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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 IgG on spacer-arm and L-arginine ligand attached poly(GMA/MMA/EGDMA) beads(Wiley, 2007) Bayramoğlu, Gülay; Şenel, Ayşegül U.; Arica, M. YakupThis work presents data on human imrnunoglobulin G (HlgG) adsorption onto L-arginine ligand attached poly(GMA/MMA/EGDMA)-based affinity beads which were synthesized from methyl methacrylate (NUVIA) and glycidiyl methacrylate (GMA) in the presence of a crosslinker (i.e., ethylene glycol dimethacrylate; EGDMA) by suspension polymerization. The epoxy groups of the poly(GMA/NMA/ EGDMA) beads were converted into amino groups after reaction with ammonia or 1,6-diaminohexane (i.e., spacer-arm). With L-arginine as a ligand, it was covalently immobilized on the an-dnated (poly(GMA/MMA/EGDMA)AA) and/or the spacer-arm attached (poly(GMA/NMA/ EGDM.A)-SA) beads, using glutaric dialdehyde as a coupling agent. Both affinity poly(GMA/MMA/EGDMA)-based beads were used in HlgG adsorption/desorption studies under defined pH, ionic strength, or temperature conditions in a batch reactor, using acid-treated poly(GMA/MMA/EGDMA) beads as a control system. The poly(GMA/MMA/EGDMA)-SA affinity beads resulted in an increase in the adsorption capacity to HlgG compared with the aminated counterpart (i.e., poly(GMA/MMA/EGDMA)-AA). The maximum adsorption capacities of the poly(GMA/MMA/EGDMA)-AA and poly(GMA/MNA/EGDMA)-SA affinity beads were found to be 112.36 and 142 mg g(-1), and the affinity constants (K-d), evaluated by the Langmuir model, were 2.48 x 10(-7) and 6.98 x 10(-7) M, respectively. Adsorption capacities of the poly(GMA/MMA/EGDMA)-AA and poly(GMA/MMA/EGDMA)-SA were decreased with HIgG by increasing the ionic strength adjusted with NaCl. Adsorption kinetic of HIgG onto both affinity adsorbents was analyzed with first- and second-order kinetic equations. The first-order equation fitted well with the experimental data. (c) 2007 Wiley Periodicals, Inc.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 Biosorption of benzidine based textile dyes "Direct Blue 1 and Direct Red 128" using native and heat-treated biomass of Trametes versicolor(Elsevier, 2007) Bayramoğlu, Gülay; Arica, M. YakupThe capacities and mechanisms of native and heat-treated white rot fungus "Trametes versicolor" biomass in removing of two different benzidine based dyes (i.e., Direct Blue 1, DB-1 and Direct Red 128, DR-128) from aqueous solution was investigated with different parameters, such as molecular weight of dye, adsorbent dosage, pH, temperature and ionic strength. In the batch system, the biosorption equilibrium time for both dyes was about 6 h. The maximum biosorption was observed at pH 6.0 for DB-1 and at pH 3.0 for DR-128 on the native and heat-treated fungal biomass. The biosorption capacities of the native and heat-treated fungal biomass (at 800 mg/L dye concentration) were found to be 101.1 and 152.3 mg/g for DB-1 and these were 189.7 and 225.4 mg dye/g biomass for DR-128, respectively. The Freundlih and Temkin adsorption isotherm models were used for the mathematical description of the biosorption equilibrium. The Freundlich and Temkin models were able to describe the biosorption equilibrium of DB-1 and DR-128 on the native and heat-treated fungal preparations. The Freundlich model also showed that the small molecular weight dye (i.e., DR-128) had a higher affinity of adsorption that than of the higher molecular weight dye (i.e., DB-1). The dye biosorption on the fungal biomass preparations followed the second order kinetics model. (C) 2006 Elsevier B.V. All rights reserved.Öğe Biosorption of mercury(II), cadmium(II) and lead(II) ions from aqueous system by microalgae Chlamydomonas reinhardtii immobilized in alginate beads(Elsevier, 2006) Bayramoğlu, Gülay; Tüzün, İlhami; Çelik, Gökçe; Yilmaz, Meltem; Arica, M. YakupThe potential use of the immobilized microalgae (in Ca-alginate) of Chlamydomonas reinhardtii to remove Hg(II), Cd(II) and Pb(II) ions from aqueous solutions was evaluated using bare Ca-alginate bead as a control system. Ca-alginate beads containing immobilized microalgae were incubated for the uniform growth at 22 degrees C for 5 days. Effects of pH, temperature, initial concentration of metal ions and