Isolation and Optimization of PAH-Degradative Bacteria from Contaminated Soil for PAHs Bioremediation

The objective of the present study is to isolate PAH-degradativebacteria from petroleum-contaminated soils and to optimize theirdegradative conditions including pH, glucose, nitrogen andphenanthrene concentrations required for bioremediationpurposes. Several bacterial strains were isolated throughenrichment and one strain, Burkholderia cocovenenans (BU-3)that was tentatively identified by the Biolog system,demonstrated a high removal rate of phenanthrene over otherstrains. More than 95% in 100 and 500 mg L-1 and 65% in1000 mg L-1 of phenanthrene contents was reduced in theculture media, respectively. Maximum rate of phenanthrene removalup to 4.2 mg hr-1 occurred in the culture containing 1000 mgL-1 phenanthrene. Media at a pH between 6.5 to 7.0 weremore favorable for the degradation of phenanthrene by BU-3.Although increasing glucose concentrations from 0.45 to 3 gL-1 resulted in a better bacterial growth of the isolatedbacteria, the degradation of phenanthrene was reducedsignificantly. Nitrogen supplement did not exert a significanteffect on bacterial growth and phenanthrene degradation. Theisolated Burkholderia cocovenenans BU-3 demonstrated to bea feasible strain for degradation of phenanthrene at a neutralpH, even up to a phenanthrene concentration of 1000 mg L-1.