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University of California-Davis

Superfund Research Program

Optimizing Bioremediation for Risk Reduction Using Integrated Bioassay, Non-Target Analysis and Genomic Mining Techniques

Project Leader: Thomas Michael Young
Co-Investigator: Frank J. Loge
Grant Number: P42ES004699
Funding Period: 2017-2023
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Project Summary (2017-2022)

The research team is developing and evaluating a comprehensive and integrated suite of analytical, computational, and bioassay based approaches for assessing overall reductions in toxicity resulting from bioremediation of Superfund (SF) sites. These tools will then be applied to optimize biodegradation of two contaminant mixtures, triazine herbicides and polycyclic aromatic hydrocarbons representative of environmental exposures faced by the Center’s community partners the Yurok Tribe, through systematic investigation of carbon sources, electron acceptors, and reactor detention times.

Although both of these contaminant mixtures are known to biodegrade, transformation products (TPs) accumulate and are widely found in groundwater (triazines) and/or have increased toxicity compared to parent compounds (PAHs). Bioreactor performance is characterized by measuring shifts in microbial community composition, bioassay activity, and both target and nontarget chemical concentrations measured with GC and LC high resolution mass spectrometry (HRMS). This combination of measurements provides unique insights into interactions among contaminant transformations, microbial populations, and overall reductions in human and ecosystem risks.

Novel enzyme engineering approaches are used to identify rate limiting steps in triazine mineralization and to isolate or design improved enzymes to carry out these steps. Microorganisms with improved ability to degrade triazines are prepared and tested in the bioreactors to assess ability to remove target compounds and to reduce overall bioactivity compared to standard enrichment approaches.

The project’s central hypothesis is that chemical hazard reduction during SF site remediation can be best characterized through broad consideration of both contaminant destruction and byproduct formation. The project researchers further hypothesize that a minimum suite of highthroughput assays can be defined to effectively capture the overall risk reduction during remediation and that this suite of assays can guide optimization of bioreactor design and operation. This project supports a paradigm shift in the SRP away from reducing concentrations of specific constituents and toward the overall reduction of deleterious biological effects.

The project is strongly integrated with the overall program, drawing on HRMS, metabolomics, and statistical expertise in the Analytical Chemistry Core, the full range of bioassays available in the Bioanalytical and Statistics Core, immunoassays from the Immunoassays for Human and Environmental Health Monitoring project, especially for triazines and TPs, as well as integrative bioassays for ER and oxidative stress being developed by the Critical Role of Mitochondrial Oxidative Stress (MOS) in Chemical Induced Cardiac Toxicity and Monitoring Endoplasmic Reticulum Stress Caused by Chronic Exposure to Chemicals projects. The bioassay suite developed here will be used to analyze environmental samples collected through the Community Engagement Core and the overall workflow will be transferred to a broader user community with the assistance of the Research Translation Core.

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