Formation of hydroxylated polybrominated diphenyl ethers from laccase-catalyzed oxidation of bromophenols. (November 2015) - Lin, Kunde
Highlights: OH-PBDEs were produced by the laccase-catalyzed oxidation of 2, 4-DBP and 2, 4, 6-TBP. 2′-OH-BDE68, 2, 2′-diOH-BB80, and 1, 3, 8-TrBDD were produced from 2, 4-DBP. 2′- and 4′-OH-BDE-121 were produced from 2, 4, 6-TBP. Laccase-catalyzed conversion of bromophenols may be a formation route for OH-PBDEs. Abstract: Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been frequently found in the marine biosphere as emerging organic contaminants. Studies to date have suggested that OH-PBDEs in marine biota are natural products. However, the mechanisms leading to the biogenesis of OH-PBDEs are still far from clear. In this study, using a laccase isolated from Trametes versicolor as the model enzyme, we explored the formation of OH-PBDEs from the laccase-catalyzed oxidation of simple bromophenols (e.g., 2, 4-DBP and 2, 4, 6-TBP). Experiments under ambient conditions clearly showed that OH-PBDEs were produced from 2, 4-DBP and 2, 4, 6-TBP in presence of laccase. Polybrominated compounds 2′-OH-BDE68, 2, 2′-diOH-BB80, and 1, 3, 8-TrBDD were identified as the products from 2, 4-DBP, and 2′-OH-BDE121 and 4′-OH-BDE121 from 2, 4, 6-TBP. The production of OH-PBDEs was likely a result of the coupling of bromophenoxy radicals, generated from the laccase-catalyzed oxidation of 2, 4-DBP or 2, 4, 6-TBP. The transformation of bromophenols by laccase was pH-dependant, and was also influenced by enzymatic activity. In view of the abundance of 2, 4-DBP and 2, 4, 6-TBP and the phylogenetic distribution of laccases in the environment, laccase-catalyzed conversion of bromophenols may be potentially an important route for the natural biosynthesis of OH-PBDEs.