Influence of NaCl and Na2SO4 on the kinetics and dye decolorization ability of crude laccase from Ganoderma lucidum

In a solid state medium using yellow passion fruit waste as substrate, the basidiomycete Ganoderma lucidum produced a laccase as the main ligninolytic enzyme. This crude enzyme presented Michaelian behavior with both substrates tested, namely 3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and the anthraquinone dye remazol brilliant blue R (RBBR). The K-M's for these substrates were, respectively, 0.232 x 10(-3) and 0.602 x 10(-3) M. The actions of NaCl and Na2SO4, two important salts usually found in textile wastewaters, were investigated. The enzyme was inhibited by NaCl, but not by Na2SO4. Inhibition by NaCl was of the mixed type with two different inhibition constants. The enzyme was able to completely decolorize RBBR in the presence of 1.0 M Na2SO4 and 50% decolorization was found in the presence of 0.1 M NaCl. Such properties certainly make the enzyme a good agent for textile dye effluent treatment considering the fact that wastewaters of this industry usually contain high concentrations of NaCl and Na2SO4. (C) 2010 Elsevier Ltd. All rights reserved.