Isolation and identification of 17β-estradiol degrading bacteria and its degradation pathway

The widespread presence of 17β-estradiol (E2) in the environment is an emerging problem because it poses a potential threat to human health and aquatic organisms. In this study, a strain of E2 degrading bacteria was isolated from activated sludge. 16s rRNA analysis combined with physiological and biochemical detection confirmed that the bacterium was Ochrobactrum sp. strain FJ1. At an initial E2 concentration of 15 mg L^-1, strain FJ1 degraded 98 ± 1% of E2 after 10 days. Furthermore, when methanol was added as an additional carbon source, the biomass of strain FJ1 increased by 35 ± 1%, and E2 degradation efficiency was slightly inhibited. Compared with E2 alone when glucose, sodium acetate, and methanol were added as additional carbon sources, biomass decreased by 20 ± 1, 13 ± 1 and 35 ± 1%, respectively. Analysis of the degradation products of E2 by LC/Q-TOF-MS confirmed that the major degradation products of E2 were estrone (E1) and 4,16-OH-E1, which was further degraded by strain FJ1 to several other unknown compounds. Based on SEM and FTIR analysis, the morphology of the bacteria became thicker and the thickness of the cell walls decreased under initial E2 stress, and thereafter E2 was transported into the bacteria primarily via several proteins on the cell surface. Considering the ability and efficiency of Ochrobactrum sp. strain FJ1 to degrade high E2 content, the strain could provide a new bioremediation technology for the effective biodegradation of E2. Finally, a potential bioremediation pathway of E2 by Ochrobactrum sp. strain FJ1 was proposed.