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1.
A model is developed, allowing estimation of the share of inelastic interparticle collisions in total energy dissipation for stirred suspensions. The model is restricted to equal-sized, rigid, spherical particles of the same density as the surrounding Newtonian fluid. A number of simplifying assumptions had to be made in developing the model. According to the developed model, the share of collisions in energy dissipation is small.List of Symbols
b
parameter in velocity distribution function (Eq. (28))
-
c
K
factor in Kolmogoroff spectrum law (Eq. (20))
-
D
t(r
p
) m2/s
characteristic dispersivity at particle radius scale (Eq. (13))
-
E(k, t) m3/s2
energy spectrum as function of k and t (Eq. (16))
-
E
K
(k) m3/s2
energy spectrum as function of k in Kolmogoroff-region (Eq. (20))
-
E
p
dimensionless mean kinetic energy of a colliding particle (Eq. (36))
-
E
cp
dimensionless kinetic energy exchange in a collision (Eq. (37))
-
G(x, s)
dimensionless energy spectrum as function of x and s (Eq. (16))
-
G
B(x)
dimensionless energy spectrum as function of x for boundary region (Eq. (29))
-
G
K(x)
dimensionless energy spectrum as function of x for Kolmogoroff-region (Eq. (21))
-
g m/s2
gravitational acceleration
-
I
cp
dimensionless collision intensity per particle (Eq. (38))
-
I
cv
dimensionless volumetric collision intensity (Eq. (39))
-
k l/m
reciprocal of length scale of velocity fluctuations (Eq. (17))
-
K
dimensionless viscosity (Eq. (13))
-
n(2)
dimensionless particle collision rate (Eq. (12))
-
n(r) l/s
particle exchange rate as function of distance from observatory particle center (Eq. (7))
-
r m
vector describing position relative to observatory particle center (Eq. (2))
-
r m
scalar distance to observatory particle center (Eq. (3))
-
r
pm
particle radius (Eq. (1))
-
s
dimensionless time (Eq. (10))
-
SC kg/ms3
Severity of collision (Eq. (1))
-
t s
time (Eq. (2))
-
u(r, t) m/s
velocity vector as function of position vector and time (Eq. (2))
-
u(r, t) m/s
magnitude of velocity vector as function of position vector and time (Eq. (3))
-
u
r(r, t) m/s
radial component of velocity vector as function of position vector and time (Eq. (3))
-
u
r
(r, t) m/s
magnitude of radial component of velocity vector as function of position vector and time (Eq. (3))
-
u
(r, t) m/s
latitudinal component of velocity vector as function of position vector and time (Eq. (3))
-
u
(r, t) m/s
magnitude of latitudinal component of velocity vector as function of position vector and time (Eq. (3))
-
u
(r, t) m/s
longitudinal component of velocity vector as function of position vector and time (Eq. (3))
-
u
(r, t) m/s
magnitude of longitudinal component of velocity vector as function of position vector and time (Eq. (3))
-
u
gsm/s
superficial gas velocity
-
u(r) m/s
root mean square velocity as function of distance from observatory particle center (Eq. (3))
-
ur(r) m/s
root mean square radial velocity component as function of distance from observatory particle center (Eq. (4))
-
u (r) m/s
root mean square latitudinal velocity component as function of distance from observatory particle center (Eq. (4))
-
u (r) m/s
Root mean square longitudinal velocity component as function of distance from observatory particle center (Eq. (4))
-
w(x)
dimensionless root mean square velocity as function of dimensionless distance from observatory particle center (Eq. (11))
-
V
pm3
particle volume (Eq. (36))
-
w(2)
dimensionless root mean square collision velocity (Eq. (34))
-
w
*
parameter in boundary layer velocity equation (Eq. (24))
-
x
dimensionless distance to particle center (Eq. (9))
-
x
*
value of x where G
Band G
K-curves touch (Eq. (32))
-
x
K
dimensionless micro-scale (Kolmogoroff-scale) of turbulence (Eq. (15))
-
volumetric particle hold-up
-
m2/s3
energy dissipation per unit of mass
-
m2/s
kinematic viscosity
-
kg/m3
density
-
(r) m3/s
fluid-exchange rate as function of distance to observatory particle center
-
Latitudinal co-ordinate (Eq. (5))
-
Longitudinal co-ordinate (Eq. (5)) 相似文献
2.
