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    Adsorption of heavy metal ions onto ethylene diamine-derived and Cibacron Blue F3GA-incorporated microporous poly(2-hydroxyethyl methacrylate) membranes
    (Elsevier Science Bv, 2000) Denizli, A; Say, R; Patir, S; Arica, MY
    Microporous poly( 2-hydroxyethylmethacrylate) (PHEMA) membranes carrying ethylene diamine (EDA) and Cibacron Blue F3GA were prepared for the removal of heavy metal ions (i.e. mercury, copper, lead and cadmium) from aqueous solutions containing different amounts of these ions (5-700 mu g 1(-1)) and at different pH values (2.0-8.0). The non-specific adsorption of heavy metal ions on the underived membranes was very low (3.3 mmol/m(2) for Hg(II), 0.5 mmol/m(2) for Cu(II), 1.2 mmol/m(2) for Pb(II) and 1.1 mmol/m(2) for Cd(II)). Cibacron Blue F3GA attachment significantly increased the heavy metal adsorption (16.3 mmol/m(2) for Hg(II), 19.9 mmol/m(2) for Cu(II), 23.4 mmol/m(2) for Pb(II) and 38.4 mmol/m(2) for Cd(LI)). When the heavy metal ions competed (in the case of the adsorption from a mixture) the adsorption capacities were 7.1 mmol/m(2) for Hg(II), 17.9 mmol/m(2) for Cu(II), 6.2 mmol/m(2) for Pb(II) and 9.1 mmol/m(2) for Cd(lI). The observed order in adsorption was found to be Cd(II) > Pb(II) > Cu(II) > Hg(II) for non-competitive conditions. The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. Desorption of heavy metal ions was achieved using 0.1 M HNO3. These membranes are suitable for repeated use for more than five cycles without considerable loss of adsorption capacity. (C) 2000 Elsevier Science B.V. All rights reserved.
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    Biosorption of inorganic mercury and alkylmercury species on to Phanerochaete chrysosporium mycelium
    (Elsevier Sci Ltd, 1999) Saglam, N; Say, R; Denizli, A; Patir, S; Arica, MY
    The biosorption of inorganic mercury (HgCl2), methyl mercury (CH3HgCl) and ethyl mercury (C2H5HgCl) onto the dry biomass of Phanerochaete chryosponum was studied from aqueous media which concentrations in the range of 5-500 mg l(-1). The surface charge density varied with pH, and the concentration of mercury species adsorbed significantly increased from pH 3.0 to maximum levels at pH 8.0. The biosorption of mercury ions by Phanerochaete chrysosporium increased as the initial concentration of Hg(II) ion increased in the adsorption medium. A biosorption equilibrium were established after about 6 h, the adsorbed Hg(II) ion did not significantly change further with time. The dissociation constant (k(d)) values were 72, 63, and 61 mg l(-1) for CH3HgCl, C2H5HgCl and for Hg(II), respectively. The maximum biosorption capacity (q(m)) at pH 7.0 was 79 mg for CH3HgCI, 67 mg for C2H5HgCl and 61 mg for Hg(II) per g of dried fungal biomass. The affinity order of mercury species was CH3HgCl > C2H5HgCl > and Hg(II). (C) 1999 Elsevier Science Ltd. All rights reserved.
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    Immobilization of glucoamylase onto spacer-arm attached magnetic poly(methylmethacrylate) microspheres: characterization and application to a continuous flow reactor
    (Elsevier Science Bv, 2000) Arica, MY; Yavuz, H; Patir, S; Denizli, A
    Magnetic poly(methylmethacrylate) microspheres (MPMMA) were prepared by the solvent evaporation method and a 6-carbon spacer-arm (i.e. hexamethylene diamine, HMDA) was covalently attached by the reaction of carbonyl groups of poly(methylmethacrylate). Glucoamylase was then covalently immobilized through the spacer-arm of the MPMMA microspheres by using either carbodiimide (CDI) or cyanogen bromide (CNBr) as a coupling agent. The activity yield of the immobilized glucoamylase was 57% for CDI coupling and 73% for CNBr coupling. Kinetic parameters were determined for both immobilized glucoamylase preparations as well as for the free enzyme. The K-m values for immobilized glucoamylases CDI coupling (12.5 g l(-1) dextrin) and CNBr coupling (9.3 g l(-1) dextrin) were higher than that of the free enzyme (2.1 g l(-1) dextrin) whereas V-max values were smaller for the immobilized glucoamylase preparations. The optimum operational temperature was 5 degreesC higher for both immobilized preparations than that of the free enzyme. Operational, thermal and storage stabilities were found to be increased with immobilization. (C) 2000 Elsevier Science B.V. All rights reserved.
