title: Tailor-made biocatalysts based on scarcely studied acidic horseradish peroxidase for biodegradation of reactive dyes.
abstract: Peroxidases (EC 1.11.1.7) have enormous biotechnological applications. Usage of more abundant, basic isoforms of peroxidases in diagnostic kits and/or in immunochemistry has led to under exploitation and disregard of horseradish peroxidase (HRP) acidic isoforms. Therefore, acidic horseradish peroxidase (HRP-A) isoenzyme was used for the preparation of a biocatalyst with improved ability in dye decolorization. Ten biocatalysts were prepared by covalent binding of enzyme to chitosan and alginate, adsorption followed by cross-linking on inorganic support (aluminum oxide), and encapsulation in spherical calcium alginate beads via polyethylene glycol. Model dyes of 50 to 175 mg l-1were removed by the biocatalysts. Among the tested biocatalysts, the three with the highest specific activity and biodegradation rate were further studied (Chitosan-HRP, Al-Gel-HRP and Al-HRP-Gel). The impact of hydrogen peroxide concentration on dye decolorization was examined on the Chitosan-HRP biocatalyst, since the HRP is susceptible to inhibition/inactivation by high H2O2. On the other hand, H2O2is needed as a co-substrate for the HRP, and the H2O2/dye ratio can greatly influence decolorization efficiency. Concentrations of H2O2ranging from 0.22 to 4.4 mM showed no difference in terms of impact on the biocatalyst decolorization efficiency. The high decolorization efficiency of the biocatalysts was validated by the removal of 25 and 100 mg l-1anthraquinone (Remazol Brilliant Blue R (RBBR)), triphenylmethane (Coomassie Brilliant Blue (CBB)), acridine (Acridine Orange (AO)), and formazan metal complex dye (Reactive Blue 52 (RB52)). After the seven consecutive decolorization cycles, the decolorization was still 53, 78, and 67% of the initial dye for the Al-HRP-Gel, Al-Gel-HRP, and Chitosan-HRP immobilizate, respectively. The results obtained showed potential of otherwise neglected acidic HRP isoforms as a cost-effective biocatalyst with significant potential in wastewater dyestuff treatment.
authors.affiliation: Department of Chemistry, Institute of Chemistry, Technology, and Metallurgy, Njegoševa 12, P.O. Box 815, Belgrade, 11000, Serbia. bjanovic@chem.bg.ac.rs.
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Janović
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, 11000, Serbia.
authors.forename: Milica Lj
authors.initials: ML
authors.lastname: Mićić Vićovac
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, 11000, Serbia.
authors.forename: Zoran M
authors.initials: ZM
authors.lastname: Vujčić
authors.affiliation: Department of Chemistry, Institute of Chemistry, Technology, and Metallurgy, Njegoševa 12, P.O. Box 815, Belgrade, 11000, Serbia.
authors.forename: Miroslava T
authors.initials: MT
authors.lastname: Vujčić
mesh_terms: D055162:Biocatalysis; D001673:Biodegradation, Environmental; D004396:Coloring Agents / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism
chemical_list: D004396:Coloring Agents; D007527:Isoenzymes; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase
keywords: Biocatalyst; Decolorization; Horseradish peroxidase; Immobilization; Isoenzymes; Reactive dyes