Hexavalent chromium reduction by a dichromate-resistant gram-positive bacterium isolated from effluents of tanneries

A gram-positive, chromium (Cr)-resistant bacterial strain (ATCC 700729) was isolated from effluent of tanneries. It was grown in media containing pota ssium dichromate concentration up to XO mg mi of the medium. The dichromate reducing capability of the bacterium was checked by estimating the amount of Cr VI in the medium before and after introduction of bacterial culture. The influence of factors like pH of the medium, concentration of Cr, and th e amount of the inoculum was studied to determine the ability of the bacter ium to reduce Cr VI in the medium under various conditions. In a medium con taining dichromate 20 mg ml(-1) more than 87% reduction of dichromate ions was achieved within 72 h. The feasibility of the use of this bacterial stra in for detoxification of dichromate in the industrial wastewater has been a ssessed. The isolated strain can be exploited for specific environmental cl ean-up operations.