Application of laccase on effective biodegradation of two azo dyes: Optimization using Response Surface Methodology (RSM)

Synthetic dyes present in industrial effluents, including textile, paper, etc., due to having toxic effects on living organisms, especially human health, and compatibility with living in aquatic conditions, have attracted great attention. The application of common physicochemical methods for dye wastewater treatment has encountered serious problems. Biological treatment, especially enzymatic methods, can be employed for effective and environmental- friendly treatment of dye effluents. Laccase, belonging to the blue multi-copper oxidases category, can oxidize a wide variety of substrates, especially synthetic dyes. In this study, laccase was used to biodegrade two azo dyes, i.e. Direct Red 23 and Acid Blue 92. Face-centered central composite design (FCCCD) was used to optimize the main parameters of the decolorization process. The optimum conditions to maximize the bio-decolorization process of AB92 were X1=11.93, X2=4.78, and X3=93.10, with a decolorization extent of 93.10%. These conditions for DR23 were X1=15.81, X2=3.61, and X3=99.58, with a decolorization extent of 98.34%. The optimum conditions for both dyes showed that the enzymatic decolorization favored lower dye concentration.

Keywords:

laccase , dye , enzymatic decolorization , central composite design.