![Mechanism of hexavalent chromium detoxification by microorganisms and bioremediation application potential: A review [An article from: International Biodeterioration & Biodegradation]](https://www.ebooknetworking.net/books/B00/0PD/bigB000PDSGV2.jpg)
Mechanism of hexavalent chromium detoxification by microorganisms and bioremediation application potential: A review [An article from: International Biodeterioration & Biodegradation]
Book Details
Author(s)K.H. Cheung, J.D. Gu
PublisherElsevier
ISBN / ASINB000PDSGV2
ISBN-13978B000PDSGV2
MarketplaceFrance 🇫🇷
Description
This digital document is a journal article from International Biodeterioration & Biodegradation, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.
Description:
Chromium has been widely used in various industries. Hexavalent chromium (Cr^6^+) is a priority toxic, mutagenic and carcinogenic chemical, whereas its reduced trivalent form (Cr^3^+) is much less toxic and insoluble. Hence, the basic process for chromium detoxification is the transformation of Cr^6^+ to Cr^3^+. A number of aerobic and anaerobic microorganisms are capable of reducing Cr^6^+. In the presence of oxygen, microbial reduction of Cr^6^+ is commonly catalyzed by soluble enzymes, except in Pseudomonas maltophilia O-2 and Bacillus megaterium TKW3, which utilize membrane-associated reductases. Recently, two soluble Cr^6^+ reductases, ChrR and YieF, have been purified from Pseudomonas putida MK1 and Escherichia coli, respectively. ChrR catalyzes an initially one-electron shuttle followed by a two-electron transfer to Cr^6^+, with the formation of intermediate(s) Cr^5^+ and/or Cr^4^+ before further reduction to Cr^3^+. YieF displays a four-electron transfer that reduces Cr^6^+ directly to Cr^3^+. The membrane-associated Cr^6^+ reductase of B. megaterium TKW3 was isolated, but its reduction kinetics is as yet uncharacterized. Under anaerobic conditions, both soluble and membrane-associated enzymes of the electron transfer system were reported to mediate Cr^6^+ reduction as a fortuitous process coupled to the oxidation of an electron donor substrate. In this process, Cr^6^+ serves as the terminal electron acceptor of an electron transfer chain that frequently involves cytochromes (e.g., b and c). An expanding array of Cr^6^+ reductases allows the selection of enzymes with higher reductive activity, which genetic and/or protein engineering may further enhance their efficiencies. With the advancement in technology for enzyme immobilization, it is speculated that the direct application of Cr^6^+ reductases may be a promising approach for bioremediation of Cr^6^+ in a wide range of environments.
Description:
Chromium has been widely used in various industries. Hexavalent chromium (Cr^6^+) is a priority toxic, mutagenic and carcinogenic chemical, whereas its reduced trivalent form (Cr^3^+) is much less toxic and insoluble. Hence, the basic process for chromium detoxification is the transformation of Cr^6^+ to Cr^3^+. A number of aerobic and anaerobic microorganisms are capable of reducing Cr^6^+. In the presence of oxygen, microbial reduction of Cr^6^+ is commonly catalyzed by soluble enzymes, except in Pseudomonas maltophilia O-2 and Bacillus megaterium TKW3, which utilize membrane-associated reductases. Recently, two soluble Cr^6^+ reductases, ChrR and YieF, have been purified from Pseudomonas putida MK1 and Escherichia coli, respectively. ChrR catalyzes an initially one-electron shuttle followed by a two-electron transfer to Cr^6^+, with the formation of intermediate(s) Cr^5^+ and/or Cr^4^+ before further reduction to Cr^3^+. YieF displays a four-electron transfer that reduces Cr^6^+ directly to Cr^3^+. The membrane-associated Cr^6^+ reductase of B. megaterium TKW3 was isolated, but its reduction kinetics is as yet uncharacterized. Under anaerobic conditions, both soluble and membrane-associated enzymes of the electron transfer system were reported to mediate Cr^6^+ reduction as a fortuitous process coupled to the oxidation of an electron donor substrate. In this process, Cr^6^+ serves as the terminal electron acceptor of an electron transfer chain that frequently involves cytochromes (e.g., b and c). An expanding array of Cr^6^+ reductases allows the selection of enzymes with higher reductive activity, which genetic and/or protein engineering may further enhance their efficiencies. With the advancement in technology for enzyme immobilization, it is speculated that the direct application of Cr^6^+ reductases may be a promising approach for bioremediation of Cr^6^+ in a wide range of environments.
