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1.
R. Luttmann M. Thoma H. Bucholz W. Scheiding K. Schürgerl 《Applied microbiology and biotechnology》1981,13(3):145-150
Summary Using the model presented in part I, the measured time and spacial variations of process variables were simulated with satisfactory accuracy. Especially the experimentally found minima of the longitudinal dissolved oxygen concentration profiles in the substrate limiting growth range, which are caused by the transition from oxygen transfer limited to substrate limited growth along the tower, can be simulated with great accuracy.Symbols L
length
- M
mass
- T
time
- K
temperature
- MM
mole mass
- a
Specific gas/liquid interfacial area with regard to the liquid volume in the tower (L–1)
- DSR
Substrate feed rate (ML–3T–1)
- KO
Saturation constant of Monod kinetics with regard to oxygen (ML–3)
- KS
Saturation constant of Monod kinetics with regard to the substrate (ML–3)
- KST
Constant
- KL
Mass transfer coefficient (LT–1)
- kLa
Volumetric mass transfer coefficient (T–1)
- kLaE
Volumetric mass transfer coefficient at the entrance (T–1)
- kLa
Volumetric mass transfer coefficient at large distances from the entrance (T–1)
- kLa
0
Volumetric mass transfer coefficient in the absence of substrate (ethanol) (T–1)
- LR
Gas-liquid layer height in the tower (L)
- LR
Height of the loop (L)
-
- OB
Dissolved oxygen concentration in the loop liquid (ML–3)
- OF
Dissolved oxygen concentration in the tower liquid (ML–3)
- O
F
*
Saturation value of OF (ML–3)
- OTR
Oxygen transfer rate (ML–3T–1)
- P
Pressure
-
Oxygen transfer rate (ML–3T)
- SB
Substrate concentration in the loop liquid (ML–3)
- SD
Substrate concentration at which kLa=2 kLa
0
(ML–3)
- SF
Substrate concentration in the tower liquid (ML–3)
- T
Absolute temperature
- t
Time (T)
- uGo
Superficial gas velocity in the tower
- VR
Reactor volume (L3)
- VG
Volumetric gas flow rate in the tower (L3T–1)
- VB
Volumetric liquid flow rate in the loop (L3T–1)
- VF
Volumetric liquid flow rate in the tower (L3T–3)
- Vu
Liquid recycling rate (L3T–1)
- XB
Biomass concentration in the loop liquid (ML–3)
- XF
Biomass concentration in the tower liquid (ML–3)
- x
Longitudinal coordinate in the tower (L)
- x*
Longitudinal coordinate in the loop (L)
- xOG
O2 mole fraction in the gas phase
- YX/O
Yield coefficient of biomass with regard to oxygen
- YX/S
Yield coefficient of biomass with regard to substrate
- z=x/LR
Dimensionless longitudinal coordinate in the tower
- z*=x*/LB
Dimensionless longitudinal coordinate in the loop
-
Constant (LR is the distance from the aerator on which kL a is space dependent)
-
Liquid recirculation ratio
- G
Mean relative gas holdup in the tower
-
exp
Experimentally determined (T–1)
-
max
Maximum specific growth rate (T–1)
-
F
Liquid density (ML–3)
- A
At the exit
- E
At the inlet 相似文献
2.
Summary Equations are described which relate nutrient feed rate to specific microbial growth rate in fed batch culture. Fed batch cultures are classified into three types: 1) those allowing constant specific microbial growth rate, 2) those in which the rate of change of flow rate is constant and 3) those in which the nutrient flow rate is constant. The basic properties of these three types are described.Symbols
F
medium flow rate, L3 T–1
-
F
o
medium flow rate at zero time, L3 T–1
-
g
rate of change of flow rate with time, L3 T–2
-
K
v
volume constant, being the total cell weight at zero time divided by the product of the yield coefficient and growth-limiting substrate concentration in the feed, L3
-
s
r
growth limiting substrate concentration in the feed, ML–3
-
V
volume of liquid in the growth vessel, L3
-
V
f
volume of medium fed to the growth vessel, L3
-
V
o
volume of liquid in the growth vessel at zero time, L3
-
X
total weight of cells, M
-
x
concentration of cells, ML–3
-
X
g
total weight of cells grown, M
-
X
o
total weight of cells at zero time, M
-
Y
yield coefficient, weight of cells grown per unit weight of growth-limiting substrate
-
specific microbial growth rate, T–1 相似文献
3.
