Optimization of conditions for methyl blue decolorization by Paenibacillus ehimensis W3.2MR3 based on Plackett-Burman design and response surface methodology

Treatment of textile wastewater containing synthetic dyes using microorganisms has emerged as a promising, cost-effective, and environmentally sustainable alternative. The objective of this study was to determine the optimal values of the factors directly affecting the decolorization process of methyl blue by Paenibacillus ehimensis W3.2MR3. A Plackett-Burman design was employed as a multifactorial experiment to screen the physical and chemical factors influencing bacterial dye decolorization efficiency, including pH (A: 6–8), temperature (B: 30–50 °C), carbon source (C: 0.5–2.0 g/L), shaking speed (D: 0–300 rpm), nitrogen source (E: 1–2 g/L), inoculum ratio (F: 1–5% v/v), and dye concentration (G: 50–200 mg/L). The Plackett-Burman design results identified pH, inoculum ratio, and dye concentration as the most significant factors, with the highest posterior probabilities recorded for the inoculum ratio (F: 68.16%), pH (A: 65.86%), and dye concentration (G: 29.85%). Subsequently, the response surface method with Box-Behnken design was applied to optimize pH, inoculum ratio, and dye concentration across three levels, yielding optimal conditions of pH 7.49, 3.79% v/v inoculum ratio, and 86.23 mg/L dye concentration, with a maximum decolorization efficiency of 91.38 ± 0.84%. Decolorization efficiency of MB by P. ehimensis W3.2MR3 on the 3-D graphic for response surface optimization of pH, Inoculum ratio, and dye concentrations as well as plot of the relationship between predicted and observed values of MB • The isolated Paenibacillus ehimensis W3.2MR3 was able to remove methyl blue more than 90%. • Plackett-Burman Design and Response Surface Methodology were applied to optimize the conditions for methyl blue removal by Paenibacillus ehimensis W3.2MR3. • The significance of this study lies in its identification of the correlations between influencing factors and the MB decolorization efficiency of P. ehimensis W3.2MR3. • The pH, inoculum ratio, and dye concentration are the key factors affecting the MB discoloration with the optimum values of 7.5, 3.8 (%), and 86.2 (mg/L), respectively.