biosorbent dosages on the adsorption of Hg(II), Cd(II) and Pb(II) ions were studied. Adsorption of Hg(II), Cd(II) and Pb(II) ions on the immobilized microalgae showed highest values at around pH 5.0 to 6.0. The adsorption equilibrium was represented with Langnmir and Freundlich adsorption isotherms. The adsorption of these ions on the immobilized microalgae followed second-order kinetics and equilibrium was established in about 60 min. The temperature change in the range of 5-40 degrees C did not affect the adsorption capacities of the immobilized microalgae. The immobilized-algal systems can be regenerated using 2 M NaCl for Hg(II), Cd(II) and Pb(II) ions. (c) 2006 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 Heparin-coated poly(hydroxyethyl methacrylate/albumin) hydrogel networks: In vitro hemocompatibility evaluation for vascular biomaterials(Wiley, 2008) Bayramoglu, Gülay; Yilmaz, Meltem; Batislam, Ertan; Arica, M. YakupHuman serum albumin (AL) containing poly(hydroxyethyl methacrylate) (pHEMA; in tube form with an inner diameter of 6 mm) was synthesized for blood-contacting hydrogel networks via UV-initiated photopolymerization. at 25 degrees C. Tensile and breaking tests of pHEMA and pHEMA-AL-1-4 hydrogel networks were studied at their equilibrium water content. The mechanical strength of the hydrogel networks was found to be lowered by an increase in the ratio of AL in the polymer networks. To increase the blood compatibility and prevent thrombus formation, the surface of the pHEMA and pHEMA-AL-3 hydrogel compositions were coated with heparin (HEP). Contact-angle studies showed that the polarities (%) of the pHEMA-AL-3 and pHEMA-AL-3-HEP hydrogel networks were significantly increased in comparison with that of pure pHEMA. The fibrinogen adsorption and platelet adhesion were also reduced after the incorporation of AL and HEP into/onto hydrogel networks in comparison with the pure pHEMA control. Blood compatibility tests of the prepared hydrogel networks, which were intended to be used as blood-contacting materials, were examined with various parameters, such as the hemolytic activity, prothrombin time, activated thromboplastin time, and loss of blood cells in blood. (C) 2008 Wiley Periodicals, Inc.Öğe Immobilization of β-galactosidase onto magnetic poly(GMA–MMA) beads for hydrolysis of lactose in bed reactor(Elsevier, 2007) Bayramogğu, Gülay; Tunali, Yagmur; Arica, M. YakupIn the present study, novel magnetic beads were prepared from glycidylmethacrylate and methylmethacrylate via suspension polymerization in the presence of a cross-linker (i.e. ethylenedimethylmethacrylate). The magnetic poly(GMA-MMA) beads were characterized with scanning electron microscope, FT-IR and ESR spectrophotometers. The reactive character of the epoxy groups allowed the attachment of the amino groups. The aminated magnetic beads were used for the covalent immobilization of beta-galactosidase via glutaric dialdehyde activation. The maximum amount of immobilized beta-galactosidase on the magnetic poly(GMA-MMA) beads was 9.87 mg/g support. The values of Michaelis constants K-m for immobilized beta-galactosidase was significant larger, indicating decreased affinity by the enzyme for its substrate, whereas V-max values were smaller for the immobilized beta P-galactosidase. However, the beta-galactosidase immobilized on the magnetic poly(GMA-MMA) beads resulted in an increase in enzyme stability with time. Optimum operational temperature for immobilized enzyme was 5 degrees C higher than that of the free enzyme and was significantly broader. Finally, a bed reactor with P-galactosidase immobilized was used for hydrolysis of lactose. The enzyme reactor operated continuously at 35 degrees C for 60 h and the immobilized enzyme lost about 12% of its initial activity after this period. (C) 2006 Elsevier B.V. All rights reserved.