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Affinity separation of plasma proteins using a newly synthesized methacrylamidoalanine incorporated porous pHEMA membranes
(Marcel Dekker Inc, 2002) Yavuz, H.; Patir, S.; Say, R.; Arica, Y.; Denizli, A.
In this study, we synthesized a novel adsorbent to obtain high protein-adsorption capacity utilizing 2-methacrylamidoalanine (MAAL) containing membrane. Amino acid-ligand MAAL was synthesized by using methacrylochloride and alanine. Then, poly(2-hydroxyethylmethacrylate-co-2-methacrylamidoalanine) [p(HEMA-co-MAAL)] membranes were prepared by UV-initiated photopolymerization of HEMA and MAAL in the presence of an initiator (azobisisobutyronitrile, AIBN). Synthesized MAAL was characterized by nuclear magnetic resonance spectroscopy. p(HEMA-co-MAAL) membranes were characterized by swelling studies, porosimeter, scanning electron microscopy, Fourier transform-infra red spectroscopy, and elemental analysis. These membranes have macropores in the size range 5-10 mum. Different metal ions including Zn(II), Ni(II), Co(II), and Cu(II) were chelated on these membranes. p(HEMA-co-MAAL) were used in the adsorption of human serum albumin (HSA) from aqueous media containing different amounts of albumin (0.1-5.0 mg L-1) and at different pH values (4.0-8.0). The maximum HSA adsorption was observed at pH 5.0. The nonspecific adsorption of HSA on the pHEMA membranes was negligible 0.9 mug cm(-2). MAAL incorporation significantly increased the HSA adsorption (1.76 mg cm(-2)). The HSA adsorption capacities of the metal-incorporated membranes were Greater than that of the p(HEMA-co-MAAL) membranes under the same conditions. Higher HSA adsorption capacity was observed from the human plasma (2.88 mg HSA cm(-2)).
Application of NaOH treated Polyporus versicolor for removal of divalent ions of Group IIB elements from synthetic wastewater
(Elsevier Sci Ltd, 2002) Satiroglu, N.; Yalcinkaya, Y.; Denizli, A.; Arica, M.Y.; Bektas, S.; Genç, O.
Three different forms of Polyporus versicolor, i.e. alkali-pretreated, heat-inactivated and active, were used for the removal of the divalent ions of Group JIB elements from aquatic systems. The biosorption of Zn(II), Cd(II) and Hg(II) ions on three different forms of P. versicolor was studied in aqueous solutions in the concentration range of 30-700 mg/l. Maximum biosorption capacities of alkali-pretreated, heat-inactivated and active forms of P. versicolor was found as 139.3, 70.8, and 54.1 mg/g for Zn(II); 232.2, 118.2, and 90.0 mg/g for Cd(II) and 290.3 168.9, and 131.4 mg/g for Hg(11), respectively. For the divalent ions of Group 1111 elements, the order of affinity of the biosorbents was found as, NaOH treated > heat-inactivated > active. The order of the amount of metal ions adsorbed, on the other hand, was, Hg(II) > Cd(II) > Zn(II) on a weight base. The electro-negativities and standard electrode potentials of these elements show a definite trend with the biosorption capacity values. Biosorption equilibria were established in about 60 min and the equilibria were well described by Langmuir isotherms. Temperature change between 15 and 45 degreesC did not affect the biosorption capacity. The effect of pH was also investigated and the maximum biosorption of metal ions on the three different forms of P. versicolor were observed at pH 6.0. The reusability experiments and synthetic wastewater studies were carried out with the most effective form; alkali-pretreated P. versicolor. The biosorbent could be regenerated using 10 mM HCl solution, with up to 98% recovery and it could be reused in five biosorption-desorption cycles without any considerable loss in biosorption capacity. The alkali-treated P. versicolor removed 60, 73, and 81% of Zn(II), Cd(II) and Hg(II) ions from synthetic wastewater samples, respectively. (C) 2002 Elsevier Science Ltd. All rights reserved.
Biosorption of cadmium from aquatic systems by carboxymethyleellulose and immobilized Trametes versicolor
(Elsevier Science Bv, 2002) Yalcinkaya, Y.; Soysal, L.; Denizli, A.; Arica, M.Y.; Bektas, S.; Genc, O.