Summary The solubility of oxygen in the liquid phase of a bioreactor was changed by a ramp change of temperature, and kLa was determined from the resulting return to equilibrium of dissolved oxygen activity. The maximum kLa that can be measured by this method in a standard laboratory scale bioreactor is 145 h–1 corresponding to a temperature change rate of 320°C h–1.Nomenclature p
Difference between pG and pL (% saturation)
- T
Ramp change of temperature (°C)
- E
Temperature-compensated output from the oxygen electrode (A)
- Eu
Uncompensated output from the oxygen electrode (A)
- kLa
Overall volumetric mass transfer coefficient (h–1)
- kLaTm
Overall volumetric mass transfer coefficient at temperature Tm (h–1)
- PG
Dissolved oxygen activity in equilibrium with the gas phase (% saturation)
- pL
Dissolved oxygen activity (% saturation)
- pLm
Dissolved oxygen activity at time tm (% saturation)
- t
Time (h)
- tm
Time of maximum p (h)
- T
Temperature (°C)
- Tcal
Calibration temperature of the oxygen electrode (°C)
- Tm
Final temperature after a temperature shift (°C)
- Tn
Temperature at time tn 相似文献
4.
A family of 10 competing, unstructured models has been developed to model cell growth, substrate consumption, and product formation of the pyruvate producing strain Escherichia coli YYC202 ldhA::Kan strain used in fed-batch processes. The strain is completely blocked in its ability to convert pyruvate into acetyl-CoA or acetate (using glucose as the carbon source) resulting in an acetate auxotrophy during growth in glucose minimal medium. Parameter estimation was carried out using data from fed-batch fermentation performed at constant glucose feed rates of
qVG=10 mL h–1. Acetate was fed according to the previously developed feeding strategy. While the model identification was realized by least-square fit, the model discrimination was based on the model selection criterion (MSC). The validation of model parameters was performed applying data from two different fed-batch experiments with glucose feed rate
qVG=20 and 30 mL h–1, respectively. Consequently, the most suitable model was identified that reflected the pyruvate and biomass curves adequately by considering a pyruvate inhibited growth (Jerusalimsky approach) and pyruvate inhibited product formation (described by modified Luedeking–Piret/Levenspiel term).List of symbols cA
acetate concentration (g L–1)
- cA,0
acetate concentration in the feed (g L–1)
- cG
glucose concentration (g L–1)
- cG,0
glucose concentration in the feed (g L–1)
- cP
pyruvate concentration (g L–1)
- cP,max
critical pyruvate concentration above which reaction cannot proceed (g L–1)
- cX
biomass concentration (g L–1)
- KI
inhibition constant for pyruvate production (g L–1)
- KIA
inhibition constant for biomass growth on acetate (g L–1)
- KP
saturation constant for pyruvate production (g L–1)
- KP
inhibition constant of Jerusalimsky (g L–1)
- KSA
Monod growth constant for acetate (g L–1)
- KSG
Monod growth constant for glucose (g L–1)
- mA
maintenance coefficient for growth on acetate (g g–1 h–1)
- mG
maintenance coefficient for growth on glucose (g g–1 h–1)
- n
constant of extended Monod kinetics (Levenspiel) (–)
- qV
volumetric flow rate (L h–1)
- qVA
volumetric flow rate of acetate (L h–1)
- qVG
volumetric flow rate of glucose (L h–1)
- rA
specific rate of acetate consumption (g g–1 h–1)
- rG
specific rate of glucose consumption (g g–1 h–1)
- rP
specific rate of pyruvate production (g g–1 h–1)
- rP,max
maximum specific rate of pyruvate production (g g–1 h–1)
- t
time (h)
- V
reaction (broth) volume (L)
- YP/G
yield coefficient pyruvate from glucose (g g–1)
- YX/A
yield coefficient biomass from acetate (g g–1)
- YX/A,max
maximum yield coefficient biomass from acetate (g g–1)
- YX/G
yield coefficient biomass from glucose (g g–1)
- YX/G,max
maximum yield coefficient biomass from glucose (g g–1)
-
growth associated product formation coefficient (g g–1)
-
non-growth associated product formation coefficient (g g–1 h–1)
-
specific growth rate (h–1)
- max
maximum specific growth rate (h–1) 相似文献
5.
