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The majority of mycotoxins produced by Aspergillus fungi are immunosuppressive agents, and their cytotoxicity may impair defense mechanisms in humans. The objective of the study was evaluation of the cytotoxicity of fungi isolated from an environment where inpatients with impaired immunity were present. The materials comprised 57 fungal strains: Aspergillus fumigatus, Aspergillus niger. Aspergillus ochraceus, Aspergillus flavus, Aspergillus versicolor and Aspergillus ustus isolated from hospital rooms in Cracow. The cytotoxicity of all the strains was evaluated using the MTT test (3-(4,5-dimethylthiazol-2-yl) 2,5 diphenyltetrazolium bromide). To emphasize the differences in cytotoxicity among the particular strains, variance analysis (ANOVA) and Tukey's difference test were used. Out of 57 Aspergillus strains tested, 48 (84%) turned out to be cytotoxic. The cytyotoxicity was high (+++) in 21 strains, mainly in A. fumigatus. The least cytotoxic were A. niger fungi, this being statistically significant (p<0,05). To protect a patient from the adverse effects of mycotoxins, not only his or her immunity status should be evaluated but also the presence of fungi in hospital environment and their cytotoxicity should be monitored (possible exposure).
Microbial conversions are gaining importance in the synthesis of important drug metabolites and their intermediates as they are good alternative to chemical synthesis since they are enantio-selective and regio-selective and even can be carried out at ambient temperature and atmospheric pressure. Till date, biocatalytic reduction of acetophenone and its derivatives has been widely reported. In the present study, we have made an attempt to carry out the microbial bioreduction of o-hydroxyacetophenone by screening some of the selected microorganisms which were obtained from culture collection centre as well as those which are isolated in our Microbiology lab. The selected microorganisms include Aspergillus ochraceous, Aspergillus flavus, Aspergillus tubingenesis, Aspergillus niger, Rhizopus stolanifer MTCC 162, Rhizopus stolanifer MTCC 2591 and Baker’s yeast.Among the seven microorganisms screened for the bioreduction of o-hydroxyacetophenone, Baker’s yeast and Aspergillus tubingenesis showed significant bioconversion where as Aspergillus ochraceous exhibited the least bioconversion.In our earlier study it was found that Aspergillus flavus has the required bioreductase enzyme, which showed the maximum conversion of p-chloroacetophenone to p-chlorophenylethanol. Hence optimization of culture conditions to get maximum enzyme expression and hence maximum conversion was thought off. The parameters considered for the study include effect of various Carbon sources, Nitrogen source, Metal ions, incubation Temperature and media pH on enzyme expression. The optimized culture a condition at which maximum bioconversion was achieved was maltose among various carbon sources. Tryptone was found to have maximum effect among the nitrogen sources. Media pH 7.6 and incubation temperature of 35 °C was found to be favourable for maximum enzyme activity. Among various divalent metal salts, addition of magnesium sulphate to the media significantly increased the enzyme activity.
Przedstawiono krótką charakterystykę problemu tworzenia się obcego zapachu w żywności, w wyniku rozwoju mikroflory. Opisano kilka charakterystycznych metabolitów mikroorganizmów, odpowiedzialnych za zapach grzybowy, stęchły, ziemisty, jełki, czosnkowy i owocowy, które wpływając niekorzystnie na walory sensoryczne produktu, stanowią problem technologiczny. W wielu przypadkach wskazują one na proces mikrobiologicznego psucia się żywności.
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