Öğe Immunoglobulin G adsorption behavior of L-histidine ligand attached and Lewis metal ions chelated affinity membranes(Elsevier Science Bv, 2006) Bayramoğlu, Gülay; Çelik, Gökçe; Arica, M. YakupImmobilized metal affinity membranes were prepared by chelating Cu(II) and Fe(III) ions on poly(2-hydroxyethyl methacrylate-glycidyl methacrylate), poly(HEMA-GMA) membranes using L-histidine as a chelating ligand. To achieve this goal, the poly(HEMA-GMA) membrane was prepared via UV initiated photopolymerization. A spacer-arm (i.e., 1,6-diaminohexane) was introduced through the epoxy groups of the membrane (poly(HEMA-GMA)-SA). A chelating ligand (i.e., L-histidine amino acid) was covalently attached on the poly(HEMA-GMA) and/or poly(HEMAGMA)-SA using glutaric dialdehyde as a coupling agent, poly(HEMA-GMA)-H and poly(HEMA-GMA)-SAH membranes, respectively. Then, Cu(II) and Fe(III) ions were chelated through poly(HEMA-GMA)-SAH membrane. The binding characteristics of human immunoglobulin G (IgG) to IMAC membranes and the selectivity of Cu(II) and Fe(III) ions to the IgG have been investigated from aqueous solution using L-histidine attached membrane (poly(HEMA-GMA)-SAH) as a control system. The experimental data was analyzed using two adsorption kinetic models, the pseudo-first-order and the pseudo-second-order, to determine the best-fit equation for the adsorption of IgG onto L-histidine incorporated and/or different metals ion immobilized affinity membranes. The first-order equation in the affinity membrane systems is the most appropriate equation to predict the adsorption capacity for all the tested adsorbents. Moreover, the effect of spacer-arm on the adsorption capacity was evaluated using poly(HEMA-GMA)-H membrane as a control system. The IgG binding order on the affinity membranes was poly(HEMA-GMA)-SAHCu(II) > poly(HEMA-GMA)-SAH-Fe(III) > poly(HEMA-GMA)-SAH > poly(HEMA-GMA)-H. Finally, the polarities and the surface free energies of the affinity membranes were determined by contact angle studies. (c) 2006 Elsevier B.V. All rights reserved.Öğe Performance of different metal-dye chelated affinity adsorbents of poly(2-hydroxyethyl methacrylate) in lysozyme separation(Marcel Dekker Inc, 2000) Arica, M. Yakup; Denizli, A.The triazine dye Cibacron Blue F3GA was covalently immobilized as an affinity ligand onto microporous poly(2-hydroxyethyl methacrylate) (pHEMA) membranes. Three different metal ions [i.e.. Fe(III), Zn(II), or Cu(II)] were then chelated with the immobilized Cibacron Blue F3GA molecules. Lysozyme adsorption onto these affinity adsorbents from aqueous solutions containing different amounts of lysozyme at different pH was investigated in a batch system. Lysozyme adsorption capacity of all of the metal-dye-immobilized membranes was greater than that of the dye-immobilized membranes. The nonspecific adsorption of the protein on the pHEMA membranes was negligible. The adsorption phenomena appeared to follow a typical Lang muir isotherm. The maximum capacity (q(m)) of the Fe(III)-Zn(II),-or Cu(II)-dye chelated membranes for lysozyme adsorption (384, 326, and 306 mug/cm(2)) was greater than that of the dye-immobilized membrane (224 mug lysozyme/cm(2)), respectively. The dissociation constant (k(d)) values were found to be 2.51 x 10(-7) M with dye-immobilized membrane, and 2.32 X 10(-7), 2.38 X 10(-7), and 2.40 x 10(-7) M with the Fe(III)-Zn(II),-and Cu(II)-dye-chelated membranes, respectively. More than 95% of the adsorbed lysozyme was desorbed in 60 min in the desorption medium containing 0.5 M KSCN at pH 8.0.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 and characterization of sulfonyl-hydrazine attached poly(styrene-divinylbenzene) beads for separation of albumin(Elsevier Science Bv, 2007) Bayramoğlu, Gülay; Şenkal, Filiz B.; Çelik, Gökçe; Arica, M. YakupNovel sulfonyl-hydrazine carrying poly(styrene-divinylbenzene), poly(S-DVB)-S-NH2 ion-exchange beads (size between 210 and 425 mu m) were prepared via suspension polymerization and, were first used as an ion-exchange support for adsorption of human serum albumin (HSA) from aqueous solution. The influence of pH, equilibrium time, ionic strength and initial albumin concentration on the adsorption capacity of the poly(SDVB)-S-NH2 ion-exchange beads has been investigated in a batch system and the unmodified poly(S-DVB) beads were used as control system. Maximum HSA adsorption onto poly(S-DVB)-S-NH2 ion-exchange beads was found to be 63.05 mg/g at pH 7.0. The experimental equilibrium data for HSA adsorption onto poly(S-DVB)-S-NH2 beads was well described by the Langmuir isotherm model. Kinetic parameters of this adsorption system were also analyzed for HSA adsorption onto beads and, the first-order rate equations were favorable. Finally, the poly(S-DVB)-S-NH2 beads was used for the purification of HSA from whole human serum and, the purity of the eluted HSA from the beads was determined as 89% by HPLC from single step purification protocol. (c) 2006 Elsevier B.V. All rights reserved.