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Abstract
Microbial reduction of toxic Cr6+ to the less toxic Cr3+ is potentially a useful bioremediation process. Among the matrices tested for whole cell immobilization of an efficient chromate-reducing Streptomyces griseus strain, PVA-alginate was the most effective and was used for reduction of Cr(VI) in a bioreactor. Cr6+ reduction efficiency decreased as Cr6+ was increased from 2 to 12 mg l-1 but increased with an increase in biomass concentration. However, increasing the flow rate from 2 to 8 ml h-1 did not significantly affect Cr6+ reduction. The reduction was faster in simulated effluent than in synthetic medium and complete removal of 8 mg Cr6+ l-1 from effluent and synthetic medium occurred in 2 and 12 h, respectively. Our results indicate that immobilized S. griseus cells could be applied for the large-scale bioremediation of chromate-containing effluents and wastewaters. [PUBLICATION ABSTRACT]