Observations on the preferential biodegradation of selected components of polyaromatic hydrocarbon mixtures

The capacity of the naphthalene degrading enzyme (NAH) system of Pseudomona s fluorescens 5R and a number of other NAH system bacterial isolates to deg rade mixtures of polyaromatic hydrocarbons (PAHs) and heterocyclic compound s were examined. It was found that all the examined organisms displayed sim ilar patterns of preferential compound degradation when presented with the same mixture. Using strains that possess portions of the NAH system, this p referential degradation was localized to the activity of naphthalene dioxyg enase. Comparisons of the first-order rates of compound degradation with th e structures of the mixture components indicated that increased deviation f rom the base structure of naphthalene led to slower disappearance. Structur al features that were found to decrease the rate of compound degradation in clude an increase in the number of methyl substituents and an increase in t he size of a substituent. (C) 2000 Elsevier Science Ltd. All rights reserve d.