Biosurfactant-Enhanced In Situ Metal Remediation

Background
The U.S. EPA ATSDR lists five of the top 20 hazardous substances as metals including arsenic (#1), lead (#2), mercury (#3), cadmium (#7), and chromium (#16). Innovative strategies that are as cost-effective, noninvasive, and as environmentally benign as possible are needed to remediate metal-contaminated sites.

The isolation of microbial produced surfactants occurs via the following process: 1) grow bacteria and produce surfactant, 2) separate bacteria from surfactant, 3) isolate surfactant using solid phase extraction, 4) use HPLC to purify, 5) use mass spectrometer and NMR to identify and characterize. Once purified you can identify the binding force between surfactant and metal source (known as the conditional stability constant). Photo shows pure rhamnolipid biosurfactant.

Objectives
1. Define the conditions under which biosurfactants can be successfully used as soil washing agents to remove metals from contaminated sites.

2. Explore the diversity of biosurfactant-producing microorganisms in contaminated and uncontaminated soils.

Significant Findings
1. Demonstrated conditions under which two biosurfactants, rhamnolipid and cyclodextrin, can be used to enhance remediation of metal-contaminated sites. These materials can be considered environmentally benign washing agents that are capable of removing the readily extractable (soluble and exchangeable) metal fractions. Results suggest that biosurfactants may have application for sites that must be remediated in an environmentally sensitive manner.

2. Definition of the distribution of biosurfactant-producing microorganisms in the environment: 1) biosurfactant-producing microbes are found in a majority of soils, 2) biosurfactant-producing microbes are especially common in soils with metal-contamination.

3. Discovery and structural characterization of a new class of biosurfactants: the flavolipids produced by Flavobacterium sp. MTN11.

Publications

Contact
Raina Maier
rmaier@ag.arizona.edu
520-621-7231