Yuan-Kun Lee Sun-Yeun Ding Chye-Hock Hoe Chin-Seng Low 《Journal of applied phycology》1996,8(2):163-169
Chlorella sorokiniana was cultured in heterotrophic or mixotrophic mode in outdoor enclosed tubular photobioreactor. The culture temperature was maintained at 32–35 °C. At night, theChlorella culture grew heterotrophically, and 0.1 M glucose was completely consumed. The biomass growth yield of glucose was 0.35 ± 0.001 g-biomass g-glucose–1. During the day, the algal culture grew mixotrophically and the biomass growth yield was 0.49 g-biomass g-glucose–1 in low density culture (initial biomass concentration, Xo = 2 g l–1), 0.56 g-biomass g-glucose–1 in medium density culture (Xo = 4 g l–1) and 0.46 g-biomass g-glucose–1 in high density culture (Xo = 7 g l–1). The daily area productivity of the culture, with Xo = 4 g l–1 corresponded to 127 g-biomass m–2 d–1 during the day and 79 g-biomass m–2 d–1 during the night. In all the cultures, the dissolved O2 concentration increased in the morning, reached the maximum value at noon, and then decreased in the afternoon. The dissolved CO2 concentration remained at 3 mBar in the morning and increased in the afternoon. Glycolate was not found to accumulate in culture medium. 相似文献
6.
Prostaglandins A2, B1, E1, E2, F1α and F2α were added to cultures of human epidermal cells (keratinocytes) for 24 hours at 37°C, and the effects on 3H-thymidine uptake into DNA was measured. At 70 μg/ml all prostaglandins tested except PGF2α inhibited the uptake of 3H-thymidine greater than 50%. However, at 35 μg/ml, PGA2 and PGB1 were the only two prostaglandins to show significant inhibition, 96% and 51% respectively. At 17.5 μg/ml only PGA2 caused substantial inhibition, 68%. In order to determine if the PGA2 action was mediated by membrane receptors propranolol, phentolamine, metiamide and prostynoic acid were added in conjunction with PGA2. None of the above receptor antagonists were able to reduce the PGA2-induced inhibition of 3H-thymidine uptake. These results indicate that the pre-incubation of human keratinocytes with prostaglandins for 24 hours results in a decrease of 3H-thymidine incorporation in DNA. The precise mechanism of action is unknown at this time. 相似文献
7.
Ana L. Obaid Thomas F. Leininger Edward D. Crandall 《The Journal of membrane biology》1980,52(2):173-179
Summary A stopped-flow rapid reaction apparatus was used for measuring changes in extracellular pH (pH
o
) of red cell suspensions under conditions wheredpH
o
/dt was determined by the rate of HCO
3
–
/X
– exchange across the membrane (X
–=Cl–, Br–, F–, I–, NO
3
–
or SCN–). The rate of the exchange at 37°C decreased forX
– in the order: Cl–>Br–>F–>I–>NO
3
–
>SCN–, with rate constants in the ratios 10.860.770.550.520.31. When HCO
3
–
is exchanged for Cl–, Br–, F–, NO
3
–
or SCN–, a change in the rate-limiting step of the process takes place at a transition temperature (T
T
) between 16 and 26°C. In I– medium, however, no transition temperature is detected between 3 and 42°C. AlthoughT
T
varies withX
–, the activation energies both above and belowT
T
are similar for Cl–, Br–, NO
3
–
and F–. The values of activation energy are considerably higher whenX
–=I– or SCN–. The apparent turnover numbers calculated for HCO
3
–
/X
– exchange (except forX
–=I–) at the correspondingT
T
ranged from 140 to 460 ions/site ·sec for our experimental conditions. These findings suggest that: (i) HCO
3
–
/X
– exchange for allX
– studied takes place via the rapid anion exchange pathway; (ii) the rate of HCO
3
–
/X
– exchange is influenced by the specific anions involved in the 11 obligatory exchange; and (iii) the different transition temperatures in the Arrhenius diagrams of the HCO
3
–
/X
– exchange do not seem to be directly related to a critical turnover number, but may be dependent upon the influence ofX
– on protein-lipid interactions in the red blood cell membrane. 相似文献
8.