Trametes versicolor basidio spores immobilized onto carboxymethylcellulose were used for the removal of cadmium ions from aqueous solutions. The biosorption of Cd(II) ions on carboxymethylcellulose and both immobilized live and heat-killed fungal mycelia of T. versicolor was studied from aqueous solutions in the concentration range of 30-700 mg/L. The biosorption of Cd(II) ions by the carboxymethylcellulose and both immobilized live and heat-inactivated immobilized preparations increased as the initial concentration of cadmium ions increased in the medium. Maximum biosorption capacity for immobilized live and heat-inactivated fungal mycelia of T. versicolor was found as 124 and 153 mg Cd(II)/g, respectively whereas the amount of Cd(II) ions adsorbed on the plain carboxymethylcellulose beads was 43 mg/g. Biosorption equilibria were established in about I h and the correlation regression coefficients show that the adsorption process can be well defined by Langmuir equation. The temperature change between 15 and 45 degreesC did not affect the biosorption capacity. The effect of pH was also investigated and the maximum adsorption of Cd(II) ions on the carboxymethylcellulose and both live and heat-inactivated immobilized fungal mycelia were observed at pH 6.0. The carboxymethylcellulose-fungus beads could be regenerated using 10 mM HCl, with up to 98% recovery. The biosorbents were used in five biosorption-desorption cycles and no notable loss in the biosorption capacity was observed. 84% and 68% of cadmium ions were removed from synthetic waste water samples for 100 and 200 mg/L initial concentrations, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.
Biosorption of cadmium(II), lead(II) and copper(II) with the filamentous fungus Phanerochaete chrysosporium
(Elsevier Sci Ltd, 2001) Say, R.; Denizli, A.; Arıca, M.Y.
The biosorption from artificial wastewaters of heavy metals (Cd(II), Pb(II) and Cu(II)) onto the dry fungal biomass of Phanerochaete chryosporium was studied in the concentration range of 5-500 mg 1(-1). The maximum absorption of different heavy metal ions on the fungal biomass was obtained at pH 6.0 and the biosorption equilibrium was established after about 6 h. The experimental biosorption data for Cd(II), Pb(II) and Cu(II) ions were in good agreement with those calculated by the Langmuir model. (C) 2000 Elsevier Science Ltd. All rights reserved.
Biosorption of Hg(II) and Cd(II) from aqueous solutions: Comparison of biosorptive capacity of alginate and immobilized live and heat inactivated Phanerochaete chrysosporium
(Elsevier Sci Ltd, 2002) Kacar, Y.; Arpa, C.; Tan, S.; Denizli, A.; Genc, O.; Arica, M.Y.
Basidiospores of P. chryosporium were immobilized into Ca-alginate beads via entrapment, and the beads incubated for vegetation at 30 degreesC for 5 days. The alginate beads and both entrapped live and heat inactivated fungal mycelia of Phanerochaete chryosporium were used for the removal of Hg(II) and Cd(II) ions from aqueous solution in the concentrations range of 30-500 mg l (-1). The biosorption of Hg(II) and Cd(II) ions by the biosorbents increased as the initial concentration of Hg(II) and Cd(11) ions increased in the medium. A biosorption equilibrium was established in about 1 h and the adsorbed heavy metal ions did not change further with time. The effect of pH was also investigated and the maximum biosorption of Hg(11) and Cd(II) ions on all the tested biosorbents were obtained between pH 5.0 and 6.0. Temperature over the range 15-45 degreesC had no significant effect on the biosorption capacity. The equilibrium was well described by Langmuir and Freundlich biosorption isotherms. The alginate-fungus beads could be regenerated using 10 mM HCl, up to 97% recovery. The biosorbents were reused in three biosorption-desorption cycles with negligible decrease in biosorption capacity. (C) 2002 Elsevier Science Ltd. All rights reserved.
Biosorption of mercury by carboxymethylcellulose and immobilized Phanerochaete chrysosporium
(Elsevier Science Bv, 2002) Saglam, A.; Yalcinkaya, Y.; Denizli, A.; Arica, M.Y.; Genc, O.; Bektas, S.
