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Öğe Enantioselective enzymatic hydrolysis of racemic drugs by encapsulation in sol-gel magnetic sporopollenin(SPRINGER, 2012) Yilmaz, ElifCandida rugosa lipase was encapsulated within a sol-gel procedure and improved considerably by fluoride-catalyzed hydrolysis of mixtures of octyltriethoxysilane and tetraethoxysilane in the presence of magnetic sporopollenin. The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e., the hydrolysis of p-nitrophenylpalmitate (p-NPP), and the enantioselective hydrolysis of racemic naproxen methyl ester, mandelic acid methyl ester or 2-phenoxypropionic acid methyl ester that were studied in aqueous buffer solution/isooctane reaction system. The encapsulated magnetic sporopollenin (Spo-M-E) was found to give 319 U/g of support with 342% activity yield. It has been observed that the percent activity yields and enantioselectivity of the magnetic sporopollenin encapsulated lipase were higher than that of the encapsulated lipase without support. The substrate specificity of the encapsulated lipase revealed more efficient hydrolysis of the racemic naproxen methyl ester and 2-phenoxypropionic acid methyl ester than racemic mandelic acid methyl ester. It was observed that excellent enantioselectivity (E > 400) was obtained for encapsulated lipase with magnetic sporopollenin with an ee value of S-Naproxen and R-2 phenoxypropionic acid about 98%.Öğe Enhancement of the Activity and Enantioselectivity of Lipase by Sol-Gel Encapsulation Immobilization onto beta-cyclodextrin-Based Polymer(SPRINGER, 2012) Yilmaz, Elif; Sezgin, MehmetCandida rugosa lipase was encapsulated within a chemically inert sol-gel support prepared by polycondensation with tetraethoxysilane and octyltriethoxysilane in the presence of beta-cyclodextrin-based polymer. The catalytic activity of the encapsulated lipases was evaluated both in the hydrolysis of p-nitrophenylpalmitate and the enantioselective hydrolysis of racemic Naproxen methyl ester. It has been observed that the percent activity yield of the encapsulated lipase was 65 U/g, which is 7.5 times higher than that of the covalently immobilized lipase. The beta-cyclodextrin-based encapsulated lipases had higher conversion and enantioselectivity compared with covalently immobilized lipase. The study confirms an excellent enantioselectivity (E > 300) for the encapsulated lipase with an enantiomeric excess value of 98% for S-naproxen.Öğe Immobilization of Candida rugosa lipase on glass beads for enantioselective hydrolysis of racemic Naproxen methyl ester(ELSEVIER SCI LTD, 2011) Yilmaz, Elif; Can, Keziban; Sezgin, Mehmet; Yilmaz, MustafaCandida rugosa lipase (CRL) was immobilized on glutaraldehyde-activated aminopropyl glass beads by using covalent binding method or sal-gel encapsulation procedure and improved considerably by fluoride-catalyzed hydrolysis of mixtures of RSi(OCH3)(3) and Si(OCH3)(4). The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP). It has been observed that the percent activity yield of the encapsulated lipase was 166.9, which is 5.5 times higher than that of the covalently immobilized lipase. The enantioselective hydrolysis of racemic Naproxen methyl ester by immobilized lipase was studied in aqueous buffer solution/isooctane reaction system and it was noticed that particularly, the glass beads based encapsulated lipases had higher conversion and enantioselectivity compared to covalently immobilized lipase. In short, the study confirms an excellent enantioselectivity (E > 400) for the encapsulated lipase with an ee value of 98% for S-Naproxen. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Immobilization of Candida rugosa lipase on magnetic sol-gel composite supports for enzymatic resolution of (R,S)-Naproxen methyl ester(ELSEVIER, 2011) Yilmaz, Elif; Sezgin, Mehmet; Yilmaz, MustafaIn the present study, the Candida rugosa lipase (CRL) was encapsulated within a chemically inert sol-gel support prepared by polycondensation with tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) in the presence and absence of magnetic Fe3O4 nanoparticles or sporopollenin with Fe3O4 as additive. The catalytic properties of the immobilized lipases were evaluated through model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP), and the enantioselective hydrolysis of racemic Naproxen methyl ester that was studied in aqueous buffer solution/isooctane reaction system. The results indicate that the sporopollenin based encapsulated lipase (Fe3O4-Spo-E) particularly has higher conversion and enantioselectivity compared to the encapsulated lipase without supports (lipase-enc). It has also been noticed that the sporopollenin based encapsulated lipase has excellent enantioselectivity (E = > 400) as compared to the free enzyme (E = 166) with an ee value of similar to 98% for S-Naproxen. (C) 2010 Elsevier B.V. All rights reserved.