The influence of nitrogen concentration and ammonium/nitrate ratio on N-uptake,mineral composition and yield of citrus 总被引:9,自引:0,他引:9
In short-term water culture experiments with different 15N labeled ammonium or nitrate concentrations, citrus seedlings absorbed NH4
+ at a higher rate than NO3
–. Maximum NO3
– uptake by the whole plant occurred at 120 mg L–1 NO3
–-N, whereas NH4
+ absorption was saturated at 240 mg L–1 NH4
+-N. 15NH4
+ accumulated in roots and to a lesser degree in both leaves and stems. However, 15NO3
– was mostly partitioned between leaves and roots.Adding increasing amounts of unlabeled NH4
+ (15–60 mg L–1 N) to nutrient solutions containing 120 mg L–1 N as 15N labeled nitrate reduced 15NO3
– uptake. Maximum inhibition of 15NO3
– uptake was about 55% at 2.14 mM NH4
+ (30 mg L–1 NH4
+-N) and it did not increase any further at higher NH4
+ proportions.In a long-term experiment, the effects of concentration and source of added N (NO3
– or NH4
+) on nutrient concentrations in leaves from plants grown in sand were evaluated. Leaf concentration of N, P, Mg, Fe and Cu were increased by NH4
+ versus NO3
– nutrition, whereas the reverse was true for Ca, K, Zn and Mn.The effects of different NO3
–-N:NH4
+-N ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at 120 mg L–1 total N on leaf nutrient concentrations, fruit yield and fruit characteristics were investigated in another long-term experiment with plants grown in sand cultures. Nitrogen concentrations in leaves were highest when plants were provided with either NO3
– or NH4
+ as a sole source of N. Lowest N concentration in leaves was found with a 75:25 NO3
–-N/NH4
+-N ratio. With increasing proportions of NH4
+ in the N supply, leaf nutrients such as P, Mg, Fe and Cu increased, whereas Ca, K, Mn and Zn decreased. Yield in number of fruits per tree was increased significantly by supplying all N as NH4
+, although fruit weight was reduced. The number of fruits per tree was lowest with the 75:25 NO3
–-N:NH4
+-N ratio, but in this treatment fruits reached their highest weight. Rind thickness, juice acidity, and colour index of fruits decreased with increasing NH4
+ in the N supply, whereas the % pulp and maturity index increased. Percent of juice in fruits and total soluble solids were only slightly affected by NO3
–:NH4
+ ratio. 相似文献
9.
Protein Synthesis in Bromegrass (Bromus inermis Leyss) Cultured Cells during the Induction of Frost Tolerance by Abscisic Acid or Low Temperature 总被引:10,自引:9,他引:1
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Bromus inermis Leyss cell cultures treated with 75 micromolar abscisic acid (ABA) at both 23 and 3°C developed more freezing resistance than cells cultured at 3°C. Protein synthesis in cells induced to become freezing tolerant by ABA and low temperature was monitored by [14C]leucine incorporation. Protein synthesis continued at 3°C, but net cell growth was stopped. Most of the major proteins detected at 23°C were synthesized at 3°C. However, some proteins were synthesized only at low temperatures, whereas others were inhibited. ABA showed similar effects on protein synthesis at both 23 and 3°C. Comparative electrophoretic analysis of [14C]leucine labeled protein detected the synthesis of 19, 21 and 47 kilodalton proteins in less than 8 hours after exposure to exogenous ABA. Proteins in the 20 kilodalton range were also synthesized at 3°C. In addition, a 31 kilodalton protein band showed increased expression in freezing resistant ABA treated cultures after 36 hours growth at both 3 and 23°C. Quantitative analysis of [14C]leucine labeled polypeptides in two-dimensional gels confirmed the increased expression of the 31 kilodalton protein. Two-dimensional analysis also resolved a 72 kilodalton protein enriched in ABA treated cultures and identified three proteins (24.5, 47, and 48 kilodaltons) induced by low temperature growth. 相似文献
10.
Barreto Crespo M. T. Carrondo M. J. T. 《Journal of industrial microbiology & biotechnology》1994,13(1):63-69
Summary The influence of different operational parameters, such as the dilution rate (D) and the bleeding rate (B), in the production of a flocculent strain ofLactobacillus plantarum was studied. The effect of the dilution rate was demonstrated to be related to the lactic acid concentration inside the reactor. The effect of the bleeding rate was shown to be critical in the stabilization of the operation (due to a better pH control). It also allowed a continuous recovery of cells outside the reactor. Viability testing of the lactic starter cultures showed that operation with cell purge increased the viability of the starter cultures obtained.Nomenclature
B
Bleeding rate, h–1
-
D
Dilution rate, h–1
-
F
Feed flow rate, L h–1
-
I
Feed velocity, m h–1
-
Specific growth rate, h–1
-
v
Lactic acid specific productivity, g g–1 h–1
-
P
Product concentration (lactic acid), g L–1
-
P
out
Product concentration leaving the system, g L–1
-
Q
b
Bleeding flow rate, L h–1
-
R
Recirculation velocity, m h–1
-
S
Substract concentration, g L–1
-
t
Time, h
-
T
p
Time of ascensional flow (length of the column/total ascensional velocity), h
-
T
r
Residence time (1/D), h
-
V
Volume of the reactor, L
-
X
Cell concentration, g L–1
-
X
out
Cell concentration leaving the system, g L–1 相似文献
11.
