Abstract

Many natural and synthetic dyes present in industrial effluents are resistant to degradation by conventional treatments. The decolorization of indigo dye and indigo dye-containing textile wastewater was carried out using the newly isolated ligninolytic fungus strainGanoderma weberianum TZC1. This strain was shown to decolorize both indigo dye and its effluents efficiently; the optimal pH and temperature ranges for activity were pH 4.0-5.0 and 28-33°C for indigo dye, and pH 3.0 and 28-33°C for indigo dye effluents, respectively. A decolorization efficiency of 92% for indigo dye was achieved by the cultivation of G.weberianum TZC1 for 1 h at an initial dye concentration of 20 mg l^-1. The highest decolorization efficiency for the indigo dye effluent (A₆₅₀=0.52) was 25%, and it was achieved by the cultivation of the culture containing equal volumes of the dye effluent and mycelial pellets for 1 h. The correlation between decolorization rate and initial concentration of indigo dye can be interpreted by Michaelis-Menten model. The Michaelis constant (K_m) and the maximum specific decolorization rate (V_max) were 24.33 mg l^-1 and 13.99 mg g FW^-1h^-1, respectively. In addition, analyses of lignin peroxidase, manganese peroxidase and laccase activities as well as native polyacrylamide gel electrophoresis ofG. weberianum TZC1 crude enzyme, confirmed that laccase played a major role in indigo dye decolorization. Furthermore, G. weberianum was shown to be used efficiently and repeatedly in repeated-batch decolorization operations for both indigo dye and its effluents. Our results suggest that the strain G. weberianum TZC1 had promising applications in the treatment of indigo dye-containing wastewater.

Key words:  Decolorization, G. weberianum, indigo dye, indigo dye-containing textile effluent, laccase.