Crude extracts or supernatants of broken cells of Clostridium formicoaceticum reduce unbranched, branched, saturated and unsaturated carboxylates at the expense of carbon monoxide to the corresponding alcohols. The presence of viologens with redox potentials varying from E
0=-295 to-650 mV decreased the rate of propionate reduction. The more the propionate reduction was diminished the more formate was formed from carbon monoxide. The lowest propionate reduction and highest formate formation was observed with methylviologen. The carbon-carbon double bond of E-2-methyl-butenoate was only hydrogenated when a viologen was present. Formate as electron donor led only in the presence of viologens to the formation of propanol from propionate. The reduction of propionate at the expense of a reduced viologen can be followed in cuvettes. With respect to propionate Michaelis Menten behavior was observed. Experiments are described which lead to the assumption that the carboxylates are reduced in a non-activated form. That would be new type of biological reduction.Non-standard abbreviations glc
Gas liquid chromatography
- HPLC
high performance liquid chromatography
- RP
reverse phase; Mediators (the figures in parenthesis of the mediators are redox potentials E
0 in mV)
- CAV2+
carbamoylmethylviologen, 1,1-carbamoyl-4,4-dipyridinium dication (E
0=-296 mV)
- BV2+
benzylviologen, 1,1-dibenzyl-4,4-dipyridinium dication (E
0=-360 mV)
- MV
methylviologen, 1,1-dimethyl-4,4-dipyridinium-dication (E
0=-444 mV)
- DMDQ2+
dimethyldiquat, 4,4-dimethyl-2,2-dipyridino-1,1-ethylendication (E
0=-514 mV)
- TMV2+
tetramethylviologen, 1,1,4,4-tetramethyl-4,4-dipyridinium dication (E
0=-550 mV)
- PDQ2+
propyldiquat, 2,2-dipyridino-1,1-propenyl dication (E
0=-550 mV)
- DMPDQ2+
dimethylpropyldiquat, 4,4-dimethyl-2,2-dipyridino-1,1-propenyl dication (E
0=-656 mV)
- PN
productivity number=mmol product (obtained by the uptake of one pair of electrons) x (biocatalyst (dry weight) kg)-1×h-1 相似文献
3.
M. Pokkinen Z. R. Flores Bustamante H. Asama I. Endo P. Linko 《Bioprocess and biosystems engineering》1992,7(7):319-323
The on-line calculated specific rates of growth, substrate consumption and product formation were used to diagnose microbial activities during a lactic acid fermentation. The specific rates were calculated from on-line measured cell mass, and substrate and product concentrations. The specific rates were more sensitive indicators of slight changes in fermentation conditions than such monitored data as cell mass or product concentrations.List of Symbols
1/h
specific rate of cell growth
-
1/h
specific rate of substrate consumption
-
1/h
specific rate of product formation
-
*
dimensionless specific rate of cell growth
-
*
dimensionless specific rate of substrate consumption
-
*
dimensionless specific rate of product formation
-
max 1/h
maximum specific rate of cell growth
-
max 1/h
maximum specific rate of substrate consumption
-
max 1/h
maximum specific rate of product formation
-
X g/l
cell mass concentration
-
S g/l
substrate concentration
-
S
*
dimensionless substrate concentration
-
S
0 g/l
initial substrate concentration
-
P g/l
product concentration 相似文献
4.
Summary Five subunits (-, -, -, - and -subunits) of the six -and -subunits) in the F1 portion (F1ATPase) of sweet potato (Ipomoea batatas) mitochondrial adenosine triphosphatase were isolated by an electrophoretic method. The - and -subunits were not distinguishable immunologically but showed completely different tryptic peptide maps, indicating that they were different molecular species. In vitro protein synthesis with isolated sweet potato root mitochondria produced only the -subunit when analyzed with anti-sweet potato F1ATPase antibody reacting with all the subunits except the -subunit. Sweet potato root poly(A)+RNA directed the synthesis of six polypeptides which were immunoprecipitated by the antibody: two of them immunologically related to the -subunit and the others to the - and -subunits. We conclude that the -subunit of the F1ATPase is synthesized only in the mitochondria and the -, - and -subunits are in the cytoplasm. 相似文献
5.
Analysis of gas exchange in seedlings of Acer saccharum: integration of field and laboratory studies
In the field, photosynthesis of Acer saccharum seedlings was rarely light saturated, even though light saturation occurs at about 100 mol quanta m-2 s-1 photosynthetic photon flux density (PPFD). PPFD during more than 75% of the daylight period was 50 mol m-2 s-1 or less. At these low PPFD's there is a marked interaction of PPFD with the initial slope (CE) of the CO2 response. At PPFD-saturation CE was 0.018 mol m-2 s-1/(l/l). The apparent quantum efficiency (incident PPFD) at saturating CO2 was 0.05–0.08 mol/mol.
