Comparison of indigo carmine decolorization by <i>Pseudomonas</i> <i>aeruginosa</i> and crude laccase enzyme from <i>Funalia</i> <i>trogii</i>

The effects of incubation time, temperature, initial pH, and dye concentration on the indigo carmine decolorization activity of Pseudomonas aeruginosa ATCC 10145 and some factors on the decolorization potential of crude laccase enzyme obtained from Funalia trogii ATCC 200800 were comparatively investigated. This bacterium showed effective decolorization activity at all agitation and temperature values. Indigo carmine was greatly decolorized by P. aeruginosa at all pH values except pH 10. A decrease in decolorization activity occurred with increasing dye concentration, but this bacterium effectively decolorized the dye within 24 h. The decolorization process was through microbial metabolism, not biosorption. No decolorization or laccase activity could be obtained by the cell-free intracellular extract or culture filtrate of this bacterium. On the other hand, crude laccase effectively decolorized indigo carmine under highly acidic conditions, especially at pH 3.0 as 57% in 300 seconds. This activity decreased progressively due to the increase in pH values. In a short incubation period and at high temperature values, the crude laccase enzyme removed the color of the dye at 50 °C (56%), 60 °C (45%), and 70 °C (38%). These data are important for improving methods for decolorization of textile dyes used at high temperatures in various industrial applications.