Yasemin Kaçar

Entrapment of white-rot fungus Trametes versicolor in Ca-alginate beads: preparation and biosorption kinetic analysis for cadmium removal from an aqueous solution

The biosorption of cadmium ions onto entrapped Trametes versicolor mycelia has been studied in a batch system. The maximum experimental biosorption capacities for entrapped live and dead fungal mycelia of T. versicolor were found as 102.3 +/- 3.2 mg Cd(II) g(-1) and 120.6 +/- 3.8 mg Cd(II) g(-1), respectively. Biosorption equilibrium was established in about 1 h and biosorption was well described by the Langmuir and Freundlich biosorption isotherms. The change in the biosorption capacity with time was found to fit the pseudo-second-order equation. Since the biosorption capacities were relatively high for both entrapped live and dead forms, those fungal forms 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 a significant loss in the biosorption capacity.

Hydrolysis of sucrose by invertase immobilized onto novel magnetic polyvinylalcohol microspheres

Abstract 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°C higher for immobilized enzyme than that of the free enzyme. The operational inactivation rate constant ( k opi ) of the immobilized invertase at 35°C with 200 mM sucrose was 5.83×10 −5 min −1 . Thermal and storage stabilities were found to increase with immobilization.

Covalent immobilization of lipase onto hydrophobic group incorporated poly(2-hydroxyethyl methacrylate) based hydrophilic membrane matrix

Abstract 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 α-α ′ -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 ° C the thermal stability constants were 1.1×10 −1 min for free enzyme and 1.2×10 −2 min for the immobilized enzyme. The immobilized enzyme activity was found to be quite stable in repeated experiments.

Reversible immobilization of lipase on phenylalanine containing hydrogel membranes

Poly(2-hydroxyethylmethacrylate-co-methacrylamidophenlyalanine) poly(HEMA-MAPA) membranes were prepared by UV-initiated photopolymerization of HEMA and MAPA. Lipase immobilization onto these membranes from aqueous solutions containing different amounts of lipase at different pH was investigated in a batch system. The lipase adsorption capacity of the membranes was increased as the MAPA ratio increased in the membrane structure. The maximum lipase immobilization capacity of the poly(HEMA-MAPA-3) membrane was 135 μg cm−2. The optimum temperature was 5°C higher than that of the free enzyme and was significantly broader. The storage stability increased with immobilization. The enzyme could be repeatedly adsorbed and desorbed without any significant loss in adsorption capacity.

Procion Green H-E4BD-immobilized porous poly(hydroxyethylmethacrylate) ion-exchange membrane: preparation and application to lysozyme adsorption

Abstract Lysozyme adsorption onto Procion Green HE-4BD-immobilized poly(2-hydroxyethylmethacrylate) (pHEMA) membrane were investigated. The membrane were prepared by ultraviolet-initiated photopolymerization of HEMA in the presence of an initiator (α-α′-azoisobutyronitrile; AIBN). The water content of the dye-immobilized membrane was 69%, the amount of immobilized dye on the membrane was 0.544 μmol ml −1 and it used in the lysozyme adsorption studies. Lysozyme adsorption on these membranes from aqueous solutions containing different amounts of lysozyme at different pH was investigated in batch reactors. Lysozyme adsorption capacity of the dye-immobilized membrane was 13.33 mg ml −1 . The maximum lysozyme adsorption capacity ( q m ) of the dye-immobilized wet membrane was 14.14 mg ml −1 and the dissociation constant ( k d ) value was found to be 0.707 mg ml −1 lysozyme. More than 95% of the adsorbed lysozyme were desorbed in 120 min in the desorption medium containing 0.5 M KCl at pH 6.0.

Preparation of reversibly immobilized lysozyme onto Procion Green H-E4BD-attached poly(hydroxyethylmethacrylate) film for hydrolysis of bacterial cells

Abstract The flat sheet support for enzyme immobilization was prepared by UV-initiated photopolymerization of 2-hydroxyethyl-methacrylate (HEMA) in the presence of an initiator (αα′-azoisobutyronitrile; AIBN). An affinity dye, Procion Green H-E4BD, was attached covalently under alkaline conditions and the pHEMA-Procion Green H-E4BD-attached film was used for the immobilization of lysozyme via adsorption. The amount of attached dye on the pHEMA film was 160 μmol m 2 and the water content of the dye-attached pHEMA film was 69%. The lysozyme adsorption capacity of the dye-attached pHEMA film was determined under conditions of different pH and with different initial concentrations of enzyme in the medium. The maximum lysozyme adsorption capacity of the dye-attached pHEMA film, under the specified experimental conditions was 3.92 g m −2 . Non-specific adsorption of the lyzozyme on the pHEMA film was negligible. Optimum reaction pH was 6.0 for the free and 7.0 for adsorbed enzyme. The free enzyme had an optimum temperature of 35°C, whereas it shifted to 40°C for the immobilized enzyme system. The enzyme could be repeatedly adsorbed and desorbed from the dye-attached pHEMA film without any significant loss in adsorption capacity.

Paraoksonaz1 (Pon1) Enzimi ve Polimorfizmleri

Paraoxonase enzyme has initially been identified as a protective barrier against organophosphorus poisoning. In the recent years, a wide range of investigations were conducted on this enzyme and the knowledge about its functions and the etiopathogenetic role in some diseases has been clarified in depth.