Aerobic bacteria were adapted to reduce iron(III) under a nitrogen atmosphere and the presence of elemental sulfur as an electron donor. It was shown that increasing the amount of sulfur (1-5 g) had little effect on the process kinetics. In anaerobic bottom sediments, Sulfobacillus (45.7%) and Acidisphaera (32.7%) predominated. Microorganisms showed the fastest reduction activity when glycerol was used as an electron donor. Four weeks of anaerobic-controlled bioreduction of laterites yielded nickel and magnesium at 33.3% and 77.3%, respectively, which could have potential applications in the processing of laterites.