Isolation and Characterization of Different Bacterial Strains from Soils, With the Potential of Degrading Polychlorinated Biphenyls (PCBs) Under Aerobic Conditions

Abstract

Polychlorinated biphenyl (PCBs) are persistent organic compounds used between 1930 and 1970 as thermal insulators in electrical equipment such as transformers, electrical condensers, heat exchangers, and hydraulic systems. Currently, this xenobiotic is a potential source of pollution to soil and water resources. This research aimed to isolate and characterize bacteria strains possessing a high potential to degrade PCBs contained in used dielectric oils. The bacteria strains were isolated from a soil sample taken from “Alao” Hydroelectric Power Center. Four culture media were used for the soil sample culturing: Agar for Standard Methods Medium (STD), Phosphorus, Ammonium, and Salts Medium (PAS), Minimum Medium (Mm), and Minimum Medium (Mm) supplemented with 25 µL of oil contaminated with 43,6 ppm of PCBs. The isolation, screening, and stabilization process were carried out using three culture media: STD, PAS, and Mm, each supplemented with 25 µL of oil contaminated with 43,6 ppm of PCBs. Nineteen bacterial colonies were isolated and exposed to a higher concentration of PCBs. Eighteen colonies could tolerate 250 µL of oil contaminated with 500 ppm of PCBs. Once stabilized and purified these bacteria strains, were characterized according to their microscopic and macroscopic characteristics and tolerance to heavy metals. Through biochemical tests, 18 strains were identified belonging to Providencia alcalifaciens, Proteus mirabillis, Providencia rettgeri, Providencia stuartii, Pseudomona alcaligenes, Morganella morganii, and Shigella disenteriae