共查询到10条相似文献,搜索用时 234 毫秒
1.
Sabri A. Jacques P. Weekers F. Baré G. Hiligsmann S. Moussaïf M. Thonart P. 《Applied biochemistry and biotechnology》2000,84(1-9):391-399
The thermodependence of growth kinetic parameters was investigated for the Antarctic psychrophilic strain Rhodotorula aurantiaca and a psychrotrophic strain of the same species isolated in Belgium (Ardennes area). Cell production, maximum growth rate
(μmax), and half-saturation constant for glucose uptake (Ks) of both yeasts were temperature dependent. For the two yeasts, a maximum
cell production was observed at about 0°C, and cell production decreased when temperature increased. The μmax values for both strains increased with temperature up to a maximum of 10°C for the psychrophilic strain and 17°C for the
psychrotrophic strain. For both yeasts, Ks for glucose was relatively constant at low temperatures. It increased at temperatures
above 10°C for the psychrophilic strain and 17°C for the psychrotrophic strain. Although its glucose affinity was lower, the
psychrotrophic strain grew more rapidly than the psychrophilicone. The difference in growth rate and substrate affinity was
related to the origin of the strain and the adaptation strategy of R. aurantiaca to environmental conditions. 相似文献
2.
Penna Thereza Christina Vessoni Chiarini Eb Machoshvili Irene Alexeevna Ishii Marina Pessoa Adalberto 《Applied biochemistry and biotechnology》2002,98(1-9):791-802
The recombinant green fluorescent protein (gfp
uv
) was expressed by Escherichia coli DH5-α cells transformed with the plasmid pGFPuv. The gfp
uv
was selectively permeabilized from the cells in buffer solution (25 mM Tris-HCl, pH 8.0), after freezing (−70°C for 15 h), by four freeze (−20°C)/thaw cycles interlaid by sonication. The average
content of released gfp
uv
(experiment 2) was 7.76, 34.58, 39.38, 12.90, and 5.38%, for the initial freezing (−70°C) and the first, second, third and
fourth freeze/thaw cycles, respectively. Superfusion on freezing was observed between −11°C and −14°C, after which it reached
−20°C at 0.83°C/min. 相似文献
3.
L. N. Yang F. Xu L. X. Sun Z. C. Tan H. D. Tan Z. B. Zhao J. G. Liang 《Journal of Thermal Analysis and Calorimetry》2006,85(3):807-810
A microcalorimetric
technique based on the bacterial heat output was applied to evaluate the influence
of antibiotics PIP (Piperacillin Sodium)
and composite preparation of PIP and SBT (Sulbactam
Sodium) on the growth of E. coli
DH5α. The power–time curves of the growth metabolism of E. coli DH5α were studied using a TAM Air Isothermal
Microcalorimeter at 37°C. By analyzing the power–time curves, the
parameters such as growth rate constants (k),
inhibitory ratio (I), the maximum heat
power (P
m) and the
time of the maximum heat power (t
m)
were obtained. The results show that different concentrations of antibiotics
affect the growth metabolism of E. coli
DH5α. The PIP in the concentration range of 0–0.05 μg mL–1
has a stimulatory effect on the E. coli
DH5α growth, while the PIP of higher concentrations (0.05 –0.25
μg mL–1) can inhibit its growth. It seems
that the composite preparation composed of PIP and SBT cannot improve the
inhibitory effect on E. coli DH5α
as compared with the PIP. 相似文献
4.
Lou DW Saito Y Zarzycki PK Ogawa M Jinno K 《Analytical and bioanalytical chemistry》2006,385(1):96-104
An improved high-performance liquid chromatographic method for separation of a number of ginsenosides has been developed.
The influence of temperature (from 0 to 25°C) on the retention and separation of the ginsenosides was studied by applying
a binary mobile phase (acetonitrile/water, 82:18 v/v) and a diol column (LiChrospher 100 Diol). The column temperature is
one of the more important parameters for the retention and separation of the components investigated. Selected thermodynamic
parameters, including changes of enthalpy (ΔH°) and entropy (ΔS°), were estimated from linear van’t Hoff plots, and possible retention mechanisms were discussed. Moreover, the best separation
conditions were selected based on optimization criteria including maximum retention time (t
R max), minimum resolution (R
s
min), and relative resolution product (r). Temperature regions close to 14°C offered the highest selectivity and almost equal distribution of the ginsenosides peaks
across the chromatogram. Under such isocratic conditions, excellent separation of chromatographic standards and selected ginseng
samples was achieved in less than 16 min. 相似文献
5.
The mineralogical composition of the Kütahya calcium bentonite (CaB) from Turkey was obtained as mass% of 60% calcium rich
smectite (CaS), 30% opal-CT (OCT), trace amount illite (I), and some non-clay impurities by using chemical analysis (CA),
X-ray diffraction (XRD), and thermal analysis (TG-DTA) data. The crystallinity, porosity, and surface area of the samples
heated between 25–1300°C for 2 h were examined by using XRD, TG, DTA and N2-adsorption-desorption data. The position of the 001 reflection which is the most characteristic for CaS does not affect from
heating between 25–600°C and then disappeared. The decrease in relative intensity (I/I
0) from 1.0 to zero and the increase in full width at half-maximum peak height (FWHM) from 0.25 to 1.0° of the 001 reflection
show that the crystallinity of the CaS decreased continuously by rising the heating temperature from 25 to 900°C and then
collapsed. The most characteristic 101 reflection for opals intensifies greatly between 900 and 1100°C with the opal becoming
more crystalline.
The total water content of the natural bentonite after dried at 25, 105 and 150°C for 48 h were determined as 8.8, 5.0 and
2.5%, respectively. The mass loss occurs between 25 and 400°C over two steps with the maximum rate at 80 and 150°C, respectively.
