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Hexavalent chromium, a priority pollutant, is well known for its carcinogenicity, mutagenicity, and teratogenicity in humans, animals, and plants. Biosorption is an attractive technique for the treatment of chromium pollution. This study was aimed to optimize the effect of various process parameters on biosorption of Cr6+ by Pseudomonas putida SKG-1 employing conventional one-factor-at-a-time and response surface methodology (RSM) approaches in a batch process. In conventional method, the maximum Cr6+ biosorption (97%) was achieved at 6.0 g dead cell biomass l−1, pH 3.0, and 35°C during 195 min contact time with an initial Cr6+ concentration of 50 mg l−1 under shaking (150 rpm). Whereas in RSM approach, a slightly enhanced Cr6+ biosorption (98%) was obtained only in 180 min by P. putida cells (8.0 g l−1). The correlation coefficient (R2) of biosorption data to Cr6+ simulated by the Langmuir, Freundlich, and D–R isotherm models was 0.9953, 0.8482, and 0.8916, respectively. The best fit was obtained...

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 (A620 1.31) and dye discoloration (95.2%) at optimum temperature 35°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.