Abstract
Five chromate-reducing strains were isolated from the chromium landfill and two of them, XW-2 and XW-4 were identified as Bacillus sp. The strain of XW-4 was selected to study the resistance to Cr(VI) and its ability to reduce Cr(VI). The strain was found to tolerate Cr(VI) concentration as high as 100 mg/l, but the cells growth was affected by the presence of Cr(VI), especially at the concentration of 100 mg/l. The experiments also demonstrated that toxic Cr(VI) was reduced effectively into comparatively less toxic Cr(III) by the strain of Bacillus sp., XW-4, and bacterial Cr(VI) reduction was enhanced significantly by addition of glucose. The optimum initial pH for Cr(VI) reduction was 9 and final pH value of 5-6 was observed for initial pH 4-10. The cells reduced Cr(VI) more efficiently at 37 degrees C, compared with that at 20 and 47 degrees C. Within the same incubation time, more amount of Cr(VI) was reduced at higher initial Cr(VI) concentration ranging from 10 to 80 mg/l. Bacterial Cr(VI) reduction was not influenced by NO3- and SO42-. (c) 2006 Published by Elsevier Ltd.