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Öğe Adsorption of Cr(VI) onto PEI immobilized acrylate-based magnetic beads: Isotherms, kinetics and thermodynamics study(Elsevier Science Sa, 2008) Bayramoglu, Guelay; Arica, M. YakupMagnetic poly(GMA-EGDMA) beads were prepared from glycidylmetharylate (GMA) and ethyleneglycol dimethacrylate (EGDMA) in the presence of Fe3O4 nano-powder via suspension polymerization. After polymerization, the magnetic beads were coated with polyethyleneinnine (PEI). Elemental analysis of PEI immobilized beads for the free amine group content was estimated as 258.8 mu mol/g polymer. The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), and scanning electron microscopy (SEM). ESR data revealed that the beads were highly super-paramagnetic. The magnetic beads were used for the removal of Cr(VI) ions from aqueous solutions in batch mode. Adsorption equilibrium was established in about 120 min. The maximum adsorption of Cr(VI) on the magnetic beads was observed at around pH 2.0. The maximum adsorption capacity of the magnetic beads was 137.7 mg/g. The effects of adsorbent dosage, ionic strength and temperature have been also reported. (C) 2007 Elsevier B.V. All rights reserved.Öğe Adsorption of trypsin onto magnetic ion-exchange beads of poly(glycidylmethacrylate-co-ethyleneglycoldimethacrylate)(John Wiley & Sons Inc, 2008) Arica, M. Yakup; Akyol, Ali Berkan; Bayramoglu, GuelayMagnetic beads were prepared from glycidyl methacrylate (GMA), and ethyleneglycol dimethylmethacrylate (EGDMA) in the presence of Fe3O4 nanopowder via suspension polymerization. The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), and scanning electron microscopy (SEM). ESR data revealed that the beads were highly super-paramagnetic. The effects of contact time, pH, ionic strength, and temperature on the adsorption process have been studied. Adsorption equilibrium was established in about 120 min. The maximum adsorption of trypsin on the magnetic beads was obtained as 84.96 mg g(-1) at around pH 7.0. At increased ionic strength, the contribution of the electrostatic component to the overall binding decreased, and so the adsorption capacity. The experimental equilibrium data obtained trypsin adsorption onto magnetic beads fitted well to the Langmuir isotherm model. The result of kinetic analyzed for trypsin adsorption onto magnetic ion-exchange beads showed that the second order rate equation was favorable. It was observed that after six adsorption-elution cycle, magnetic beads can be used without significant loss in trypsin adsorption capacity. Finally, the magnetic beads were used for separation of bovine serum albumin (BSA) and trypsin from binary solution in a batch system. (c) 2007 Wiley Periodicals, Inc.Öğe Alcohol determination via covalent enzyme immobilization on magnetic beads(Elsevier Science Sa, 2008) Kiralp, Senem; Topcu, Asuman; Bayramoglu, Guelay; Arica, M. Yakup; Toppare, LeventAlcohol oxidase was covalently immobilized onto magnetic beads of two different sizes, 75-150 mu m and 50-75 mu m in diameter, fabricated in the presence of glycidylmethacrylate and methylmethacrylate via suspension polymerization in the presence of a cross-linker (i.e., ethylenedimethylmethacrylate). The activity of the enzyme on smaller microspheres was found to be almost 4.8 fold higher than that of the larger counterparts. Although enzyme loading was same for both fractions, activity and the affinity of immobilized enzyme were significantly altered. The effects of various parameters such as temperature, pH, operational and storage stability were examined. The substantial change in the activity of enzyme was also observed in stability experiments in favor of large size magnetic beads. For all stability experiments including storage stability, the 75-150 mu m fraction was found to be more sentinel support for the enzyme. (C) 2007 Elsevier B.V. All rights reserved.