Response surface methodology for optimization of process variable for reactive orange 4 dye discoloration by Pseudomonas putida SKG-1 strain and bioreactor trial for its possible use in large-scale bioremediation

In this study, Pseudomonas putida SKG-1 isolate employed earlier for pulp-/paper-mill effluent discoloration, was used for bioremediation of reactive orange 4 azo dye under varied cultural and nutritional conditions. The optimization through one-factor-at-a-time approach revealed maximum growth (A(620) 1.31) and dye discoloration (95.2%) at optimum temperature 35 degrees C, pH 8.0, inoculum dose 5.0%, sucrose 0.7%, peptone 0.25%, and 50 mg reactive orange 4 dye L-1 within 72 h of incubation. Under response surface methodology (RSM; using Box-Behnken design) approach, the dye discoloration enhanced to 97.8% at reactive orange 4 concentration of 50 mg L-1, sucrose 0.7%, and peptone 0.28% during 72 h of incubation. In bioreactor trial, the maximum dye discoloration (98% within 60 h) was achieved in 12 h advance compared to RSMs trial.