Yazar "Tukel, S. Seyhan" seçeneğine göre listele

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    Kinetic properties and storage stability of catalase immobilized on to florisil
    (Natl Inst Science Communication-Niscair, 2007) Ozyilmaz, Gul; Tukel, S. Seyhan; Alptekin, Ozlem
    The covalent immobilization of bovine liver catalase (CAT) oil to florisil via glutaraldehyde was investigated. Optimum immobilization pH and temperature were determined as pH 6.0, 10 degrees C respectively, while the amount of initial CAT per, of carrier and immobilization time was determined as 5 mg . g(-1) and 120 min, respectively. The V-max values for free and immobilized CAT were found to be 1.7 x 10(5) and 2.0 x 10(4) mu mol H2O2 . min(-1) mg protein(-1), respectively, whereas K-M values were 33.3 mM and 1722.0 mM respectively. Operational stability was determined by using a stirred batch-type column reactor. Immobilized CAT retained about 40% of its initial activity after 50 uses. It showed higher storage stability than free CAT at 4 degrees C and 25 degrees C. Its storage stability increased with increasing relative humidity (RH) from 0 to 20% of the medium. The highest storage stability was obtained in 20% RH, however, further increase in RH from 40 to 100% significantly decreased the storage stability.
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    Simultaneous and sequential co-immobilization of glucose oxidase and catalase onto florisil
    (Korean Soc Microbiology & Biotechnology, 2007) Ozyilmaz, Gul; Tukel, S. Seyhan
    The co-immobilization of Aspergillus niger glucose oxidase (GOD) with bovine liver catalase (CAT) onto florisil (magnesium silicate-based porous carrier) was investigated to improve the catalytic efficiency of GOD against H2O2 inactivation. The effect of the amount of bound CAT on the GOD activity was also studied for 12 different initial combinations of GOD and CAT, using simultaneous and sequential coupling. The sequentially co-immobilized GOD-CAT showed a higher efficiency than the simultaneously co-immobilized GOD-CAT in terms of the GOD activity and economic costs. The highest activity was shown by the sequentially co-immobilized GOD-CAT when the initial amounts of GOD and CAT were 10 mg and 5 mg per gram of carrier. The optimum pH, buffer concentration, and temperature for GOD activity for the same co-immobilized GOD-CAT sample were then determined as pH 6.5, 50 mM, and 30 degrees C, respectively. When compared with the individually immobilized GOD, the catalytic activity of the co-immobilized GOD-CAT was 70% higher, plus the reusability was more than two-fold. The storage stability of the co-immobilized GOD-CAT was also found to be higher than that of the free form at both 5 degrees C and 25 degrees C. The increased GOD activity and reusability resulting from the co-immobilization process may have been due to CAT protecting GOD from inactivation by H2O2 and supplying additional O-2 to the reaction system.