Catabolism of 2,7-dichloro- and 2,4,8-trichlorodibenzofuran by Sphingomonas sp strain RW1

Abstract

Due to their physicochemical and toxicological properties, polychlorinated dibenzofurans are regarded as a class of compounds providing reason for serious environmental concern. While the nonhalogenated basic structure dibenzofuran is effectively mineralized by appropriate bacterial strains, its polychlorinated derivatives are not. To elucidate the ability of the strain Sphingomonas sp RW1 to metabolize some of these chlorinated derivatives, we performed turnover experiments using 2,7-dichloro- and 2,4,8- trichlorodibenzofuran. As indicated by the oxygenuptake rates determined for these two chlorinated dibenzofurans, Sphingomonas sp RW1 can catabolize these chlorinated dibenzofurans yielding small quantities of oxidation products, which we isolated and subsequently characterized employing GC/MS and 1H- as well as 13C-NMR spectroscopy. In the case of 2,7-dichlorodibenzofuran, two metabolites accumulated, which we identified as 6-chloro- and 7-chloro-2- methyl-4H-chromen-4-one. The single metabolite isolated from the turnover experiments performed with 2,4,8-trichlorodibenzofuran was unequivocally identified as 6,8-dichloro-2-methyl-4H-chromen-4-one.