and PPFD-saturated CO2 exchange was 6–8 mol m-2 s-1. The ratio of internal CO2 concentration to external (C
i
/C
a
) was 0.7 to 0.8 except during sunflecks when it decreased to 0.5. The decrease in C
i
/C
a
during sunflecks was the result of the slow response of stomates to increased PPFD compared to the response of net photosynthesis. An empirical model, which included the above parameters was used to simulate the measured CO2 exchange rate for portions of two days. Parameter values for the model were determined in experiments separate from the daily time courses being sumulated. Analysis of the field data, partly through the use of simulations, indicate that the elimination of sunflecks would reduce net carbon gain by 5–10%.List of symbols
A
measured photosynthetic rate under any set of conditions (mol m-2 s-1)
-
A
m
(atm)
measured photosynthetic rate at saturating PPFD, 350 l/l CO2 and 21% (v/v) O2 (mol m-2 s-1)
-
C
constant in equation of Smith (1937, 1938)
-
C
a
CO2 concentration in the air (l/l)
-
C
i
CO2 concentration in the intercellular air space (l/l)
-
C
i
/*
C
i
corrected for CO2 compensation point, i.e., C
i
-I
*, (l/l)
- CE
initial slope of the CO2 response of photosynthesis (mol m-2 s-1/(l/l))
- CEM
CE at PPFD saturation
-
E
transpiration rate (mmol m-2 s-1)
-
F
predicted photosynthetic rate (mol m-2 s-1)
-
G
leaf conductance to H2O (mol m-2 s-1)
-
I
photosynthetic photon flux density (mol m-2 s-1)
-
N
number of data points
-
P
m
predicted photosynthetic rate at saturating CO2 and given PPFD (mol m-2 s-1)
-
P
ml
predicted photosynthetic rate at saturating CO2 and PPFD (mol m-2 s-1)
-
R
d
residual respiratory rate (mol m-2 s-1)
-
T
a
air temperature (°C)
-
T
l
leaf temperature (°C)
-
V
reaction velocity in equation of Smith (1937, 1938)
-
V
max
saturated reaction velocity in equation of Smith (1937, 1938)
- VPA
vapor pressure of water in the air (mbar/bar)
- VPD
vapor pressure difference between leaf and air (mbar/bar)
-
X
substrate concentration in equation of Smith (1937, 1938)
-
initial slope of the PPFD response of photosynthesis at saturating CO2 (mol CO2/mol quanta)
- (atm)
initial slope of the PPFD response of photosynthesis at 340 l/l CO2 and 21% (v/v) O2 (mol CO2/mol quanta)
-
I
*
CO2 compensation point after correction for residual respiration (l/l)
-
PPFD compensation point (mol m-2 s-1) 相似文献
6.
Erika Staudacher Thomas Dalik Petra Wawra Friedrich Altmann Leopold März 《Glycoconjugate journal》1995,12(6):780-786
An 1,3-fucosyltransferase was purified 3000-fold from mung bean seedlings by chromatography on DE 52 cellulose and Affigel Blue, by chromatofocusing, gelfiltration and affinity chromatography resulting in an apparently homogenous protein of about 65 kDa on SDS-PAGE. The enzyme transferred fucose from GDP-fucose to the Asn-linkedN-acetylglucosaminyl residue of an N-glycan, forming an 1,3-linkage. The enzyme acted upon N-glycopeptides and related oligosaccharides with the glycan structure GlcNAc2Man3 GlcNAc2. Fucose in 1,6-linkage to the asparagine-linked GlcNAc had no effect on the activity. No transfer to N-glycans was observed when the terminal GlcNAc residues were either absent or substituted with galactose.N-acetyllactosamine, lacto-N-biose andN-acetylchito-oligosaccharides did not function as acceptors for the 1,3-fucosyltransferase.The transferase exhibited maximal activity at pH 7.0 and a strict requirement for Mn2+ or Zn2+ ions. The enzyme's activity was moderately increased in the presence of Triton X-100. It was not affected byN-ethylmaleimide.Abbreviations 1,3-Fuc-T
GDP-fucose:-N-acetylglucosamine(Fuc to Asn-linked GlcNAc)1,3-fucosyltransferase
- 1,6-Fuc-T
GDP-fucose:-N-acetylglucosamine(Fuc to Asn-linked GlcNAc) 1,6-fucosyltransferase
- PA
pyridylamino
- GnGn
GlcNAc1-2Man1-6(GlcNAc1-2Man1-3)Man1-4GlcNAc1-4GlcNAc
- GnGnF3
GlcNAc1-2Man1-6(GlcNAc1-2Man1-3)Man1-4GlcNAc1-4(Fuc1-3)GlcNAc
- GnGnF6
GlcNAc1-2-Man1-6(GlcNAc1-2Man1-3)Man1-4GlcNAc1-4(Fuc1-6)GlcNAc
- GnGnF3F6
GlcNAc1-2Man1-6(GlcNAc1-2Man1-3)Man1-4GlcNAc1-4(Fuc1-3)[Fuc1-6]GlcNAc
- MM
Man1-6(Man1-3)Man1-4GlcNAc1-4GlcNAc
- MMF3
Man1-6(Man1-3)Man1-4GlcNAc1-4(Fuc1-3)GlcNAc
- MMF3F6
Man1-6(Man1-3)Man1-4GlcNAc1-4(Fuc1-3)[Fuc1-6]GlcNAc 相似文献
7.