Summary The linear growth phase in cultures limited by intracellular (conservative) substrate is represented by a flat exponential curve. Within the range of experimental errors, the presented model fits well the data from both batch and continuous cultures ofEscherichia coli, whose growth is limited in that way.List of symbols D
dilution rate, h–1
- KS
saturation constant, g.L–1
- S
concentration of the limiting substrate, g.L–1
- Si
concentration of the limiting substrate accumulated in the cells, g.g–1
- So
initial concentration of the limiting substrate, g.L–1
- t
time of cultivation, h
- t1
time of exhaustion of the limiting substrate from medium, h
- to
beginning of exponential phase, h
- X
biomass concentration, g.L–1
- X1
biomass concentration at the time of exhaustion of the limiting substrate from the medium, g.L–1
- Xo
biomass concn. at the beginning of exponential phase, g.L–1
-
biomass concn. at steady-state, g.L–1
- Y
growth yield coefficient (biomass/substrate)
-
specific growth rate, h–1
- m
maximum specific growth rate, h–1 相似文献
12.
Y. Kowyama 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1983,65(4):303-308
Summary To determine the time and duration of the first and second DNA synthetic phases in fertilized egg cells and central cells of rice, a total of 753 ovules were sampled at 2 h intervals during the first 30 h after pollination and exposed to 3H-thymidine for 2 h at 25 °C. Autoradiographic observation of labeled nuclei was made for fertilized egg cells, as well as for central and antipodal cells. The first and second DNA synthetic phases in fertilized egg cells were found 8–12 h and 21–25 h after pollination, respectively. The durations of each cell-cycle phase in the egg cell were estimated to be 4–6 h for G1, 4 h vor S and for G2, and 2 h for M. In the central cell, the first DNA synthesis took place at 3–4 h after pollination, i.e., immediately after fertilization, followed by the formation of the primary endosperm nucleus. Antipodal cells also showed labeled nuclei in the early stages after fertilization. The first divisions of fertilized egg cell and primary endosperm nucleus were observed at 16–18h and at 4–6 h after pollination, respectively. The present observations suggest that sperm and egg nuclei participate in fertilization with haploid amount (1C) of DNA and fertilized egg cell originates thus in 2C state. 相似文献
13.
J. Herbert Taylor 《Chromosoma》1977,62(4):291-300
CHO cells were pulse labeled with 3H-thymidine after synchronization and blockage at the beginning of S phase for various intervals. The distribution of initiation sites for DNA replication and rates of chain growth were measured in autoradiographs prepared from these cells. Origins used for replication are widely distributed at or near the beginning of S phase, but usable origins increase continuously for many hours when FdU is used to block the synthesis of thymidylate. Potential origins are located about four microns apart, but in normal replication in these fibroblasts only one in 15 to 20 potential origins are used for initiation. On the other hand, when cells are held at the beginning of S phase for 12–14 h, about one-half of the potential origins are activated in part of the DNA and utilized when the cell is released from the block by supplying 3H-thymidine (10–6M). Chain growth during a short pulse decreases with time of the blockage at what appears to be a linear rate. However, cells can replicate long continuous stretches of their DNA with only 2×10–8M thymidine available in the medium for several hours when synthesis is blocked by FdU. The total amount of DNA replicated is, however, much less than when a concentration of 10–6 M thymidine is supplied for the same period. The origins which are finally used under any experimental condition appear to be a random sample of the total potential origins which are distributed in a regular repeating sequence along the DNA at about 12 kilobase intervals. 相似文献
14.
