Browsing by Subject "Composition effects"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Effect of oxygen supply on metabolism of immobilized and suspended Escherichia coli
    (John Wiley & Sons Inc, New York, NY, United States, 1996) Inanç, E.; Miller J. E.; DiBiasio, D.
    The effect of reduced oxygen supply on the production of a recombinant protein (plasmid-encoded β-galactosidase) was investigated in Escherichia coli. A novel modified bubble tank reactor was used to provide a direct comparison between immobilized and suspended cells in identical environments except for the immobilization matrix. Decreased oxygen supply led to increased β-galactosidase synthesis by both immobilized and suspended cells. Immobilized cells produced similar amounts of β-galactosidase as the suspended cells. Lactose consumption and acetate production, on a per cell basis, were significantly higher in immobilized cells, suggesting that immobilized cells utilized fermentative metabolism. However, a transport analysis of the immobilized cell system showed that immobilized cells were not subject to either external or internal mass transfer gradients.The effect of reduced oxygen supply on the production of a recombinant protein (plasmid-encoded β-galactosidase) was investigated in Escherichia coli. A novel modified bubble tank reactor was used to provide a direct comparison between immobilized and suspended cells in identical environments except for the immobilization matrix. Decreased oxygen supply led to increased β-galactosidase synthesis by both immobilized and suspended cells. Immobilized cells produced similar amounts of β-galactosidase as the suspended cells. Lactose consumption and acetate production, on a per cell basis, were significantly higher in immobilized cells, suggesting that immobilized cells utilized fermentative metabolism. However, a transport analysis of the immobilized cell system showed that immobilized cells were not subject to either external or internal mass transfer gradients.
  • Thumbnail Image
    ItemOpen Access
    Sorption studies of Cs+ and Ba2+ cations on magnesite
    (Elsevier, 1998-05-11) Shahwan, T.; Süzer, Şefik; Erten, H. N.
    The adsorption behavior of Cs+ and Ba2+ cations on magnesite has been studied as a function of time, cation concentration and temperature, utilizing both the radiotracer method and X-ray photoelectron spectroscopy (XPS). Saturation was approached in about I day for both cations. The sorption data were found to follow Freundlich type isotherms. Sorption of both Cs+ and Ba2+ cations were found to be exothermic in nature with ΔH0 (kJ/mol) of -37, -13 and ΔS0 (kJ/mol·K) of -0.09, -0.009, respectively. Negative ΔG0 values were obtained for both cations, indicating the spontaneity of their sorption on magnesite. The magnitude of ΔG0 suggest that ion exchange is the dominating sorption mechanism. The adsorption behavior of Cs+ and Ba2+ cations on magnesite has been studied as a function of time, cation concentration and temperature, utilizing both the radiotracer method and X-ray photoelectron spectroscopy (XPS). Saturation was approached in about 1 day for both cations. The sorption data were found to follow Freundlich type isotherms. Sorption of both Cs+ and Ba2+ cations were found to be exothermic in nature with ΔH0 (kJ/mol) of -37, -13 and ΔS0 (kJ/mol·K) of -0.09, -0.009, respectively. Negative ΔG0 values were obtained for both cations, indicating the spontaneity of their sorption on magnesite. The magnitude of ΔG0 suggest that ion exchange is the dominating sorption mechanism.