The exact distinction of the dehydration temperatures for the adsorbed water and interlayer water is seen almost impossible.
The temperature interval, maximum rate temperature, and mass loss during dehydroxylation are 400–800°C, 670°C and 4.6–5.0%,
respectively. The maximum rate temperatures for decrystallization and recrystallization are 980 and 1030°C, respectively.
The changes in specific micropore volume (V
mi), specific mesopore volume (V
me), specific surface area (S) were discussed according to the dehydration and dehydroxylation of the CaS. The V
mi, V
me and S reach to their maxima at around 400°C with the values of 0.045, 0.115 cm3 g−1 and 90 m2 g−1, respectively. The radii of mesopores for the bentonite heated at 400°C are distributed between 1–10 nm and intensified approximately
at 1.5 nm. 相似文献
6.
Luiza P. V. Calsavara Flávio F. De Moraes Gisella M. Zanin 《Applied biochemistry and biotechnology》1999,79(1-3):789-806
The enzyme cellobiase Novozym 188, which is used for improving hydrolysis of bagasse with cellulase, was characterized in
its commercial available form and integrated kinetic models were applied to the hydrolysis of cellobiose. The specific activity
of this enzyme was determined for pH values from 3.0–7.0, and temperatures from 40–75°C, with cellobiose at 2 g/L. Thermal
stability was measured at pH 4.8 and temperatures from 40–70°C. Substrate inhibition was studied at the same pH, 50°C, and
cellobiose concentrations from 0.4–20 g/L. Product inhibition was determined at 50°C, pH 4.8, cellobiose concentrations of
2 and 20 g/L, and initial glucose concentration nearly zero or 1.8 g/L. The enzyme has shown the greatest specific activity,
17.8 U/mg, at pH 4.5 and 65°C. Thermal activation of the enzyme followed Arrhenius equation with the Energy of Activation
being equal to 11 kcal/mol for pH values 4 and 5. Thermal deactivation was adequately modeled by the exponential decay model
with Energy of Deactivation giving 81.6 kcal/mol. Kinetics parameters for substrate uncompetitive inhibition were: Km=2.42 mM, V
max=16.31 U/mg, Ks=54.2 mM. Substrate inhibition was clearly observed above 10 mM cellobiose. Product inhibition at the concentration studied has usually doubled the time necessary to reach the same conversion
at the lower temperature tested. 相似文献
7.
The speed of sound and density of 2-hydroxy-5-methyl acetophenone in dimethylformamide have been measured over the range of
temperatures 25–40 °C. From the experimentally determined data, values of apparent molar volume (V
ϕ), adiabatic compressibility (βs), apparent molar adiabatic compressibility (K
s,ϕ) and their limiting values have been computed. Values at infinite dilution provide information regarding solute–solvent interaction.
The density and velocity increases with increase in concentration and decreases with increase in temperature. These results
have been analyzed in terms of molecular interactions between acetophenone and dimethylformamide. 相似文献
8.
G. Rezaei Behbehani A. A. Saboury S. Tahmasebi Sarvestani M. Mohebbian M. Payehghadr J. Abedini 《Journal of Thermal Analysis and Calorimetry》2010,102(2):793-798
The thermodynamic parameters of interaction between theophylline and Human Serum Albumin (HSA) in buffer solution (30 mM)
of pH = 7 at 27 °C was investigated by isothermal titration calorimetry (ITC). The thermodynamic quantities of the binding
mechanism, the number of binding sites (g), the dissociation binding constant (K
d), the molar enthalpy of binding (ΔΗ) and other thermodynamic parameters can be obtained by the extended solvation theory. 相似文献
9.
S. -Y. Cheng J. -M. Tseng S. -Y. Lin J. P. Gupta C. -M. Shu 《Journal of Thermal Analysis and Calorimetry》2008,93(1):121-126
Tert-butyl peroxybenzoate (TBPB) is one of the sensitive and hazardous chemicals which have been popularly employed in petrifaction
industries in the past. This study attempted to elucidate its unsafe characteristics and thermally sensitive structure so
as to help prevent runaway reactions, fires or explosions in the process environment. We employed differential scanning calorimetry
(DSC) to assess the kinetic parameters (such as exothermic onset temperature (T
0), heat of reaction (ΔH), frequency factor (A)), and the other safety parameters using four different scanning rates (1, 2, 4 and 10°C min−1) combined with curve-fitting method.
The results indicated that TBPB becomes very dangerous during decomposition reactions; the onset temperature and reaction
heat were about 100°C and 1300 J g−1, respectively. Through this study, TBPB accidents could be reduced to an accepted level with safety parameters under control.
According to the findings in the study and the concept of inherent safety, TBPB runaway reactions could be thoroughly prevented
in the relevant plants. 相似文献
10.
Eri Yoshida 《Colloid and polymer science》2007,285(8):941-945
Light scattering and transmission electron microscope (TEM) measurements were preformed for micelles of a nonamphiphilic poly(vinylphenol)-block-polystyrene diblock copolymer (PVPh-b-PSt) to determine the shape of the micelles. The micelles were prepared by the self-assembly of the copolymer in 1,4-dioxane,
a nonselective solvent, in the presence of 1,4-butanediamine. The logarithm of the normalized time correlation function of
the scattered field, lnG1(τ), linearly decayed versus the delay time, τ. The diffusion coefficient measured in the range of the scattering angles from 30° to 150° was almost independent of the
square of the magnitude of the scattering vector. The linear decay of lnG1(τ) vs τ and the angular-independence of the diffusion coefficient suggested that the monodisperse spherical micelles were formed
by the micellization. The TEM observations confirmed the formation of uniform spheres. 相似文献