Phanerochaete chrysosporium basidiospores immobilized onto carboxymethylcellulose were used for the removal of mercury ions from aqueous solutions. The biosorption of Hg(II) ions onto carboxymethylcellulose and both immobilized live and heat-inactivated fungal mycelia of Phanerochaete chrysosporium was studied using aqueous solutions in the concentration range 30-700 mg l(-1). The biosorption of Hg(II) ions by the carboxymethylcellulose and both live and heat-inactivated immobilized preparations increased as the initial concentration of mercury ions increased in the medium. Maximum biosorption capacity for immobilized live and heat-inactivated fungal mycelia of Phanerochaete chrysosporium was found to be 83.10 and 102.15 mg Hg(II) g(-1), respectively, whereas the amount of Hg(II) ions adsorbed onto the plain carboxymethylcellulose beads was 39.42 mg g(-1). Biosorption equilibria were established in approximately 1 h and the correlation regression coefficients show that the adsorption process can be well defined by a Langmuir equation. Temperature changes between 15 and 45 C did not affect the biosorption capacity. The effect of pH was also investigated and the maximum adsorption of Hg(II) ions onto the carboxymethylcellulose and both live and heat-inactivated immobilized fungal mycelia was observed at pH 6.0. The carboxymethylcellulose-fungus beads could be regenerated using 10 mM HCl, with up to 95% recovery. The biosorbents were used in three biosorption-desorption cycles and no significant loss in the biosorption capacity was observed. (C)2002 Elsevier Science B.V All rights reserved.
Cadmium and mercury uptake by immobilized Pleurotus sapidus
(Scientific Technical Research Council Turkey, 2002) Yalçınkaya, Y.; Arıca, M.Y.; Soysal, L.; Denizli, A.; Genç, O.; Bektaş, S.
Pleurotus sapidus basidiospores immobilized onto Ca-alginate beads were used for the removal of cadmium and mercury ions from aqueous solutions. The biosorption of Cd(II) and Hg(II) ions on the alginate beads and both immobilized live and heat inactivated fungal mycelia of Pleurotus sapidus was studied from aqueous solutions in the concentration range of 30-500 mg L-1. The biosorption of Cd(II) and Hg(II) ions by the alginate and both live and heat inactivated immobilized preparations increased as the initial concentration of the ions increased in the medium. Maximum biosorption capacity for immobilized live and heat inactivated fungal mycelia of Pleurotus sapidus was found to be 96.57 mg g(-1) (0.86 mmol g(-1)) and 127.12 mg g(-1) (1.13 mmol g(-1)) for Cd(II) and 207.89 mg g(-1)(1.04 mmol g(-1)) and 287.43 mg g(-1) (1.43 mmol g(-1)) for Hg(II), respectively. The electronegativities and standard electrode potentials of the divalent ions of Group II elements show a definite trend with sorption capacity. Biosorption equilibria were established in about I h and were very well described by Langmuir isotherms. The temperature change between 1.5 and 4.5degreesC did not affect the biosorption capacity. The effect of pH was also investigated and the maximum uptake of metal ions on the alginate and both live and inactivated immobilized fungal mycelia were observed between pH 3.0 and 7.0. The alginate-fun.-us beads were regenerated using 10 mM HCl, with up to 97% recovery, the biosorbents were reused in three biosorption-desorption cycles without any considerable loss in the biosorption capacity.
Comparative biosorption of mercuric ions from aquatic systems by immobilized live and heat-inactivated Trametes versicolor and Pleurotus sajur-caju
(Elsevier Sci Ltd, 2003) Arica, M.Y.; Arpa, C.; Kaya, B.; Bektas, S.; Denizli, A.; Genc, O.
