Degradation of polychlorinated biphenyls (PCBs) by four bacterial isolates obtained from the PCB-contaminated soil and PCB-contaminated sediment

Abstract

We investigated the PCB-degrading abilities of four bacterial strains isolated from long-term PCB-contaminated soil (Alcaligenes xylosoxidans and Pseudomonas stutzeri) and sediments (Ochrobactrum anthropi and Pseudomonas veronii) that were co-metabolically grown on glucose plus biphenyl which is an inducer of the PCB catabolic pathway. The aim of study was to determine the respective contribution of biomass increase and expression of degrading enzymes on the PCB degrading abilities of each isolate. Growth on 5 g l−1 glucose alone resulted in the highest stimulation of the growth of bacterial strains, whereas grown on 10 mg l−1, 100 mg l−1, 1 g l−1, or 5 g l−1 biphenyl did not effected the bacterial growth. None of the strains used in this study was able to grow on PCBs as the sole carbon source. Cells grown on glucose exhibited enhanced degradation ability due to an increased biomass. Addition of biphenyl at concentrations of 1 or 5 g l−1 did not increase total PCB degradation, but stimulated the degradation of highly chlorinated congeners for some of the strains. The degradation of di- and tri-chlorobiphenyls was significantly lower for cells grown on 5 g l−1 biphenyl independently on glucose addition. The highest degradation of the PCBs was obtained for A. xylosoxidans grown in the presence of glucose. Thus A. xylosoxidans appears to be the most promising among the four bacterial isolates for the purpose of bioremediation.