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排序方式: 共有104条查询结果,搜索用时 46 毫秒
1.
The reversible hydrolysis of maltose to glucose by immobilized glucoamylase entrapped in spherical solid particles is studied theoretically. For this purpose a known kinetic model taking into account these reversible reactions and the competitive synthesis of iso-maltose was adopted. The mass transfer limitations in the bulk liquid and in the pores of the particles containing the enzyme are considered, using Fick's law. On the basis of mathematical modelling the optimum conditions for biocatalyst performance are established. An appropriate combination of particle size and initial substrate concentration may lead to reduction of undesirable mass transfer resistance and therefore product inhibition and to an improved selectivity of the biocatalyst with respect of glucose formation.List of Symbols
C
i
kmoles/m3
current concentration ofi-th component along the radius
-
C
oi
kmoles/m3
bulk concentration ofi-th component
-
C
i
*
kmoles/m3
concentrations ofi-th component on the pellet surface
-
D
si
,D
i
m2/s
internal and molecular diffusion coefficient ofi-th component
-
W
M
kmoles/m3·s
reaction rate of maltose hydrolysis
-
W
IM
kmoles/m3·s
reaction rate of iso-maltose formation
-
W
G
kmoles/m3·s
reaction rate of glucose production
-
R
0
m
pellet radius
-
r m
current radius of the pellet
-
t s
time coordinate
-
r
0
ratio of the time step to the square of the radial coordinate
-
Re
Reynolds number =w·R/v
-
Sc
Schmidt number =v/D
-
Bi
Biot number = R/D
-
A
j
,B, C
j
coefficients in the system of linear equations, Eq. (8)
-
X
i
dimensionless degree of transformation
-
NR
number of independent reactions
-
N
number of division sections of the pellet radius
-
G kmoles/m3
concentration of glucose
-
M kmoles/m3
concentration of maltose
-
IM kmoles/m3
concentration of isomaltose
-
K
m
kmoles/m3
Michaelis constant
-
V
max kmoles/m3·s
maximum reaction rate in Eq. (6)
-
K
i
kmoles/m3
inhibition constant
-
K
1eq
,K
2eq
equilibrium constants in Eq. (6)
-
, h
steps along the time and radial coordinate in the pellet
-
m/s
mass transfer coefficient
-
dimensionless radius of the pellet
-
computation accuracy
Indices
i
number of reaction component
-
j
index along the radius of the pellet
-
k
index along the time coordinate
This work was accomplished with thanks to the financial support of the Bulgarian National Fund for Scientific Investigations —Grant No. MU-1-BE/93. 相似文献
2.
C T Dragomir A Barbier D Ungureanu V Ionescu E Pausescu R Chirvasie D Ghitescu G Filipescu 《Physiological chemistry and physics》1975,7(4):287-308
Investigation of the ionic behavior of glycerinated muscle fibers showed that the residual structures of this biologic cellular material, lacking functional membranes, are able to discriminate between alkaline ions. The characteristics of the ionic selectivity of the glycerinated fibers change with their functional state and with the presence in the medium of certain nonionic substances. Among the more important features of ionic distribution between the membrane-free fibers and the medium are the following: (1) There is evident adsorption of potassium on the fibers, in the absence of ATP. (2) This adsorption increases in contraction and decreases in relaxation. (3) At high ionic concentrations, in contrast to what occurs at low potassium concentrations, the glycerinated muscle prefers sodium to potassium, but even under these conditions both ions are accumulated in the fibers to far greater levels than in the medium. This strongly suggests a Donnan ionic equilibrium developing parallel to the adsorption process. (4) Nonionic substances of the general anesthetic group markedly alter the ionic selectivity of the glycerinated fibers, probably by their action on the water's physical state. A mechanism is proposed for the observed ionic adsorption specific of the muscle-a mechanism in which actin-myosin coupling plays the cardinal adsorption role. In the general interpretation of the data a synthetic concept is advanced according to which an entire set of processes and factors concurs with the distribution of ions between the muscle and the medium. 相似文献
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6.
Iankov ID Petrov DP Mladenov IV Haralambieva IH Kalev OK Balabanova MS Mitov IG 《Microbes and infection / Institut Pasteur》2004,6(10):901-910
Protective properties of immunoglobulin A (IgA) monoclonal antibodies (MAbs) directed against O and H antigens of Salmonella enterica serotype Enteritidis (S. enteritidis) were evaluated in a model of generalized infection after intranasal (i.n.) inoculation of BALB/c mice. Passive i.n. instillation of antibodies 1 h before i.n. challenge did not prevent infection, and mice developed rapid inflammatory response in the lower respiratory tract. The passive systemic immunization was partially protective and a single intravenous (i.v.) injection of both O and H antigen specific IgA antibodies prolonged survival period of the infected animals. Permanent secretion of O:9 specific IgA MAb 177E6 into the respiratory tract in a "backpack" tumor model protected 50% of animals infected i.n. with a high dose of virulent S. enteritidis strain. Thus, secretory IgA (S-IgA) directed against O:9 antigen alone can prevent bacterial invasion in the respiratory epithelium. 相似文献
7.
