حذف كروم شش ظرفيتي در محيط¬هاي آبي آلوده با استفاده از باكتري¬هاي سودوموناس پوتيدا و گونه¬ي كوپرياويدوس، و سلول¬هاي تثبيت شده آن¬ها در حامل¬هاي مناسب

Hexavalent chromium is a heavy and polluting metal that can negatively affect human and animal health. Pseudomonas putida and Copriavidus bacteria are among the bacteria that can convert hexavalent chromium into trivalent chromium, which is less toxic. This research determines the optimal conditions for the removal and absorption of hexavalent chromium by these bacteria using statistical and spectroscopic methods. It also confirms the presence of chromate reductase gene in Pseudomonas putida bacteria using PCR method. Finally, it eva‎luates the efficiency and stability of these bacteria in the presence of copper nanoparticles and in synthetic wastewater environments. The results showed that Pseudomonas putida and Copriavidus inhibit at least 120 ppm and 160 ppm of hexavalent chromium, respectively. In optimal conditions, Pseudomonas putida removed and absorbed 98.22% of primary hexavalent chromium in tryptone broth medium with 100 ppm in 36 hours. Copriavidus removed and absorbed 73.83% of primary hexavalent chromium in nutrient broth medium with 50 ppm in 48 hours. Co-cultivation in NB medium with 100 ppm of primary hexavalent chromium removed and absorbed 84.43% of it in 60 hours. Pseudomonas putida cells resting in synthetic effluent without NPCu removed and absorbed 28.88% of initial 100 ppm hexavalent chromium. In the sample treated with NPCu, this value increased to 36.56%. Copriavidus removed and adsorbed 51.32% of the initial 50 ppm hexavalent chromium in NPCu-free synthetic effluent. In the sample treated with NPCu, this value reached 67.52%. Co-cultivation in synthetic wastewater without NPCu removed and absorbed 70.68% of hexavalent chromium with initial 100 ppm. In the sample treated with NPCu, this value reached 78.85%. NPCu-free Pseudomonas putida immobilized on construction pumice removed and absorbed 24.75% of hexavalent chromium at an initial ppm of 100 ppm. With NPCu, this value reached 26.16%. Copriavidus without NPCu immobilized on construction pumice removed and absorbed 42.14% of hexavalent chromium at an initial 50 ppm. With NPCu, this value reached 61.4%. Co-culture without NPCu immobilized on construction pumice removed and absorbed 34.84% of hexavalent chromium at initial 100 ppm. With NPCu, this value reached 51.43%. Pseudomonas putida treated with NPCu immobilized on construction pumice was able to reduce hexavalent chromium in synthetic wastewater in 8 cycles. Copriavidus treated with NPCu stabilized on construction pumice was able to reduce hexavalent chromium in synthetic wastewater in 2 cycles. Co-cultivation treated with NPCu stabilized on construction pumice was able to reduce hexavalent in synthetic wastewater in 6 cycles. The results of this research showed that co-cultivation treated with NPCu and stabilized on construction pumice has an effective role in reducing hexavalent chromium in synthetic wastewater.

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