The decolourisation of Reactive Black 5 (RB5) by immobilised Funalia trogii was investigated. Cultures of F trogii immobilised on Luffa cylindrica sponge could effectively decolourise the dye. The effect of mycelial age was also studied, and decolourisation rate of a 3-day-old age culture was higher (8.22 mg dye/g dmw day) than those of 0- and 6-day-old cultures (6.86 and 7.80 mg dye/g dmw day). Macroscopic and microscopic examinations showed that dye was not biosorbed on the fungal mycelium. The growth of E trogii was inhibited by all tested dye concentrations with compared to controls but this effect was minimised when the fungus was completely immobilised on the sponge. Using optimal mycelial age, cultures of L. cylindrica sponge were tested for their ability for dye decolourisation at different initial concentration. The kinetic parameters of decolourisation were calculated according to Lineweaver-Burk plots (K-m of 106.04 mg dye/l and V-max of 117.64 mg dye/l day). (C) 2004 Elsevier Ltd. All rights reserved.