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: 36Citation - Scopus: 39Transesterification of Sunflower Oil on Single Step Sol-Gel Made Al2o3 Supported Cao Catalysts: Effect of Basic Strength and Basicity on Turnover Frequency(Elsevier Ltd., 2012) Umdu, Emin Selahattin; Şeker, ErolThe activities of single step sol-gel made calcium oxide on alumina catalysts were studied as a function of CaO loading, methanol/oil molar ratio and the amount of the catalyst in the transesterification of sunflower oil at 50°C. Also, the turnover frequency (TOF) of the catalysts was calculated to better understand the relationship between the basicity/basic strength and the catalytic activity. From volcano curve (TOF vs. basic strength), it was found that under 50°C and methanol/oil molar ratio of 9, 60% CaO/Al 2O 3 had the highest turnover frequency, 0.028s -1, whereas 85% CaO/Al 2O 3 showed the highest biodiesel yield, ∼96.6%, but TOF obtained on it was 0.012s -1. It seemed that 60% CaO catalyst had the proper basic strength to obtain the highest TOF. © 2011 Elsevier Ltd.Article Citation - WoS: 273Citation - Scopus: 327Transesterification of Nannochloropsis Oculata Microalga's Lipid To Biodiesel on Al2o3 Supported Cao and Mgo Catalysts(Elsevier Ltd., 2009) Umdu, Emin Selahattin; Tuncer, Mert; Şeker, ErolIn this study, we present the activities of Al2O3 supported CaO and MgO catalysts in the transesterification of lipid of yellow green microalgae, Nannochloropsis oculata, as a function of methanol amount and the CaO and MgO loadings at 50 °C. We found that pure CaO and MgO were not active and CaO/Al2O3 catalyst among all the mixed oxide catalysts showed the highest activity. Not only the basic site density but also the basic strength is important to achieve the high biodiesel yield. Biodiesel yield over 80 wt.% CaO/Al2O3 catalyst increased to 97.5% from 23% when methanol/lipid molar ratio was 30.Article Citation - WoS: 11Citation - Scopus: 16Partial Purification of Hen Egg White Lysozyme by Ethanol Precipitation Method and Determination of the Thermal Stability of Its Lyophilized Form(Türkiye Klinikleri Journal of Medical Sciences, 2007) Gemili, Seyhun; Umdu, Emin Selahattin; Yaprak, Nilgün; Üstok, Fatma Işık; Yener, Fatih Yalçın Güneş; Mecitoğlu Güçbilmez, Çiğdem; Altınkaya, Sacide; Yemenicioğlu, AhmetLysozyme was partially purified from hen egg white by precipitation of non-lysozyme protein impurities during incubation in the prence of ethanol. The thermal stability of the obtained partially purified enzyme was also characterized. The incubation of diluted egg white for 2-8 h in the presence of 20% ethanol was not very effective for the partial purification of lysozyme by precipitation of major egg white proteins; however, 4- to 6-h or 6-h to 8-h incubation of diluted egg white in the presence of 30% and 40% ethanol could be employed more effectively for partial purification of lysozyme. Without applying the incubation period, the highest specific activity was obtained by the treatment of egg white with 40% ethanol. Thus, ethanol at this concentration could be used for a continuous process of partial purification. For batch lysozyme purification, on the other hand, incubation in the presence of 30% ethanol was more appropriate. The activities and protein contents of dialyzed and lyophilized enzymes obtained by 6 h-incubation in the presence of 20%, 30%. and 40% ethanol precipitations were 1878, 6669, and 6115 U/mg powder, and 0.98, 0.90, and 0.93 mg protein per mg powder, respectively. The ranges of thermal inactivation parameters, such as D (D80°C = 29.2-59 min, D90°c = 8.8-21 min) and z (Z80-90°c = 17.4-22.3 °C) values of the enzyme, clearly indicated the moderate and variable heat stability of lyophilized lysozymes obtained from different batches of egg white.