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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 Covalent immobilization of lipase onto hydrophobic group incorporated poly(2-hydroxyethyl methacrylate) based hydrophilic membrane matrix(Elsevier Sci Ltd, 2002) Bayramoğlu, G.; Kacar, Y.; Denizli, A.; Arica, M.Y.In this study, a hydrophobic group containing monomer, 2-methacrylamidophenyalanine (MAPA) was prepared by using methacrylochloride and phenylalanine. Then, poly(2-hydroxyethyl methacrylate-co-methacrylamido-phenlyalanine) (pHEMA-MAPA) membranes were prepared by UV-initiated photopolymerization of HEMA and MAPA in the presence of an initiator alpha-alpha'-azobisisobutyronitrile (AIBN). The lipase was immobilized onto these membranes by covalent bonding through carbodiimide activation. The amount of enzyme loading on the membranes was increased as the MAPA ratio increased in the membrane structure. Immobilization improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with immobilization and at 60 degreesC the thermal stability constants were 1.1 x 10(-1) min for free enzyme and 1.2 x 10(-2) min for the immobilized enzyme. The immobilized enzyme activity was found to be quite stable in repeated experiments. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Dye-ligand immobilized IPNs membrane for removal heavy metal ions(Wiley-V C H Verlag Gmbh, 2003) Bayramoğlu, G.; Yalçın, E.; Genç, O.; Arica, M.Y.We have developed a novel approach to obtain high metal sorption capacity utilizing a membrane containing chitosan and an immobilized reactive dye (i.e. Reactive Yellow-2). The composite membrane was characterized by SEM, FTIR, swelling test, and elemental analysis. The membrane has uniform small pores distribution and the pore dimensions are between 5 and 10 pm, and the HEMA:chitosan ratio was 50:1. The reactive dye immobilized composite membrane was used in the removal of heavy metal ions [i.e., Pb(II), Hg(II) and Cd(II)] from aqueous medium containing different amounts of these ions (5-600 mg 1(-1)) and at different pH values (2.0-7.0). The maximum adsorption capacities of heavy metal ions onto the composite membrane under non-competitive conditions were 64.3 mmol m(-2) for Pb(II), 52.7 mmol m(-2) for Hg(II), 39.6 mmol m(-2) for Cd(II) and the affinity order was Pb(II) > Hg(II)>Cd(II).Öğe Entrapment of Lentinus sajor-caju into Ca-alginate gel beads for removal of Cd(II) ions from aqueous solution: preparation and biosorption kinetics analysis(Elsevier Science Bv, 2002) Bayramoğlu, G.; Denizli, A.; Bektaş, S.; Arıca, M.Y.A white rot fungus species Lentinus sajor-caju biomass was entrapped into alginate gel via a liquid curing method in the presence of Ca(II) ions. The biosorption of cadmium(II) by the entrapped live and dead fungal biomass has been studied in a batch system. The heat-treatment process enhanced the biosorption capacity of the immobilized fungal biomass. The effect of initial cadmium concentration, pH and temperature on cadmium removal has been investigated. The maximum experimental biosorption capacities for entrapped live and dead fungal mycelia of L. sajur-caju were found to be 104.8 +/- 2.7 mg Cd(II) g(-1) and 123.5 +/- 4.3 mg Cd(II) g(-1), respectively. The kinetics of cadmium biosorption was fast, approximately 85% of biosorption taking place within 30 min. The biosorption equilibrium was well described by Langmuir and Freundlich adsorption isotherms, The change in the biosorption capacity with time is found to fit pseudo-second-order equations. Cadmium binding properties of entrapped fungal preparations have been determined applying the Ruzic equations. Since the biosorption capacities are relatively high for both entrapped live and dead forms, they could be considered as suitable biosorbents for the removal of cadmium in wastewater treatment systems. The biosorbents were reused in three consecutive adsorption/desorption cycles without significant loss in the biosorption capacity. