Identification of Aerobic Polychlorinated Biphenyl Degrading Bacteria

Polychlorinated biphenyls (PCBs) are synthetic aromatic compounds containing two benzene rings with one to ten chlorine atoms. There are concerns about the health risks of these compounds in the environment due to their toxicity, persistence, and biological accumulation. PCBs wastes must be treated before being discharged to the environment because they will pollute the water, soil, and air. Microbial degradation of PCBs is considered as one of the most effective methods for removing these compounds from the environment. The purpose of this study was to identify aerobic PCB biodegrading bacteria. This study was performed with sequencing batch biofilm reactor (SBBR) at lab scale. Polyurethane foam was used as the medium. The synthetic wastewater included a co-substrate (acetone as a solvent for PCBs) and a main substrate (transformer oil containing PCBs as carbon source) and also microelements. After achieving adequate microbial population and adaptation of microorganisms to PCB compounds, identification of degrading microbial species was performed by 16S rRNA gene sequencing of the isolated bacteria. Gene sequencing of the isolated bacteria showed that Rhodococcus spp., Pseudomonas spp., Pseudoxanthomonas spp., Agromyces spp., and Brevibacillus spp. were the dominant PCB degrading bacteria. PCB compounds can be degraded by some microorganisms under aerobic or anaerobic conditions. They can at least be reduced to low-chlorinated congeners despite their chemical stability and toxicity. This study identified 5 bacterial species capable of degrading PCBs in transformer oil.