Biodegradation of conjugated estrogens in wastewater treatment: species, mechanisms, and influencing factors

Estrogenic pollutants, especially conjugated estrogens (CEs), have become an important environmental problem due to their potential interference with aquatic ecosystems and threats to human health. As an effective means, biodegradation plays a key role in the removal of CEs in natural and artificial systems. After long-term adaptation and domestication, the bacterial species that can tolerate and degrade CEs were retained, thereby achieving efficient removal of CEs. In this paper, the important role of bacteria in the biodegradation of CEs was reviewed. The bacterial species and pure isolates related to the biodegradation of CEs were described in detail. The mechanism of enzymatic hydrolysis and the subsequent degradation process of free estrogen were discussed. The biodegradation products and possible degradation pathways of CEs were summarized. In addition, the effects of environmental factors on the biodegradation efficiency of CEs were also discussed. This paper aims to summarize the research progress of CE biodegradation and put forward future research prospects.