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Öğe Ca-alginate as a support for Pb(II) and Zn(II) biosorption with immobilized Phanerochaete chrysosporium(Elsevier Sci Ltd, 2003) Arica, M.Y.; Arpa, C.; Ergene, A.; Bayramoglu, G.; Genç, O.The basidio spores of Phanerochaete chryosporium were immobilized in alginate gel beads, and the immobilized spore containing alginate beads were incubated for the growth of fungus. The biosorption of Pb2+ and Zn2+ ions on alginate beads and both immobilized live and heat inactivated fungus was studied from artificial waste waters in the concentrations range of 30-600 mg 1(-1). The surface charge density of the biosorbents varied with the pH of the medium and the maximum biosorption of heavy metal ions on the biosorbents was obtained between pH 5.0 and 6.0. The biosorption of Pb2+ and Zn2+ on the biosorbents increased as the initial concentration of Pb2+ and Zn2+ ions increased in the medium. Biosorption equilibrium was established about 1 h, the adsorbed heavy metal ions did not significantly change further with time. The maximum biosorption capacity (q(m)) of alginate beads and both immobilized live and heat inactivated fungus were 230, 282 and 355 mg for Pb2+ and 30, 37 and 48 mg for Zn per gram of dry biosorbents, respectively. The experimental biosorption equilibrium data for Pb2+, and Zn2+ ions were in good agreement with those calculated by Langmuir model. The affinity order of heavy metal ions was Pb2+ > Zn2+, (C) 2003 Elsevier Science Ltd. All rights reserved.Öğe DNA adsorption on a poly-L-lysine-immobilized poly(2-hydroxyethyl methacrylate) membrane(Wiley, 2003) Senel, S.; Bayramoglu, G.; Arica, M.Y.The DNA adsorption properties of poly-L-lysine-immobilized poly(2-hydroxyethyl methacrylate) (pHEMA) membrane were investigated. The pHEMA membrane was prepared by UV-initiated photopolymerization and activated with epichlorohydrin. Poly-L-lysine was then immobilized on the activated pHEMA membrane by covalent bonding, via a direct chemical reaction between the amino group of poly-L-lysine and the epoxy group of pHEMA. The poly-L-lysine content of the membrane was determined as 1537 mg m(-2). The poly-L-lysine-immobilized membrane was utilized as an adsorbent in DNA adsorption experiments. The maximum adsorption of DNA on the poly-L-lysine-immobilized pHEMA membrane was observed at 4 degreesC from phosphate-buffered salt solution (pH 7.4, 0.1 M; NaCl 0.5 M) containing different amounts of DNA. The non-specific adsorption of DNA on the plain pHEMA membrane was low (about 263 mg m(-2)). Higher DNA adsorption values (up to 5849 mg m(-2)) were obtained in which the poly-L-lysine-immobilized pHEMA membrane was used. (C) 2003 Society of Chemical Industry.Öğe Membrane with incorporated hydrophobic ligand for hydrophobic interaction with proteins: application to lipase adsorption(Wiley, 2002) Bayramoglu, G.; Denizli, A.; Arica, M.Y.In this study, phenylalanine as a hydrophobic ligand was covalently attached on a comonomer, methacryloyl chloride. Then, poly(2-hydroxyethyl methacrylate-co-methacrylamido-phenylalanine), poly(HEMA/MAPA), membranes were prepared by UV-initiated photopolymerization of 2-hydroxyethyl methacrylate and methacrylamido-phenylalanine. The lipase adsorption of these poly(HEMA/MAPA) membranes was determined by changing the hydrophobic ligand density, pH, temperature and concentration of lipase in the adsorption medium. The lipase adsorption capacity of the membranes increased as the ligand density on the membrane surface increased. The nonspecific adsorption of lipase on the poly(2-hydroxyethyl methacrylate) membranes was negligible (12 mug cm(-2) of membrane). The adsorption phenomena appeared to follow a typical Langmuir isotherm. The maximum adsorption capacity (Q(m)) of the poly(HEMA/MAPA-5) membrane for lipase was 215 mug cm(-2) of membrane. The equilibrium constant (k(d)) value was 1.43mg ml(-1). The lipase could repeatedly be adsorbed and desorbed on the affinity membrane without any significant loss in the adsorption capacity of the membrane. (C) 2002 Society of Chemical Industry.Öğe Preparation and characterisation of surfaces properties of poly(hydroxyethylmethacrylate-co-methacrylolyamido-histidine) membranes: application for purification of human immunoglobulin G(Elsevier, 2004) Arica, M.Y.; Yalcin, E.; Bayramoglu, G.In this study, an affinity membrane containing L-histidine as an amino acid ligand was used in separation and purification of human immunoglobulin G (HIgG) from solution and human serum. The polarities and the surface free energies of the affinity membranes were determined by contact angle measurements. HIgG adsorption and purification onto the affinity membranes from aqueous solution and human serum were investigated in a batch and a continuous system. Effect of different system parameters such as ligand density, adsorbent dosage, pH, temperature, ionic strength and HIgG initial concentration on HIgG adsorption were investigated. The maximum adsorption capacity of p(HEMA-MAAH-4) membranes for HIgG was 13.06 mg ml(-1). The reversible HIgG adsorption on the affinity membrane obeyed both the Langmuir and Freundlich isotherm models. The adsorption data was analysed using the first- and second-order kinetic model and the experimental data was well described by the first-order equations. In the continuous system, the purity of the eluted HIgG, as determined by HPLC, was 93% with recovery 58% for p(HEMA-MAAH-4) membrane. The affinity membranes are stable when subjected to sanitization with sodium hydroxide after repeated adsorption-elution cycles. (C) 2004 Elsevier B.V. All rights reserved.