Biodegradation of 17β-estradiol by Bacterial Co-culture Isolated from Manure

Animal wastes are potential sources of natural and steroidal estrogen hormones into the environment. These hormones can be removed by microorganisms with induced enzymes. Two strains of 17β-estradiol-degrading bacteria (LM1 and LY1) were isolated from animal wastes. Based on biochemical characteristics and 16 S rDNA gene sequences, we identified strains LM1 and LY1 as belonging to the genus of Acinetobacter and Pseudomonas, respectively. Bacterial co-culture containing LM1 and LY1 bacterial strains could rapidly remove approximately 98% of E2 (5 mg L^-1) within 7 days. However, strains LM1 and LY1 degraded 77% and 68% of E2 when they were incubated alone, respectively. More than 90% of 17β-estradiol (E2, ≤ 20 mg L^-1) could be removed by bacterial co-culture. Low C/N ratio (1:35) was more suitable for bacterial growth and E2 degradation. The optimal pH for bacterial co-culture to degrade E2 ranged from 7.00 to 9.00. Coexisting sodium acetate, glucose and sodium citrate decreased E2 degradation in the first 4 days, but more E2 was removed when they were depleted. The growth of the bacterial co-culture was not significantly decreased by Ni, Pb, Cd or Cu at or below 0.8, 1.2, 1.6 or 0.8 mg L^-1, respectively. These data highlight the usefulness of bacterial co-culture in the bioremediation of estrogen-contaminated environments.