PAK-Abbau durch Bakterien.

During the last few decades, polycyclic aromatic hydrocarbons (PAH) have been the object of numerous investigations concerning their formation, environmental distribution and fate, effects on mammalian metabolism and biodegradation. Here, current knowledge about bacterial degradation of PAH is briefly reviewed, and its significance for the remediation of PAH-contaminated soil discussed. Consequently, aspects that are relevant for application of bioremedial techniques are treated in preference to others. Various PAH have been shown to be degraded or at least transformed by bacterical consortia in soil, sediments or aqueous ecosystems or utilized as a source of carbon and energy by bacterial pure cultures. Biochemical pathways have been completely elucidated for bacterical catabolism of naphthalene, anthracene and phenanthrene. Metabolites derived from degradation of some additional PAH have been indentified and degradation pathways have been proposed. Some principal rules for biodegrada tion of linear and angular PAH can be derived from various publications. Usually, the annealed aromatic rings are gradually degraded via catabolic sequences common to the biodegradation of monoaromatic compounds. Dead end metabolites are formed preferentially by recyclization of ring fission products from clustered PAH. Also the formation of carcinogenic metabolites is possible, but it remains unclear whether these are released under conditions of remediation. Biodegradation of high molecular weight PAH in particular is generally limited biological factors such as low enzyme affinity and low transport rates as well as by physical factors such as strong adsorption and low solubilization. It has been demonstrated in bench scale systems that bacterial biodegradations of PAH can be drastically enhanced using appropriate solvents as mediators for solubilization for these compounds.