Alicia Mimbrera Luis Rivas Faustino Mollinedo Emilio Muñoz Vicente Larraga 《Molecular and cellular biochemistry》1983,56(1):73-80
Summary The combined use of proteolytic digestion and lactoperoxidase catalyzed labelling with [125I] applied to membrane-bound or soluble pure F1-ATPase from Micrococcus lysodeikticus has allowed us to establish the topography of its , , and subunits within the protein molecule and with respect to the plane of the membrane.The subunit is most externally located to the membrane bilayer looking towards the cytoplasmic face, a position consistent with its proposed catalytic role. The and subunits lie in an intermediate layer between the subunits and the membrane, in which the subunit occupies a central position within the F1-ATPase molecule in contact with the subunit. The subunit appears to be tightly bound to the F0 component of the ATPase complex, probably buried in the membrane bilayer. A molecular arrangement of M. lysodeikticus ATPase is proposed that, taking into account the subunit stoichiometry 3 3 2 2 (MW 420 000), accommodates the role assigned to each subunit and most, if not all, the known properties of this bacterial energy-transducing protein. 相似文献
8.
A. Normandin J. Thibault B. P. A. Grandjean 《Bioprocess and biosystems engineering》1994,10(3):109-113
Feedforward neural networks are a general class of nonlinear models that can be used advantageously to model dynamic processes. In this investigation, a neural network was used to model the dynamic behaviour of a continuous stirred tank fermenter in view of using this model for predictive control. In this system, the control setpoint is not known explicitly but it is calculated in such a way to optimize an objective criterion. The results presented show that neural networks can model very accurately the dynamics of a continuous stirred tank fermenter and, the neural model, when used recursively, can predict the state variables over a long prediction horizon with sufficient accuracy. In addition, neural networks can adapt rapidly to changes in fermentation dynamics.List of Symbols
F
Dimensionless flow rate (F/
V0)
-
F m3/h
Flow rate
-
F
0 m3/h
Inlet flow rate
-
J
Objective cost function
-
K
i
Dimensionless constant in Eq. (3) (k
i
/s0)
-
k
i
kg/m3
Substrate inhibition constant in Haldane model
-
k
m
Dimensionless constant in Eq. (3) (k
s
/s0)
-
k
m
kg/m3
Substrate inhibition constant in Haldane model
-
n
prediction horizon
-
S
Dimensionless substrate concentration (s/s0)
-
s kg/m3
Substrate concentration
-
t h
Time
-
v
Dimensionless volume (V/V0)
-
V m3
Liquid volume in fermenter
-
W
ij
, W
jk
Weight matrices in neural network
-
X
Dimensionless biomass concentration
-
x kg/m3
Biomass concentration
-
Y
Biomass/substrate yield coefficient
-
Weighting factor in Eq. (4)
-
Dimensionless specific growth rate (/
)
-
1/h
Maximum specific growth rate
-
1/h
Specific growth rate
-
Dimensionless time (
t) 相似文献
9.
In washed cells of cadmium-sensitive Staphylococcus aureus 17810S oxidizing glutamate, initial Cd2+++ influx via the Mn2+ porter down membrane potential () was fast due to involvement of energy generated by two proton pumps—the respiratory chain and the ATP synthetase complex working in the hydrolytic direction. Such an unusual energy drain for rapid initial Cd2+ influx is suggested to be due to a series of toxic events elicited by Cd2+ accumulation down generated via the redox proton pump: (i) strong inhibition of glutamate oxidation accompanied by a decrease of electrochemical proton gradient (
H
+) formation via the respiratory chain, (ii) automatic reversal of ATP synthetase from biosynthetic to hydrolytic mode, which was monitored by a decrease of
H
+-dependent ATP synthesis, (iii) acceleration of the initial Cd2+ influx down generated the reversed ATP synthetase, the alternative proton pump hydrolyzing endogenous ATP. The primary, cadmium-sensitive targets in strain 17810S seem to be dithiols located in the cytoplasmic glutamate oxidizing system, prior to the membrane-embedded NADH oxidation system. Inhibition by Cd2+ of
H
+-dependent ATP synthesis and of pH gradient (pH)-linked [14C]glutamate transport is a secondary effect due to cadmium-mediated inhibition of
H
+ generation at the cytoplasmic level. In washed cells of cadmium-resistant S. aureus 17810R oxidizing glutamate, Cd2+ accumulation was prevented due to activity of the plasmid-coded Cd2+ efflux system. Consequently,
H
+-producing and -requiring processes were not affected by Cd2+. 相似文献
10.