Summary A constant temperature hot film anemometer has been used to evaluate mean liquid flow velocity, bubble frequency, turbulence scale and intensity, and the rate of energy dissipation by liquid phase bubble flow.Symbols M
mass
- L
lenght
- T
time
- a
gas/liquid interfacial area L2
- a=a/VL
specific gas/liquid interfacial area with regard to the volume of the liquid L–1
- d
bubble diameter L
- d
mean bubble diameter L
- de
dynamic equilibrium (maximum stable) bubble size L
- dp
primary bubble diameter L
- ds
Sauter bubble diameter L
- E
specific energy dissipation rate with regard to the volume of the liquid ML–1T–3
- E VL
energy dissipation rate ML2T–3
- E=E/
since =1 g cm–3, E has the same numerical value as E. Therefore, the symbol E is used everywhere in the present paper for E and called energy dissipation rate (S. s–2=Stokes. s–2) L2T–3
- EG or G
local relative gas hold up L2T–3
- f()
autocorrelation function [Eq. (10)] L2T–3
- f(r)
cross correlation function [Eq. (11)] L2T–3
- g
acceleration of gravity LT–2
- k
constant LT–2
- kL
mass transfer coefficient LT–1
- kLa
volumetric mass transfer coefficient with regard to the volume of the liquid T–1
- N0
number of crossings of u and T–1
- nB
bubble frequency T–1
- r
distance between two points 1 and 2 of the cross correlation function L
- t
time T
- u
momentaneous liquid velocity LT–1
-
mean liquid velocity LT–1
-
mean square fluctuation velocity L2T–2
-
intensity of turbulence LT–1
- x
position coordinate L
- V
volume of the bubbling layer in the column L3
- VL
volume of the bubble free layer in the column L3
- V
electrical voltage (in Fig. 2) L3
- v
velocity scale [Eq. (6)] LT–1
- Wecrit
critical Weber number [Eq. (4)] LT–1
- wSG
superficial gas velocity LT–1
- wSL
superficial liquid velocity LT–1
- G or EG
local relative gas hold up LT–1
-
smallest scale [Eq. (6)] L
-
time delay in the autocorrelation function [Eq. (10)] T
-
energy dissipation scale [E. (15)] L
- f:
Taylor's vorticity scale [E. (14)] L
-
kinematic viscosity of the liquid L2T–1
-
density of the liquid ML–3
-
surface tension MT–2
-
dynamic pressure of the turbulence [Eq. (8)] ML–1T–2
- p
primary (at the aerator)
- e
equilibrium (far from the aerator) 相似文献
15.
Zheng Meiying Du Guocheng Chen Jian Lun Shiyi 《World journal of microbiology & biotechnology》2002,18(8):767-771
Batch transglutaminase (MTG) fermentations by Streptovertivillium mobaraense WSH-Z2 at various temperatures ranging from 25 to 35 °C were studied. Dry cell weight and MTG activity could reach their maximal values of 25.1 g/l and 2.94 U/ml, respectively at 30 °C. One typical equation was used to describe the relationship between specific growth rate and culture temperature by comparing several typical equations. Different lag time was observed under various culture temperature. The low lag time was observed under high culture temperature. X = –a
0(T – T
0)2 + X
1 + a
1 (1 – exp(a
2 (T – T
1))) and U = –a
0
(T – T
0
)2 + U
0 + a
1
(1 – exp(a
2
(T – T
1
))) could be used to describe the relationship between temperature and the maximal dry cell weight as well as the maximal MTG activity at each temperature. 相似文献
16.
Both conventional and genetic engineering techniques can significantly improve the performance of animal cell cultures for the large-scale production of pharmaceutical products. In this paper, the effect of such techniques on cell yield and antibody production of two NS0 cell lines is presented. On the one hand, the effect of fed-batch cultivation using dialysis is compared to cultivation without dialysis. Maximum cell density could be increased by a factor of ~5–7 by dialysis fed-batch cultivation. On the other hand, suppression of apoptosis in the NS0 cell line 6A1 bcl-2 resulted in a prolonged growth phase and a higher viability and maximum cell density in fed-batch cultivation in contrast to the control cell line 6A1 (100)3. These factors resulted in more product formation (by a factor ~2). Finally, the adaptive model-based OLFO controller, developed as a general tool for cell culture fed-batch processes, was able to control the fed-batch and dialysis fed-batch cultivations of both cell lines.Abbreviations A membrane area (dm2) - c Glc,F glucose concentration in nutrient feed (mmol L–1) - c Glc,FD glucose concentration in dialysis feed (mmol L–1) - c Glc,i glucose concentration in inner reactor chamber (mmol L–1) - c Glc,o glucose concentration in outer reactor chamber (dialysis chamber) (mmol L–1) - c Lac,FD lactate concentration in dialysis feed (mmol L–1) - c Lac,i lactate concentration in inner reactor chamber (mmol L–1) - c Lac,o lactate