Person: DEMİR, SERAP
Loading...
Email Address
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
DEMİR
First Name
SERAP
Name
7 results
Search Results
Now showing 1 - 7 of 7
Publication Metadata only Preparation and characterization of UV-curable polymeric support for covalent immobilization of xylanase enzyme(ELSEVIER, 2011) KAHRAMAN, MEMET VEZİR; Akdemir, Zumrut Seden; Demir, Serap; Kahraman, M. Vezir; Apohan, Nilhan KayamanThe hydroxyl group of poly(ethylene glycol) monoacrylate (PEGMA) was activated by 1 1'-carbonyldiimidazole (CDI) and then a xylanase enzyme was immobilized to amine active PEGMA UV-curable polymeric support formulation was prepared by mixing the xylanase bonded PEGMA aliphatic polyester 2-hydroxyethyl methacrylate (HEMA) poly(ethylene glycol) diacrylate (PEGDA) and photoinitiator After UV irradiation the enzymatic activity of the polymeric matrix was evaluated and compared with the corresponding free enzyme By immobilization the temperature resistance of the enzyme was improved and showed maximum activity at 60 C pH dependent activities of the free and immobilized enzymes were also investigated and it was found that the pH of maximum activity for the free enzyme was 60 while for the optimal pH of the immobilized enzyme was 65 The immobilized enzyme retained 75% of its activity after 33 runs The morphology of the polymeric support was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) coupled with SEM was used to explore the chemical composition The results have confirmed the evidence of enzyme in the structure of the polymeric material (c) 2010 Elsevier B V All rights reservedPublication Metadata only alpha-Amylase immobilization on functionalized nano CaCO3 by covalent attachment(WILEY-V C H VERLAG GMBH, 2012) KAHRAMAN, MEMET VEZİR; Demir, Serap; Gok, Sevda Burcu; Kahraman, Memet VezirIn this study, a-amylase was immobilized on glutaraldehyde activated silanized calcium carbonate nanoparticles by a using covalent binding method. The surface modified nano calcium carbonate (CaCO3) were characterized using FTIR and SEM. Immobilization yield was found as 199.43 mg/g of calcium carbonate nanoparticles. The maximum activity was observed at pH 6.5. The immobilized enzyme had a higher activity at elevated temperature (5090 degrees C) than the free one. Reuse studies demonstrated that the immobilized enzyme could reuse 25 times while retaining 18.2% of its activity. Free enzyme lost its activity completely within 15 days. Vmax values for the free and immobilized enzymes were calculated as 10 and 0.35 mg/mL/min, respectively.Publication Metadata only Physical and Covalent Immobilization of Lipase onto Amine Groups Bearing Thiol-Ene Photocured Coatings(HUMANA PRESS INC, 2017) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Muhsir, Pelin; Demir, SerapIn this study, amine groups containing thiol-ene photocurable coating material for lipase immobilization were prepared. Lipase (EC 3.1.1.3) from Candida rugosa was immobilized onto the photocured coatings by physical adsorption and glutaraldehyde-activated covalent bonding methods, respectively. The catalytic efficiency of the immobilized and free enzymes was determined for the hydrolysis of p-nitrophenyl palmitate and also for the synthesis of p-nitrophenyl linoleate. The storage stability and the reusability of the immobilized enzyme and the effect of temperature and pH on the catalytic activities were also investigated. The optimum pH for free lipase and physically immobilized lipase was determined as 7.0, while it was found as 7.5 for the covalent immobilization. After immobilization, the optimum temperature increased from 37 A degrees C (free lipase) to 50-55 A degrees C. In the end of 15 repeated cycles, covalently bounded enzyme retained 60 and 70 % of its initial activities for hydrolytic and synthetic assays, respectively. While the physically bounded enzyme retained only 56 % of its hydrolytic activity and 67 % of its synthetic activity in the same cycle period. In the case of hydrolysis V (max) values slightly decreased after immobilization. For synthetic assay, the V (max) value for the covalently immobilized lipase was found as same as free lipase while it decreased dramatically for the physically immobilized lipase. Physically immobilized enzyme was found to be superior over covalent bonding in terms of enzyme loading capacity and optimum temperature and exhibited comparable re-use values and storage stability. Thus, a fast, easy, and less laborious method for lipase immobilization was developed.Publication Metadata only Preparation, characterization, and in vitro evaluation of isoniazid and rifampicin-loaded archaeosomes(WILEY, 2018) OGAN, AYŞE; Attar, Azade; Bakir, Ceren; Yuce-Dursun, Basak; Demir, Serap; Cakmakci, Emrah; Danis, Ozkan; Birbir, Meral; Ogan, AyseThe ability of Archaea to adapt their membrane lipid compositions to extreme environments has brought in archaeosomes into consideration for the development of drug delivery systems overcoming the physical, biological blockades that the body exhibits against drug therapies. In