Characterization and Heavy Metal Bioremediation Potential of <i>Halomonas</i> Isolates from the Bolivian Altiplano

Abstract

The Bolivian Altiplano has an ongoing history of heavy metal pollution due to years of uncontrolled mining in this region. Heavy metals are a threat to natural environments such as lakes and soils with cultural and economic importance for the local communities. The extreme environmental conditions of the Bolivian Altiplano translate into alkaline soils with high concentration of minerals, high radiation and considerable daily temperature oscillations. Halophilic and halotolerant microorganisms isolated from such environments have interesting biotechnological applications including bioremediation of metal polluted waters and soils. Here, bacterial strains from the Bolivian Altiplano were characterized and biosorption capacity evaluated for three heavy metals (Pb⁺², Cd⁺² and Zn⁺²) in variable concentrations. Four strains were able to grow in multimetal medium with a final concentration of 100 mg. L^-1, with a higher tolerance to Pb⁺². The four isolates were selected for further characterization and were identified as different species of <i>Halomonas </i>genus. The best heavy metal biosorption rates for the four isolates were found at pH 7 and 37°C. Additionally, the fastest uptake rate for all three metals was under 120 minutes in the four chosen isolates. The biosorption process was best described by Langmuir isotherm for all isolates exposed to the three metals separately. The four <i>Halomonas</i> isolates showed a bioremediation potential for heavy metal polluted substrates, although the highest biosorption capacity values were from isolate Ss_is3 notably for Pb⁺². This study provides new information about the potential biotechnological capacities of <i>Halomonas</i> strains isolated from mineral soils in the Andes.