Öğe Covalent immobilization of chloroperoxidase onto magnetic beads: Catalytic properties and stability(Elsevier, 2008) Bayramoglu, Guelay; Kiralp, Senem; Yilmaz, Meltem; Toppare, Levent; Arica, M. YakupAmino groups containing magnetic beads were used in covalent immobilization of the enzyme "chloroperoxidase (CPO)" which is one of a few enzymes that can catalyse the peroxide dependent oxidation of a wide spectrum of organic and inorganic compounds. The magnetic poly(glycidylmethacrylate-methylmethacrylate-etbyleneglycol dimethacrylate), magnetic p(GMA-MMA-EGDMA) beads were prepared via suspension polymerization in the presence of ferric ions. The magnetic beads were characterized with scanning electron microscope (SEM), Fourier transform infrared (FTIR), Mossbauer spectroscopy and vibrating sample magnetometer (VSM). The magnetic beads were derivatized sequentially with ammonia and glutaraldehyde, and CPO was covalently immobilized on the support via reaction of the amino groups of the enzyme under mild conditions. The effect of various parameters including pH, temperature and enzyme concentration on the immobilization efficiency of CPO onto glutaric dialdhyde activated magnetic beads was evaluated. Magnetic measurement revealed that the resultant CPO-immobilized magnetic beads were superparamagnetic with a saturation magnetization of 18.2 emu/g. The analysis of FTIR spectra confirmed the binding of CPO on the magnetic beads. The maximum amount of immobilized CPO on the magnetic beads was 2.94 mg/g support. The values of Michaelis constants Km for immobilized CPO was significantly larger, indicating decreased affinity by the enzyme for its substrate, whereas V-max values were smaller for the immobilized CPO. However, the CPO immobilized on the magnetic beads resulted in an increase in enzyme stability with time. (c) 2007 Elsevier B.V. All rights reserved.Öğe Enzymatic removal of phenol and p-chlorophenol in enzyme reactor: Horseradish peroxidase immobilized on magnetic beads(Elsevier Science Bv, 2008) Bayramoglu, Guelay; Arica, M. YakupHorseradish peroxidase was immobilized on the magnetic poly(glycidylmethacrylate-co-methylmethacrylate) (poly(GMA-MMA)), via covalent bonding and used for the treatment of phenolic wastewater in continuous systems. For this purposes, horseradish peroxidase (HRP) was covalently immobilized onto magnetic poly(GMA-MMA) beds using glutaraldehyde (GA) as a coupling agent. The maximum HRP immobilization capacity of the magnetic poly(GMA-XMA)-GA beads was 3.35 mg g(-1). The immobilized HRP retained 79% of the activity of the free HRP used for immobilization. The immobilized RRP was used for the removal of phenol and p-chlorophenol via polymerization of dissolved phenols in the presence of hydrogen peroxide (H2O2). The effect of pH and temperature on the phenol oxidation rate was investigated. The results were compared with the free HRP, which showed that the optimum pH value for the immobilized HRP is similar to that for the free HRR The optimum pH value for free and immobilized HRP was observed at pH 7.0. The optimum temperature for phenols oxidation with immobilized HRP was between 25 and 35 degrees C and the immobilized HRP has more resistance to temperature inactivation than that of the free form. Finally, the immobilized HRP was operated in a magnetically stabilized fluidized bed reactor, and phenols were successfully removed in the enzyme reactor. (C) 2007 Elsevier B.V. All rights reserved.Öğe Preparation and Characterization of Infection-Resistant Antibiotics-Releasing Hydrogels Rods of Poly[hydroxyethyl methacrylate-co-(poly(ethylene glycol)-methacrylate]: Biomedical Application in a Novel Rabbit Penile Prosthesis Model(Wiley, 2008) Arica, M. Yakup; Tuglu, Devrim; Basar, M. Murad; Kilic, Dilek; Bayramoglu, Guelay; Batislam, ErtanIn this work, preparation and characterization of novel three different antibiotic loaded penile prosthesis in the rod form were investigated by copolymerization of 2-hydroxyethylmethacrylate (HEMA) with poly(ethylene glycol)-methacrylate, (PEG-MA). To achieve this goal, a series of novel copolymer hydrogels were prepared in rod form using HEMA and PEG-MA monomers via UV initiated photopolymerization. The thermal stability of the copolymer was found to be lowered by increase in the ratio of PEG-MA in the rod structure. Contact angle measurements on the surface of copolymer hydrogel demonstrated that the copolymer gave rise to a significant hydrophilic surface compared with pure poly(HEMA). The blood protein adsorption and platelet adhesion were significantly reduced on the surface of the copolymer hydrogels compared with control pure poly(HEMA). Poly(HEMA:PEG-MA;1:1)-1 formulation containing different antibiotics (20 mg antibiotic/g polymer) released about 90, 91, and 55% of the total loaded cephtriaxon, vancomycin, and