Isolation and Characterization of Chromate Resistant and Reducing Bacteria from Tannery Effluent of Chittagong, Bangladesh

Abstract

Context: Waste water containing Chromium (Cr⁶⁺) is by far the most important environmental challenge being faced.

Objectives: The present study was planned on the isolation and characterization of chromate resistant and reducing bacterial strains in order to use them for detoxification of chromate.

Materials and Methods: Water samples were collected to isolate microorganisms from tannery effluent of Baluchara, Chittagong and inoculated into Luria-Bertani medium with added Cr⁶⁺ as K₂Cr₂O₇. The organisms have been identified and studied for Cr⁶⁺ reduction-ability in growth dependent manner.

Results: A total of 35 isolates have been selected as potential organism belonging to the species of Moraxella (14.3%), Bacillus (11.43%), Streptococcus (25.72%), Staphylococcus (5.7%), Salmonella (12.3%), E. coli (13.3%), Enterobacter (11.3%), Hafnia alvei (2.45%) and Alcaligenes (3.5%). The selected isolates were able to tolerate at least 500 mg/l of Cr⁶⁺. The total Cr⁶⁺ concentration of the effluent sample analysed was found to be about 23.73 mg/l as determined by Atomic Absorption Spectrophotometry. Two of the isolates reduced 38% and 32% of Cr⁶⁺ added to the medium. Another 7 isolates showed Cr⁶⁺; reducing capability ranging from 18 to 22%.

Conclusion: As the isolates have turned out to successfully reduce Cr⁶⁺ in this study, these can be used for the development of bioremediation process.

Key words: Enzymatic reduction; Bioremediation; Chromium; Ecotoxicity; Tannery.

DOI: 10.3329/jbs.v17i0.7104

J. bio-sci. 17: 71-76, 2009