Mycoremediation of azo dyes using <i>Cyberlindnera fabianii</i> yeast strain: Application of designs of experiments for decolorization optimization

Abstract

This study investigated the dye decolorization capacity of three yeast strains. Cyberlindnera fabianii was shortlisted for its high decolorization capacity and was further tested on various azo dyes. Based on the color of the biomass, and the UV-Vis analysis, Acid Red 14 was selected as a model dye, to examine the enzymatic biodegradation. The results showed significant increase in the intracellular and extracellular activities of laccase, tyrosinase, manganese peroxidase, and azoreductase. Phytotoxicity assessment indicated that the AR14 biodegradation by-products were not phytotoxic compared to the original dye molecules. Regarding the decolorization optimization, the screening of factors using the Plackett-Burman design showed that pH, dye concentration, and shaking speed had significant effects. These factors and their combined effect were evaluated using response surface methodology with the Box-Behnken model. The pH was the most significant factor, followed by dye concentration. The analysis of the contour plot and the 3D response surface diagram showed that the decolorization was inversely proportional to the increase in the initial dye concentration, but proportional to the initial pH and shaking speed. At optimal conditions (pH = 5.154, AR14 = 50 mg/L), C. fabianii could decolorize more than 97% of AR14 within 12 hr. PRACTITIONER POINTS: Cyberlindnera fabianii is a successful candidate for dye mycoremediation. Oxidase and reductase are the key enzymes involved in the biodegradation of azo dyes. By-products of Acid red 14 biodegradation are not phytoxic compared to the original dye. Design of experience tools enables to determine optimum conditions for efficient decolorization.