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161.
Paula Veríssimo Cristina Esteves Carlos Faro Euclides Pires 《Biotechnology letters》1995,17(6):621-626
The flowers of cardoon (genus Cynara) are traditionally used in Portugal for cheese making. In this work the vegetable rennet of the species Cynara cardunculus L. was characterized in terms of enzymic composition and proteolytic specificity of its proteinases (cardosin A and cardosin B). Cardosin A was found to cleave insulin B chain at the bonds Leu15-Tyr16, Leu17-Val18 and Phe25-Tyr26. In addition to the bonds mentioned cardosin B cleaves also Glu13-Ala14, Ala14-Leu15 and Phe24-Phe25 indicating that it has a broader specificity. The kinetic parameters for the hydrolysis of the synthetic peptide Leu-Ser-Phe(NO2)-Nle-Ala-Leu-oMe were also determined and compared to those of chymosin and pepsin. The results obtained indicate that in terms of specificity and kinetic parameters cardosin A is similar to chymosin whereas cardosin B is similar to pepsin. It appears therefore that the enzyme composition of cardoon rennet closely resembles that of calf rennet. 相似文献
162.
J. M. Barrasa S. Camarero A. T. Martínez K. Ruel 《Applied microbiology and biotechnology》1995,43(4):766-770
The ultrastructural patterns characterizing wheat straw degradation by the ligninolytic fungi Phanerochaete chrysosporium and Trametes versicolor were studied. During fungal attack, the less lignified tissues were degraded first, whereas the xylematic and sclerenchymatic fibers underwent a delayed attack. In straw samples degraded by T. versicolor, partial delignification, defibrillation and swelling of cell walls, often causing separation between primary and secondary walls, were observed. By contrast, the formation of erosions and fissures, with minor lignin removal, characterized the attack to the cell wall by P. chrysosporium. At an advanced stage of decay, KMnO4 staining demonstrated abundant electron-dense material around hyphae and in the proximity of the cell-wall surface. In the case of P. chrysosporium, spherical black bodies were found in the erosions and fissures produced during fungal attack. 相似文献
163.
Ninety-fourStaphylococcus aureus strains isolated from chronic and recurrent skin and respiratory tract infections were investigated for several virulence
factor expressions. Production of protein A was noticed in all of the tested strains in amounts from less than 0.1 to more
than 2.5 ng per 106 bacterial cells. The percentage of the extracellularly produced protein A was found to lie between 4.5 and 27.8%. Two strains
(both from the respiratory tract) produced more than 50 % of protein A in the extracellular form and one strain did not produce
any detectable amount of the extracellular protein A; 99 % of the tested strains produced the clumping factor, 96% staphylocoagulase,
79 % staphylokinase and 90 % gelatinolytic activity; 79 % produced α-toxin exclusively or in combination with δ- or β-toxin;
8 % of strains produced β-toxin. There were differences in β-toxin production between strains from the respiratory tract (5
%) and skin infections (25 %). δ-Toxin was produced by 53 % of the strains. In each of the tested strains a complex of virulence
factors was detected. The importance of inactivated extracellular products (especially α- and δ-toxin and in the case of skin
infections also β-toxin) as components of staphylococcal whole-cell vaccine was suggested.
Dedicated to Professor C. John on the occasion of his 75th birthday 相似文献
164.
165.
A new, non-radioactive and cheap colorimetric method for determination of activity of sialyltransferases of various specifities using natural substrates based on 2-thiobarbituric acid assay is presented. The assay was tested with three different sialyltransferases (a-2,3 and a-2,6) and compared with the radioactive assay. 相似文献
166.
Several aspects of community organization wereanalyzed comparatively in a small side-arm of theParaná River (Correntoso) and a shallowfloodplain lake (El Tigre) (31° 41 S and60° 42 W), in relation to the hydrology of thesystem. Taxonomic and morphological composition inthe river differed from that in the lake: the riverhad lower species richness (151 vs 218),different contributions of some Classes to totalspecies number (higher Cyano-, Zygo- andDiatomophyceae vs higher Chlorophyceae), anddiffent proportions of nannoplanktonic algae (67.5%vs 80.7%) and netplanktonic filamentousspecies (18.2% vs 4.2%). Phytoplanktonbiomass, higher in the lake than in the river due tothe retention time, was mostly dominated bynannoplankton and netplankton. Loticphytoplankton was dominated by typical fluvialspecies of Diatomophyceae (R-strategists). Riverconditions seem to maintain a subclimacticcommunity, which was little impacted by the flushingof populations from floodplain lakes. Water levelwas the main factor controlling phytoplanktonbiomass, species diversity (H), evenness (E) andcommunity change rate () in the river. Inthe lake, phytoplankton had an autogenicsuccessional sequence during the isolation phase (C-to S-strategists) and other responses todisturbance, mainly during the flood(R-strategists). Frequent changes in phytoplanktoncomposition, biomass, H, E and , revealed aenvironmental instability in the lake, which may beexplained by interactions of external factors(hydrology and climatology) and those of internalorigin, such as nutrients and grazing. 相似文献
167.
In mixed culture of Lactobacillus hilgardii X1B and Leuconostoc oenos X2L, isolated from Argentinian wines, an amensalistic growth response was observed: Leuconostoc oenos did not grow, and after 24 h of incubation at 30°C no viable cells were detected. In pure and mixed cultures, Lactobacillus hilgardii produced hydrogen peroxide early in the growth cycle, reaching the maximum at 24 h. The values of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for the action of hydrogen peroxide on the growth of Leuconostoc oenos were: 4.08g ml-1 and 17.00 g ml-1 respectively. 相似文献
168.
Summary A versatile, cheap and automated system is designed for the measurement of small gas flows produced in laboratory-scale fermentation processes. An automatic sampling device for programmed times is linked to the flow meter. The displacement of a liquid by the gas being measured is the principle on which both the meter and the sampling device are based. The operation of the system is controlled by a simple electronic circuit. 相似文献
169.
The effects of metanephrine and normetanephrine have been compared with those from equiactive doses of the origin compounds, adrenaline and noradrenaline, on the pressor responses in rat, in order to determine whether their effects are owed, at least partially, to a releasing presynaptic action of the catecholamines in normal animals as well as those pretreated with reserpine, guanethidine and 6-OH-dopamine. Their effects have likewise been studied in isolated perfused renal arteries both in normal and reserpinized rats. None of the adrenolytic agent used were able either to reduce the duration of the hypertensive response or to accelerate tachyphylaxis. Identical results were obtained in renal artery preparations. It is thus concluded that the catecholamines stored in presynaptic endings are not involved in the observed phenomena and it is suggested that they might depend on the high doses required to produce effects equiactive to those of the origin substances. 相似文献
170.