Trametes versicolor and Pleurotus sajur-caju mycelia immobilized in Ca-alginate beads were used for the removal of mercuric ions from aqueous solutions. The sorption of Hg(II) ions by alginate beads and both immobilized live and heat-killed fungal mycelia of T versicolor and P. sajur-caju was studied in the concentration range of 0.150-3.00 mmol dm(-3). The biosorption of Hg(II) increased as the initial concentration of Hg(II) ions increased in the medium. Maximum biosorption capacities for plain alginate beads were 0.144+/-0.005 mmol Hg(II)/g; for immobilized live and heat-killed fungal mycelia of T versicolor were 0.171+/-0.007 mmol Hg(II)/g and 0.383+/-0.012 mmol Hg(II)/g respectively; whereas for live and heat-killed P. sajur-caju, the values were 0.450+/-0.014 mmol Hg(II)/g and 0.660+/-0.019 mmol Hg(II)/g respectively. Biosorption equilibrium was established in about 1 h and the equilibrium adsorption was well described by Langmuir and Freundlich adsorption isotherms. Between 15 and 45 degreesC the biosorption capacity was not affected and maximum adsorption was observed between pH 4.0 and 6.0. The alginate-fungus beads could be regenerated using 10 mmol dm(-3) HCl solution, with up to 97% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Heat-killed T versicolor and P. sajur-caju removed 73% and 81% of the Hg(II) ions, respectively, from synthetic wastewater samples. (C) 2003 Elsevier Science Ltd. All rights reserved.
Comparison of adsorption performances of metal-chelated polyamide hollow fibre membranes in lysozyme separation
(Elsevier Science Bv, 2002) Şenel, S.; Kassab, A.; Arıca, Y.; Say, R.; Denizli, A.
Commercially available microporous polyamide hollow fibres are modified by acid hydrolysis to activate the reactive groups and subsequently binding of the ligand, i.e. Cibacron Blue F3GA. Then the Cibacron Blue F3GA-derived hollow fibres were loaded with different metal ions (i.e. Zn(II), Cu(II), Ni(II)) to form the metal chelate. The internal polymer matrix was characterised by scanning electron microscopy. The effects of pH, initial concentration of lysozyme, metal type and temperature on the adsorption of lysozyme to the metal-chelated hollow fibres were examined in a batch reactor. The non-specific adsorption of lysozyme onto the polyamide hollow fibres was 1.8 mg/g. Cibacron Blue F3GA immobilisation increased the lysozyme adsorption up to 62.3 mg/g. Metal-chelated hollow fibres showed a significant increase of the adsorption efficiency. Lysozyme adsorption capacities of Zn(II), Cu(II) and Ni(Il)-chelated hollow fibres were different. The maximum capacities of Zn(II), Cu(II) or Ni(Il)-chelated hollow fibres were 144.2, 75.2 and 68.6 mg/g, respectively. Significant amount of the adsorbed lysozyme (up to 97%) was eluted in 1 h in the elution medium containing 1.0 M NaSCN at pH 8.0 and 25 mM EDTA at pH 4.9. Repeated adsorption-desorption process showed that this novel metal-chelated polyamide hollow fibres are suitable for lysozyme adsorption. (C) 2002 Published by Elsevier Science B.V.
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.
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.
Dye-affinity hollow-fibres and their lysozyme adsorption-desorption characteristics
(John Wiley & Sons Ltd, 2001) Şenel, S.; Akgöl, S.; Arica, Y.; Denizli, A.
Dye-affinity adsorption is increasingly used for protein separation. Hollow-fibres have advantages as adsorbents in comparison to conventional bead supports because they are not compressible and can eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of polyamide hollow-fibres to which Reactive Green HE-4BD was attached for adsorption of lysozyme. The hollow-fibre was characterized by scanning electron microscopy. These dye-carrying hollow-fibres (26.3 mu mol g(-1)) were used in the lysozyme adsorption-elution studies. The effect of initial concentration of lysozyme and medium pH on the adsorption efficiency of dye-attached hollow-fibres was studied in a batch system. The non-specific adsorption of lysozyme on the polyamide hollow-fibres was 1.8 mgg(-1). Reactive Green HE-4BD attachment significantly increased the lysozyme adsorption up to 41.1 mgg(-1). Langmuir adsorption model was found to be applicable in interpreting lead adsorption by Reactive Green HE-4BD attached hollow fibres. Significant amount of the adsorbed lysozyme (up to 95%) was eluted in lh in the elution medium containing 1.0M NaSCN at pH 8.0. In order to determine the effects of adsorption conditions on possible conformational changes of lysozyme structure, fluorescence spectrophotometry was employed. We concluded that polyamide dye-affinity hollow-fibres can be applied for lysozyme adsorption without causing any significant conformational changes. Repeated adsorption-elution processes showed that these dye-attached hollow-fibres are suitable for lysozyme adsorption. (C) 2001 Society of Chemical Industry.
