Biodegrading of pyrene by a newly isolated Pseudomonas putida PL2

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic compounds derived from natural sources and anthropogenic processes, which have been recommended as priority pollutants. Degradation of PAHs in the environment is becoming more necessary and urgent. In the current study, strain PL2, which is capable of growing aerobically on pyrene (PYR) as the sole carbon source, was isolated from hydrocarbons-contaminated soil and then identified as Pseudomonas putida by morphological and physiological characteristics as well as 16S rDNA sequence. The strain PL2 was able to degrade 50.0% of the pyrene at 28°C within 6 days in the presence of 50 mg/L pyrene, while the strain PL2 degraded 50.0% of the pyrene within 2 days when a solution of 50 mg/L pyrene and 50 mg/L phenanthrene was used. In addition, phenanthrene was shown to increase the biodegradation efficiency of pyrene by the strain PL2. The order of degradation by the strain PL2 was pH 6.0 > pH 7.0 > pH 5.0 > pH 8.0. The degradation rate of PYR in the soil by the strain PL2 reached 70.0% at the 10^th day. The dynamics of PYR degradation in soil by PL2 was fit to the first order model and the strain PL2 was shown to efficiently degrade PYR in soil. The current study showed that P. putida PL2 was a novel bacterium that could degrade pyrene and holds great promise for use in PAHs bioremediation in soil.