Abstract

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.

Highlights

  • Textile dyes are the main pollutants in the textile and dyeing industry’s wastewater

  • The effect of incubation time on biodecolorization To test the effect of incubation time on biodecolorization of indigo carmine dye, the bacterium was incubated in 50 mg/L dye-containing medium under static and agitated (150 rpm) conditions for 6 h

  • The decolorization of indigo carmine dye by this bacterium was not strongly dependent on the conditions tested. This strain could be used to treat textile wastewaters containing indigo dyes. This dye was decolorized by crude laccase of F. trogii to various extents depending on the incubation conditions

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Summary

Introduction

Textile dyes are the main pollutants in the textile and dyeing industry’s wastewater. 5%–10% of the dyes used are released into the environment with wastewater, and the colored wastewater negatively affects photosynthetic activity and dissolved oxygen concentration in water bodies into which it is released. The decolorization of this type of wastewater is generally more important than the remediation of the other colorless organic substances (Banat et al, 1996; Wong and Yu, 1999). Textile dyes are highly recalcitrant to biological degradation. Textile and dyeing industry wastewater is not effectively decolorized by conventional biological treatment systems such as activated sludge systems. There have been many studies on decolorization of wastewater containing dyes using various methods and biological systems (Yesilada et al, 2003; Barka et al, 2008; Ramya et al, 2008; Manivannan et al, 2011)

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