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.
Fibronectin purification from human plasma in a packed-bed column system with gelatin immobilized PHEMA microspheres
(Vsp Bv, 2001) Kayirhan-Denizli, F.; Arıca, M.Y.; Denizli, A.
Bioaffinity chromatography has a unique and powerful role that is used as a purification tool in the production of therapeutic plasma protein derivatives. In this study, a bioaffinity-ligand, i.e. gelatin, was covalently immobilized with PHEMA microspheres (150-200 tm in diameter). The affinity sorbent carrying 7.5 mg gelatin g(-1) polymer was then used to separate fibronectin from human plasma in a packed-bed column system. Fibronectin separation from human plasma on unmodified PHEMA microspheres was 0.45 mg g(-1), while much higher adsorption values, up to 21.8 mg g(-1), were obtained with gelatin-immobilized microspheres. The fibronectin adsorption capacity of the microspheres decreased with an increase in the recirculation rate of plasma. Fibronectin adsorption increased with decreasing temperature, and the maximum adsorption achieved at 4 degreesC (26.3 mg fibronecting(-1)). Up to 94.7% of the adsorbed fibronectin was desorbed by using 2 M urea in the presence of I Ni sodium chloride as elution agent. The adsorption-desorption cycle was repeated ten times using the same affinity column. There was no remarkable reduction in the adsorption capacity of the gelatin-immobilized PHEMA microspheres.
Heavy metal separation capacity of a porous methacrylamidophenylalanine containing membrane based on a polyhydroxyethyl methacrylate matrix
(Marcel Dekker Inc, 2001) Denizli, A.; Say, R.; Patir, S.; Arica, Y.
The abilities of various sorbent materials for heavy metal removal have been reported in the literature. We have developed a novel approach to obtain high metal-sorption capacity utilizing a membrane containing 2-methacrylamidophenylalanine. Metal-complexing ligand 2-methacrylamidophenylalanine (MAPA) was synthesized through the use methacrylo chloride and phenylalanine. Then, poly(2-hydroxyethyhmethacrylate-co-2-methacrylamidophenylalanine) (p(HEMA-co-MAPA)) membranes were prepared by UV-initiated photopolymerization of HEMA and MAPA in the presence of the initiator azobisisobutyronitrile. MAPA monomer was characterized by nuclear magnetic resonance spectroscopy. p(HEMA-co-MAPA) membranes were characterized by swelling studies, scanning electron microscopy, Fourier transform infrared spectroscopy, and elemental analysis. These membranes have large pores; the micropore dimensions are approximately 5-10 mum. p(HEMA-co-MA-PA) affinity membranes with a swelling ratio of 133.2% and containing 18.9 mmol MAPA/m(2) were used in the removal of the heavy-metal ions of copper, nickel, and mercury from aqueous media containing different amounts of these ions (5-600 mg/L) and at different pH values (2.0-7.0). The maximum adsorption capacities of heavy metal ions onto the MAPA-containing membranes under noncompetitive conditions were 23.8 = mmol/m(2) for Cu(II), 29.1 mmol/m(2) for Ni(II), and 50.3 mmol/m(2) for Hg(II). The affinity order was Hg(II) > Ni(II) > Cu(II). The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at approximately pH 5.0. Adsorption of heavy metal ions from artificial wastewater was also studied. The adsorption capacities were 11.9 mmol/m(2) for Cu(II), 7.33 mmol/m(2) for Ni(II), and 9.79 mmol/m(2) for Hg(II). Desorption of heavy metal ions was performed using 0.1 M HNO3. The p(HEMA-co-MAPA) membranes are suitable for more than five cycles without noticeable loss of capacity.
Hydrolysis of sucrose by invertase immobilized onto novel magnetic polyvinylalcohol microspheres
(Elsevier Sci Ltd, 2001) Akgöl, S.; Kaçar, Y.; Denizli, A.; Arıca, M.Y.