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 Purification of lysozyme from egg white by Reactive Blue 4 and Reactive Red 120 dye-ligands immobilised composite membranes(Elsevier Sci Ltd, 2005) Arica, M. Yakup; Bayramoğlu, GülayA composite membrane was synthesized from 2-hydroxyethylmethacryl ate (HEMA) and chitosan (pHEMA/chitosan) via UV initiated photo-polymerisation. Reactive Blue 4 (Blue-4) and Reactive Red 120 (Red-120) were immobilised onto pHEMA/chitosan membranes. In the first part of this study, the binding characteristics of lysozyme to different dye-ligand immobilized membranes have been studied from aqueous solution using the plain membrane as a control system. The polarity of the investigated membranes was determined by contact angle measurement. The adsorption capacities of both dye-ligand immobilised membranes increased with increasing temperature but decreased with increasing NaCl concentration. The adsorption isotherm fitted both the Langmuir and the Freundlich models. A theoretical analysis has been conducted to estimate the thermodynamic contributions (changes in enthalpy, entropy and Gibbs free energy) for the adsorption of lysozyme to different dye-ligand immobilised composite membranes. In the second part, their purification efficacy of lysozyme from egg white was investigated. The purity of the eluted lysozyme was analysed by HPLC. The purity of lysozyme extracted from egg white was 84% with Red-120 immobilised membrane. This was 21% for Blue-4 immobilised membrane. The recovery yields were 72% and 16% for Red-120 and Blue-4 immobilised membranes, respectively. The Red 120 immobilised membrane provided an efficient method to purify lysozyme from egg white. showing high adsorption capacity and high selectivity for the lysozyme. On the other hand, the Blue-4 immobilised composite membrane had a lower adsorption capacity and selectivity than that of the Red-120 immobilised one. Purification was monitored by determination of lysozyme activity using Micrococcus lysodeiktictis as substrate. The dye-ligand immobilised composite membranes are stable when subjected to sanitization with sodium hydroxide after repeated separation-elution cycles. (C) 2004 Elsevier Ltd. All rights reserved.Öğe Removal of Cd(II), Hg(II), and MID ions from aqueous solution using p(HEMA/Chitosan) membranes(Wiley, 2007) Bayramoğlu, Gülay; Arica, M. Yakup; Bektaş, SemaAn interpenetration network (IPN) was synthesized from 2-hydroxyethyl methacrylate (HEMA) and chitosan, p(HEMA/chitosan) via UV-initiated photo-polymerization. The selectivity to different heavy metal ions viz Cd(II), Pb(II), and Hg(II) to the IPN membrane has been investigated from aqueous solution using bare pHEMA membrane as a control system. Removal efficiency of metal ions from aqueous solution using the IPN membranes increased with increasing chitosan content and initial metal ions concentrations, and the equilibrium time was reached within 60 min. Adsorption of all the tested heavy metal ions on the IPN membranes was found to be pH dependent and maximum adsorption was obtained at pH 5.0. The maximum adsorption capacities of the IPN membrane for Cd(II), Pb(II), and Hg(II) were 0.063, 0.179, and 0.197 mmol/g membrane, respectively. The adsorption of the Cd(II), Hg(II), and Pb(II) metal ions on the bare pHEMA membrane was not significant. When the heavy metal ions were in competition, the amounts of adsorbed metal ions were found to be 0.035 mmol/g for Cd(II), 0.074 mmol/g for Hg(II), and 0.153 mmol/g for Pb(II), the IPN membrane is significantly selective for Pb(II) ions. The stability constants of IPN membrane-metal ions complexes were calculated by the method of Ruzic. The results obtained from the kinetics and isotherm studies showed that the experimental data for the removal of heavy metal ions were well described with the second-order kinetic equations and the Langmuir isotherm model. (c) 2007 Wiley Periodicals, Inc.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.