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe Immobilization of a thermostable α-amylase onto reactive membranes: kinetics characterization and application to continuous starch hydrolysis(Elsevier Sci Ltd, 2004) Bayramoğlu, G.; Yilmaz, M.; Arica, M.Y.Epoxy groups containing porous membranes were prepared by UV-initiated photopolymerisation of hydroxyethylmethacrylate (HEMA) and glycidyl methacrylate (GMA). Epoxy supports could provide multipoint covalent attachment of enzymes, therefore, to stabilize their three-dimensional structure. alpha-Amylase was immobilized onto the poly(HEMA-GMA-1-3) membranes by means of the amide linkage formation between the amino groups of alpha-amylase and the epoxy groups of the support. The alpha-amylase immobilization capacity of the membranes was increased as the GMA ratio increased in the membrane structure. The retained activity of the immobilized alpha-amylase was 76% with poly(HEMA-GMA-2) membrane. The decrease in activity of the immobilized a-amylase could be considered to be due to reduced conformational flexibility of the immobilized alpha-amylase molecules for binding its large substrate, starch, as a result of the covalent immobilization. The immobilized alpha-amylase has more resistance to temperature inactivation than that of the free form. The optimum pH value of alpha-amylase was not affected by the immobilization reaction, but the pH profile was broadened for the immobilized enzyme. Kinetic parameters were determined for immobilized alpha-amylase as well as for the free enzyme. The values of the Michaelis constant K-m of alpha-amylase, were significantly larger (ca. 2.3 times) upon immobilization, indicating decreased affinity of the enzyme for its substrate, whereas V-max was smaller for immobilized a-amylase. In a 120 h continuous operation at 35 degreesC only 4% of immobilized alpha-amylase activity was lost. The operational inactivation rate constant (k(opi)) of the immobilized a-amylase with 2% starch was 8.06x 10(-6) min(-1). (C) 2003 Elsevier Ltd. All rights reserved.Öğe A novel pH sensitive porous membrane carrier for various biomedical applications based on pHEMA/chitosan: Preparation and its drug release characteristics(Wiley-V C H Verlag Gmbh, 2003) Bayramoğlu, G.; Arica, M.Y.The synthetic hydrogels based on pHEMA have been widely studied and used in biomedical fields. Numerous techniques exist for entrapment of drugs or proteins in the hydrogels. The suitable biomaterials for biomedical applications include poly(hydroxyethyl methacrylate), (pHEMA), and chitosan. In this work, a novel pH sensitive interpenetrating polymer networks (IPNs) were prepared in the membrane form by using 2-hydroxyethyl-methacrylate monomer (HEMA) and chitosan via UV initiated photo-polymerization in the presence of an initiator (i.e., alpha-alpha'-azo-isobutyronitrile; AIBN). UV-free-radical polymerization techniques are often used to synthesize hydrogels for controlled release applications. A series of HEMA and chitosan IPNs hydrogels were prepared and the equilibrium swelling studies were conducted to investigate swelling behaviors of the membrane according to the pH of the swelling medium. The swelling properties of the membrane were changed with the medium pH. The equilibrium water uptake is reached in about 60 min. The pHEMA/chitosan membrane thickness and density was measured to be 600 gm and 1.26 g cm(-3), respectively. Antibiotic release experiments were also performed with amoxicillin loaded pHEMA/chitosan membrane in physiological saline solution. The IPNs membrane loaded with 100mg antibiotic (i.e., amoxicillin) g hydrogel released around 80 % of the amoxicillin in 10 h at pH 7.4. The presented well-characterized novel pHEMA/chitosan membrane is a potential candidate for transdermal antibiotic carrier or a support in bioseparation.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 Procion Brown MX-5BR attached and Lewis metals ion-immobilized poly(hydroxyethyl methacrylate)/chitosan IPNs membranes: Their lysozyme adsorption equilibria and kinetics characterization(Pergamon-Elsevier Science Ltd, 2002) Bayramoğlu, G.; Kaya, B.; Arica, M.Y.Interpenetration networks (IPNs) in membrane form were synthesized from 2-hydroxyethyl methacrylate (HEMA) and chitosan (pHEMA/chitosan) via UV-initiated photo-polymerization in the presence of an initiator alpha, alpha'-azoisobutyronitrile. Procion Brown MX-5BR (PB MX-5BR) was covalently attached onto IPNs membrane as a metal chelating dye-ligand. Two different Lewis metal ions (Fe(III) or Cu(II)) were immobilized onto the dye-ligand for utilization in the immobilized metal affinity chromatography (IMAC). The binding characteristics of a model protein (lysozyme) to IMAC adsorbents and selectivity of immobilized metal ions (Fe(III) and Cu(II)) to the lysozyme have been investigated from aqueous solution using the dye-ligand-attached IPNs membrane as a control system. The experimental data was analysed using the two adsorption kinetic models the pseudo-first-order and pseudo-second order to determine the best-fit equation for the adsorption of lysozyme onto dye-ligand and IMAC