Anaerobic degradation of phenol and 2-chlorophenol by Rhodopseudomonas palustris

The advantage of anaerobic degradation processes of recalcitrant aromatic compounds are relativly low production of biomass and the possibility of dehalogenation of highly chlorinated compounds. Phototrophic bacteria are known for their diverse metabolism, however, there is only little information about phototrophic degradation of phenol and chlorinated aromatic compounds. Newly isolated and culture collection strains of Rhodopseudomonas palustris could transform (2-Cl)-phenol in the presence of a second carbon source to (3-Cl)-4-OH-phenylacetic acid, which were identified by HPLC, GC-MS and NMR analysis. Dechlorination was demonstrated by stoichiometric release of Cl- in the culture fluid. The occurrence of 4-OH-phenylacteic acid has never been observed in the degradation of phenol under methanogenic or nitrate reducing conditions. Under these conditions phenol is first carboxylated to benzoate or p-OH-benzoate prior to reduction of the aromatic ring and complete mineralization.