gentamicin in 48 h at pH 7.4, respectively. Finally, antibiotics loaded biocompatible poly(HEMA:PEG-MA;1:1)-1 hydrogel compositions was used as a penile prosthesis in preventing cavernous tissue infections in a rabbit prosthesis model. The efficacy of the three different antibiotics loaded hydrogel system was evaluated in four different groups of rabbits, in which various infectious agents were inoculated. The animals were sacrificed after predetermined time periods, and clinical, histological and microbiological assessment on the implant side were carried out to detect infections. Eventually, we concluded that three different antibiotic loaded penile prostheses (i.e. poly(HEMA:PEG-MA;1:1)-1 hydrogel systems) were as effective as parenteral antibiotics applications. (C) 2007 Wiley Periodicals, Inc.Öğe Preparation of methacrylamide grafted and dye-ligand immobilized PET fibers: Studies of adsorption and purification of lysozyme(John Wiley & Sons Inc, 2008) Karakisla, Meral; Bayramoglu, Guelay; Arica, M. YakupIn this study, novel affinity chromatographic fibers was prepared from methacrylamide grafted poly(ethylene terephthalate), PET-g-pMAA, using benzoyl-peroxide as an initiator. A dye ligand (i.e., Procion Brown) as a ligand was then covalently immobilized on the different amount of pMAAm grafted PET fibers, (PET-g-pMAAm-PB). The fibers were characterized by surface area measurement, infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Adsorptive properties of the composite fibers were tested using a model protein (i.e., lysozyme). To achieve these purposes, the influence of pH, ionic strength, initial lysozyme concentration, and temperature on adsorption system has been investigated and evaluated. A maximum lysozyme adsorption PET-g-pMAAm-PB fiber was obtained as 43.9 mg g(-1) at pH 7.5. The experimental equilibrium data obtained for lysozyme adsorption onto PET-g-pMAAm-PB fibers fitted well to the Langmuir isotherm model. The result of kinetic analyzed for lysozyme adsorption onto affinity fibers showed that the second-order rate equation was favorable. The purity of the eluted lysozyme, as determined by HPLC, was 84% with recovery 73% for PET-g-pMAAm-PB fiber. Experiments on regeneration and dynamic adsorption were also performed. It appears that PET-g-pMAAm-PB fibers can be applied for lysozyme separation without causing any denaturation. (C) 2008 Wiley Periodicals, Inc.Öğe Preparation of nanofibrous polymer grafted magnetic poly(GMA-MMA)-g-MAA beads for immobilization of trypsin via adsorption(Elsevier, 2008) Bayramoglu, Guelay; Yilmaz, Meltem; Senel, Ayseguel Uelkue; Arica, M. YakupPoly (glycidylmethacrylate-methylmethacrylate), poly(GMA-MMA) beads were prepared via suspension polymerization in the presence of ferric ions. The epoxy groups of the poly(GMA-MMA) beads were converted into amino groups during magnetization reaction, and then were grafted with methacrylic acid (MAA) via graft copolymerization. The magnetic beads were characterized by surface area measurement, swelling test, scanning electron microscope (SEM), electron spin resonance (ESR) and Mossbauer spectroscopy. The enzyme "trypsin" was immobilized on the magnetic beads via adsorption. The maximum adsorption was obtained at pH 7.0. At 2.0 mg/mL initial trypsin concentration, the maximum immobilization capacity was 123.2 mg trypsin/g beads and retained about 84.2% of its initial activity. The immobilized trypsin could not be desorbed by enzyme reaction solution in the pH range of 5.0-9.0, and could be desorbed by 1.0 M formic acid solution containing 1 M NaCl. (C) 2007 Elsevier B.V. All rights reserved.Öğe Preparation of poly (glycidylmethacrylate-methylmethacrylate) magnetic beads: Application in lipase immobilization(Elsevier Science Bv, 2008) Bayramoglu, Guelay; Arica, M. YakupMagnetic bead was prepared from the monomers glycidylmethacrylate (GMA) and methylmethacrylate (MMA) via suspension copolymerization in the presence of ferric ions. The magnetic beads were characterized with scanning electron microscope (SEM), FT-IR and ESR spectrophotometers. The beads were sieved and 100-150 mu m size of fraction was used in enzyme immobilization. The specific surface area of the magnetic beads was measured by the BET method and was found to be 16.2 m(2)/g beads. The reactive character of the epoxy groups allowed the attachment of the