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    Invertase immobilized on spacer-arm attached poly(hydroxyethyl methacrylate) membrane: Preparation and properties
    (John Wiley & Sons Inc, 2000) Arica, MY; Senel, S; Alaeddinoglu, NG; Patir, S; Denizli, A
    Microporous poly(2-hydroxyethyl methacrylate) (pHEMA) membrane was prepared by UV-initiated photopolymerization. The spacer arm (i.e., hexamethylene diamine) was attached covalently and then invertase was immobilized by the condensation reaction of the amino groups of the spacer arm with carboxyl groups of the enzyme in the presence of carbodiimides. The values of the Michael's constant K-m of invertase were significantly larger (ca. 2.5 times) upon immobilization, indicating decreased affinity by the enzyme for its substrate, whereas V-max was smaller for the immobilized invertase. Immobilization improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with immobilization and at 70 degrees C the half times for the activity decay were 12 min for the free enzyme and 41 min for the immobilized enzyme. The immobilized enzyme activity was found to be quite stable in repeated experiments. (C) 2000 John Wiley & Sons, Inc.
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    Synthesis and adsorption properties of poly(2-hydroxyethylmethacrylate-co-methacrylamidophenylalanine) membranes for copper ions
    (Elsevier Science Bv, 2000) Denizli, A; Say, R; Patir, S; Arica, Y
    In the first step of this study, the metal complexing ligand, 2-methacrylamidophenylalanine (MAPA), was synthesized by using methacrylochloride and phenylalanine. The MAPA monomer was characterized by NMR. Then, poly(2-hydroxyethylmethacrylate -co-2-methacrylamidophenylalanine) [p(HEMA-co-MAPA)] membranes were prepared by UV-initiated photo-polymerization of HEMA and MAPA in the presence of an initiator (azobisisobutyronitrile? AIBN). p(HEMA-co-MAPA) membranes were characterized by FTIR and elemental analysis. These p(HEMA-co-MAPA) affinity membranes with a swelling ratio of 133.2%, and containing 18.9 mmol MAPA/m(2), were used in the adsorprion-desorption of copper(II) ions from synthetic solutions. Adsorption equilibria was reached in about 2 h. The maximum adsorption of Cu(II) ions onto pHEMA was about 0.54 mmol Cu(II)/m(2). The MAPA incorporation significantly increased the Cu(II) adsorption capacity by chelate formation of Cu(II) ions with MAPA molecules (23.8 mmol Cu(II)/m(2)), which was observed at pH 7.0. The chelating membrane can be easily regenerated by 0.1 M HNO3 with higher effectiveness. (C) 2000 Elsevier Science B.V. All rights reserved.
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    Synthesis of Poly[(hydroxyethyl methacrylate)-co-(methacrylamidoalanine)] Membranes and Their Utilization as an Affinity Sorbent for Lysozyme Adsorption
    (Wiley-V C H Verlag Gmbh, 2001) Garipcan, B; Bereli, N; Patir, S; Arica, Y; Denizli, A
    Various adsorbent materials have been reported in the literature for protein separation. We have developed a novel and new approach to obtain high protein-adsorption capacity utilizing a 2-methacrylamidoalamne-containing membrane. An amino acid ligand 2-methacrylamidoalanine (MAAL) was synthesized from methacrylochloride and alanine. Then, poly[(2-hydro-xyethel methacrylate)-co-(2-methacrylamidoalanine)] [p(HEMA-co-MAAL)] membranes were prepared by UV-initiated photopolymerization of HEMA and MAAL. The synthesized MAAL monomer was characterized by NMR spectrometry. p(HEMA-co-MAAL) membranes were characterized by swelling studies, porosimeter, scanning electron microscopy,FT-IR spectroscopy and elemental analysis. These membranes have large pores; the micropore dimensions are around 5-10 mum. p(HEMA-co-MAAL) affinity membranes with a swelling ration of 198.9%, and containing 23.9 (mmol MAAL).m(-2) were used in the adsorption of lysozyme (0.1-3.0 mg.ml(-1)) and at different pH values (4.0-8.0). The effect of Cu(II) incorporation on lysozyme adsorption was also studied. The non-specific adsorption of lysozyme on the pHEMA membranes was 0.9 mug-cm(-2). Incorporation of MAAL molecules into the polymeric structure significantly increased the lysozyme adsorption up to 2.96 mg.cm(-2). The lysozyme-adsorption capacity of the membranes incorporated with Cu(III) (9.98 mg.cm(-2)) was greater than that of the p(HEMA-co-MAAL) membranes. More than 85% of the adsorbed lysozyme was desorbed in 1 h in the desorption medium containing 1.0 M NaCl. The p(HEMA-co-MAAL) membranes are suitable for repeated use for more than 5 cycles without noticable loss of capacity. These features make p(HEMA-co-MAAL) membrane a very good candidate for bioaffinity adsorption. Adsorption rates of lysozyme: MAAL loading: 23.9 mmol.m(-2); pH: 7.0; temperature: 20 degreesC; total external membrane surface area in each batch: 100 cm(2).l(-1); Each point is the average of five parallel studies.