WRHSRC Research Program:
Aerobic Cometabolic Processes

Focus Group Leader:

Daniel Arp, Oregon State University

Technical Description:

Aerobic cometabolic processes are studied for the remediation of dilute CAH plumes. Aerobic cometabolic processes are well suited for this purpose because contaminant concentrations can be reduced to low levels, while maintaining groundwater quality (Semprini, 1997). Center investigators have been leaders in the development of in-situ cometabolic processes and in performing pilot-scale field demonstrations of cometabolic treatment (Semprini et al.,1990; Hopkins et al., 1993; Hopkins and McCarty, 1995; McCarty et al., 1998).

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Project 1-OSU-02:

Aerobic Cometabolism of Chlorinated Aliphatic Hydrocarbon Compounds with Butane-Grown Microorganisms

Principal Investigators:

Daniel Arp, Peter Bottomley, Lynda Ciuffetti, Mark Dolan, Steve Giovannoni, Lewis Semprini, Ken Williamson,Oregon State University

Project Initiated: 2002

 

Project Summary:

In this project the CAH degrading properties of several individual strains of butane-oxidizing bacteria and fungi that are known to possess distinctly different butane monooxygenases is being examined. The work is directed towards the aerobic cometabolism of a broad range of CAHs and CAH mixtures. Research on three sub-projects has continued during the past year. Research by Peter Bottomley and Dan Arp examined the CAH degrading properties of several individual strains of butane-oxidizing bacteria, Pseudomonas butanovora, Nocardioides CF8, and Mycobacterium vaccae JOB5, that are genotypically distinct from each other, and that are known to possess distinctly different butane monooxygenases (BMO). Their studies focused the inactivation of the butane monooxygenases, the BMO, resulting from transformation of different CAHs as well as the potential from BMO induction upon exposure to CAHs. Research by Lewis Semprini and Mark Dolan is evaluating 1,1,1-TCA and 1,1-DCE cometabolism by a Rhodocococcus sp. that has been bioaugmented into the continuous flow laboratory column packed aquifer solids from the Moffett Air Field In-Situ Test facility. Studies have shown effective and long term removal of 1,1,1-TCA in the column upon bioaugmentation and growth butane. Molecular based PCR probes have detected the bioaugmented microorganism in the column groundwater effluent after bioaugmentation and throughout the column test. Studies directed by Kenneth Williamson and Lynda Ciuffetti are evaluating the ability of a fungi, Graphium sp., to degrade a range of volatile organic compounds including chlorinated aliphatic hydrocarbons (CAHs), trichloromethanes and polyaromatic hydrocarbons (PAHs). The study also aims to demonstrate that these reactions are catalyzed by an alkane inducible cytochrome P450 monooxygenase through heterologous expression assays with yeast. The investigators are using cloning techniques to study the P450 monooxygenase in different types of fungi. In another related project, supported by an EPA STAR fellowship, the alkane monooxygenase activity will be conferred to plants, and the kinetics and fate of environmentally significant compounds (fuel oxygenates, chlorinated solvents and PAHs) in these transgenic plants will be determined.

The diagram above illustrates cometabolism of TCE.

 

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Project 2-OSU-05:

Aerobic Cometabolism of Chlorinated Ethenes by Microorganisms that Grow on Organic Acids and Alcohols

Principal Investigators:

Peter Bottomley, Daniel Arp, Mark Dolan, Lewis Semprini, Oregon State University

Project Initiated: 2004

 

Project Summary:

The selection of monitored natural attenuation as a remedy for sites contaminated with chlorinated aliphatic hydrocarbons is frequently being chosen. At many sites undergoing monitored natural attenuation, and some sites undergoing enhanced anaerobic transformation where substrates are added, the transformation process often stops at cis-dichloroethene. Aerobic cometabolism may play an important role in the intrinsic remediation of these less chlorinated products that result from the incomplete reductive transformation of perchloroethene and trichloroethene. The proposed work will evaluate the potential of microorganisms that grow on organic acids (or other non-saturated hydrocarbon substrates) and still express a monooxygenase to cometabolize chloroethenes. Preliminary evidence we have gathered through field observations and in laboratory studies with a pure culture and an enrichment culture shows some potential for aerobic cometabolism does exist when the cultures are grown on organic acids. The specific objectives of the work are to:

1. Isolate pure cultures that can transform cis-dichloroethene and vinyl chloride when grown on acetate, propionate, and butyrate,
2. conduct biochemical and transformation studies with Pseudomonas butanovora and the new isolate(s) from batch reactors to characterize induction of monooxygenases and provision of reductant for the monooxygenase-catalyzed reaction;
3. proceed to reactor tests where rates of substrate addition can be controlled, including batch reactor quasi-steady-state tests and chemostat tests. The experiments build on our previous work with butane-oxidizing bacteria and a butanol enrichment culture that expresses a phenol monooxygenase. The results should provide insight to the feasibility of cometabolism for removing chlorinated ethenes during monitored natural attenuation as well as in engineered field processes.

Project Update Slide (November 2004):

To download a copy of this slide, click here.

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