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Öğe Antibacterial and antifungal activity of Heracleum sphondylium subsp artvinense (conferenceObject)(Elsevier Science Bv, 2005) Kaçar, Y.; Tan, S.; Ergene, A.; Güler, P.; Mirici, S.; Hamzaoglu, E.; Yildirim, S.…Öğe Congo Red attached monosize poly(HEMA-co-MMA) microspheres for use in reversible enzyme immobilisation(Elsevier Science Sa, 2002) Yavuz, H.; Bayramoğlu, G.; Kaçar, Y.; Denizli, A.; Arica, M.Y.Monosize and non-porous poly(2-hydroxyethylmethacrylate-co-methylmethacrylate) (poly(HEMA-co-MMA)), microspheres were prepared by dispersion polymerisation of HEMA and MMA in an ethanol-water medium in the presence of an initiator (alpha,alpha'-azobisisobutyronitrile, AIBN). An affinity dye, i.e. Congo Red (CR) was attached covalently and then Fe3+ ions were incorporated. The poly(HEMA-co-MMA)-CR attached and poly(HEMA-co-MMA)-CR-Fe3+ incorporated microspheres were used in the immobilisation of glucose oxidase (GOD) via adsorption. The adsorption capacities of these microspheres were determined by varying the concentration of GOD in the adsorption medium. GOD adsorption capacities of the Fe3+ incorporated microspheres (165 mg g(-1)) was greater than that of the dye-attached microspheres (126 mg g(-1)). The non-specific adsorption of the GOD on the poly(HEMA-co-MMA) microspheres was negligible. The K values for both immobilised poly(HEMA-co-MMA)-CR-GOD (7.2) and poly(HEMA-co-MMA)-CR-Fe3+-GOD (6.8) were higher than that of the free enzyme (6.6 mM). Optimum reaction pH was 5.0 for free and 7.0 for both immobilised preparations. Optimum reaction temperature of the adsorbed enzymes was 10degreesC higher than that of the free enzyme and was significantly broader. After 10 successive uses the retained activity of the adsorbed enzyme was 93%. It was observed that enzyme could be repeatedly adsorbed and desorbed on the CR attached poly(HEMA-co-MMA) microspheres without significant loss in adsorption capacity or enzyme activity. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe Hydrolysis of sucrose by invertase immobilized onto novel magnetic polyvinylalcohol microspheres(Elsevier Sci Ltd, 2001) Akgöl, S.; Kaçar, Y.; Denizli, A.; Arıca, M.Y.The magnetic polyvinylalcohol (PVAL) microspheres were prepared by crosslinking glutaraldehyde. 1,1 ' -Carbonyldiimidazole (CDI), a carbonylating agent was used for the activation of hydroxyl groups of polyvinylalcohol, and invertase immobilized onto the magnetic PVAL microspheres by covalent bonding through the amino group. The retained activity of the immobilized invertase was 74%. Kinetic parameters were determined for immobilized invertase, as well as for the free enzyme. The K-m values for immobilized invertase (55 mM sucrose) were higher than that of the free enzyme (24 mM sucrose), whereas V-max values were smaller for the immobilized invertase. The optimum operational temperature was 5 degreesC higher for immobilized enzyme than that of the free enzyme. The operational inactivation rate constant (k(opi)) of the immobilized invertase at 35 degreesC with 200 mM sucrose was 5.83 x 10(-5) min(-1). Thermal and storage stabilities were found to increase with immobilization. (C) 2001 Elsevier Science Ltd. All rights reserved.Öğe Poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) reactive membrane utilised for cholesterol oxidase immobilisation(John Wiley & Sons Ltd, 2002) Akgöl, S.; Bayramoğlu, G.; Kaçar, Y.; Denizli, A; Arıca, M.Y.Poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) p(HEMA-GMA) membrane was prepared by UV-initiated photopolymerisation of 2-hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA) in the presence of an initiator, azobisisobutyronitrile (AIBN). Cholesterol oxidase was immobilised directly on the membrane by forming covalent bonds between its amino groups and the epoxide groups of the membrane. An average of 53 mug of enzyme was immobilised per cm(2) of membrane, and the bound enzyme retained about 67% of its initial activity. Immobilisation improved the pH stability of the enzyme as well as its temperature stability. The optimum temperature was 5degreesC higher than that of the free enzyme and was significantly broader. The thermal inactivation rate constants for free and immobilised preparations at 70degreesC were calculated as k(i (free)) 1.06 x 10(-1) min(-1) and k(i (imm)) 2.68 x 10(-2) min(-1), respectively. The immobilised enzyme activity was found to be quite stable in the repeated experiments. (C) 2002 Society of Chemical Industry.Öğe Reversible immobilization of lipase on phenylalanine containing hydrogel membranes(Elsevier Sci Ltd, 2001) Arıca, M.Y.; Kaçar, Y.; Ergene, A.; Denizli, A.Poly(2-hydroxyethylmethacrylate-co-methacrylamidophenlyalanine) poly(HEMA-MAPA) membranes were prepared by UV-initiated photopolymerization of HEMA and MAPA. Lipase immobilization onto these membranes from aqueous solutions containing different amounts of lipase at different pH was investigated in a batch system. The lipase adsorption capacity of the membranes was increased as the MAPA ratio increased in the membrane structure. The maximum lipase immobilization capacity of the poly(HEMA-MAPA-3) membrane was 135 mug cm(-2). The optimum temperature was 5 degreesC higher than that of the free enzyme and was significantly broader. The storage stability increased with immobilization. The enzyme could be repeatedly adsorbed and desorbed without any significant loss in adsorption capacity. (C) 2001 Elsevier Science Ltd. All rights reserved.