N. Schilling 《Planta》1982,154(1):87-93
The de novo synthesis of maltose in spinach (Spinacia oleracea L.) was shown to be catalyzed by a maltose synthase, which converts two molecules of -d-glucose-1-phosphate (-G1P) (Km 1.5 mmol l-1) to maltose and 2 orthophosphate (Pi). This enzyme was purified 203-fold by fractionated ammonium sulfate precipitation and by column chromatography on Sepharose 6B. The addition of -G1P (15 mmol l-1) to the isolation buffer is required to stabilize the enzyme activity during the extraction and purification procedure. Molecular weight determination by gel filtration yielded a value of 95,000. -Gluconolactone, ATP and Pi are competitive inhibitors toward the substrate -G1P. The maltose synthase catalyzes an exchange of the phosphate group of -G1P with [32P] orthophosphate; this transfer reaction suggests that the synthesis of maltose occurs via a glucose-enzyme in a double displacement reaction. The physiological role of this enzyme as a starch initiator system is discussed.Abbreviations Fru
fructose
- Glc
glucose
- -G1P
-d-glucose-1-phosphate
- -G1P
-d-glucose-1-phosphate
- G6P
d-glucose-6-phosphate
This enzyme is tentatively called maltose synthase in this publication 相似文献
11.
Mengli Cai Ying Huang Jianhua Liu Ramaswamy Krishnamoorthi 《Journal of biomolecular NMR》1995,6(2):123-128
Summary Three different conformations of proline rings in a protein in solution, Up, Down and Twist, have been distinguished, and stereospecific assignments of the pyrrolidine -, - and -hydrogens have been made on the basis of 1H-1H vicinal coupling constant patterns and intraresidue NOEs. For all three conformations, interhydrogen distances in the pairs -3, 3-3, 2-2, 2-2, and 3-3 (2.3 Å) are shorter than those in the pairs -2, 2-3, 3-2, 2-3, and 3-2 (2.7–3.0 Å), resulting in stronger NOESY cross peaks. For the Up conformation, the 3-2 and 2-3 spin-spin coupling constants are small (<3 Hz), and weak cross peaks are obtained in a short-mixing-time (10 ms) TOCSY spectrum; all other vicinal coupling constants are in the range 5–12 Hz, and result in medium to strong TOCSY cross peaks. For the Down form, the -2, 2-3, and 3-2 vicinal coupling constants are small, leading to weak TOCSY cross peaks; all other couplings again are in the range 5–12 Hz, and result in medium to strong TOCSY cross peaks. In the case of a Twist conformation, dynamically averaged coupling constants are anticipated. The procedure has been applied to bovine pancreatic trypsin inhibitor and Cucurbita maxima trypsin inhibitor-V, and ring conformations of all prolines in the two proteins have been determined. 相似文献
12.
The permeabilized cells of Trigonopsis variabilis CCY 15-1-3 having D-amino acid oxidase (DAAO) activity were used to convert cephalosporin C (CPS-C) into 7-(-ketoadipyl amido) cephalosporanic acid (CO-GL-7-ACA) in a batch bioreactor with good aeration and stirring during the process. The deacylation of 7--(4-carboxybutanamido)-cephalosporanic acid (GL-7-ACA) to 7-cephalosporanic acid (7-ACA) by permeabilized cells of Pseudomonas species 3635 having 4--(4-carboxybutamido)-cephalosporanic acid acylase (GL-7-ACA acylase) activity was performed in a batch bioreactor. A spectrophotometric method for the determination of CO-GL-7-ACA and 7-ACA was proposed. Experimental data were fitted by non-linear regression with parameters optimization. The sorption method (without reaction) was applied for the determination of cephalosporin effective diffusion coefficients in Ca-pectate gel beads. These beads were prepared by dropping a potassium pectate gel suspension of inactive permeabilized cells of Trigonopsis variabilis and Pseudomonas species, crosslinked with glutaraldehyde, into a stirred 0.2 M calcium chloride solution. Concentrations of appropriate cephem components were measured by the refractive method. Values of effective diffusion coefficients were calculated by the Fibbonacci optimization method.List of Symbols
c
L mol/dm3
concentration on the surface of a bead
-
c
L0
mol/dm3
initial cephalosporin concentration
-
c
L
mol/dm3
equilibrium cephalosporin concentration in the solution
-
c
s1
mol/dm3
concentration of CPS-C
-
c
s2
mol/dm3
concentration of GL-7-ACA
-
D
ei
m2/s
effective diffusion coefficient of the components
-
K
i
mol/dm3
inhibition parameter in Eq. (2)
-
K
m
i
mol/dm3
Michaelis constant in Eq. (1)
-
K
m
2 mol/dm3
Michaelis constant in Eq. (2)
-
n
number of beads
-
q
n
nonzero positive roots in Eq. (7)
-
r
1 mol/(dm3·s)
rate of the conversion of CPS-S to CO-GL-7-ACA
-
r
2 mol/(dm3·s)
rate of the conversion of GL-7-ACA to 7-ACA
-
R m
radius of the bead
- S(
)
symbol for total residual sum of squares in Eq. (1)
-
t s
time
-
V
m
1 mol/(dm3·s)
max. reaction rate in Eq. (1)
-
V
m
2 mol/(dm3·s)
max. reaction rate in Eq. (2)
-
V
L
dm3
volume of the solution excluding the space occupied by beads
-
V
s
dm3
volume of beads
-
y
i
mol/(dm3 · s)
symbol for experimental data in Eq. (1)
-
i
mol/(dm3· s)
symbol for calculated data in Eq. (1)
-
P
porosity, defined by Eq. (5)
-
dimensionless parameter, defined by Eq. (6)
The authors wish to thank Dr. P. Gemeiner of Slovak Academy of Sciences for rendering of pectate gel. This work is supported by Ministry of Education (Grant No. 1/990 935/93) 相似文献
13.