The magnetic polyvinylalcohol (PVAL) microspheres were prepared by crosslinking glutaraldehyde. 1,1 ' -Carbonyldiimidazole (CDI), a carbonylating agent was used for the activation of hydroxyl groups of polyvinylalcohol, and invertase immobilized onto the magnetic PVAL microspheres by covalent bonding through the amino group. The retained activity of the immobilized invertase was 74%. Kinetic parameters were determined for immobilized invertase, as well as for the free enzyme. The K-m values for immobilized invertase (55 mM sucrose) were higher than that of the free enzyme (24 mM sucrose), whereas V-max values were smaller for the immobilized invertase. The optimum operational temperature was 5 degreesC higher for immobilized enzyme than that of the free enzyme. The operational inactivation rate constant (k(opi)) of the immobilized invertase at 35 degreesC with 200 mM sucrose was 5.83 x 10(-5) min(-1). Thermal and storage stabilities were found to increase with immobilization. (C) 2001 Elsevier Science Ltd. All rights reserved.
Immobilization of catalase via adsorption onto L-histidine grafted functional pHEMA based membrane
(Elsevier Science Bv, 2001) Akgöl, S.; Kacar, Y.; Özkara, S.; Yavuz, H.; Denizli, A.; Arica, M.Y.
Poly(2-hydroxyethylmethacrylate) (pHEMA) based flat sheet membrane was prepared by UV-initiated photopolymerization technique. The membrane was then grafted with L-histidine. Catalase immobilization onto the membrane from aqueous solutions containing different amounts of catalase at different pH was investigated in a batch system. The maximum catalase immobilization capacity of the pHEMA-histidine membrane was 86 mug cm(-2). The activity yield was decreased with the increase of the enzyme loading. It was observed that there was a significant change between V-max value of the free catalase and V-max value of the adsorbed catalase on the pHEMA-histidine membrane. The K-m value of the immobilized enzyme was higher 1.5 times than that of the free enzyme. Optimum operational temperature was 5 degreesC higher than that of the free enzyme and was significantly broader. It was observed that enzyme could be repeatedly adsorbed and desorbed without loss of adsorption capacity or enzyme activity. (C) 2001 Elsevier Science B.V. All rights reserved.
Immobilization of glucoamylase on the plain and on the spacer arm-attached poly(HEMA-EGDMA) microspheres
(John Wiley & Sons Inc, 2001) Arıca, M.Y.; Yavuz, H.; Denizli, A.
Immobilization glucoamylase onto plain and a six-carbon spacer arm (i.e., hexamethylene diamine, HMDA) attached poly(2-hydroxyethylmethacrylate-ethylen col dimethacrylate) [poly(HEMA-EGDMA] microspheres was studied. The microspheres were prepared by suspension polymerization and the spacer arm was attached covalently by the reaction of carbonyl groups of poly(HEMA-EGDMA). Glucoamylase was then covalently immobilized either on the plain of microspheres via CNBr activation or on the spacer arm-attached microspheres via CNBr activation and/or using carbodiimide (CDI) as a coupling agent. Incorporation of the spacer arm resulted an increase in the apparent activity of the immobilized enzyme with respect to enzyme immobilized on the plain of the microspheres. The activity yield of the immobilized glucoamylase on the spacer arm-attached poly(HEMA-EGDMA) microspheres was 63% for CDI coupling and 82% for CNBr coupling. This was 44% for the enzyme, which was immobilized on the plain of the unmodified poly(HEMA-EGDMA microspheres via CNBr coupling. The Km values for the immobilized glucoamylase preparations ton the spacer arm-attached microspheres) via CDI coupling 0.9% dextrin (w/v) and CNBr coupling 0.6% dextrin (w/v) were higher than that of the free enzyme 0.2% dextrin (w/v). The temperature profiles were broader for both immobilized preparations than that of the free enzyme. The operational inactivation rate constants (k(iop)) of immobilized enzymes were found to be 1.42 x 10(-5) min(-1) for CNBr coupled and 3.23 x 10(-5) min(-1) for CDI coupled glucoamylase. (C) 2001 John Wiley & Sons, Inc.
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.
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.

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