title: Yeast extract promotes decolorization of azo dyes by stimulating azoreductase activity in Shewanella sp. strain IFN4.
abstract: Biological treatment of azo dyes commonly requires a combined anaerobic-aerobic process in which initial decolorization is achieved by reductive cleavage of azo bonds on the parent molecule. The present study was conducted to examine the relative importance of co-substrates for driving reductive decolorization of azo dyes by Shewanella sp. strain IFN4 using whole cells and enzyme assays. Results showed that the dye decolorization by strain IFN4 was faster in medium containing 1gL(-1) yeast extract (YE) as compared to nine other co-substrates. Moreover, only YE stimulated azoreductase activity (increased from 1.32 to 4.19U/mg protein). Increasing the level of YE up to 8gL(-)(1) resulted into 81% decolorization of the dye in 1h along with an increase in azoreductase activity up to 6.16U/mg protein. Among the components of YE, only riboflavin stimulated the decolorization process as well as enzyme activity. Moreover, strain IFN4 demonstrated flavin reductase activity, and a significant correlation (r(2)=0.98) between flavin reduction and dye reduction by this strain emphasized the involvement of flavin compounds in the decolorization process. The results of this study show that YE serves both as a source of reducing equivalents and an electron shuttle for catalyzing dye reduction.
authors.affiliation: Department of Environmental Sciences, University of California Riverside, Riverside 92521, USA; Soil Science Division, Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad 38000, Pakistan; Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Faisalabad 38040, Pakistan. Electronic address: imran1631@gmail.com.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Imran
authors.affiliation: Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Faisalabad 38040, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Arshad
authors.affiliation: Department of Botany and Plant Sciences, University of California Riverside, Riverside 92521, USA.
authors.forename: Fayek
authors.initials: F
authors.lastname: Negm
authors.affiliation: Department of Environmental Sciences, PMAS Arid Agriculture University, Rawalpindi 46300, Pakistan.
authors.forename: Azeem
authors.initials: A
authors.lastname: Khalid
authors.affiliation: Department of Soil, Water and Agricultural Engineering College of Agricultural and Marine Sciences, Sultan Qaboos University, 123, Oman.
authors.forename: Baby
authors.initials: B
authors.lastname: Shaharoona
authors.affiliation: Department of Environmental Sciences & Engineering, Government College University, Faisalabad 38040, Pakistan.
authors.forename: Sabir
authors.initials: S
authors.lastname: Hussain
authors.affiliation: University of Agriculture Faisalabad, Sub-campus Burewala, Pakistan.
authors.forename: Sajid
authors.initials: S
authors.lastname: Mahmood Nadeem
authors.affiliation: Department of Environmental Sciences, University of California Riverside, Riverside 92521, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Crowley
mesh_terms: D001391:Azo Compounds / Q000378:metabolism*; D004396:Coloring Agents / Q000378:metabolism*; D045424:Complex Mixtures / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009601:Nitroreductases; D010084:Oxidation-Reduction; D020592:Shewanella / Q000378:metabolism*; D015003:Yeasts / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D045424:Complex Mixtures; D009247:NADH, NADPH Oxidoreductases; D009601:Nitroreductases; C021106:azoreductase
keywords: Azo dyes; Electron shuttle; Redox mediator; Riboflavin; Shewanella; Yeast extract