Öğe Immobilization of Candida rugosa lipase on sporopollenin from Lycopodium clavatum(ELSEVIER, 2009) Tutar, Havva; Yilmaz, Elif; Pehlivan, Erol; Yilmaz, MustafaSporopollenin is a natural polymer obtained from Lycopodium clavatum, which is highly stable with constant chemical structure and has high resistant capacity to chemical attack. In this study, immobilization of lipase from Candida rugosa (CRL) on sporopollenin by adsorption method is reported for the first time. Besides this, the enzyme adsorption capacity, activity and thermal stability of immobilized enzyme have also been investigated. It has been observed that under the optimum conditions (Spo-E-(0.3)), the specific activity of the immobilized lipase on the sporopollenin by adsorption was 16.3 U/mg protein, which is 0.46 times less than that of the free lipase (35.6 U/mg protein). The pH and temperature of immobilized enzyme were optimized, which were 6.0 and 40 degrees C respectively. Kinetic parameters V-max and K-m were also determined for the immobilized lipase. It was observed that there is an increase of the K-m value (7.54 mM) and a decrease of the V-max value (145.0 U/mg-protein) comparing with that of the free lipase. (C) 2009 Elsevier B.V. All rights reserved.Öğe Immobilized copper-ion affinity adsorbent based on a cross-linked beta-cyclodextrin polymer for adsorption of Candida rugosa lipase(TAYLOR & FRANCIS LTD, 2009) Yilmaz, Elif; Sezgin, Mehmet; Yilmaz, MustafaLipase from Candida rugosa was immobilized on a beta-cyclodextrin-based polymer by adsorption and subsequent cross-linking with epichlorohydrin (EP-CD). The ligand iminodiacetic acid (IDA) was then bonded with the cross-linked beta-cyclodextrin (EP-CD-IDA). This affinity adsorbent was further chelated with Cu2+ for the purpose of binding affinity and stability. The properties of the immobilized lipase were assayed and compared with those of the free enzyme. Results showed that 266 mu g protein with an activity of 17.85 U was bound per gram of matrix, giving 188% of the specific activity of the free enzyme and a total recovered activity of 79.7% under the optimum conditions. The pH and thermal stabilities of lipase were improved after immobilization on the beta-cyclodextrin-based polymer (EP-CD-IDA-Cu2+). In addition, experimental results indicated that the residual activity of the immobilized lipase was 50% after eight cycles of reuse.Öğe Improvement of catalytic properties of Candida Rugosa lipase by sol-gel encapsulation in the presence of magnetic calix[4]arene nanoparticles(ROYAL SOC CHEMISTRY, 2011) Sayin, Serkan; Yilmaz, Elif; Yilmaz, MustafaCandida rugosa lipase (CRL) was encapsulated within a chemically inert sol-gel support prepared by polycondensation with tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) in the presence of N-methylglucamine based calix[4]arene magnetic nanoparticles. The results indicate that the magnetic calix[4]arene based encapsulated lipase particularly has shown high conversion and enantioselectivity. It has also been noticed that the magnetic calix[4]arene based encapsulated lipase has excellent enantioselectivity (E = 460) as compared to the free enzyme (E = 166) with an ee value of >98% for S-Naproxen.Öğe Preparation and characterization of pH-sensitive semi-interpenetrating network hybrid hydrogels with sodium humate and kaolin(ELSEVIER SCIENCE BV, 2018) Yilmaz, Elif; Kaya, Gulcihan Guzel; Deveci, HuseyinPoly(acrylamide-co-methacrylic acid) semi-interpenetrating network (semi-IPN) hybrid hydrogels including sodium humate and kaolin were successfully synthesized as confirmed with X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR) analyses. Scanning electron microscopy (SEM) analysis indicated uniform dispersed morphology of the hydrogels. It was specified with thermogravimetric-derivative thermogravimetric analysis (TGA-DTG) that the addition of kaolin provided to increase thermal decomposition temperatures of the hydrogels. The semi-IPN hybrid hydrogel exhibited highest equilibrium swelling percent (ESP) of 28,700% and 3440% in distilled water and 0.1 M NaCl, respectively. The hydrogels had better swelling behavior in basic medium compared to acidic medium. While the ESP value of semi-IPN hybrid hydrogel was about 1590% at pH 2, it was determined as 7046% at pH 9. Each hydrogel showed non-Fickian type diffusion and excellent biocompatibility (> 0.94). The results suggested that the obtained pH-sensitive semi-IPN hydrogels with unique properties can be used as biomaterial, adsorbent, membrane, sensor component and so on.