Degradation of 17 α-ethynyl estradiol by Pseudomonas citronelolis BHUWW1 and its degradation pathway

Abstract

17 α-ethynylestradiol (EE2) is the main component of birth control medications and is in huge demand worldwide. A major part of this hormone is excreted in the environment, where it acts as Endocrine Disrupting Compound (EDC). Thus, the removal of this hormone from the environment is essential. In this study, a bacterial strain identified as Pseudomonas citronelolis BHUWW1 was isolated from sewage-contaminated water of the Assi River by using enrichment in minimal medium supplemented with EE2 as a sole source of carbon. The strain was able to metabolize 94% of 10 mg/L of EE2 after eight days of incubation. Supplementation of co-carbon sources showed a positive impact on EE2 degradation. It was observed that supplementation with sodium acetate, sucrose, and glucose increased the efficiency of EE2 degradation. In the presence of metal ions, a decrease in EE2 degradation was observed. However, the strain BHUWW1 was able to degrade EE2 in the presence of tested metal ions. The metabolites arising after degradation of EE2 were identified by GC MS and a possible pathway of degradation was elucidated. It was observed that EE2 was first converted to estrone and then to 17 β-estradiol (E2). E2 was then hydroxylated, which led to an opening of the ring structure and its subsequent degradation. A few metabolites such as methyl succinic acid, ethyl malonic acid, and 4- hydroxyl butanoic acid formed during the degradation were also identified. The results of this study clearly demonstrate the role of strain BHUWW1 in the remediation of this hormone.