Comparison of indigo carmine decolorization by Pseudomonas aeruginosa and crude laccase enzyme from Funalia trogii

Abstract

The effects of incubation time, temperature, initial pH, and dye concentration on the indigo carmine decolorization activityof Pseudomonas aeruginosa ATCC 10145 and some factors on the decolorization potential of crude laccase enzyme obtained fromFunalia trogii ATCC 200800 were comparatively investigated. This bacterium showed effective decolorization activity at all agitation andtemperature values. Indigo carmine was greatly decolorized by P. aeruginosa at all pH values except pH 10. A decrease in decolorizationactivity occurred with increasing dye concentration, but this bacterium effectively decolorized the dye within 24 h. The decolorizationprocess was through microbial metabolism, not biosorption. No decolorization or laccase activity could be obtained by the cell-freeintracellular extract or culture filtrate of this bacterium. On the other hand, crude laccase effectively decolorized indigo carmine underhighly acidic conditions, especially at pH 3.0 as 57% in 300 seconds. This activity decreased progressively due to the increase in pHvalues. 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 hightemperatures in various industrial applications.