Isolation, Identification and PAH-Degrading Performance of an Endophytic Bacterium Enterobacter sp. PRd5

Endophytic bacteria with PAH-degrading ability have shown great potential in reducing the PAH contamination in soils and plants. In this study, eight pyrene-degrading endophytic bacterial strains, belonging to Enterobacter sp., Chitinophaga sp., Xanthomonas sp. etc, were isolated from the inner plants growing in PAH-contaminated sites. The degradation rates of pyrene (50 mg·L^-1) by these strains ranged from 7.59% to 45.50% after 10-day cultivation under 30℃ and 150 r·min^-1. Having great potential in pyrene degradation, strain Enterobacter sp. PRd5 was selected as the representative for systematical investigation of its pyrene biodegradation ability under different culture conditions. The results show that 41.37%-50.63% of pyrene could be removed by Enterobacter sp. PRd5 from media after 10-day cultivation at 30℃ and 150 r·min^-1. More than 95% of naphthalene (500 mg·L^-1), fluorine (100 mg·L^-1), and phenanthrene (50 mg·L^-1), which are 2-3 ringed PAHs, were removed by Enterobacter sp. PRd5 after 7-day cultivation. Remarkably, 35.89% of fluoranthene (50 mg·L^-1) and 17.44% of benzoapyrene (10 mg·L^-1) were removed by Enterobacter sp. PRd5 from the media after 10-day cultivation, suggesting that strain PRd5 has great capability of degrading 4-5 ringed PAHs. Furthermore, the study indicate that pH value of 6.0-8.0, temperature of 25-35℃, ρ(NaCl) ≤ 10 g·L^-1, inventory 10-30 mL·(100 mL)^-1 flask, 3%-17% inoculation quantity, initial pyrene concentration of 25-50 mg·L^-1, and 100 mg·L^-1 additional glucose are favorable for pyrene biodegradation by Enterobacter sp. PRd5.