title: Ligninase-mediated removal of 17beta-estradiol from water in the presence of natural organic matter: efficiency and pathways.
abstract: Lignin peroxidase (LiP) is excreted by certain lignin-degrading fungi, such as white rot fungus Phanerochaete chrysosporium, in natural environments and is thus widely present in the natural environment. We have found in our earlier studies that LiP mediates effective reactions of a few natural and synthetic estrogens to form oligomeric products via radical coupling. We in particular examined the identity and property of the products resulting from 17beta-estradiol (E2) in LiP-mediated oxidative coupling reactions, and the results suggest that such reactions hold great potential in water/wastewater treatment to remove E2 and estrogenicity. Herein, we report a further investigation to postulate possible reaction pathways of E2 with the assistance of ab initio molecular modeling and to more systematically examine the reaction behavior of E2 under sequenced reaction conditions and in systems containing natural organic matter (NOM) at different levels. Our molecular modeling suggested the coupling of E2 likely proceeded via covalent bonding between two E2 radicals at their unsubstituted carbons in phenolic rings. Results obtained from sequenced reagent feed experiments revealed that the coupling products tended to be consumed with increment enzyme treatments, suggesting that most E2 coupling products may still be LiP substrates that can undergo further coupling reactions under catalysis. Higher concentration of NOM present in the reaction system tended to reduce E2 transformation. NOM moieties seemed to couple to each other upon reaction with LiP, which was evidenced by the development of a characteristic absorbance band.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China.
authors.forename: Liang
authors.initials: L
authors.lastname: Mao
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Huang
authors.forename: Qi
authors.initials: Q
authors.lastname: Luo
authors.forename: Junhe
authors.initials: J
authors.lastname: Lu
authors.forename: Xi
authors.initials: X
authors.lastname: Yang
authors.forename: Shixiang
authors.initials: S
authors.lastname: Gao
mesh_terms: D001673:Biodegradation, Environmental; D004958:Estradiol / Q000378:metabolism*; D009930:Organic Chemicals / Q000737:chemistry*; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000378:metabolism*; D020075:Phanerochaete / Q000201:enzymology; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D004958:Estradiol; D010105:Oxygenases; C044391:ligninase