Dye decolorization by <Emphasis Type="Italic">Trametes hirsuta</Emphasis> immobilized into alginate beads

Summary The present paper studies the production of laccase by Trametes hirsuta immobilized into alginate beads in an airlift bioreactor. In order to enhance laccase production fresh ammonium chloride was added, which led to the production, of high laccase activities (around 1000 U l⁻¹). The bioreactor operated for 40 days without operational problems and the bioparticles maintained their shape throughout fermentation. Dye decolorization was performed at bioreactor scale operating in the batch mode. High decolorization percentages were obtained in a short time (96% for indigo carmine and 69% for phenol red in 24 h), indicating the suitability of this process for application to synthetic dye decolorization. On the other hand, in vitro decolorization of several industrial azo dyes by crude laccase produced in the above bioreactor was also performed. It was found that some of the dyes needed the addition of 1-hydroxybenzotriazole for their decolorization.