Degradation of 17β-estradiol and its metabolites by sewage bacteria

The persistence of 17 beta -estradiol (E sub(2)) and its metabolites to microbial degradation was examined using the supernatant of an activated sludge obtained from the sewage-treatment plant in Burlington, ON, Canada. The experiments were conducted under both aerobic and anaerobic conditions. Aerobic degradation was very fast, and after 22 h, about two-thirds of the spiked E sub(2) had been oxidized to the corresponding metabolite. Five major intermediate compounds were detected, one of which was determined to be the previously unreported metabolite termed X1. The molecular structure of the metabolite could be deduced only tentatively from its molecular ion and fragmentation pattern. Under anaerobic conditions, E sub(2) was more persistent but still biodegradable by the microbial culture, as after 7 d, approximately half of the spiked compound was removed concurrently with a buildup of the corresponding metabolite, E sub(1). All five metabolites were degraded, which suggested that the microorganisms may be able to degrade other estrogen-like chemicals. The probable biodegradative pathway is outlined.