Production of biosurfactants by bacteria isolated from a mine tailing zone in Southern Mexico and their resistance to heavy metals

Abstract

Tailings generated through mining processes often create leachates containing high concentrations of heavy metals such as As, Fe, Mn, Zn and Pb. These high concentrations of heavy metals result in environ-mental damage such as contamination of soil, groundwater and air, which represents a huge problem for individuals living near mining areas. An alternative for soil metal removal is microbiological processes including the production of biosurfactants, possibly a survival mechanism for adverse conditions of mine tailings and leachates. Moreover, mine tailings are materials that have attracted interest among researchers, because they can be exploited by innovative techniques like phytomining. In this study, we sampled the leachates of the “El fraile” mine tailings and identified 103 bacteria capable of growth on these leachates. We observed that 11 bacteria produce a high amount of biosurfactants and developed the multi-metal tolerance with higher concentration gradient of Pb, Cd, Cu, Fe, Zn and As. We showed that the bacteria tolerate 853 nM of As and up to 12 nM of Pb, 17 nM of Cd, 10.6 nM of Cu, 22 nM of Fe and 10.5 nM of Zn. We determined that the bacterial isolates clustered within five phylogenetic groups that were very close: Enterobacter, Klebsiella, Artherobacter, Pantoea and Solibacillus groups. A bank of strains resistant to heavy metals and producers of biosurfactants was obtained for future studies on the mechanism of absorption or assimilation of heavy metals and light was shed on the alternative use of these bacteria in bioremediation of metal pollution. Key words: Bacteria, metals, biosurfactants, mine tailings.