Transgenic Citrate-Producing Plants for Lead PhytoremediationEPA Contract Number: 68D02018
Title: Transgenic Citrate-Producing Plants for Lead Phytoremediation
Investigators: Elless, Mark P.
Small Business: Edenspace Systems Corporation
EPA Contact: Manager, SBIR Program
Project Period: April 1, 2002 through September 1, 2002
Project Amount: $69,660
RFA: Small Business Innovation Research (SBIR) - Phase I (2002) RFA Text | Recipients Lists
Research Category: SBIR - Waste , Hazardous Waste/Remediation , Small Business Innovation Research (SBIR)
Description:In 1991, the Secretary of the U.S. Department of Health and Human Services called lead "the number one environmental threat to the health of children in the United States." Lead poisoning affects 890,000 U.S. children between the ages of 1 and 5, causing aggressive behavior, hyperactivity, and learning problems. In adults, increased lead levels have been linked to kidney problems, high blood pressure, damaged hearing, blindness, brain damage, and mental retardation. A major source of lead exposure is dust stirred up in sites contaminated by lead paint, leaded gasoline, or lead from mining or industrial activities. This widespread problem affects an estimated 18 percent of U.S. homes. A promising alternative to excavation and replacement of soil is extraction of lead using living plants. Lead phytoremediation relies on the use of crop species, including turf grasses, with a combination of chelating agents and other amendments that induce enhanced plant availability of the contaminant and higher plant uptake rates. The cost of such amendments can range up to $20,000 per acre per growing season. Furthermore, sites with sandy, well-drained soil over shallow groundwater may need to use a water-impermeable liner to prevent slowly degrading chelating agents such as ethylenediamine tetraacetic acid (EDTA) from leaching metals into groundwater. Costs associated with installing and maintaining a liner can more than double the total cost of phytoextraction, and the need for a liner may render phytoremediation impractical for many sites.
Edenspace Systems Corporation proposes to use transgenic technology to provide plants with the ability to exude significant amounts of a rapidly biodegradable chelating agent?citric acid?from their roots, enabling cost savings of more than 70 percent in the phytoextraction of lead from contaminated soil. A citrate synthase (CS) transgene has been placed under the control of plant promoters to overexpress the gene in roots, producing approximately 10 times the endogenous levels of root citrate found in nontransgenic plants. In Phase I, citrate synthesis, promoter "on-off switches," and lead uptake will be explored in CS-transgenic tobacco, Nicotiana tabacum, and canola (Brassica napus). Canola is closely related to a major phytoremediating species, Indian mustard (Brassica juncea). At many sites, plant production of rapidly biodegradable chelating agents precisely at the root/soil interface where metal uptake occurs may eliminate both the need to apply expensive amendments and the need for a liner. Attainment of the project's goals may, therefore, reduce the substantial public health hazard of soil lead and other metals by realizing phytoremediation's low-cost potential.