Pentachlorophenol dechlorination and simultaneous Cr^sup 6+^ reduction by Pseudomonas putida SKG-1 MTCC (10510): characterization of PCP dechlorination products, bacterial structure, and functional groups

It is the first report in which a novel psychrotrophic Pseudomonas putida SKG-1 strain was evaluated for simultaneous bioremediation of pentachlorophenol and Cr6+ under various cultural and nutritional conditions. Pentachlorophenol (PCP) dechlorination products, bacterial structure, and functional groups were characterized by gas chromatography and mass spectrometry (GCMS), scanning electron microscope and energy dispersive X-ray spectroscopy (SEMEDS), and Fourier-transform infrared (FTIR) techniques. The strain was extremely tolerant to excessively higher individual concentration of PCP (1,400 mg l1) and Cr6+ (4,300 mg l1). Increasing concentration of PCP and Cr6+ exerted inhibitory effect on bacterial growth and toxicants removal. The strain exhibited growth, and concomitantly remediated both the pollutants simultaneously over a broad pH (7.09.0) and temperature (28 32 C) range; maximum growth, PCP dechlorination(87.5 %), and Cr6+ removal (80.0 %) occurred at optimum pH 8.0 and 30 C (from initial PCP 100 mg l1 and Cr6+ 500 mg l1) under shaking (150 rpm) within 72 h incubation. Optimization of agitation (125 rpm) and aeration(0.4 vvm) in bioreactor further enhanced PCP dechlorination by ~10 % and Cr6+ removal by 2 %. A direct correlation existed between growth and bioremediation of both the toxicants. Among other heavy metals, mercury exerted maximum and cobalt minimum inhibitory effect on PCP dechlorination and Cr6+ removal. Chromate reductase activity was mainly associated with the supernatant and cytosolic fraction of bacterial cells. GCMS analysis revealed the formation of tetrachloro-p-hydroquinone, 2,4,6-trichlorophenol, and 2,6-dichlorophenol as PCP dechlorination products. FTIR spectrometry indicated likely involvement of carbonyl and amide groups in Cr3+ adsorption, and SEMEDS showed the presence of chromium on P. putida surface. Thus, our promising isolate can be ecofriendly employed for biotreatment of various industrial wastes contaminated with high PCP and Cr6+ concentrations. [PUBLICATION ABSTRACT]