adsorbents. The second-order equation for the adsorption of lysozyme on the dye-ligand, dye-ligand-Fe(III) and dye-ligand-Cu(II) membrane systems is the most appropriate equation to predict the adsorption capacity for all the tested adsorbents. The reversible lysozyme adsorption on the dye-ligand and IMAC adsorbents obeyed the Temkin isotherm. The lysozyme adsorption capacities of the dye-ligand, dye-ligand-Fe(III) and dye-ligand-Cu(II) immobilized IPNs membranes were 79.1, 147.4, and 128.2 mg ml(-1), respectively. The adsorption of the lysozyme on the pHEMA/chitosan membrane plain was about 8.3 mg ml(-1). (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Procion Green H-4G immobilized on a new IPN hydrogel membrane composed of poly(2-hydroxyethylmethacrylate)/chitosan: preparation and its application to the adsorption of lysozyme(Elsevier Science Bv, 2002) Bayramoğlu, G.; Arica, M.Y.The adsorption of lysozyme has been investigated on the Procion Green H-4G immobilized novel poly(2-hydroxyethyl methacrylate)/chitosan) (pHEMA/chitosan; IPN) porous hydrogel membrane. The IPN membranes were prepared by UV initiated photo-polymerization using 2-HEMA and chitosan. The IPN membrane reached an equilibrium swelling within about 60 min. The water content of the dye immobilized membrane was 50 +/- 2% and the amount of immobilized Procion Green H-4G on the membrane was 0.678 mumol ml(-1). The rates of adsorption of lysozyme on pHEMA/chitosan and pHEMA/chitosan-dye immobilized membranes were measured in a stirred cell, The adsorption capacities of these membranes were determined by changing pH and the concentration of lysozyme in the adsorption medium. The adsorption phenomena appeared to follow a typical Langmuir isotherm. Lysozyme adsorption capacity of the pHEMA/chitosan and pHEMA/chitosan-dye immobilized membranes were 0.18 and 14.06 mg ml(-1), respectively. The maximum lysozyme adsorption capacity (q(m)) of the pHEMA-chitosan-dye immobilized membranes was 20.28 mg ml(-1) and the dissociation constant (K-d) value was found to be 1.01 mg ml(-1) lysozyme. The experimental data were also analysed using first order Van't Hoff equation for lysozyme-adsorbent interactions, the change in entropy and Gibbs energy of binding were determined at different temperatures and the enthalpy of the system was calculated as 2.5 kcal mol(-1). All of the adsorbed lysozyme were desorbed in 60 min in the desorption medium containing 1.0 M KSNC at pH 8.0. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe Selective recovery of mercury by Procion Brown MX 5BR immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes(Elsevier Science Bv, 2002) Genç, O.; Arpa, C.; Bayramoğlu, G.; Arıca, M.Y.; Bektaş, S.Metal chelating membranes have advantages as adsorbents in comparison to conventional microspheres or beads because they are not compressible and they considerably eliminate internal diffusion limitations. The aim of this communication was to explore in detail the performance of Procion Brown MX 5BR immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes, (also called interpenetrating network, IPN, membranes) for removal of three toxic heavy metal ions, namely, Cd(II), Pb(II) and Hg(II) from aquatic systems. The composite membranes were characterized by elemental analysis, scanning electron microscopy and Fourier Transform Infrared (FTIR) spectroscopy. The incorporated amount of the Procion Brown NIX 5BR was calculated. as 0.036 mumol/cm(2) from the nitrogen and sulphur stoichiometry. The adsorption capacity for selected heavy metal ions from aqueous media containing different amounts of these ions (30-400 mg/L) and at different pH values (2.0-6.0) was investigated. Adsorption capacity of the membranes increased with time during the first 45 min and then levelled off toward the equilibrium adsorption. The maximum amounts of heavy metal ions adsorbed were found as 18.5, 22.7 and 68.8 mg/g for Cd(H), Pb(H) and Hg(H), respectively. Competitive adsorption of the metal ions was also studied. When the metal ions competed, the adsorbed amounts were found as 1.8 mg Cd(II)/g, 2.2 mg Pb(II)/g and 52.6 mg Hg(II)/g. Under competitive conditions, the system showed a very high selectivity for Hg(H) ions. The membrane can be regenerated by washing with a solution of nitric acid (0.01 M). The desorption ratio achieved was as high as 95%. These membranes are suitable for repeated use for more than five adsorption/desorption cycles without any considerable loss in adsorption capacity. (C) 2002 Elsevier Science B.V. All rights reserved.