Gene expression datasets are large and complex, having many variables and unknown internal structure. We apply independent component analysis (ICA) to derive a less redundant representation of the expression data. The decomposition produces components with minimal statistical dependence and reveals biologically relevant information. Consequently, to the transformed data, we apply cluster analysis (an important and popular analysis tool for obtaining an initial understanding of the data, usually employed for class discovery). The proposed self-organizing map (SOM)-based clustering algorithm automatically determines the number of 'natural' subgroups of the data, being aided at this task by the available prior knowledge of the functional categories of genes. An entropy criterion allows each gene to be assigned to multiple classes, which is closer to the biological representation. These features, however, are not achieved at the cost of the simplicity of the algorithm, since the map grows on a simple grid structure and the learning algorithm remains equal to Kohonen's one. 相似文献
8.
Iankov ID Petrov DP Mladenov IV Haralambieva IH Ivanova R R Velev V Mitov IG 《FEMS immunology and medical microbiology》2002,33(2):107-113
Hybridomas were generated after intragastral immunization of BALB/c mice with live Salmonella suberu and subsequent fusion between isolated spleen lymphoblasts and myeloma cells. Three monoclonal antibodies (MAbs) of immunoglobulin A (IgA) isotype were selected and characterized. All of them were found to recognize the H:g epitope in enzyme-linked immunosorbent assay and immunoblotting but did not react with all H:g-expressing strains in slide agglutination test. All MAbs strongly agglutinated Salmonella enteritidis type strain and a large number of S. enteritidis clinical isolates. They were not bactericidal in the presence of complement. All hybridoma clones produced secretory IgA forms, which were found in the gastrointestinal tract of mice bearing hybridoma as a subcutaneous 'backpack' tumor or after intravenous application of purified MAbs. The IgA MAbs stability demonstrated in different tests together with their antigen specificity and strong agglutination ability make them a useful diagnostic tool for serotyping of Salmonella strains. 相似文献
9.
Haralambieva IH Iankov ID Petrov DP Mladenov IV Mitov IG 《FEMS immunology and medical microbiology》2002,33(2):71-76
A murine monoclonal antibody (MAb) 202D7 of IgG3 isotype recognizes a lipopolysaccharide (LPS) epitope of Chlamydia spp. and cross-reacts with the Re chemotype LPS of Salmonella and Escherichia coli. The antibody exhibits strong complement activating properties and stimulates phagocytosis of Salmonella enterica serovar Minnesota Re mutant by murine macrophages. Salmonella Re mutants are non-invasive for cell monolayers but still can enter and replicate in L-929 murine fibroblast cells. The entry of bacteria within the cells increases five-fold in the presence of MAb 202D7. The antibody mediates attachment and enhances five-fold the infectivity of Chlamydia pneumoniae into L-929 cells, which suggests a possible IgG-mediated mechanism of entry and survival of the pathogen in fibroblast cells. 相似文献
10.
Kostova I Dinchev D Rentsch GH Dimitrov V Ivanova A 《Zeitschrift für Naturforschung. C, Journal of biosciences》2002,57(1-2):33-38
The known furostanol saponins methylprotodioscin and protodioscin and two new sulfated saponins, sodium salt of 26-O-beta-glucopyranosyl-22alpha-methoxy-(25R)-furost-5-ene-3beta,26-diol-3-O-alpha-rhamnopyranosyl-(1-->2)-beta-4-O-sulfo-glucopyranoside (methylprototribestin) and sodium salt of 26-O-beta-glucopyranosyl-22alpha-hydroxy-(25R)-furost-5-ene-3beta,26-diol-3-O-alpha-rhamnopyranosyl-(1-->2)-beta-4-O-sulfo-glucopyranoside (prototribestin) have been isolated from the aerial parts of Tribulus terrestris L. growing in Bulgaria. The structures of the new compounds were elucidated on the basis of 1D and 2D (DQF-COSY, TOCSY, HSQC-TOCSY, HSQC, HMBC, ROESY) NMR data, ESI mass spectra and chemical transformation. 相似文献