Biodegradation of Xenoestrogens by the Green Tide Forming Seaweed <i>Ulva</i>: A Model System for Bioremediation

Anthropogenic xenoestrogens pose serious threats to humans and the environment. <i>Ulva</i> (Chlorophyta), a green macroalga that can propagate in environments of various salinities, is a potential candidate for efficient wastewater treatment and bioremediation. In this study, we tested the class of bisphenols and ethinylestradiol and investigated the underlying removal mechanisms of these xenoestrogens. The model organism <i>Ulva mutabilis</i> demonstrated over 99% removal efficiency for bisphenols A, B, E, F, P, and Z, and partial removal of bisphenol S. <i>Ulva</i> showed complete removal capabilities even under axenic conditions, while its associated bacteria were not involved. Complete removal of 6.6 mg L^-1 of bisphenol A was achieved within 2 days and a half-time of 1.85 h. Biodegradation was the leading cause of removal, whereas bioaccumulation was minimal. The model substance bisphenol A underwent various reactions, and 20 transformation products were detected using stable isotope labeling. While most of the bisphenol A was completely biodegraded, the primary transformation products were monobromobisphenol A, bisphenol A bisulfate, and 4-hydroxypropanylphenol. This study highlights the potential of the green seaweed <i>Ulva</i> to provide a pathway for more effective and sustainable bioremediation strategies to tackle the environmental pollution caused by xenoestrogens.