Production of laccase by Trametes hirsuta grown in an immersion bioreactor and its application in the decolorization of dyes from a leather factory

An alternative system for producing laccase on a bioreactor scale by the white-rot fungus Trametes hirsuta is proposed. The experiments were performed in an immersion bioreactor (employing cuttings of stainless steel sponges as a support) and the culture medium was supplemented with copper sulfate (1 mM). Operating under these conditions, it was possible to obtain a maximum laccase activity of nearly 5,000 U/L within 9 days. In addition, the ability of the crude laccase produced to decolorize two synthetic acid dyes utilized in the leather industry (Luganil Green and Sella Solid Red) was investigated. The effect of the pH and the enzyme activity on decolorization was analyzed. It was found that a pH of 4.0 and a laccase activity of 300 U/L were optimal for Luganil dye decolorization (16.2% in 2 hours). Sella Solid Red showed its highest decolorization (around 40% in 2 hours) when used at pH 5.0 and at a laccase activity of 1,000 U/L.