A hollow fiber perfusion reactor constructed from pairs of concentric fibers forming a thin annular space is analyzed theoretically in terms of mass transfer resistances, and is shown experimentally to support the growth of an anchorage-dependent cell line in high-density culture. Hollow fiber perfusion reactors described in the literature typically employ a perfusion pathlength much greater than the distance that could be supported by diffusion alone, and analyses of these reactors typically incorporate the assumption of uniform perfusion throughout the cell mass despite many reported observations of inhomogeneous cell growth in perfusion reactors. The mathematical model developed for the annular reactor predicts that the metabolism of oxygen, carbon substrates, and proteins by anchorage-dependent cells can be supported by the reactor even in the absence of perfusion. The implications of nonuniform cell growth in perfusion reactors in general is discussed in terms of nutrient distribution. In the second part of the paper, the growth and metabolism of the mouse adrenal tumor line Y-1 in flask culture and in the annular reactor are compared. The reactor is shown to be a promising means for culturing anchorage-dependent cells at high density.List of Symbols
c mol/dm3
substrate concentration
-
D
mm2/s
effective diffusivity of substrate in the membrane
-
D
tm2/s
effective diffusivity of substrate in the cell region
-
L
pm2s/kg
hydraulic permeability of fiber
-
Pe
m
Peclet number for membrane transport,
wR1/D
m
-
Pe
t
Peclet number for transport through cell mass, v
wR2/D
t
- Q mol/m3s
zero-order consumption rate of substrate per unit volume of cell mass
-
r m
radial distance from centerline of fiber lumen
-
R
1, R
2 m
inner and outer radii of inner annular fiber (Fig. 1)
-
R
3, 4 m
inner and outer radii of outer annular fiber (Fig. 1)
-
v
wm/s
fluid velocity through the fiber wall at R
1
-
fraction of shell side filled with cells
-
dimensionless radial distance, R
3/R1
-
dimensionless radial distance, R
2/R
1
-
cm2
hydraulic conductivity
-
viscosity
-
2,
Thiele modulus
-
dimensionless radial distance, R
4/R
1 相似文献
14.
A yeast-mycelium (Y-M) transition in Candida albicans was induced by exogenous yeast extract, adenosine, adenosine 5-monophosphate (AMP), adenosine 5-diphosphate (ADP), adenosine 35 cyclic monophosphate (cAMP) and its analogue N6, O2-dibutyryl adenosine 35-cyclic monophosphate (dbcAMP) in defined liquid medium at 25°C. Adenosine 5-triphosphate (ATP) was found to delay germ tube formation in yeast cells, whereas the cAMP phosphodiesterase inhibitors, theophylline and caffeine, induced a Y-M transition. Intracellular and extracellular cyclic AMP levels increased during the yeast-mycelium transition and maximum levels of intracellular cyclic AMP coincided with maximum germ tube formation. Of the many inducers and inhibitors of germ tube and mycelium formation in C. albicans tested, including incubation at 37°C or in the presence of 1.5mM CaCl2, the calmodulin inhibitor calmidazolium (R24571) added together with CaCl2 induced the highest intra- and extracellular cyclic AMP levels. These results confirm the involvement of cyclic AMP in the yeast-mycelium transition of C. albicans. 相似文献
15.
