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81.
Lyubov Yotova Irene Tzibranska Filadia Tileva G. H. Markx Nelly Georgieva 《Journal of industrial microbiology & biotechnology》2009,36(3):367-372
A simple method for the preparation of the biocatalyst with whole cells is presented, and the applicability of the technique
for biodegradation of phenol in wastewater from the chemical industries using the basidomycetes yeast Trichosporon cutaneum is explored. Kinetic studies of the influence of other compounds contained in wastewater as naphthalene, benzene, toluene
and pyridine indicate that apart from oil fraction, which is removed, the phenol concentration is the only major factor limiting
the growth of immobilized cells. Mathematical models are applied to describe the kinetic behavior of immobilized yeast cells.
From the analysis of the experimental curves was shown that the obtained values for the apparent rate parameters vary depending
on the substrate concentration (μmaxapp from 0.35 to 0.09 h−1 and K
sapp from 0.037 to 0.4 g dm−3). The inhibitory effect of the phenol on the obtained yield coefficients was investigated too. It has been shown that covalent
immobilization of T. cutaneum whole cells to plastic carrier beads is possible, and that cell viability and phenol degrading activity are maintained after
the chemical modification of cell walls during the binding procedure. The results obtained indicate a possible future application
of immobilized T. cutaneum for destroying phenol in industrial wastewaters. 相似文献
82.
Damiano G. Mita Nadia Diano Valentina Grano Marianna Portaccio Sergio Rossi Umberto Bencivenga Immacolata Manco Carla Nicolucci Mariangela Bianco Tiziana Grimaldi Luigi Mita Svetla Georgieva Tzonka Godjevargova 《Journal of Molecular Catalysis .B, Enzymatic》2009,58(1-4):199-207
Endocrine disruptors are chemicals able to induce adverse effects into wildlife and humans owing to their ability of interfering with the endocrine system. Bisphenol A (BPA) has been chosen as model of endocrine disruptors. To reduce the BPA pollution in waters we proposed the employment of the process of thermodialysis. Two different catalytic membranes have been prepared by covalently immobilizing laccase (from Trametes versicolor) by means of a diazotation process or tyrosinase (from mushroom) by condensation. The support was a nylon membrane. The bioremediation power of both catalytic membranes has been analysed under isothermal and non-isothermal conditions.The advantages in using non-isothermal bioreactors were discussed in terms of reduction of the bioremediation times. 相似文献
83.
84.
K. Georgieva A. Ivanova S. Doncheva S. Petkova D. Stefanov E. Péli Z. Tuba 《Biologia Plantarum》2011,55(3):581-585
Desiccation of Xerophyta scabrida caused considerable damage of chloroplast ultrastructure together with a complete loss of chlorophyll. Upon rehydration,
the relative water content of the pale-green leaves almost reached that of the dark-green ones, however, the Chl content and
photosynthetic activity remained lower. The process of reconstitution of the photosynthetic apparatus in the re-greening leaves
was accompanied by changes in fatty acid (FA) content. The amount of the FA methyl esters was more than 2-fold higher in the
green leaves as compared to the dry ones and slightly increased after rehydration in the pale-green leaves. Among the three
main fatty acids in the leaves, oleic, palmitic and linoleic acid, the latter increased more than 3-fold during rehydration.
This acid is concentrated mainly in the glycolipids and this was an indirect indication for the restoration of the photosynthetic
apparatus. Our results showed that rehydration of X. scabrida led to a decrease of the saturated FA in parallel with an increase of the unsaturated FA, thus indicating increased membrane
permeability. The observed changes in the lipid content can be considered as a characteristic feature of X. scabrida and most probably of other poikilochlorophyllous species. 相似文献
85.
The reaction mechanism of mycolic acid cyclopropane synthase is investigated using hybrid density functional theory. The direct methylation mechanism is examined with a large model of the active site constructed on the basis of the crystal structure of the native enzyme. The important active site residue Glu140 is modeled in both ionized and neutral forms. We demonstrate that the reaction starts via the transfer of a methyl to the substrate double bond, followed by the transfer of a proton from the methyl cation to the bicarbonate present in the active site. The first step is calculated to be rate-limiting, in agreement with experimental kinetic results. The protonation state of Glu140 has a rather weak influence on the reaction energetics. In addition to the natural reaction, a possible side reaction, namely a carbocation rearrangement, is also considered and is shown to have a low barrier. Finally, the energetics for the sulfur ylide proposal, which has already been ruled out, is also estimated, showing a large energetic penalty for ylide formation. 相似文献
86.
87.
The aim of the present study was to establish whether there is dependence of vascular reactivity to mental stress on the levels of neuroticism and anxiety in left- and right-handers. Thirty-two left-handed and 32 righthanded volunteers (16 males and 16 females in each group) between 18 and 30 years of age were studied. During mental stress both groups demonstrated a "standard" type of response, indicating an increase of the sympathetic-adrenal activity. In left-handers, however, the magnitude of the stress vascular reactivity was significantly higher (p<0.05) in comparison with that of right-handers. In left-handed females a moderate negative correlation between vascular reactivity and the levels of neuroticism (r = -0.39) and trait anxiety (r = -0.47, F = 4.04, p = 0.06) was established. In right-handed males a moderate positive correlation between neuroticism and vascular reactivity (r = 0.35) and significant positive correlation between trait anxiety and vascular reactivity (r = 0.60, F = 7.92, p = 0.01) was found. The results obtained show that vascular reactivity to mental stress is not influenced in a specific to left- and right-handers way by the levels of negative emotionality (neuroticism and trait anxiety). 相似文献
88.
89.
Georgieva MV de Pablo Y Sanchis D Comella JX Llovera M 《Journal of neurochemistry》2011,117(3):479-493
The nerve growth factor receptor TrkA (tropomyosin-related kinase receptor) participates in the survival and differentiation of several neuronal populations. The C-terminal tail of TrkA contains a PPXY motif, the binding site of the E3 ubiquitin-ligase Nedd4-2 (neural precursor cell expressed, developmentally down-regulated 4-2). In order to analyze the role of Nedd4-2 ubiquitination on TrkA function, we generated three TrkA mutants, by introducing point mutations on conserved hydrophobic amino acids - Leu784 and Val790 switched to Ala. TrkA mutants co-localized and co-immunoprecipitated more efficiently with Nedd4-2 and consequently a strong increase in the basal multimonoubiquitination of the mutant receptors was observed. In addition, we found a decrease in TrkA abundance because of the preferential sorting of mutant receptors towards the late endosome/lysosome pathway instead of recycling back to the plasma membrane. Despite the reduction in the amount of membrane receptor caused by the C-terminal changes, TrkA mutants were able to activate signaling cascades and were even more efficient in promoting neurite outgrowth than the wild-type receptor. Our results demonstrate that the C-terminal tail hydrophobicity of TrkA regulates Nedd4-2 binding and activity and therefore controls receptor turnover. In addition, TrkA multimonoubiquitination does not interfere with the activation of signaling cascades, but rather potentiates receptor signaling leading to differentiation. 相似文献