The aim of the present paper was to investigate the feasibility of grape seeds as a support-substrate for laccase production by the white-rot fungus Trametes hirsuta under solid-state conditions, operating in laboratory-scale bioreactors. Two bioreactor configurations were considered in order to determine the most suitable one: immersion and tray. As regards bioreactor design, the tray configuration led to the highest laccase activities. In addition, the nature of the support employed (inert or non-inert) on laccase production was also evaluated. The results obtained clearly showed the superiority of grape seeds for laccase production over nylon sponge, since they produced much higher activities (around threefold). On the other hand, decolourization of structurally different dyes by the extracellular liquid obtained in the tray configuration operating with grape seeds as a support was assayed. The results showed that the individual dye structures influenced the decolourization extent. However, in all cases a decolourization kinetic of first order with respect to dye concentration was found. (c) 2005 Elsevier Ltd. All rights reserved.