Oxidative decolorization of direct blue 71 azo dye by Saccharomyces cerevisiae catalyzed by nano zero-valent iron

Abstract

The textile industries wastewater is one of the most serious sources of environmental pollution due to presence of the textile dyes. In the present study, five bacteria and three fungi were isolated on Mineral Salt Medium (MSM) supplemented with 200 mg/l of Direct Blue 71 azo dye. The most active isolate was identified by 18S-rRNA gene sequencing method as Saccharomyces cerevisiae. The decolorization and degradation of Direct Blue 71 azo dye by S. cerevisiae was investigated in presence and absence of nano-scaled zero-valent iron (NZVI). The metabolic pathway of the dye degradation was elucidated using GC/MS analysis to identify the metabolites. This procedure was supported by enzymes assay and bioinformatics analysis. Dye-decay curves showed 96% dye removal after 72 hr. in absence of the catalyst; while it was 100% after 48 hr. in presence of 0.1% NZVI. High efficiency to decolorize Direct Blue71 enables this yeast to be used in biological treatment of industrial effluent containing such azo-dyes.