title: Effect of trace metals and electron shuttle on simultaneous reduction of reactive black-5 azo dye and hexavalent chromium in liquid medium by Pseudomonas sp.
abstract: This study demonstrates the role of electron shuttles and trace metals in the biotransformation of azo dye reactive black-5 and hexavalent chromium (CrVI) that are released simultaneously in tannery effluent. Previously isolated bacterial strain Pseudomonas putida KI was used for the simultaneous reduction of the dye (100 mg L(-1)) and CrVI (2 mg L(-1)) in a mineral salts medium (MSM). Among various trace metals, only Cu(II) had a stimulating effect on the bacterial-mediated reduction process. Application of electron shuttles such as hydroquinone and uric acid at a low concentration (1mM) had a positive effect on the reduction process and caused simultaneous reduction of 100% dye and 97% CrVI in 12-18 h. Mannitol, EDTA and sodium benzoate at all concentrations (ranging from 1 to 9 mM) showed an inhibitory effect on the reduction of reactive black-5 and CrVI. An inverse linear relationship between the velocity of reaction (V) and the concentration [S] of electron shuttles was observed. The results imply that both types and concentration of an electron shuttle and trace metals can affect the simultaneous reduction of reactive black-5 and CrVI.
authors.affiliation: Department of Environmental Sciences, PMAS Arid Agriculture University, Rawalpindi 46300, Pakistan.
authors.forename: Shahid
authors.initials: S
authors.lastname: Mahmood
authors.affiliation: Department of Environmental Sciences, PMAS Arid Agriculture University, Rawalpindi 46300, Pakistan. Electronic address: azeem@uaar.edu.pk.
authors.forename: Azeem
authors.initials: A
authors.lastname: Khalid
authors.affiliation: Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Arshad
authors.affiliation: Quality Enhancement Cell, PMAS Arid Agriculture University, Rawalpindi 46300, Pakistan.
authors.forename: Riaz
authors.initials: R
authors.lastname: Ahmad
mesh_terms: D001711:Biotransformation / Q000187:drug effects; D002857:Chromium / Q000378:metabolism*; D004396:Coloring Agents / Q000378:metabolism*; D004579:Electron Transport / Q000187:drug effects; D004785:Environmental Pollutants / Q000378:metabolism*; D009282:Naphthalenesulfonates / Q000378:metabolism*; D011549:Pseudomonas / Q000187:drug effects* / Q000378:metabolism*; D014131:Trace Elements / Q000494:pharmacology*
chemical_list: D004396:Coloring Agents; D004785:Environmental Pollutants; D009282:Naphthalenesulfonates; D014131:Trace Elements; D002857:Chromium; C074702:chromium hexavalent ion; C063421:Remazol black B
keywords: Electron shuttle; Hexavalent chromium; Hydroquinone; Reactive black-5; Trace metals; Uric acid