Yazar "Senyay-Oncel D." seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim Yok
    Öğe
    Activity and stability enhancement of ?-amylase treated with sub- and supercritical carbon dioxide
    (2011) Senyay-Oncel D.; Yesil-Celiktas O.
    Various physical, chemical and genetic approaches have been applied in order to enhance enzyme stability and activity. In this study, the aim was to investigate the capability of sub- and supercritical carbon dioxide to alter the stability and activity of ?-amylase as an alternative technique. The effects of operational parameters such as pressure (50-300bar), temperature (28-80°C), CO 2 flow (2-10gmin -1) and time (60-180min) were evaluated in regard to the activity and stability of fungal based ?-amylase from Aspergillus oryzea. The activity of untreated enzyme was determined as 17,726µmol/ml/min. While both sub- and supercritical conditions enhanced the activity, the increase in flow rate had an adverse effect and the activity was decreased by 28.9% at a flow rate of 10gmin -1 under supercritical conditions. Nuclear magnetic resonance (NMR) spectra of untreated enzyme and treated samples exhibiting the lowest and the highest activities were almost identical except for the chemical shifts observed at the lowest activity sample from 4.0 to 4.4ppm which were assigned to protons of hydrogen-bonded groups. Optimum conditions were determined as 240bar, 41°C, 4gmin -1 CO 2 flow and 150min of process duration yielding 67.7% (29,728µmol/ml/min) higher activity than the untreated enzyme providing fundamental basis for enzymatic applications. © 2011 The Society for Biotechnology, Japan.
  • Küçük Resim Yok
    Öğe
    Treatment of immobilized ?-amylase under supercritical CO2 conditions: Can activity be enhanced after consecutive enzymatic reactions?
    (2013) Senyay-Oncel D.; Yesil-Celiktas O.
    Various approaches have been applied in order to enhance enzyme stability and activity. In this study, the aim was to investigate the capability of supercritical carbon dioxide (SC-CO2) to alter the activity of ?-amylase after consecutive enzymatic reactions. Therefore, ?-amylase from Aspergillus oryzae initially treated with SC-CO2 (29.7 mmol ml-1 min-1) was immobilized in Ca-alginate beads and NaY zeolite, subsequently assayed several times for the hydrolysis of soluble starch and when a lower activity value was recorded compared to the initial activity of the untreated enzyme (17.7 mmol ml-1 min -1), the immobilized samples were retreated with SC-CO2. These consecutive reactions and treatment loops were repeated till the activity cannot be increased with SC-CO2 retreatment in comparison to the initial activity of the untreated enzyme. The best results were achieved with NaY zeolite immobilized samples where four successful loops and seventeen reactions were realized till the residual activity. © 2013 Elsevier B.V. All rights reserved.