Production of biosurfactants by microorganisms 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.