amino groups during thermal precipitation reaction. The resulting magnetic beads were used for the covalent immobilization of Candida rugosa lipase via glutaraldehyde activation and glutaraldehyde was also acted a 5-carbon spacer arm. The maximum lipase immobilization on magnetic poly(GMA-MMA) was 23.4 mg g(-1). The activity yield of the lipase immobilized on the spacer-arm attached magnetic beads was up to 81%. Kinetic analysis shows that the dependence of lipolytic activity of both free and immobilized lipase on trybutyrin substrate concentration can be described by Michaelis-Menten model with good agreement. The estimated Michaelis constants (Km) for the free and immobilized lipase are 2.6 and 12.3 mM, respectively. The V-max values of free and immobilized enzymes were calculated as 984 and 773 U/mg enzymes, respectively. Employment of immobilization seemed to result in an increase in K-m and a decrease in V-max. Optimal operational temperature was 5 degrees C higher for immobilized enzyme than that of the free counterpart. Thermal and storage stabilities were found to he increase with immobilization. (c) 2008 Elsevier B.V. All rights reserved.Öğe Removal of heavy mercury(II), cadmium(II) and zinc(II) metal ions by live and heat inactivated Lentinus edodes pellets(Elsevier Science Sa, 2008) Bayramoglu, Guelay; Arica, M. YakupThe live and heat inactivated forms of Lentinus edodes pellets were used for the biosorption of Hg2+, Cd2+ and Zn2+ ions. The maximum adsorption of metal ions on the live and heat inactivated pellets of fungus was observed at pH 6.0 for all the used metal ions. The effect of temperature on the biosorption capacity was negligible in the range of 15-45 degrees C. The biosorption of Hg2+, Cd2+ and Zn2+ ions on the live and heat inactivated pellets of fungus was studied in aqueous solutions in the concentration range of 25-600 mg/L. The metal biosorption capacities of the live fungal pellets Hg2+, Cd2+ and Zn2+ were 336.3 +/- 3.7, 78.6 +/- 2.6 and 33.7 +/- 1.6 mg/g, respectively, while Hg2+, Cd2+ and Zn2+ the biosorption capacities of the heat inactivated pellets were 403.0 +/- 2.9, 274.3 +/- 3.6 and 57.7 +/- 1.1 mg/g, respectively. The adsorption capacities of the heat inactivated fungus for metals were markedly increased compared to native form. For both forms the same affinity order on a molar basis were observed for single or multi-metal ions (Hg2+ > Cd2+ > Zn2+). The Langmuir and Freundlich equilibrium models represent well the experimental data. The experimental kinetic data were analyzed using the first- and second-order kinetic models and the second-order kinetic model described the biosorption kinetics accurately for each metal ions. (C) 2008 Elsevier B.V. All rights reserved.Öğe Studies of adsorption of alkaline trypsin by poly(methacrylic acid) brushes on chitosan membranes(John Wiley & Sons Inc, 2008) Bayramoglu, Guelay; Erdogan, Hakan; Arica, M. YakupPoly(methacrylic acid)-grafted chitosan membranes (chito an-g-poly(MAA)) were prepared in two sequential steps: in the first step, chitosan membranes were prepared by phase-inversion technique and then epichlorohydrin was used as crosslinking agent to increase its chemical stability in acidic media; in the second step, the graft copolymerization of methacrylic acid onto the chitosan membranes was initiated by ammonium persulfate (APS) under nitrogen atmosphere. The chitosan-g-poly(MAA) membranes were first used as an ion-exchange support for adsorption of trypsin from aqueous solution. The influence of pH, equilibrium time, ionic strength, and initial trypsin concentration on the adsorption capacity of the chitosan-g-poly(MAA) membranes have been investigated in a batch system. Maximum trypsin adsorption onto chitosan-gpoly(MAA) membrane was found to be 92.86 mg mL(-1) at pH 7.0. The experimental equilibrium data obtained for trypsin adsorption onto chitosan-g-poly(MAA) membranes fitted well to the Langmuir isotherm model. The adsorption data was analyzed using the first- and second-order kinetic models, and the experimental data was well described by the second-order equation. More than 97% of the adsorbed trypsin was desorbed using glutamic acid solution (0.5M, pH 4.0). In addition, the chitosan-gpoly(MAA) membrane prepared in this work showed promising potential for various biotechnological applications. (C) 2007 Wiley Periodicals, Inc.
