Modeling Microbial PCB Degradation and BindingEPA Grant Number: R826652
Title: Modeling Microbial PCB Degradation and Binding
Investigators: Balaz, Stefan
Institution: North Dakota State University Main Campus
EPA Project Officer: Lasat, Mitch
Project Period: September 1, 1998 through August 31, 2001 (Extended to August 31, 2002)
Project Amount: $375,000
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text | Recipients Lists
Research Category: Sustainability , Land and Waste Management , Air , Engineering and Environmental Chemistry
A complete kinetic description of the fate of hydrophobic chemicals like polychlorinated biphenyls (PCBs) in biosystems represents a pre-condition for effective remediation decisions and risk assessment. The workload of testing numerous congeners can be reduced using model-based quantitative structure-activity relationships (QSAR) for the rate/equilibrium parameters of the fate-determining processes. One of the factors that has to be considered in the biodegradation QSAR is the possibility of multiple orientations of PCB molecules in the binding sites due to the symmetrical biphenyl skeleton.
The kinetics of distribution of PCBs in soil and aqueous media is governed by evaporation, adsorption to solid particles and biomass, and by microbial degradation. The proposed research aims at (1) development of a complete kinetic description of the fate of individual PCB congeners in aqueous media and soils as determined by structure and physicochemical properties of congeners, biomass, and soils and (2) QSAR formulation considering multiple binding modes for binding of PCBs to the degrading enzyme and for published data on binding of polychlorinated aromatic pollutants with symmetrical skeletons to toxicologically relevant proteins.
The time courses of the concentrations of PCB congeners in the respective phases (gas, water, biomass, solid particles) and degraded during in vitro incubation in presence of degrading bacterial culture in aqueous media and soils will be monitored. A compartmental model will be used to determine the rate/equilibrium parameters characterizing individual processes. These characteristics will be correlated with structure and physicochemical properties. For the microbial degradation rate constants, QSAR will be formulated taking into account multiple binding modes. The procedure will also be applied to the published data on binding of PCBs, dibenzo-p-dioxins, dibenzofurans to toxicologically relevant proteins.
The project will provide a model describing the fate of individual PCB congeners in the studied systems as a function of their structure, physicochemical properties, and the time of exposure. The degradation QSAR is expected to have better descriptive and predictive ability than the published studies and will contribute to a more accurate prediction of the fate of PCBs in the environment and during bioremediation experiments. The developed binding QSAR are also expected to have higher quality than the published results and will contribute to a more accurate prediction of binding and effects of non-tested compounds.