this study, we prepared unilamellar archaeosomes, from the polar lipid fraction extracted from Haloarcula 2TK2 strain, and explored its potential as a drug delivery vehicle. Rifampicin and isoniazid which are conventional drugs in tuberculosis medication were loaded separately and together in the same archaeosome formulation for the benefits of the combined therapy. Particle size and zeta potential of archaeosomes were measured by photon correlation spectroscopy, and the morphology was assessed by with an atomic force microscope. Encapsulation efficiency and loading capacities of the drugs were determined, and in vitro drug releases were monitored spectrophotometrically. Our study demonstrates that rifampicin and isoniazid could be successfully loaded separately and together in archaeosomes with reasonable drug-loading and desired vesicle-specific characters. Both of the drugs had greater affinity for archaeosomes than a conventional liposome formulation. The results imply that archaeosomes prepared from extremely halophilic archaeon were compatible with the liposomes for the development of stable and sustained release of antituberculosis drugs.Publication Metadata only Preparation of a Poly(ethylene glycol)-Based Cross-Linked Network from a Click Reaction for Enzyme Immobilization(WILEY-V C H VERLAG GMBH, 2019) OKTAY, BURCU; Oktay, Burcu; Demir, Serap; Kayaman-Apohan, NilhanIn this study, a polyethylene glycol (PEG)-maleimide film was prepared by a thiol-ene click reaction. The covalent immobilization of amylase was carried out onto the PEG-maleimide based photo-curable network via epoxy and C=O groups without any linker. The epoxy and carbonyl groups on the PEG backbone improved the affinity of the enzyme. The immobilization yield of amylase onto the film was 72.46%. The immobilization capacity was also determined as 313 mg/g. The thermal stability of amylase improved via covalent attachment. Immobilized amylase showed maximum activity at 40 degrees C and pH 6.5. The immobilized amylase continued to retain 66% of its initial activity after 30 days.Publication Metadata only Alpha-Amylase Immobilization on Epoxy Containing Thiol-Ene Photocurable Materials(KOREAN SOC MICROBIOLOGY & BIOTECHNOLOGY, 2013) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Danis, Ozkan; Demir, Serap; Mulazim, Yusuf; Kahraman, Memet VezirThiol-ene polymerization is a versatile tool for several applications. Here we report the preparation of epoxide groups containing thiol-ene photocurable polymeric support and the covalent immobilization of alpha-amylase onto these polymeric materials. The morphology of the polymeric support was characterized by scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) coupled with SEM was used to explore the chemical composition. The polymeric support and the immobilization of the enzyme were characterized by FTIR analysis. SEM-EDS and FTIR results showed that the enzyme was successfully covalently attached to the polymeric support. The immobilization efficiency and enzyme activity of alpha-amylase were examined at various pH (5.0-8.0) and temperature (30-80 degrees C) values. The storage stability and reusability of immobilized alpha-amylase were investigated. The immobilization yield was 276 +/- 1.6 mg per gram of polymeric support. Enzyme assays demonstrated that the immobilized enzyme exhibited better thermostability than the free one. The storage stability and reusability were improved by the immobilization on this enzyme support. Free enzyme lost its activity completely within 15 days. On the other hand, the immobilized enzyme retained 86.7% of its activity after 30 days. These results confirm that alpha-amylase was successfully immobilized and gained a more stable character compared with the free one.Publication Metadata only Covalent immobilization of a-amylase onto thermally crosslinked electrospun PVA/PAA nanofibrous hybrid membranes(WILEY, 2013) KAHRAMAN, MEMET VEZİR; Basturk, Emre; Demir, Serap; Danis, Ozkan; Kahraman, Memet VezirPoly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) nanofibers with the fiber diameter of 100150 nanometers were fabricated by electrospinning. PVA/PAA nanofibers were crosslinked by heat-induced esterification and resulting nanofiber mats insoluble in water. a-Amylase was covalently immobilized onto the PVA/PAA nanofiber surfaces via the activation of amine groups in the presence of 1,1'-carbonyldiimidazole. The immobilized a-amylase has more resistance to temperature inactivation than that of the free form and showed maximum activity at 50 degrees C. pH-dependent activities of the free and immobilized enzymes were also investigated, and it was found that the pH of maximum activity for the free enzyme was 6.5, while for the optimal pH of the immobilized enzyme was 6.0. Reuse studies demonstrated that the immobilized enzyme could reuse 15 times while retaining 81.7% of its activity. Free enzyme lost its activity completely within 15 days. Immobilized enzyme lost only 17.1% of its activity in 30 days. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012