title: Immobilization of tyrosinase on modified diatom biosilica: enzymatic removal of phenolic compounds from aqueous solution.
abstract: Acid and plasma treated diatom-biosilica particles, were modified with 3-aminopropyl triethoxysilane (APTES), and activated with glutaraldehyde. Then, tyrosinase was immobilized onto the pre-activated biosilica by covalent bonding. The biosilica properties were determined using SEM, and FTIR. The enzyme system has been characterized as a function of pH, temperature and substrate concentration. Optimum pH of the free and immobilized enzyme was found to be pH 7.0. Optimum temperatures of the free and immobilized enzymes were determined as 35 and 45 °C respectively. The biodegradation of phenolic compounds (i.e., phenol, para-cresol and phenyl acetate) has been studied by means of immobilized tyrosinase in a batch system. The immobilized tyrosinase retained about 74% of its original activity after 10 times repeated use in the batch system. Moreover, the storage stability of the tyrosinase-biosilica system resulted excellent, since they maintained more than 67% of the initial activity after eighth week storage. Highly porous structure of biosilica can provide large surface area for immobilization of high quantity enzyme. The porous structure of the biosilica can decrease diffusion limitation both substrate phenols and their products. Finally, the immobilized tyrosinase was used in a batch system for degradation of three different phenols.
authors.affiliation: Biochemical Processing and Biomaterial Research Laboratory, Faculty of Science, Gazi University, 06500 Teknikokullar, Ankara, Turkey. g_bayramoglu@hotmail.com
authors.forename: Gulay
authors.initials: G
authors.lastname: Bayramoglu
authors.forename: Aydin
authors.initials: A
authors.lastname: Akbulut
authors.forename: M Yakup
authors.initials: MY
authors.lastname: Arica
mesh_terms: D017377:Diatoms; D004800:Enzymes, Immobilized / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D011437:Propylamines / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D012996:Solutions; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D010636:Phenols; D011437:Propylamines; D012821:Silanes; D012996:Solutions; D014874:Water Pollutants, Chemical; C088294:3-aminopropyltrimethoxysilane; D012822:Silicon Dioxide; D014442:Monophenol Monooxygenase