Yazar "Kahraman, H" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim Yok
    Öğe
    Degradation of benzene, toluene and xylene by Pseudomonas aeruginosa engineered with the Vitreoscilla hemoglobin gene
    (Wiley, 2005) Kahraman, H; Geckil, H
    This study concerns the potential use of Pseudomonas aeruginosa expressing the Vitreoscilla hemoglobin gene for the degradation of important harmful aromatic compounds such as benzene, toluene, and xylene (BTX). The use of these compounds by both strains was determined as the production of cell mass (viable cell number) in a minimal medium containing any one of the BTX compounds as the sole carbon and energy source. Furthermore, the BTX degradation capability of both strains was monitored by measuring the production of 3-methylcatechol, a common intermediate. For the cells of the logarithmic phase, which were grown at high aeration/high agitation or low aeration/low agitation, the engineered strain showed a better growth rate than the host strain. With the benzene in the medium, the recombinant strain exhibited a higher (up to 4-fold) cell density than the parental wild-type strain at this phase. In contrast, regarding the cells of the late stationary phase under high aeration/high agitation conditions, the host strain had generally higher viable cell numbers than the recombinant strain. At this phase this difference was, however, less significant under the conditions of low aeration/low agitation. Similarly, in toluene containing medium (at high aeration/high agitation) the recombinant strain showed a higher cell density which was from a 15-fold to almost one order of magnitude greater than its parental strain during the logarithmic phase where the cell density of P aeruginosa remained nearly constant. Contrary to the results with benzene and toluene, both strains exhibited similar growth characteristics when they were grown in the presence of xylene. The positive effect of the oxygen uptake by the recombinant system on the BTX metabolizing activity was also apparent in a high accumulation of 3-methylcatechol in the cultures of the recombinant strain. At certain points of incubation, the hemoglobin expressing strain showed a significantly (p < 0.05) higher 3-methylcatechol accumulation than the host strain. These results demonstrated the possible potential of the Vitreoscilla hemoglobin as an efficient oxygen uptake system for the bioremediation of some compounds of environmental concern.
  • Küçük Resim Yok
    Öğe
    Genetic engineering of Enterobacter aerogenes with the Vitreoscilla hemoglobin gene
    (Elsevier, 2003) Geckil, H; Gencer, S; Kahraman, H; Erenler, SO
    Hemoglobins in unicellular organisms, like the one here in the bacterium Vitreoscilla, have greater chemical reactivity than their homologues in multicellular organisms. They can catalyze redox reactions and may protect cells against oxidative stress. The ability of Vitreoscilla hemoglobin to complement deficiencies of terminal cytochrome oxidases in Escherichia coli also suggests that this hemoglobin can receive electrons during respiration. In this study, a recombinant strain of Enterobacter aerogenes engineered to produce the Vitreoscilla Hb was investigated with regard to its susceptibility to oxidative stress. The culture response to oxidative stress produced by exogenously applied hydrogen peroxide was characterized in terms of cell growth, survival and the activities of two key antioxidant enzymes (catalase and superoxide dismutase). The influence of the physiological state of the cells and different media upon these culture dynamics was determined. Results showed that the hemoglobin-expressing strain is quite distinct in terms of growth/survival properties and activity of antioxidant enzymes from that of non-hemoglobin counterparts. (C) 2003 Editions scientitiques et medicales Elsevier SAS. All rights reserved.