title: Decolorization of two synthetic dyes using the purified laccase of Paraconiothyrium variabile immobilized on porous silica beads.
abstract: BACKGROUND
  Decolorization of hazardous synthetic dyes using laccases in both free and immobilized form has gained attention during the last decades. The present study was designed to prepare immobilized laccase (purified from Paraconiothyrium variabile) on porous silica beads followed by evaluation of both free and immobilized laccases for decolorization of two synthetic dyes of Acid Blue 25 and Acid Orange 7. Effects of laccase concentration, pH and temperature alteration, and presence of 1-hydroxybenzotriazole (HBT) as laccase mediator on decolorization pattern were also studied. In addition, the kinetic parameters (Km and Vmax) of the free and immobilized laccases for each synthetic dye were calculated.
  
  
  RESULTS
  Immobilized laccase represented higher temperature and pH stability compare to free one. 39% and 35% of Acid Blue 25 and Acid Orange 7 was decolorized, respectively after 65 min incubation in presence of the free laccase. In the case of immobilized laccase decolorization percent was found to be 76% and 64% for Acid Blue 25 and Acid Orange 7, respectively at the same time. Increasing of laccase activity enhanced decolorization percent using free and immobilized laccases. Relative decolorization of both applied dyes was increased after treatment by laccase-HBT system. After nine cycles of decolorization by immobilized laccase, 26% and 31% of relative activity were lost in the case of Acid Blue 25 and Acid Orange 7, respectively.
  
  
  CONCLUSIONS
  To sum up, the present investigation introduced the immobilized laccase of P. variabile on porous beads as an efficient biocatalyst for decolorization of synthetic dyes.
authors.forename: Seyedeh-Shaghayegh
authors.initials: SS
authors.lastname: Mirzadeh
authors.forename: Seyed-Mostafa
authors.initials: SM
authors.lastname: Khezri
authors.forename: Shahla
authors.initials: S
authors.lastname: Rezaei
authors.forename: Hamid
authors.initials: H
authors.lastname: Forootanfar
authors.affiliation: Department of Pharmaceutical Biotechnology, Faculty of Pharmacy and Biotechnology Research Center, Tehran University of Medical Sciences, Tehran 14176, Iran. ahmahvi@yahoo.com.
authors.forename: Amir Hossein
authors.initials: AH
authors.lastname: Mahvi
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Faramarzi