Identification of dye-decolorizing bacteria from textile industry effluents and optimization of decolorization process using response surface methodology

ABSTRACT Textile dye pollution is a major environmental concern due to the discharge of dye-rich effluents into water bodies. Biological methods, especially microbial decolorization, provide a sustainable solution. In this study, bacterial isolate S-3 was obtained from textile effluent and tested for dye decolorization activity. It achieved over 85% removal of Reactive Red (RR), Reactive Yellow (RY), and Basic Blue (BB) within 48 h at 50 ppm, while Basic Violet (BV) showed limited removal, indicating the role of dye structure in the degradation process. 16S rRNA gene sequencing revealed 97.49% similarity to Pseudomonas aeruginosa, which was supported by biochemical and morphological tests. Phylogenetic analysis confirmed its affiliation, and secondary structure prediction of the 16S rRNA gene revealed stable motifs important for ribosomal function. Optimization of decolorization using response surface methodology and central composite design was assessed to evaluate the effects of pH, temperature, and dye concentration. Quadratic regression models for RR, RY, and BB showed strong correlation with experimental results (R2 = 0.9–1.0). Optimal conditions were a slightly alkaline pH (7.2–7.6), moderate temperature (31.8–34 °C), and an intermediate dye concentration (56.6–72.4 ppm). This study highlights the strong potential of P. aeruginosa strain S-3 for bioremediation of dye-contaminated effluents.