ISOLATION AND ESTIMATION OF REDUCTION POTENTIAL OF CR(VI) REDUCING BACTERIA FROM TANNERY WASTES

Abstract

Chromium (Cr) is a heavy metal, naturally found in biosphere. The two oxidation states i.e. Cr+3 and Cr+6 are of biological concern. Cr+3 occurs in environment in less toxic and insoluble form whereas Cr+6 is soluble and more toxic to living cells. This study aims to isolate chromate resistant bacterial strains from tannery polluted site of Lahore, Pakistan. Sixteen (UT1, UT2, UT3, UT4, UT5, UT6, UT8, UT10, UT11, UT12, UT17, UT18, UT20, UT21, UT22, AKR2) different chromate resistant bacteria were isolated at an initial concentration of 1500 mg/L K2CrO4. Morphological and biochemical analysis showed gram positive cocci and catalase and oxidase positive character. Heavy metals and antibiotics resistant profiling exhibited multiple heavy and antibiotic resistance. These strains could tolerate 3000 mg/L of K2CrO4 in Luria broth. Strain UT8 and UT20 exhibited highest Cr(VI) reduction potential of 77% and 74%, respectively at an initial concentration of 1500 mg/L K2CrO4. Strain UT11 revealed maximum exopolysaccharide (EPS) production i.e. 31mg under Cr(VI) stress condition (1500 mg/L). These strains can be suitable candidates for the remediation of chromate contaminated sites