Laccase-Mediated Transformations of Endocrine Disrupting Chemicals Abolish Binding Affinities to Estrogen Receptors and Their Estrogenic Activity in Zebrafish

Endocrine disrupting chemicals (EDCs) are known to mainly affect aquatic organisms, producing negative effects in aquaculture. Transformation of the estrogenic compounds 17 beta-estradiol (E2), bisphenol-A (BPA), nonylphenol (NP), and triclosan (TCS) by laccase of Coriolopsis gallica was studied. Laccase is able to efficiently transform them into polymers. The estrogenic activity of the EDCs and their laccase transformation products was evaluated in vitro as their affinity for the human estrogen receptor alpha (hER alpha) and for the ligand binding domain of zebrafish (Danio rerio) estrogen receptor alpha (zfER alpha LBD). E2, BPA, NP, and TCS showed higher affinity for the zfER alpha LBD than for hER alpha. After laccase treatment, no affinity was found, except a marginal affinity of E2 products for the zfER alpha LBD. Endocrine disruption studies in vivo on zebrafish were performed using the induction of vitellogenin 1 as a biomarker (VTG1 mRNA levels). The use of enzymatic bioreactors, containing immobilized laccase, efficiently eliminates the endocrine activity of BPA and TCS, and significantly reduces the effects of E2. The potential use of enzymatic reactors to eliminate the endocrine activity of EDCs in supply water for aquaculture is discussed.