The bioaccumulation of chromium(VI), nickel(II), copper(II), and reactive dye by the yeast Rhodotorula mucilaginosa has been investigated in media containing molasses as a carbon and energy source. Optimal pH values for the yeast cells to remove the pollutants were pH 4 for copper(II) and dye, pH 6 for chromium(VI) and dye, and pH S for nickel(II) and dye in media containing 50 mg l(-1) heavy metal and 50 mg l(-1) Remazol Blue. The maximum dye bioaccumulation was observed within 4-6 days and uptake yields varied from 93% to 97%. The highest copper(II) removal yields measured were 30.6% for 45.4 mg l(-1) and 32.4% for 95.9 mg l(-1) initial copper(II) concentrations. The nickel(II) removal yield was 45.5% for 22.3 mg l(-1), 38.0% for 34.7 mg l(-1), and 30.3% for 62.2 mg l(-1). Higher chromium(VI) removal yields were obtained, such as 94.5% for 49.2 mg l(-1) and 87.7% for 129.2 mg l(-1) initial chromium(VI) concentration. The maximum dye and heavy metal bioaccumulation yield was investigated in media with a constant dye (approximately 50 mg l(-1)) and increasing heavy metal concentration. In the medium with 48.9-98.8 mg l(-1) copper(II) and constant dye concentration, the maximum copper(II) bioaccumulation was 27.7% and 27.9% whereas the maximum dye bioaccumulation was 96.1% and 95.3%. The maximum chromium(VI) bioaccumulation in the medium with dye was 95.2% and 80.3% at 48.2 and 102.2 mg l(-1) chromium(VI) concentrations. In these media dye bioaccumulation was 76.1% and 35.1%, respectively. The highest nickel(II) removal was 6.1%, 20.3% and 16.0% in the medium with 23.8 mg l(-1) nickel(II) + 37.8 mg l(-1) dye, 38.1. mg l(-1) nickel(II) + 33.4 mg l(-1) dye and 59.0 mg l(-1) nickel(II)+ 39.2 mg l(-1) dye, respectively. The maximum dye bioaccumulation yield in the media with nickel(II) was 94.1%, 78.0% and 58.7%, respectively. (C) 2008 Elsevier B.V All rights reserved.