Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 23Citation - Scopus: 26Cr(vi) Sorption by Using Clinoptilolite and Bacteria Loaded Clinoptilolite Rich Mineral(Elsevier Ltd., 2012) Cansever Erdoğan, Beyhan; Ülkü, SemraBatch sorption experiments were performed in order to understand the potential value of local clinoptilolite rich mineral and its bacteria loaded form in Cr(VI) sorption. The results indicated that Cr(VI) sorption capacities of the sorbents were increased after bacteria loading and the clinoptilolite rich mineral is a promising material in Cr(VI) sorption. Zeta potential and Fourier Transform IR (FTIR) analysis were performed to explain the possible mechanism involved in the Cr(VI) sorption. The results revealed that non-electrostatic forces played a significant role rather than the electrostatic forces. The existence of non-electrostatic forces was confirmed by the FTIR results. © 2011 Elsevier Inc. All rights reserved.Article Citation - WoS: 18Citation - Scopus: 21Evaluation of Heat Treated Clay for Potential Use in Intervention Mortars(Elsevier Ltd., 2010) Budak, Meral; Akkurt, Sedat; Böke, HasanIn this study, raw material compositions, basic physical, mineralogical, microstructural and hydraulic properties of lime mortars used in two selected historic buildings were determined by XRD, SEM-EDS and TGA analyses. The results showed that the mortars were hydraulic due to the use of pozzolanic aggregates. Taking into account the hydraulic characteristics of mortars due to the use of pozzolanic aggregates, the possibility of obtaining hydraulic mortars by using pozzolanic aggregates produced from heated commercial clays was investigated. For this purpose, four clay samples used in the ceramic industry in Turkey were heated at varying temperatures of 400, 450, 500, 550, 600, 800, and 1200°C with a heating rate of 10°C/min. Pozzolanic properties of heated clay samples were determined. The results showed that commercial clays studied are well suited for use as pozzolanic aggregates when they are heated between 500 and 700. °C. This is also confirmed by testing the compressive strengths of the three month aged laboratory-produced mortars that contained thermally treated clay (at 600°C) as pozzolanic aggregates. Compressive strength of this mortar was around 5. MPa which is satisfactorily high. © 2009 Elsevier B.V.Article Citation - WoS: 23Citation - Scopus: 26Partial Purification and Preparation of Bovine Lactoperoxidase and Characterization of Kinetic Properties of Its Immobilized Form Incorporated Into Cross-Linked Alginate Films(Elsevier Ltd., 2007) Mecitoğlu, Çiğdem; Yemenicioğlu, AhmetLactoperoxidase (LPS), purified directly from bovine rennet whey by Toyopearl-SP cation-exchange chromatography and lyophilized by using dextran as supporting material, maintained almost 70 and 60% of its activity after almost 2 and 5 months storage at -18 °C, respectively. Incorporation of the prepared LPS into alginate films between 0.08 and 0.69 mg/cm2 (516-4325 U/cm2) caused the immobilization of most of the enzyme and gave films with LPS activity between 0.05 and 2.8 U/cm2, determined in the presence of 8 μM H2O2. Between 2 and 24 μM H2O2 concentrations, a two-fold increase in H2O2 concentration caused 1.5-2.5-fold increase in LPS activity of films incorporated with 0.24-0.28 mg/cm2 (1200 U/cm2) LPS. The Q10 and Ea of immobilized enzyme activity between 4 and 16 °C were 1.69 and 34.6 kJ/mol, respectively. However, in the 16-30 °C range, the temperature change had almost no effect on LPS activity of films. The optimal activity of immobilized LPS was observed at pH 6.0, but the enzyme maintained 30-85% of its activity between pH 3.0 and 7.0. The immobilized LPS also had a high stability between pH 4.0 and 6.0. The results of this study showed the good potential of LPS-incorporated alginate films in forming a natural antimicrobial mechanism in different foods.Article Citation - WoS: 21Citation - Scopus: 29Partial Purification and Kinetic Characterization of Mushroom Stem Polyphenoloxidase and Determination of Its Storage Stability in Different Lyophilized Forms(Elsevier Ltd., 2007) Şimşek, Şebnem; Yemenicioğlu, AhmetMonophenolase (1011 ± 626 U/g AP) and diphenolase activities (5163 ± 3059 U/g AP) of PPO in acetone powders (APs) of different mushroom stems varied considerably. However, the limited variation of average dipenolase (L-DOPA) to monophenolase (L-tyrosine) activity ratio (5.4 ± 0.7) in crude extracts showed the homogeneity of PPO from different mushroom stems. The change in extraction material or partial purification method (ammonium sulfate or acetone precipitation) did not affect the temperature stability, temperature and pH dependency and Km of monophenolase activity considerably. However, some changes were observed in pH stability and substrate specificity of PPO in different parties of mushroom stems. The most important aspects of mushroom stem PPO are its lower diphenolase to monophenolase activity ratio than mushroom cap PPO, low temperature dependency of activity between 25 and 40 °C (Ea = 30 kJ/mol), broad optimum pH between 6 and 8, but lack of activity pH ≤5, and ability to use phloridzin as substrate. The mushroom stem PPOs partially purified and lyophilized by using sucrose, dextran or alginate showed moderate to high stability at -18 °C for 6-6.5 months. Thus, the mushroom stems obtained as a waste material during mushroom processing may be used as a more homogenous source than whole mushrooms to obtain PPO used for different industrial, clinical or research purposes.Article Citation - WoS: 44Citation - Scopus: 50Thermal Behaviour of a Zeolitic Tuff(Elsevier Ltd., 2007) Çağlar Duvarcı, Özlem; Akdeniz, Yelda; Özmıhçı Ömürlü, Filiz; Ülkü, Semra; Balköse, Devrim; Çiftçioğlu, MuhsinNatural zeolites undergo structural changes after heating which open their possible use in different fields, related to their chemical and physical properties, such as building stone, lightweight aggregate, ceramic foam, concrete bricks, tiles, porcelain stoneware and additive in puzzolonic cements. In this study, thermal behavior of zeolitic tuff quarried from Gördes-Manisa, region of Turkey was investigated. Zeolitic rocks were first reduced to 2 μm and pellets were prepared by dry-pressing. The pellets were heated for 30 min in the temperature range of 200-1200 °C. Heating the tuff up to 600 °C did not cause any structural change detectable by X-Ray powder diffraction (X-Ray), Fourier Transform Infrared Spectroscopy (FTIR) and thermal characterization methods with regard to the original sample, while further increase in the temperature caused structural breakdown of zeolitic tuff. The appearance of the broad low intensity peaks in X-Ray diffraction diagrams indicated most probably a partial transformation of crystal structure into an amorphous structure. The Scanning Electron Microscopy (SEM) micrographs showed that the crystals seen in the original rock sample were broken during grinding and pressing processes. The crystal structure disappeared above 1000 °C and the spherical pores was observed at 1200 °C. Chemical composition of the zeolitic tuff did not change significantly with respect to temperature. The highest density (2.28 g/cm3) and hardness (387 Hv) were obtained by sintering the pellets at 1000 °C for 30 min.