Cr(VI) or Cu(II) Removal by Indigenous Yeasts Isolated from Argentinean Polluted Sites.

VILLEGAS L; RIVADENEIRA J; DELGADO O D; AMOROSO M J; DE FIGUEROA L I C

Brasil

Conferencia; Eleventh International Congress on Yeasts (ICY 2004); 2004

Yeasts in Science and Technology, the Quest for Sustainable Developments

Heavy metals pollution is one of the most serius environmental problems. Mining and industrial activities are the main sources of heavy metal contamination. Iron, Zinc, Nickel, Chromium and Cupper play an important role as trace elements in biochemical reactions but these heavy metal ions are toxic at higher concentrations, producing serious public health problems. Traditional technologies for the removal of these heavy metals are very expensive and may have several disadvantages. New techniques like biosorption, are required for reducing their concentrations to environmental acceptable levels at low costs. Microorganisms possess a potential for accumulating or removing many heavy metal cations and they are the most inexpensive source of biomass. The aim of this work was to study yeast strains capable to uptake Cu2+ or Cr6+. Soil and water samples were collected from different contaminated sites where mine and tannery factories discharge their effluents containing Cu+2 and Cr+6 respectively. Only 27 indigenous yeasts, were isolated from these samples and their heavy metals uptake was evaluated in relationship to their biomass developments. These microorganisms were cultured in minimal medium containing 0.1 to 1 mM of Cu2+ or Cr6+, cultures without the addition of heavy metals were performed as controls. The growth was followed by turbidity measurements at O.D.620 nm and by dry weight. Heavy metal concentrations were determined intracellularly and in free cell supernatants by both, atomic absorption spectrophotometer and colorimetric methods. The growth rates and the heavy metals uptake decreased when the initial Cu2+and Cr6+ concentrations in the medium were increased. The isolates were grouped using the RFLP restriction patterns from the ribosomal region. These results play an important role for understanding how these microorganisms develop resistance mechanisms for heavy metals when they are in toxic concentrations.