title: Very stable silica-gel-bound laccase biocatalysts for the selective oxidation in continuous systems.
abstract: Cerrena unicolor laccase was immobilized by adsorption and covalent bonds formation on silica-gel carriers, functionalized with different organosilanes and surface densities. The effects of protein concentration, pH value of the coupling mixture and the enzyme purity on immobilization efficiency of the best carrier, moderately modified (0.75 mmol/g carrier) with 3-aminopropyltriethoxysilane were investigated. Activity of the best biocatalysts, expressed in ABTS oxidation, was 4028 U/mL of the carrier or 3530 U/mg of bound protein. Properties of immobilized laccase were determined to find excellent thermal stability improvement; t(1/2) for freely suspended enzyme was 2-3 min at 80 degrees C, whereas after immobilization over 100 min. Kinetic experiments in both batch and packed-bed reactors gave only four times lower k(cat)/K(m) value than for the native enzyme. A packed-bed reactor with silica-gel-bound laccase beads appeared to be very efficient in ABTS oxidation and its exceptional potentials were shown in the continuous decolorization of indigo carmine for 18 days without loss in activity. This system offers perfect ability to degrade recalcitrant dyes, but we can also envisage its use, with ABTS acting as a mediator, in regeneration of nicotinamide cofactors.
authors.affiliation: Wrocław University of Technology, Faculty of Chemistry, Department of Bioorganic Chemistry, Wrocław, Poland.
authors.forename: Adriana
authors.initials: A
authors.lastname: Rekuć
authors.forename: Jolanta
authors.initials: J
authors.lastname: Bryjak
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Szymańska
authors.forename: Andrzej B
authors.initials: AB
authors.lastname: Jarzebski
mesh_terms: D001487:Basidiomycota / Q000201:enzymology*; D052160:Benzothiazoles / Q000378:metabolism; D055162:Biocatalysis; D001709:Biotechnology / Q000379:methods*; D003116:Color; D004789:Enzyme Activation; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000378:metabolism*; D005782:Gels; D007203:Indigo Carmine / Q000378:metabolism; D007700:Kinetics; D042845:Laccase / Q000378:metabolism*; D010084:Oxidation-Reduction; D012822:Silicon Dioxide / Q000378:metabolism*; D013451:Sulfonic Acids / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
chemical_list: D052160:Benzothiazoles; D004800:Enzymes, Immobilized; D005782:Gels; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D012822:Silicon Dioxide; D007203:Indigo Carmine; D042845:Laccase