Öğe Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes for heavy metal removal(Elsevier Science Bv, 2003) Genç, O.; Soysal, L.; Bayramoglu, G.; Arica, M.Y.; Bektas, S.The effective removal of toxic heavy metals from environmental samples still remains a major topic of present research. Metal-chelating membranes are very promising materials as adsorbents when compared with conventional beads because they are not compressible, and they eliminate internal diffusion limitations. The purpose of this study was to evaluate the performance of a novel adsorbent, Procion Green H-4G immobilized poly(hydroxyethylmethacrylate (HEMA)/chitosan) composite membranes, for the removal of three toxic heavy metal ions, namely, Cd(II), Pb(II) and Hg(II) from aquatic systems. The Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes were characterized by elemental analysis, scanning electron microscopy and Fourier transform infrared (FTIR) spectroscopy. The immobilized amount of the Procion Green H-4G was calculated as 0.018 +/- 0.003 mumol/cm(2) from the nitrogen and sulphur stoichiometry. The adsorption capacity of Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes 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. The amount of Cd(II), Pb(II) and Hg(II) adsorbed onto the membranes measured at equilibrium, increased with time during the first 45 min and then remained unchanged toward the equilibrium adsorption. The maximum amounts of heavy metal ions adsorbed were 43.60 +/- 1.74, 68.81 +/- 2.75 and 48.22 +/- 1.92 mg/g for Cd(II), Pb(II) and Hg(II), respectively. The heavy metal ion adsorption on the pHEMA/chitosan membranes (carrying no dye) were relatively low, 6.31 +/- 0.13 mg/g for Cd(II), 18.73 +/- 0.37 mg/g for Pb(II) and 18.82 +/- 0.38 mg/g for Hg(II). Competitive adsorption of the metal ions was also studied. When the metal ions competed with each other, the adsorbed amounts were 12.74 +/- 0.38 mg Cd(II)/g, 28.80 +/- 0.86 mg Pb(II)/g and 18.41 +/- 0.54 mg Hg(II)/g. Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) membranes can be regenerated by washing with a solution of nitric acid (0.01 M). The percent desorption achieved was as high as 95%. These novel membranes are suitable for repeated use for more than five adsorption/desorption cycles without any considerable loss in adsorption capacity. Adsorption equilibria were well described by Langmuir equation. It can be concluded that Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) membranes may effectively be used for the removal of Cd(II), Pb(II) and Hg(II) ions from aqueous solutions. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe Reversible immobilization of tyrosinase onto polyethyleneimine-grafted and Cu(II) chelated poly(HEMA-co-GMA) reactive membranes(Elsevier, 2004) Arica, M.Y.; Bayramoglu, G.The present study describes the preparation of poly(HEMA-co-GMA) reactive membranes that were grafted with polyethylenimine (PEI) following UV photo-polymerization. The immobilization of tyrosinase was carried out via multi-point ionic interactions based on -NH2 groups of PEI and Cu(II) ions. Tyrosinase is a copper-dependent enzyme, which should show a binding affinity for the chelated Cu(II) ions on the membrane surfaces. The tyrosinase immobilization was positively correlated with the input enzyme amount in the immobilization medium. The maximum tyrosinase immobilization capacities of the poly(HEMA-co-GMA)-PEI and poly(HEMA-co-GMA)-PEI-Cu(II) membranes were 19.3 and 24.6 mg/m(2), respectively. The enzyme activity when assessed at various pH and temperatures gave broader range for immobilized preparations when compared to free enzyme. The poly (HEMA-co-GMA)-PEI-Cu(II) tyrosinase membranes retained 82% of their initial activity at the end of 120 h of continuous reaction. Moreover, upon storage for 3 months the activity of the immobilized membranes retained 46% of their initial levels. After deactivation of the enzyme, the poly(HEMA-co-GMA)-PEI membrane was easily regenerated, re-chelated with the Cu(II) ions and reloaded with the enzyme for repeated use. The mild immobilization conditions, easy and rapid membrane preparation, one-step enzyme adsorption at substantially higher levels and membrane reusability are the beneficial properties of such systems and offers promising potential in several biochemical processes. (C) 2003 Elsevier B.V. All rights reserved.Öğe Reversible immobilization of urease onto Procion Brown MX-5BR-Ni(II) attached polyamide hollow-fibre membranes(Elsevier Sci Ltd, 2002) Akgol, S.; Yalcinkaya, Y.; Bayramoglu, G.; Denizli, A.; Arıca, M.Y.Urease was immobilized onto Procion Brown MX-5BR attached and Ni(II) incorporated microporous polyarnide hollow-fibre membrane via adsorption. Urease immobilization onto the polyamide hollow-fibre membrane from aqueous solutions containing different amounts of urease at different pH was investigated in a batch system. The maximum urease immobilization capacity of the polyamide hollow-fibre membrane was 78 mg g(-1) fibre. The retained adsorbed enzyme activity was found to be 37%. However, the urease adsorption onto the polyamide fibre resulted in a threefold increase in enzyme stability with time at 50 degreesC. The Km values were 18 and 22 mM for the free and the immobilized enzymes, respectively. The V-max values were 59.7 U mg(-1) for the free and 25.9 U mg(-1) for the immobilized enzyme. The optimum pH (7.0) apparently was shifted 1.0 unit acidic region upon immobilization via adsorption. The optimum reaction temperature for the free and the immobilized enzymes were determined to be 45 and 55 degreesC, respectively. The dye-Ni(II) attached polyamide hollow-fibre membranes could be repeatedly used for the adsorption/desorption of enzyme without any significant loss in adsorption capacity. (C) 2002 Elsevier Science Ltd. All rights reserved.
