BACKGROUND: Dyes used in textile industries and released to their wastewaters are serious ecological problems as they are hard to degrade by common means used in wastewater treatment plants. White-rot fungi can biodegrade textile dyestuffs using their extracellular enzyme system. However, it is difficult to keep them in functional form in conventional wastewater treatment systems, because of their specific nutritional and physiological requirements. Selection of a suitable bioreactor type and mode of operation are crucial for successful implementation of white rot fungi in waste water treatment processes. RESULTS: Both Remazol Brilliant Blue R (RBBR) and Reactive Orange 16 (RO16) were decolorized efficiently in the trickle-bed reactor. A degree of decolorization exceeding 80% was achieved within 2 days with all mycelium carriers and both dyes. In reactors packed with plastic kitchen scourers and luffa sponge slices the decolorization degree reached 90% within 2 days. The initial rate of decolorization of RBBR dye was notably higher than the rate of 8016 decolorization. The lowest liquid hold-up value (1-1.5%) was achieved in the reactor packed with the plastic kitchen scourers, the largest hold-up value (3-5%) was observed in the reactor filled with luffa sponge. The longest mean retention time, 430 s, was achieved in the reactor with the luffa carrier at a liquid flow rate of 6.81 cm(3) min(-1); the shortest mean retention times (10-20 s) were achieved in the reactor filled with the plastic kitchen scourers. Broad liquid residence time distributions were observed in tracer experiments at all volumetric flow rates. CONCLUSIONS: The ability of I. lacteus to secrete laccase and manganese peroxidase enzymes in a trickle-bed bioreactor with three mycelium carriers was proved and quantified experimentally. The decolorization capability of the I. lacteus mycelium was only marginally influenced by the kind of carrier used. Basic operational characteristics of the reactor - residence times, axial dispersion and liquid hold-up - were determined at various liquid flow rates.(C) 2009 Society of Chemical Industry