Identification of bacterial strains from tannery effluent and reduction of hexavalent chromium.

ABSTRACT

Four chromium-resistant bacteria were isolated from tannery effluent collected from Burgelarab, Alexandria, Egypt. These isolates displayed different degrees of chromate reduction under aerobic conditions. Based on 16S rDNA gene sequence analysis, two of them (S3 and S4) were identified as Acinetobacter, and Pseudomonas, respectively. The minimum inhibitory concentration for Acinetobacter sp. strain S3 was 160 mg l-1, while it was 200 mg l-1 for Pseudomonas sp. strain S4. However, strain S4 was able to reduce a wide range of Cr (VI) concentrations from 20 to 200 mg l-1; while, it was reducing 64.4% of Cr (VI) at 160 mg l-1 within 72 hr. Immobilization experiments demonstrated that strain S4 in calcium alginate gel matrix was more effective than the using of free cells in chromium reduction.