Decolorization of azo dyes with immobilized Pseudomonas luteola

Immobilized Pseudomonas luteola able to reduce azo groups enzymically were used as a biocatalyst for the decolorization of wastewater containing azo dyes. Cells of P. luteola were immobilized by entrapment in natural and synthetic polymeric matrices. The effects of operational conditions (e.g., temperature, pH, dye concentration, etc.) on microbial decolorization were investigated. The reusability of the immobilized biocatalyst was evaluated with repeated-batch decolorization experiments. Immobilized cells were less sensitive to agitation rates (dissolved oxygen levels) and pH as compared with suspended cells, while the effects of temperature were similar for both suspended and immobilized cells. Michaelis-Menten kinetics was used to describe the apparent correlation between the decolorization rate and the dye concentration. After four repeated experiments, the decolorization rate of the free cells decreased by nearly 45%, while CA-, CGN-, and PAA-immobilized cells retained over 75, 85, and 80% of their original activity, respectively. The time required for 50% conversion (t_1/2) remained nearly the same for CGN- and PAA-immobilized cells during four cycles, indicating the stable decolorization efficiency of these immobilized cells.