Optimization of process parameters to enhance the bio-decolorization of Reactive Red 21 by Pseudomonas aeruginosa 23N1

Abstract

Textile industries produce a large volume of dye-contaminated wastewater through the dyeing process, which poses a high risk to the environment. The reactive dyes are commonly used as colorant organic substances as these are chemically stable and give bright colors to fabrics. This study aims to optimize the decolorization of Reactive Red 21 dye from water by Pseudomonas aeruginosa strain 23N1. The two-level factorial design has been applied to select the levels of operational parameters, which has been further optimized by rotatable central composite design-based response surface methodology. The concentration of yeast extract has shown a significant positive effect (highest coefficient estimate of 25.55) on decolorization by the strain, whereas added glucose and peptone as nutrients for bacteria have shown negative effect (coefficient estimate of − 1.71 and − 1.62, respectively) because the bacteria preferably have utilized glucose and peptone as prime carbon/nitrogen source instead of dye molecules. Quadratic model generated through central composite design using experimental data to predict decolorization percentage has shown a good correlation coefficient (R2 = 0.999) and adjusted correlation coefficient (Adj. R2 = 0.992). The decolorization percentages from model validation experiments are achieved as 93.5 ± 0.4% and 91.5 ± 0.5% for initial dye concentrations of 50 mg/L and 150 mg/L, respectively, and have demonstrated satisfactory correlation with model predicted data. Based on the result obtained, it can be suggested that the strain 23N1 could be efficiently used to decolourize RR21 dye-contaminated wastewater.