concentration in outer reactor chamber (dialysis chamber) (mmol L–1) - c LS,FD limiting substrate concentration in dialysis feed (mmol L–1) - c LS,i limiting substrate concentration in inner reactor chamber (mmol L–1) - c LS,o limiting substrate concentration in outer reactor chamber (dialysis chamber) (mmol L–1) - c Mab monoclonal antibody concentration (mg L–1) - F D feed rate of dialysis feed (L h–1) - F Glc feed rate of nutrient concentrate feed (L h–1) - K d maximum death constant (h–1) - k d,LS death rate constant for limiting substrate (mmol L–1) - k Glc monod kinetic constant for glucose uptake (mmol L–1) - k Lac monod kinetic constant for lactate uptake (mmol L–1) - k LS monod kinetic constant for limiting substrate uptake (mmol L–1) - K Lys cell lysis constant (h–1) - K S,Glc monod kinetic constant for glucose (mmol L–1) - K S,LS monod kinetic constant for limiting substrate (mmol L–1) - µ cell-specific growth rate (h–1) - µ d cell-specific death rate (h–1) - µ d,min minimum cell-specific death rate (h–1) - µ max maximum cell-specific growth rate (h–1) - P Glc membrane permeation coefficient for glucose (dm h–1) - P Lac membrane permeation coefficient for lactate (dm h–1) - P LS membrane permeation coefficient for limiting substrate (dm h–1) - q Glc cell-specific glucose uptake rate (mmol cell–1 h–1) - q Glc,max maximum cell-specific glucose uptake rate (mmol cell–1 h–1) - q Lac cell-specific lactate uptake/production rate (mmol cell–1 h–1) - q Lac,max maximum cell-specific lactate uptake rate (mmol cell–1 h–1) - q LS cell-specific limiting substrate uptake rate (mmol cell–1 h–1) - q LS,max maximum cell-specific limiting substrate uptake rate (mmol cell –1 h–1) - q Mab cell-specific antibody production rate (mg cell–1 h–1) - q MAb,max maximum cell-specific antibody production rate (mg cell–1 h–1) - t time (h) - V i volume of inner reactor chamber (culture chamber) (L) - V o volume of outer reactor chamber (dialysis chamber) (L) - X t total cell concentration (cells L–1) - X viable cell concentration (cells L–1) - Y Lac/Glc kinetic production constant (stoichiometric ratio of lactate production and glucose uptake) (–) 相似文献
17.
Friedhelm Göltenboth 《Chromosoma》1973,44(2):147-181
During meiosis in M. ehrenbergi (2n=10) and M. lingua (2n=8) male certain chromosomes never pair completely. In these bivalents only terminal pairing appears, crossing over could not be proved by 3H-thymidine autoradiography. DNA amounts of the M. ehrenbergi and M. lingua genomes are in a proportion of 10∶1. The mitotic S-phase of spermatogonia in M. ehrenbergi is twice as long as in M. lingua. In metaphase of spermatogonia a differentiated DNA replication pattern can be identified in M. ehrenbergi as late-pulse-replicating segments. After incorporation of 3H-thymidine X2-metaphase chromosomes can be found, which show single chromatid labeling, terminal and intercalary isolabeling as well as kinds of chromosome labeling, which can only result from sister strand exchange. After treating the chromosomes with low temperature, colchicine or by hydrolysis (60° C) substructures of the chromatin become visible in both spezies which however are evaluated as artefacts. — Formation of the different isolabeling types is discussed on the basis of a two-strand model of the chromosome fibril. A hypothesis is formulated that the surplusage of DNA in M. ehrenbergi is distributed over all the length of the chromatids as small parts of heterochromatin. This hypothesis is supported by investigations of the DNA replication and the contractility of the chromosomes. Furthermore, a pattern of small DNA particles can be demonstrated after partial destruction of the DNA in metaphase chromosomes of M. ehrenbergi, which could represent this intercalary heterochromatin. 相似文献
18.
Male Wistar rats aged between 8 and 12 months were injected with 7–8 µl of aqueous L-leucine-14C (specific activity: 12543 megaBq/mM) in the region of the ventral horn at the level of segments L5,6 of the spinal cord. Radioactivity was investigated in 3 mm segments of the ventral roots concerned within 1 h in all series of experiments. Estradiol dipropionate, testosterone propionate, insulin, and small doses of thyroxine were found to accelerate axonal transport of labeled material, while hydrocortisone, large doses of thyroxine, as well as castration and thyroidectomy delayed this process. It was thus concluded that axonal transport is under clear-cut hormonal control.Institute of Gerontology, Academy of Medical Sciences of the USSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 4, pp. 459–464, July–August, 1990. 相似文献
19.
