Textile dye degrading laccase from Pseudomonas desmolyticum NCIM 2112

A laccase requiring optimum temperature 60 degrees C. pH 4.0 for the activity and having apparent molecular weight 43,000 Da was purified from Pseudomonas desmolyticum NClM 2112 by three steps, including heating, anion exchange, and molecular sieve chromatography. The purification fold and yield of laccase obtained through Biogel P100 were 45.75 and 19%. respectively. Staining of native gel with L-dopa showed dark brown color band indicating the presence of laccase. in relation to hydroquinone, the substrate specificity of laccase was in the following order: DAB > o-tolidine > ABTS > L-dopa. The absence of monophenolase activity in eluted fractions conformed that the purified protein is laccase. This laccase showed substrate dependent optimum pH character. Effect of inhibitor and metal ion on enzyme activity was analyzed. UV-vis analysis showed the decolorization of Direct Blue-6, Green HE4B and Red HE7B in the presence of laccase. The FTIR spectral comparison between the control dye sample and the metabolites extracted after decolorization by purified laccase have confirmed degradation of these dyes. This study contributes for the structural requirement of a dye to be degradable by P. desmolyticum laccase and is important in order to optimize potential bioremediation systems for industrial textile process water treatment. (c) 2008 Elsevier Inc. All rights reserved.