Hydraulic model of a gas-lift bioreactor with flocculating yeast 总被引:1,自引:0,他引:1
E. Roca C. Ghommidh J. M. Navarro J. M. Lema 《Bioprocess and biosystems engineering》1995,12(5):269-272
The hydraulic model of a gas lift bioreactor, during a continuous alcoholic fermentation by using a strongly flocculating yeast, is analysed. Sucrose at two different concentrations (50 and 100 g/l) was used as substrate and the dilution rate for all the experiments was 1 h–1. The biomass concentrations were between 85 and 110 g dry weight/1. A stimulus response technique was used to obtain the Residence Time Distribution curves, a pulse of a lactose solution being used as the tracer. Mixing time was determined by means of the response to a pulse of an acid tracer. These experiments were carried out by using an on-line data-acquisition system. The bioreactor behaviour is completely homogeneous, except for high substrate and biomass concentrations. A two parameters combined model is necessary, in this case, to fit the experimental data. Mixing times are very low, in the order of 10 seconds.List of Symbols
C
T1
Tracer concentration of the tank 1 (g/l)
-
C
T10
Reference tracer concentration (g/l)
-
C
Normalized tracer concentration (dimensionless)
-
Q
0
Feed flowrate (l/h)
-
Q
1
Flow exchanged between tank 1 and 2 (l/h)
- [S]
Substrate concentration (g/l)
-
t
Time (s)
-
t
mix
Mixing time (s)
-
t
c
Circulation time (s)
-
V
Reactor total volume (l)
-
X
Biomass concentration expressed as dry weigh (g d.w./l)
-
Fraction of the total volume occupied by the highly agitated region
-
Fraction of the total flow which is exchanged between reactor 1 and 2
-
Mean residence time (s), = V/Q
0
-
Dimensionless time, = t/
The stay of E. Roca at the ISIM in Montpellier (France) was supported by a grant from the CICYT (project BIO92 0568) of the Spanish Government. 相似文献
16.
Anton F. Post 《Archives of microbiology》1986,145(4):353-357
Transitions in growth irradiance level from 92 to 7 Em-2 s-1 and vice versa caused changes in the pigment contents and photosynthesis of Oscillatoria agardhii. The changes in chlorophyll a and C-phycocyanin contents during the transition from high to low irradiance (HL) were reflected in photosynthetic parameters. In the LH transition light utilization efficiencies of the cells changed faster than pigment contents. This appeared to be related to the lowering of light utilization efficiencies of photosynthesis. As a possible explanation it was hypothesized that excess photosynthate production led to feed back inhibition of photosynthesis. Time-scales of changes in the maximal rate of O2 evolution were discussed as changes in the number of reaction centers of photosystem II in relation to photosynthetic electron transport. Parameters that were subject to change during irradiance transitions obeyed first order kinetics, but hysteresis occurred when comparing HL with LH transients. Interpretation of first order kinetic analysis was discussed in terms of adaptive response vs changes in growth rate.Non-standard abbreviations Chla
chlorophyll a
- CPC
C-phycocyanin
- PS II
photosystem II
- PS I
photosystem I
- RC II
reaction center of photosystem II
- P
photosynthetic O2-evolution
- I
irradiance, Em-2 s-1
-
light utilization efficiency of cells, mmol O2·mg dry wt-1·h-1/Em-2 s-1
-
light utilization efficiency of photosynthetic apparatus, mol O2·mol Chla
-1·h-1/Em-2 s-1
- Pmax
maximal rate of O2 evolution by cells, mol O2·mg dry wt-1·h-1
- Pmax
maximal rate of O2 evolution by photosynthetic apparatus, mol O2·mol·Chla
-1·h-1
- LL
low light, E m-2 s-1
- HL
high light, E m-2 s-1
- LH
low to high light transition
- HL
high to low light transition
-
k
specific rate of adaptation, h-1
-
specific growth rate, h-1
-
Q
pool size of cell constituent, mol·mg dry wt-1
-
q
net synthesis rate of cell constituent, mol·mg dry wt-1·h-1 相似文献
17.
I. A. Bass Zh. M. Gorlenko O. N. Danilevskaya A. D. Dmitriev E. S. Kalyaeva S. Z. Mindlin A. V. Timopheev R. S. Khesin 《Molecular & general genetics : MGG》1977,154(1):101-110
Summary In merodiploid cells containing a double dose of structural genes of RNA polymerase subunits-rpoBand rpoC-the rate of and subunits synthesis is 2 times higher than in haploidcells. Missence mutation rpoC1 (tsX) alters polypeptide and inducesthe and subunits synthesis at increased rate, particularly at a nonpermissive temperature. When rpoBCoperon carrying mutation rpoC1 is duplicated no dosage effect is observed. In the rpoC
+/rpoC1 heterodiploid the rpoC1 mutation does not significantly accelerate RNA polymerase subunits synthesis i.e. is recessive with respect to rpoC
+
Rifampicin causes 6-fold stimulation of RNA polymerase subunits synthesis in a sensitive wild-type strain. The rpoC1 mutation itself accelerates the synthesis of these subunits 3-fold. In the presence of rifampicin the mutant strain produces 13–22-fold faster as compared to wild-type strain without the drug. Thus, the effects of rifampicin and the mutation are multiplied suggesting that these factors act independently. Similar data have also been obtained with rifampicin-treated cells of rpoB22 (ts22) amber-mutant.After UV-irradiation of cells and synthesis is depressed much stronger than the total protein synthesis. Infection with a transducing phage rif
d-47 which carries rpoB gene provokes a higher rate of synthesis. When pre-irradiated cells (500 erg/mm2) are infected with this phage, the rate of synthesis grows 20-fold compared to irradiated, non-infected cells and 6.5-fold compared to intact cells.The data are discussed in terms of the possible regulatory mechanisms of RNA polymerase subunit synthesis. 相似文献
18.
