Superfund Research Program
Engineering the Physico-Chemical Environment to Enhance the Bioremediation of Developmental Toxicants in Sediment Fungal-Bacterial Biofilms
Project Summary (2017-2022)
Developmental toxicants including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and chlorophenols (e.g., pentachlorophenol - PCP) are persistent organic contaminants found at many hazardous waste sites throughout the United States. These contaminants are of great concern because they present high toxicological risk in terms of their potential for bioaccumulation in the food chain as well as adverse health effects. Hydrophobic organic contaminants (HOCs) such as PAHs, PCBs and PCP are particularly challenging to bioremediate because their chemical characteristics diminish their bioavailability to microorganisms thereby limiting their potential for efficient biodegradation. As a result of this constraint, HOC remediation strategies tend to focus on physical-chemical approaches consisting of either complete excavation of contaminated media or contaminant in situ immobilization via amendment mediated sequestration, which can have significant negative long-term impacts on local ecosystems.
In this project as part of the Duke University Superfund Research Program (SRP) Center, the researchers are exploring an alternative treatment approach which consists of identifying and stimulating cooperative bacterial-fungal biofilms for HOC biodegradation. Using this approach, select indigenous fungi will first be stimulated to degrade toxicants using nonspecific extracellular enzymes. These fungi will then generate by-products from decomposition that are more bioavailable to bacteria for subsequent biodegradation. While using remediation treatment approaches based on the production of fungal extracellular enzymes is not entirely new, this project focuses on indigenous Ascomycetes naturally associated with sediment microbial biofilms, a phylum that has received limited attention for bioremediation.
The overall objective of this Duke SRP Center project is to maximize HOC biodegradation in sediment settings by stimulating the growth of synergistic fungal-bacterial biofilms using engineered composite organic amendments. The general hypothesis is that the physico-chemical environment can be altered using composite organic amendments that stimulate the formation of cooperative bacterial-fungal biofilms. In these biofilms, indigenous fungi produce extracellular enzymes to break down hydrophobic contaminants into by-products that are more readily transported into indigenous bacterial cells and further decomposed. The specific aims for this project are to:
- Perform microbial and geochemical characterizations of contaminated sediments for the construction of a microbial association network model;
- Identify organic amendments which support the growth of cooperative fungal-bacterial biofilms and maximize HOC degradation in microcosms;
- Engineer and test composite amendments for biofilm formation that are compatible with HOC sediment treatment; and
- Implement the composite amendment strategy in large-scale mesocosms and verify fungal stimulation.
Ultimately, this project will create a framework to better understand cooperative fungal-bacterial biofilms in the context of sediment bioremediation and yield field translatable approaches for the bioremediation of HOCs.