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Updated: 04-07-13

Detoxification of Mercury Pollutant by Immobilized Yeast Strain Candida xylopsoci

Aatif Amin and Zakia Latif^*

Abstract: Keeping in mind the toxicity of mercury, this study was designed to isolate and evaluate the yeast strains for the remediation of mercury from the environment. Yeast strains, from various sources, were isolated on Yeast Extract Peptone Dextrose (YEPD) medium supplemented with different concentrations of Mercuric chloride (HgCl₂). Well plate method was used for preliminary screening of strains resistant to mercury. Seven strains were selected for phenotypic characterization on YEPD medium supplemented with HgCl₂. Mercury resistant strains were also evaluated for Hydrogen sulfide (H₂S) production on Lead acetate (LA) medium. H₂S producer yeasts co-precipitated the divalent mercury (Hg⁺²) in the form of mercuric sulfide (HgS) which is less toxic and insoluble in water. Quantification of mercury from selected strains was done by Dithizone method. Characterization of selected strains was also done by 18S rRNA (Ribosomal ribonucleic acid) sequencing. Two strains, Candida xylopsoci (Z-HS 51), with highest ability and Candida rugosa (Z-HS 13) with lowest ability to remediate mercury, were entrapped in sodium alginate. The immobilized C.xylopsoci (Z-HS 51) was also compared with free cells for its ability to reduce mercury pollutant. The reusability and shelf life of immobilized cells of C. xylopsoci (Z-HS 51) was also checked.

Department of Microbiology and Molecular Genetics, University of the Punjab, 54590 Lahore, Pakistan

^*Corresponding author’s e-mail: zakia.mmg@pu.edu.pk; umna123@yahoo.com.