Mammalian brain tubulin is an heterodimer; both and exist in 6–7 isotypic forms which differ in their amino acid sequences. By the use of isotype-specific monoclonal antibodies, we have previously shown that we can purify the
II,
III, anda
IV tubulin dimers from bovine brain. We have also observed that these isotypes differ in their distributionin vivo and their polymerization and drug-binding propertiesin vitro. We have now explored the question of whether the isotypically purified dimers differ in their overall conformation using as probes compounds of theN,N-polymethylenebis (iodoacetamide) series which are known to form discrete intrachain cross-links in-tubulin. These compounds have the structure ICH2CONH(CH2)
n
NHCOCH2I. One of these cross-links, designated
s, is between cys12 and either cys201 or cys211. The other, designated
*, is between cys239 and cys354. The
* cross-link forms in
II and
IV but not in
III; this is not surprising in view of the fact that
III has serine at position 239 instead of cysteine. However,
III is also unable to form the
s cross-link, although it appears to have all three cysteines which may be involved in the cross-link. This suggests that at least one of the sulfhydryls involved in the cross-link may be inaccessible in
III. Although both
II and
IV can form the
s cross-link, the dependence on cross-linker chain length is different.
II forms
s with derivatives in whichn=2, 4, 5, 6, and 7 but not with those in whichn=3 or 10. In contrast,
IV forms
s with derivatives in whichn=2, 3, 4, 5, 6, 7, and 10. These results imply that the
s sulfhydryls are slightly more accessible in
IV and are therefore less dependent on the conformation of the cross-linker to react with it. It appears, therefore, that the
II,
III, and
IV dimers each have unique conformations. This may help to explain the different assembly and drug-binding properties of these dimers. 相似文献
19.
P. Ayazi Shamlou S. Stavrinides N. Titchener-Hooker M. Hoare 《Bioprocess and biosystems engineering》1996,14(5):237-243
Experimental data relating to the breakage of isoelectric Soya protein precipitates in a mechanically agitated bioreactor are provided and examined in the light of a proposed mechanistic model which relates the size of the maximum attainable aggregate diameter to the energy dissipation rate in the vessel. The analysis suggests that protein precipitation results in the formation of scale-invariant fractal aggregates with a dimensionality of 2.2. Comparing the fractal dimensionality of the protein precipitates with reported values based on computer simulation studies suggests that the aggregates undergo considerable restructuring during agitation.List of Symbols
A
Hamaker constant (J)
-
D
impeller diameter (m)
-
d
p
primary particle diameter (m)
-
d
f
maximum aggregate diameter (m)
-
G
shear rate (s–1)
-
H
0
separation distance between two primary particles (m)
-
k
constant in Eq. (5)
-
K
constant in Eq. (6)
-
N
impeller speed (rpm or rps)
-
r
radial position in an aggregate, measured from the centre (m)
-
t
time of exposure to shear (mins)
-
T
e
eddy period (s–1)
-
v
f
aggregate volume (m3)
Greek Symbols
aggregate dimensionality constant
-
energy dissipation rate (W/kg)
-
dynamic viscosity of particle-free liquid (kg/ms)
-
kinematic viscosity of particle-free liquid (m2/s)
-
collision probability (–)
-
p
aggregate density (kg/m3)
-
p
continuous phase density (kg/m3)
-
aggregate mechanical strength (N/m2)
-
shear stress (N/m2)
-
particle concentration in an aggregate (m3/m3)
-
(r)
porosity at radial position, r 相似文献
20.
The location of the (13)--glucan, callose, in the walls of pollen tubes in the style of Nicotiana alata Link et Otto was studied using specific monoclonal antibodies. The antibodies were raised against a laminarinhaemocyanin conjugate. One antibody selected for further characterization was specific for (13)--glucans and showed no binding activity against either a cellopentaose-bovine serum albumin (BSA) conjugate or a (13, 14)--glucan-BSA conjugate. Binding was inhibited by (13)--oligoglucosides (DP, 3–6) with maximum competition being shown by laminaripentaose and laminarihexaose, indicating that the epitope included at least five (13)--linked glucopyranose residues. The monoclonal antibody was determined to have an affinity constant for laminarihexaose of 2.7. 104M–1. When used with a second-stage gold-labelled, rabbit anti-mouse antibody, the monoclonal antibody probe specifically located the (13)--glucan in the inner wall layer of thin sections of the N. alata pollen tubes.Abbreviations BSA
bovine serum albumin
- PBS
phosphate-buffered saline
- ELISA
enzyme linked immunosorbent assay
- DP
degree of polymerization
- PVC
polyvinyl chloride
P.J.M. is an Australian Postdoctoral Research Fellow. We wish to thank Joan Hoogenraad for her technical assistance with the tissue culture, and Althea Wright for her assistance in the preparation of this paper. 相似文献