Formation of Soluble Organo−Chromium(III) Complexes after Chromate Reduction in the Presence of Cellular Organics

• Published in: Environmental science & technology Vol. 39; no. 8; pp. 2811 - 2817
• Main Authors: Puzon, Geoffrey J, Roberts, Arthur G, Kramer, David M, Xun, Luying
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.04.2005; American Chemical Society (ACS)
• Subjects: Applied sciences; Ascorbic Acid - metabolism; Biodegradation of pollutants; Biodegradation, Environmental; Biological and medical sciences; Biological and physicochemical phenomena; Biological and physicochemical properties of pollutants. Interaction in the soil; Biotechnology; Chromates - chemistry; Chromates - metabolism; Chromium - chemistry; Chromium - metabolism; Cytochromes c - metabolism; Earth sciences; Earth, ocean, space; Electron Spin Resonance Spectroscopy; Engineering and environment geology. Geothermics; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; NAD - metabolism; Natural water pollution; Oxidation-Reduction; Pollution; Pollution, environment geology; Soil and sediments pollution; Soil Microbiology; Soil Pollutants - metabolism; Solubility; Water treatment and pollution; Microbial activity; Complexation; Metabolite; Escherichia coli; Organic ligand; Soil pollution; Cytochrome c; Chemical reduction; Chromium III; Enzymatic activity; Decontamination; Bacteria; Water pollution; Bioremediation; Chromium VI; Enterobacteriaceae
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es048967g

Microbial reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] has been investigated as a method for bioremediation of Cr(VI) contaminated environments. The produced Cr(III) is thought to be insoluble Cr(OH)3; however, recent reports suggested a more complex fate of Cr(III). A bacterial enzyme system, using NADH as the reductant, converts Cr(VI) to a soluble NAD+−Cr(III) complex, and cytochrome c-mediated Cr(VI) reduction produces cytochrome c−Cr(III) adducts. In this study, Cr(VI) reduction in the presence of cellular organic metabolites formed both soluble and insoluble organo−Cr(III) end-products. Several soluble end-products were characterized by absorbance spectroscopy and electron paramagnetic resonance spectrometry as organo−Cr(III) complexes, similar to the known ascorbate−Cr(III) complex. The complexes remained soluble and stable upon dialysis against distilled H2O and over a broad pH range. The ready formation of stable organo−Cr(III) complexes suggests that organo−Cr(III) complexes are rather common, likely representing an integral part of the natural cycling of chromium. Thus, organo−Cr(III) complexes may account for the mobile form of Cr(III) detected in the environment.