Grantee Research Project Results
1999 Progress Report: Modeling Microbial PCB Degradation and Binding
EPA Grant Number: R826652Title: Modeling Microbial PCB Degradation and Binding
Investigators: Balaz, Stefan
Institution: North Dakota State University Main Campus
EPA Project Officer: Aja, Hayley
Project Period: September 1, 1998 through August 31, 2001 (Extended to August 31, 2002)
Project Period Covered by this Report: September 1, 1999 through August 31, 2000
Project Amount: $375,000
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text | Recipients Lists
Research Category: Air , Safer Chemicals , Land and Waste Management , Sustainable and Healthy Communities
Objective:
The kinetics of distribution of polychlorinated biphenyls (PCBs) in soil and aqueous media are governed by evaporation, adsorption to solid particles and biomass, and microbial degradation. The proposed research aims include: (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) quantitative structure-activity relationships (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.
Progress Summary:
The kinetics of distribution and microbial degradation of about 50 PCB congeners in a technical mixture in an aqueous medium were monitored during the 30-day incubation. A PCB degrading bacterium Pseudomonas stutzeri, obtained from a long-term contaminated soil by enrichment in a synthetic mineral medium with biphenyl as the sole carbon source was used in the experiments. The fate of PCB was studied in the presence of the microorganism that was inactivated by addition of a known inhibitor of PCB biodegradation, 3-chlorobenzoic acid (5 mmol/L). Incubation was carried out in Erlenmeyer flasks (100 mL) that were closed with the column filled with an octadecylated sorbent (see Figure 1).
The sorbent selection was based upon its ability to quantitatively sorb the evaporated PCB congeners in the gas phase, and to elute them completely by small volumes of hexane so that the eluent can be analyzed directly for the PCB content. The amount of sorbent was optimized to fulfill two conditions: to capture the evaporated PCB congeners completely and to provide maximum airflow for the aerobic biodegradation process. The experiments showed that 0.5 g of the sorbent that forms a layer about 2 mm thick is sufficient to recover evaporated PCB congeners as checked by their mass balance in the system.
To study the processes governing the fate of PCBs separately, we carried out the experiments without biomass and with inactivated biomass. The time courses of two PCB amounts, evaporated and remaining in the aqueous phase with the biomass, were determined by congener-specific gas chromatography. The kinetics for individual congeners were described by a kinetic model comprising evaporation, degradation, and sorption.
Comparison of Work Done Versus Plan. We have collected experimental data for the fate of PCB in aqueous media in the presence and absence of inactivated microorganisms. This work represents approximately 30 percent of the planned experiments. The budget spending also is at this level. There was a short, 2-3 month delay caused by the learning curve of new analytical equipment, the gas chromatograph with double mass-spectrometer detector (GC-MS-MS). Originally, a replacement of the GC with an electron-capture detector (ECD) was budgeted for $30,000. The University, the College, and North Dakota EPSCoR supported our research by providing additional funds and a GC-MS-MS Varian Saturn 2000 was purchased. The instrument has the following distinct advantages over the planned GC-ECD: (1) ability to determine actual molecular structure of the unknown analyte; (2) universal application to many more chemicals including metabolites as compared to the limitation of the GC-ECD to chlorinated compounds; and (3) ability to quantitate coeluting analytes. We believe that the short delay is worth the gain and that the quality of the analytical technique will allow us to finish the planned research in time.
Future Activities:
The fate of PCB in degrading suspension of Pseudomonas stutzeri under similar conditions as described above will be determined. Reliable partitioning data on PCB congeners are scarce; therefore, the 1-octanol/water partition coefficients of approximately 30 PCB congeners, both individually and in mixtures, will be measured. The so-called slow-stirring method (de Bruijn, et al., 1990) will be used. The development of the receptor-mapping procedure will continue. Experiments with soil constituents monitoring the kinetics of sorption/desorption of PCB congeners will be initiated.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
| Other project views: | All 39 publications | 18 publications in selected types | All 12 journal articles |
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Balaz S, Lukacova V. A model-based dependence of the human tissue/blood partition coefficients of chemicals on lipophilicity and tissue composition. Quantitative Structure-Activity Relationships 1999;18(4):361-368. |
R826652 (1999) R826652 (Final) |
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Balaz S. Lipophilicity in trans-bilayer transport and subcellular pharmacokinetics. Perspectives in Drug Discovery and Design 2000;19(1):157-177. |
R826652 (1999) R826652 (Final) |
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Dercova K, Vrana B, Balaz S. A Kinetic distribution model of evaporation, biosorption and biodegradation of polychlorinated biphenyls (PCBs) in the suspension of Pseudomonas stutzeri. Chemosphere 1999;38(6):1391-1400. |
R826652 (1999) R826652 (Final) |
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Vrana B, Balaz S, Dercova K, Tandlich R. A kinetic distribution model of evaporation, biosorption and biodegradation of polychlorinated biphenyls (PCBs) in the suspension of Pseudomonas stutzeri. Chemosphere 1999;38(6):1391-1400 |
R826652 (1999) |
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Supplemental Keywords:
RFA, Air, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Waste, Toxics, National Recommended Water Quality, Remediation, Ecological Indicators, Ecological Risk Assessment, Ecosystem Protection, Environmental Chemistry, Ecosystem/Assessment/Indicators, Engineering, Chemistry, & Physics, Ecological Effects - Environmental Exposure & Risk, Bioavailability, Bioremediation, Physics, quantitative structure activity relationship, ecological effects, fate of PCB congeners, binding, microbial degradation, dioxin, bioremediation model, bioremediation of soils, human exposure, hydrophobic chemicals, soil, aquatic ecosystem, risk assessment, aquatic, biostabilization of PCBs, PCB, polychlorinated biphenyls, fate and transport, furans, decontamination of soil and water, enzymes, ecological exposure, chemical kinetics, bioacummulation, chemical transport, PCBs, physicochemical, biokinetic model, modelingRelevant Websites:
http://www.ndsu.nodak.edu/instruct/balaz/pcbdegrb.htm 
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.