Abstract

A chromate resistant facultative anaerobic bacterial strain (FA-3) was isolated from the treated tannery effluent of Jajmau, Kanpur (India) and was identified as Bacillus cereus. FA-3 was tolerant to 1400 μg/ml of Cr (VI) and reduced a maximum of 72% Cr (VI) at 1000 μg/ml chromate concentration. The rate of growth of B. cereus decreased with the increase in Cr (VI) concentration of the medium and the chromate reduction was directly correlated to the growth of the strain. The strain FA-3 was capable of reducing Cr (VI) under a wide range of temperatures (25 to 40°C) and pH (6 to 10) with optimum at 37°C and initial pH 8.0. Glucose (0.5%) slightly increased the Cr (VI) reduction (78%). Heavy metal ions such as Zn²⁺, Ni²⁺ and Co²⁺ slightly affected the Cr (VI) reduction, while arsenic (As³⁺) significantly affected the Cr (VI) reduction. However, in the presence of Hg²⁺, the reduction of Cr (VI) was totally inhibited. Since, the strain has potential to survive and multiply in a wide range of environmental conditions and due to its high Cr (VI) reduction efficiency in the presence of other metal cations, it can be exploited for the bioremediation of chromate containing wastes.

Key words: Treated tannery effluent, chromate resistant bacteria, minimal inhibitory concentration, heavy metal ions.