A O Ejiofor Y Chisti M Moo-Young 《Journal of industrial microbiology & biotechnology》1996,16(2):102-109
A fermentation medium based on millet (Pennisetum typhoides) flour hydrolysate and a four-phase feeding strategy for fed-batch production of baker's yeast,Saccharomyces cerevisiae, are presented. Millet flour was prepared by dry-milling and sieving of whole grain. A 25% (w/v) flour mash was liquefied with a thermostable 1,4--d-glucanohydrolase (EC 3.2.1.1) in the presence of 100 ppm Ca2+, at 80°C, pH 6.1–6.3, for 1 h. The liquefied mash was saccharified with 1,4--d-glucan glucohydrolase (EC 3.2.1.3) at 55°C, pH 5.5, for 2 h. An average of 75% of the flour was hydrolysed and about 82% of the hydrolysate was glucose. The feeding profile, which was based on a model with desired specific growth rate range of 0.18–0.23 h–1, biomass yield coefficient of 0.5 g g–1 and feed substrate concentration of 200 g L–1, was implemented manually using the millet flour hydrolysate in test experiments and glucose feed in control experiments. The fermentation off-gas was analyzed on-line by mass spectrometry for the calculation of carbon dioxide production rate, oxygen up-take rate and the respiratory quotient. Off-line determination of biomass, ethanol and glucose were done, respectively, by dry weight, gas chromatography and spectrophotometry. Cell mass concentrations of 49.9–51.9 g L–1 were achieved in all experiments within 27 h of which the last 15 h were in the fedbatch mode. The average biomass yields for the millet flour and glucose media were 0.48 and 0.49 g g–1, respectively. No significant differences were observed between the dough-leavening activities of the products of the test and the control media and a commercial preparation of instant active dry yeast. Millet flour hydrolysate was established to be a satisfactory low cost replacement for glucose in the production of baking quality yeast.Nomenclature
C
ox
Dissolved oxygen concentration (mg L–1)
-
CPR
Carbon dioxide production rate (mmol h–1)
-
C
s0
Glucose concentration in the feed (g L–1)
-
C
s
Substrate concentration in the fermenter (g L–1)
-
C
s.crit
Critical substrate concentration (g L–1)
-
E
Ethanol concentration (g L–1)
-
F
s
Substrate flow rate (g h–1)
-
i
Sample number (–)
-
K
e
Constant in Equation 6 (g L–1)
-
K
o
Constant in Equation 7 (mg L–1)
-
K
s
Constant in Equation 5 (g L–1)
-
m
Specific maintenance term (h–1)
-
OUR
Oxygen up-take rate (mmol h–1)
-
q
ox
Specific oxygen up-take rate (h–1)
-
q
ox.max
Maximum specific oxygen up-take rate (h–1)
-
q
p
Specific product formation rate (h–1)
-
q
s
Specific substrate up-take rate (g g–1 h–1)
-
q
s.max
Maximum specific substrate up-take rate (g g–1 h–1)
-
RQ
Respiratory quotient (–)
-
S
Total substrate in the fermenter at timet (g)
-
S
0
Substrate mass fraction in the feed (g g–1)
-
t
Fermentation time (h)
-
V
Instantaneous volume of the broth in the fermenter (L)
-
V
0
Starting volume in the fermenter (L)
-
V
si
Volume of samplei (L)
-
x
Biomass concentration in the fermenter (g L–1)
-
X
0
Total amount of initial biomass (g)
-
X
t
Total amount of biomass at timet (g)
-
Y
p/s
Product yield coefficient on substrate (–)
-
Y
x/e
Biomass yield coefficient on ethanol (–)
-
Y
x/s
Biomass yield coefficient on substrate (–)
Greek letters
Moles of carbon per mole of yeast (–)
-
Moles of hydrogen atom per mole of yeast (–)
-
Moles of oxygen atom per mole of yeast (–)
-
Moles of nitrogen atom per mole of yeast (–)
-
Specific growth rate (h–1)
- crit
Critical specific growth rate (h–1)
-
E
Specific ethanol up-take rate (h–1)
- max.E
Maximum specific ethanol up-take rate (h–1) 相似文献
20.
Soil N mineralization and nitrification in relation to nitrogen solution chemistry in a small forested watershed 总被引:6,自引:1,他引:5
Spatial variations in soil processes regulating mineral N losses to streams were studied in a small watershed near Toronto, Ontario. Annual net N mineralization in the 0–8 cm soil was measured in adjacent upland and riparian forest stands using in situ soil incubations from April 1985 to 1987. Mean annual rates of soil N mineralization and nitrification were higher in a maple soil (93.8 and 87.0 kg.ha–1) than in a pine soil (23.3 and 8.2 kg.ha–1 ). Very low mean rates of mineralization (3.3 kg.ha–1) and nitrification (3.4 kg.ha–1) were found in a riparian hemlock stand. Average NO3-N concentrations in soil solutions were 0.3–1.0 mg.L–1 in the maple stand and >0.06mg.L–1 in the pine stand. Concentrations of NO3–N in shallow ground water and stream water were 3–4× greater in a maple subwatershed than in a pine subwatershed. Rapid N uptake by vegetation was an important mechanism reducing solution losses of NO3–N in the maple stand. Low rates of nitrification were mainly responsible for negligible NO3–N solution losses in the pine stand. 相似文献