Response Surface Modeling for Co-Remediation of Cr6+and Pentachlorophenol byBacillus cereusRMLAU1: Bioreactor Trial and Structural and Functional Characterization by SEM-EDS and FT-IR Analyses

This is the first report on optimization of process variables for simultaneous bioremediation of pentachlorophenol (PCP) and Cr6+ employing traditional and response surface methodology (RSM). In a one-factor-at-a-time approach, the effect of PCP level exhibited maximum bacterial growth and Cr6+ (82%) and PCP (91.5%) removal at initial 100 mg PCP L−1 with simultaneous presence of 200 mg Cr6+ L−1 within a 36-h incubation. However, at varied Cr6+ concentrations, maximum growth and Cr6+ (97%) and higher PCP (59%) removal were achieved at 50 mg Cr6+ L−1 with simultaneous presence of 500 mg PCP L−1 within a 36-h incubation. The Box-Behnken design suggested 100% Cr6+ and 95% PCP remediation at 36 h under optimum conditions of 75 mg PCP and 160 mg Cr6+ L−1, pH 7.0, and 35°C; Cr6+ removal was further enhanced to 97% in bioreactor trial. Fourier transform infrared (FT-IR) analysis revealed the likely involvement of hydroxyl, amide, and phosphate groups in Cr3+ binding. Scanning electron microscopy and energy-dispersive x-ray spectroscopy (SEM-EDS) showed biosorption of reduced chromium on bacterial cell surface. This isolate can be employed for eco-friendly and effective in situ bioremediation of Cr6+ and PCP simultaneously.