Isolated indigenous yeasts from Antarctica with the ability to remove toxic hexavalent chromium

Abstract

Seven chromate-reducing yeasts isolated from Antarctic soils (with no history of Cr(VI) contamination) were evaluated as promising candidates for alleviating Cr(VI)-contamination. These yeast species have not been extensively studied regarding Cr(VI) tolerance and reduction abilities. Based on their tolerance (up to 2 mM) and ability to remove Cr(VI) from culture media, two representative isolates of Candida sake #14 and Debaryomyces hansenii #35 were chosen. The resistant yeasts were cultivated in YM medium plus 1 mM Cr(VI) at 25°C, causing a removal of ∼90 and ∼70% hexavalent chromium before reaching 96 h of culture according to growth curves of C. sake #14 and D. hansenii #35, respectively. Cr(VI) removal kinetic analysis indicated that both isolates removed Cr(VI) by reduction to Cr(III), and incorporated a small portion into the biomass. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX) confirms the biosorption process, indicating the existence of a complex remediation mechanism. In conclusion, Antarctica is an extreme environment with a potential to discover promising new candidates for the removal of Cr(VI). These results are interesting from a biotechnological point of view since psychrotolerant yeasts could be involved in the design of a profitable technology for the elimination of the toxic form of Cr.