title: Soybean peroxidase-mediated degradation of an azo dye- a detailed mechanistic study.
abstract: BACKGROUND
  Peroxidases are emerging as an important class of enzymes that can be used for the efficient degradation of organic pollutants. However, detailed studies identifying the various intermediates produced and the mechanisms involved in the enzyme-mediated pollutant degradation are not widely published.
  
  
  RESULTS
  In the present study, the enzymatic degradation of an azo dye (Crystal Ponceau 6R, CP6R) was studied using commercially available soybean peroxidase (SBP) enzyme. Several operational parameters affecting the enzymatic degradation of dye were evaluated and optimized, such as initial dye concentration, H2O2 dosage, mediator amount and pH of the solution. Under optimized conditions, 40 ppm dye solution could be completely degraded in under one minute by SBP in the presence of H2O2 and a redox mediator. Dye degradation was also confirmed using HPLC and TOC analyses, which showed that most of the dye was being mineralized to CO2 in the process.
  
  
  CONCLUSIONS
  Detailed analysis of metabolites, based on LC/MS results, showed that the enzyme-based degradation of the CP6R dye proceeded in two different reaction pathways- via symmetric azo bond cleavage as well as asymmetric azo bond breakage in the dye molecule. In addition, various critical transformative and oxidative steps such as deamination, desulfonation, keto-oxidation are explained on an electronic level. Furthermore, LC/MS/MS analyses confirmed that the end products in both pathways were small chain aliphatic carboxylic acids.
authors.forename: Liaquat
authors.initials: L
authors.lastname: Ali
authors.forename: Rowdha
authors.initials: R
authors.lastname: Algaithi
authors.forename: Hosam M
authors.initials: HM
authors.lastname: Habib
authors.forename: Usama
authors.initials: U
authors.lastname: Souka
authors.forename: Muhammad A
authors.initials: MA
authors.lastname: Rauf
authors.affiliation: Department of Chemistry, College of Science, UAE University, P,O, Box 15551, Al-Ain, United Arab Emirates. salman.ashraf@uaeu.ac.ae.
authors.forename: S Salman
authors.initials: SS
authors.lastname: Ashraf
mesh_terms: D001391:Azo Compounds / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004396:Coloring Agents / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism*; D013025:Glycine max / Q000201:enzymology*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D002245:Carbon Dioxide; C017664:ponceau 6R; D006861:Hydrogen Peroxide; D009195:Peroxidase