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MULTISUBSTRATE BIODEGRADATION KINETICS FOR BINARY AND COMPLEX MIXTURES OF POLYCYCLIC AROMATIC HYDROCARBONS
Citation:
KNIGHTES, C. D. AND C. A. PETERS. MULTISUBSTRATE BIODEGRADATION KINETICS FOR BINARY AND COMPLEX MIXTURES OF POLYCYCLIC AROMATIC HYDROCARBONS . ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 25(7):1746-1756, (2006).
Impact/Purpose:
The objective of this task is to develop, support and transfer a wide variety of tools and mathematical models that can be used to support watershed and water quality protection programs in support of OW, OSWER, and the Regions.
Description:
Biodegradation kinetics were studied for binary and complex mixtures of nine polycyclic aromatic hydrocarbons (PAHs): naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 2-ethylnaphthalene, phenanthrene, anthracene, pyrene, fluorene and fluoranthene. Discrepancies between the observed biodegradation rates and those predicted by a sole-substrate model indicate that significant substrate interactions occurred in both the binary and complex mixture experiments. For all compounds except naphthalene, biodegradation was enhanced. The observations were compared to predictions from two multi-substrate biodegradation kinetic models: one that accounts for competitive inhibition and one that does not. Both models are fully predictive in that parameters had been determined from an independent set of sole-substrate experiments. In the binary experiments, the major multi-substrate effect was biomass enhancement due to growth on naphthalene. Substrate interactions were orders-of-magnitude larger for most of the compounds in the complex mixtures, but significant competitive inhibition effects counteracted some of the biomass enhancement effect. This study has demonstrated that the sole-substrate model is inadequate to describe multi-substrate biodegradation kinetics for a broad range of PAH mixtures. While the multi-substrate model without inhibition did an adequate job of predicting the observed effects in some cases, we advocate the use of the multi-substrate model with inhibition for similar modeling efforts in light of the evidence that the model was correct more often than not. Theory supports its use because of the common enzyme pathways for biodegradation of PAHs.