Decolorization of indigo dye and indigo dye-containing textile effluent by Ganoderma weberianum

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 (Km) and the maximum specific decolorization rate (Vmax) 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.