A microbiological process using Kluyveromyces marxianus was developed for the removal of copper(II) ions in the presence of molasses as nutrient. The combined effects of molasses sucrose and copper(II) ions on the growth and copper(II) bioaccumulation properties of growing K. marxianus cells has been tested under laboratory conditions as a function of initial pH and single-molasses sucrose and dual-molasses sucrose and copper(II) ion concentrations. The optimum pH value for maximum growth and metal ion accumulation was determined as 4.0 for the microorganism. At a constant copper(II) concentration, the growth and copper(II) bioaccumulation increased with increasing concentrations of molasses sucrose up to 20 g l(-1). Although the increase in initial copper(II) concentration increased the copper(II) uptake capacity of the microorganism, the inhibition effect of copper(II) ions on the growth of K. marxianus was observed at all the concentrations of copper(II) at ail the sucrose concentrations studied. The non-competitive toxic component inhibition model (assuming the copper(II) ions as the toxic inhibitory component) was also applied to depict the relationship between the specific growth rate of microorganism and molasses sucrose and copper(II) concentrations and model parameters were determined by graphical method. (C) 2000 Elsevier Science Ltd. All rights reserved.