Decolorization of the azo dye Acid Orange 51 by laccase produced in solid culture of a newly isolated Trametes trogii strain.

Dalel Daâssi,Maria Jesus Martinez,Moncef Nasri,Hela Zouari-Mechichi,Tahar Mechichi,Fakher Frikha

doi:10.1007/s13205-012-0076-2

Abstract

This study concerns the decolorization and detoxification of the azo dye Acid Orange 51 (AO51) by crude laccase from Trametes trogii produced in solid culture using sawdust as support media. A three-level Box–Behnken factorial design with four factors (enzyme concentration, 1-hydroxybenzotriazole (HBT) concentration, dye concentration and reaction time) combined with response surface methodology was applied to optimize AO51 decolorization. A mathematical model was developed showing the effect of each factor and their interactions on color removal. The model predicted that Acid Orange 51 decolorization above 87.87 ± 1.27 % could be obtained when enzyme concentration, HBT concentration, dye concentration and reaction time were set at 1 U/mL, 0.75 mM, 60 mg/L and 2 days, respectively. The experimental values were in good agreement with the predicted ones and the models were highly significant, the correlation coefficient (R2) being 0.9. Then the desirability function was employed to determine the optimal decolorization condition for each dye and minimize the process cost simultaneously. In addition, germination index assay showed that laccase-treated dye was detoxified; however in the presence of HBT, the phytotoxicity of the treated dye was increased. By using cheap agro-industrial wastes, such as sawdust, a potential laccase was obtained. The low cost of laccase production may further broaden its application in textile wastewater treatment.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-012-0076-2) contains supplementary material, which is available to authorized users.

Highlights

IntroductionAzo dyes are the most important group of synthetic colorants
Progress in industrialization, in particular textile industries, has led to the discharge of unprecedented amount of wastewater containing synthetic dyes, which can be a source of dangerous by-products from oxidation, hydrolysis or other chemical reactions in the wastewater solution.Azo dyes are the most important group of synthetic colorants
This study concerns the decolorization and detoxification of the azo dye Acid Orange 51 (AO51) by crude laccase from Trametes trogii produced in solid culture using sawdust as support media

Summary

Introduction

Azo dyes are the most important group of synthetic colorants. They are generally considered as xenobiotic compounds that are very recalcitrant against biodegradative processes. Several azo dyes and their degradation products might be mutagenic and/or carcinogenic to microorganisms, aquatic life and human beings (Oh et al 1997; de Aragao Umbuzeiro et al 2005; Saratale et al 2011). Many studies have indicated that aromatic amines that arise from the azo reduction and cleavage of azo dyes are thought to be activated as mutagens through their N-oxidation by cytochrome P450 isozymes (Chung 2000). In the food industry some azo dyes, such as orthonitroaniline orange and amaranth (FDS-c red number 5) (Tucson University: ‘‘Health and Safety in the Arts, A Searchable Database of Health and Safety Information for Artists’’), have been banned due to toxic side effects (potential chronic toxicity)

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Conclusion