Dehalogenation of chlorinated hydroxybiphenyls by fungal laccase

Abstract

We have investigated the transformation of chlorinated hydroxybiphenyls by laccase produced by Pycnoporus cinnabarinus. The compounds used were transformed to sparingly water-soluble colored precipitates which were identified by gas chromatography-mass spectrometry as oligomerization products of the chlorinated hydroxybiphenyls. During oligomerization of 2-hydroxy-5-chlorobiphenyl and 3-chloro-4-hydroxybiphenyl, dechlorinated C---C-linked dimers were formed, demonstrating the dehalogenation ability of laccase. In addition to these nonhalogenated dimers, both monohalogenated and dihalogenated dimers were identified.

FIG. 1

Mass spectra of the C—C bond dimers formed during transformation of 3-chloro-4-hydroxybiphenyl.

FIG. 2

H NMR spectrum of the dimer 3,3′-di(4-hydroxybiphenyl) formed during transformation of 4-hydroxybiphenyl and 3-chloro-4-hydroxybiphenyl by P. cinnabarinus laccase (300 MHz; CD₃OD). The dimer structure is shown in the inset.

FIG. 3

Radicalization of 3-chloro-4-hydroxybiphenyl by laccase.