Georgia Institute of Technology researchers found bacterial species found in subsurface soil, capable of releasing inorganic phosphate (after hydrolyzing an organo-phosphate source added by the researchers) that converts uranium contamination into an insoluble and immobile form.

Funded for three years by DOE's Environmental Remediation Sciences Division, the bioremediation project is in its early stages. The research team presented the preliminary findings on March 30 at the 231st American Chemical Society National Meeting in Atlanta.

"These organisms release phosphate into the medium, but the precipitation (of uranium phosphate) occurs chemically," explained Assistant Professor of Earth and Atmospheric Sciences Martial Taillefert, co-director of the study. "That is the biomineralization of uranium and the novelty of this approach."

The process begins when the bacteria - from the genera Rhanella, Bacillus and possibly Arthrobacter-degrade an organo-phosphate compound such as glycerol-3-phosphate (G3P) or phytic acid (IP6), which can be present in subsurface soils.

"During their growth, the organisms liberate phosphate they derive from the organo-phosphate compound," said project co-director Patricia Sobecky, an associate professor of biology. "The free phosphate is released to the surrounding media, which is a solution in the lab. Then we conduct assays to see how much uranium is mineralized by the phosphate released by the bacteria."

The role of the bacteria is very important in this process because uranium cannot dissociate the organo-phosphate compound chemically. Significant uranium precipation doesn't occur with uranium alone even in the presence of organo-phosphate.

There are many forms of uranium in the environment, which are all influenced by the natural properties of soils and groundwater. The researchers need to optimize the assay conditions and the techniques to analyze the distribution of uranium species in the lab. While they know that the organisms they're studying are active in precipitating uranium phosphate, they still need to determine how chemically stable the resulting compound is and to work on the conditions that will make the microbe thrive and work chemically in a natural setting.

Source: Georgia Tech Newsroom

Photo Credit: [www.imagesco.com]