Öğe Removal of azo dyes from aqueous solutions using calix[4]arene and beta-cyclodextrin(ELSEVIER SCI LTD, 2007) Yilmaz, Aydan; Yilmaz, Elif; Yilmaz, Mustafa; Bartsch, Richard A.A calix[4]arene-based oligomer 5 and a P-cyclodextrin polymer 6 were synthesized by the condensation of p-tert-butylcalix[4]arene and beta-cyclodextrin, respectively, with hexamethylene diisocyanate. In their batch sorption of selected azo dyes, the beta-cyclodextrin polymer 6 was found to be a better azo dye sorbent than the p-tert-butylcalix[4]arene-based oligomer 5. In addition, oligomer 4 containing pendant calix[4]arene units with crown-6 functionalities on the lower rim was synthesized and its complexation of the azo dyes was investigated by liquid-liquid extraction. The calix[4]crown-6 oligomer 4 showed the highest affinity for the azo dyes. (c) 2006 Elsevier Ltd. All rights reserved.Öğe Sustainable bean pod/calcined kaolin reinforced epoxy hybrid composites with enhanced mechanical, water sorption and corrosion resistance properties(ELSEVIER SCI LTD, 2018) Kaya, Gulcihan Guzel; Yilmaz, Elif; Deveci, HuseyinThe industrial and academic world is becoming more interested in advanced composite materials owing to the increasing global awareness on environmental and social issues. From this point of view, novel epoxy hybrid composites were prepared by utilizing bean pod as an agricultural waste and calcined kaolin with the addition of varying ratios (0.5-5.0 wt%) to fixed weight of 3 wt% bean pod. The resulting hybrid composites were characterized by different analyses and tests to evaluate physico-mechanical and thermal properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed uniform dispersion of hybrid filler in the neat epoxy resin which revealed better compatibility between hybrid filler and epoxy resin. Tensile strength of hybrid composite including 2 wt% calcined kaolin (39.8 MPa) was higher than those of the other hybrid composites. The water sorption percentage of the hybrid composites was effectively decreased until 0.87% with increasing amount of calcined kaolin. The hybrid composite including 5 wt% calcined kaolin exhibited highly corrosion resistance to alkali and salty solutions compared to acidic reagents. Thermogravimetric analyses (TGA) and vicat softening temperature (VST) tests revealed that an important improvement was not observed in degradation temperatures of the hybrid composites; however, residue at 650 degrees C increased up to 21.0% in the presence of calcined kaolin. It can be said that the hybrid composites mentioned above came into prominence with high tensile strength, quite low water uptake and excellent corrosion resistance in alkali and salty environments. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Sustainable nanocomposites of epoxy and silica xerogel synthesized from corn stalk ash: Enhanced thermal and acoustic insulation performance(ELSEVIER SCI LTD, 2018) Kaya, Gulcihan Guzel; Yilmaz, Elif; Deveci, HuseyinThe synthesis of silica xerogel from corn stalk ash in ambient pressure drying was carried out by sol-gel method. With the usage of silica xerogel (0.5, 1.0 and 1.5 wt%) in epoxy resin (ER), silica xerogel/epoxy nanocomposites were successfully prepared. The uniform dispersion of silica xerogel in neat ER was observed except nano composite including 1.5 wt% silica xerogel. The low density nanocomposites showed high thermal stability and low thermal conductivity. The char residue at 600 degrees C and thermal conductivity of nanocomposite including 1.5 wt% silica xerogel were specified as 20.30% and 0.220 W/mK, respectively. The acoustic velocity of the nanocomposites was decreased with increasing amount of silica xerogel. The water sorption of the nano composites was slightly higher than neat ER. The water contact angle of the nanocomposites were between 75 degrees and 70 degrees. The study provided a new thermal and acoustic insulation material instead of expensive and health risk traditional materials.
