Characterisation of coupling products formed by biotransformation of biphenyl and diphenyl ether by the white rot fungus Pycnoporus cinnabarinus

Cells of the white rot fungus Pycnoporus cinnabarinus grown in glucose were able to hydroxylate biphenyl and diphenyl ether, although growth was inhib ited by these substrates at concentrations above 250 muM. 2- and 4-Hydroxyb iphenyl were detected as products of biphenyl metabolism and 2- and 4-hydro xydiphenyl ether as products of diphenyl ether metabolism in the culture me dia. After addition of 2-hydroxydiphenyl ether and 2-hydroxybiphenyl to cel l-free supernatants containing laccase as the only ligninolytic enzyme, dif ferent coloured precipitates were formed. HPLC analysis revealed the format ion of additional hydrophobic metabolites with one major product per transf ormation. Mass spectrometric analysis of the methyl derivatives of the poly mer mixture indicated dimers and trimers with different binding types. The main products were identified as dimers with carbon-carbon bonds in pala-po sition to the hydroxyl group of the monomers by mass spectroscopy and nucle ar magnetic resonance spectroscopy.