Chemical and Biochemical Bases for EDTA Biodegradation

This award from the Environmental Chemical Sciences Program in the NSF Division of Chemistry supports a collaborative effort of Professors ChulHee Kang and Luying Xun at Washington State University (WSU) to study the environmental fate of Ethylenediaminetetraacetic acid (EDTA). This compound is being introduced into the environment through extensive use in industrial applications. Currently, EDTA is the most abundant organic pollutant in surface waters around the world, including the US. EDTA forms strong complexes with toxic heavy metals and mobilizes them, which increases exposure of humans. Several EDTA-degrading bacteria exist in nature. However, applying those bacteria in remediation is not practical because they are not efficient enough. Studies of the key enzymes and uptake system for the bacterial EDTA-degradation pathway reveal the factors that limit the biodegradation. This knowledge is used to modify the genes to increase catalytic efficiency and helps generate effective solutions for bioremediation. The research provides the participating students with interdisciplinary training in enzymology, microbiology, and biophysical chemistry, serving as an important bridge among the key STEM units at WSU. In addition, through existing NSF-funded K-12 outreach programs and the BXC Center at WSU, expertise is provided to high school classrooms, the local Palouse Discovery Science Center and local undergraduate institutions. This enhances the training of students of diverse economic, ethnic, and geographic backgrounds.<br/><br/>The substrate-specificity, catalytic mechanism and molecular interactions of the transport and binding proteins and enzymes in the EDTA-degradation pathway of Chelativorans sp. BNC1 are investigated. This provides guidance for designing a new recombinant system with enhanced degradation capacity. Those improved EDTA-uptake and metabolizing genes are cloned into phosphite-dependent E. coli to enable the recombinant strain to degrade EDTA in wastewaters. The merit of this approach is not only in its contribution to the study of EDTA biodegradation, but also in its applicability to similar pathways for the degradation of other anthropogenic compounds. The research also addresses the chemical basis of evolutionary adaptations to non-natural chemicals.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.