共查询到20条相似文献,搜索用时 46 毫秒
1.
Margareth Krauter E. Aquarone S. Sato L. Perego Jr. W. Borzani 《Biotechnology letters》1987,9(9):647-650
Summary The ethanol yield was not affected and the ethanol productivity increased (10%) when linearly decreasing feeding rates were used instead of constant feeding rates in fed-batch ethanol fermentations.Nomenclature F
reactor feeding rate (L.h–1)
- ME
mass of ethanol in the fermentor (g)
- Ms
mass of TRS in the fermentor (g)
- Mx
mass of yeast cells (dry matter) in the fermentor (g)
- P
ethanol productivity (g.L–1.h–1)
- s
standard deviation
- So
TRS concentration in the feeding mash (g.L–1)
- t
time (h)
- T
fermentor filling-up time (h)
- TRS
total reducing sugars calculated as glucose (g.L–1)
- Xo
yeast cells concentration (dry matter) in the inoculum (g.L–1)
-
average ethanol yield (% of the theoretical value) 相似文献
2.
J. C. M. de Carvalho E. Aquarone S. Sato M. L. Brazzach K. A. Almeida W. Borzani 《Biotechnology letters》1990,12(10):777-782
Summary The ethanol yield was not affected and the ethanol productivity was increased when exponentially decreasing feeding rates were used instead of constant feeding rates in fed batch ethanol fermentations. The influences of the initial sugar feeding rate on the ethanol productivity, on the constant ethanol production rate during the feeding phase and on the initial ethanol production specific rate are represented by Monod-like equations.Nomenclature F
reactor feeding rate (L.h–1)
- Fo
initial reactor feeding rate (L.h–1)
- K
time constant; see equation (l) (h–1)
- ME
mass of ethanol in the fermentor (g)
- Ms
mass of TRS in the fermentor (g)
- Mx
mass of yeast cells (dry matter) in the fermentor (g)
- P
ethanol productivity (g.L–1.h–1)
- R
ethanol constant production rate during the feeding phase (g.h–1)
- s
standard deviation
- So
TRS concentration in the feeding mash (g.L–1)
- t
time (h)
- T
fermentor filling-up-time (h)
- T
time necessary to complete the fermentation (h)
- TRS
total reducing sugars calculated as glucose (g.L–1)
- Vo
volume of the inoculum (L)
- Vf
final volume of medium in the fermentor (L)
- Xo
yeast concentration of the inoculum (dry matter) (g.L–1)
-
ethanol yield (% of the theoretical value)
-
initial specific rate of ethanol production (h–1) 相似文献
3.
Walter Borzani Haroldo Hiss Teresinha W. de Santos Marina L. R. Vairo 《Biotechnology letters》1992,14(10):981-984
Summary A mathematical model is proposed to explain the influence of the volume fraction of inoculum on the fermentation time and ethanol productivity in semicontinuous ethanol fermentation of sugar cane blackstrap molasses by pressed yeast.Nomenclature a, b, c, d
constants, see equation (5)
- Eo
initial ethanol concentration
- Ef
final ethanol concentration
- K1, K2, K3
constants, see equation (1)
- P
ethanol productivity
- Pc
calculated values of P
- Pe
experimental values of P
- r
correlation coefficient
- So
initial TRS concentration
- Sm
TRS concentration of the feeding mash
- T
fermentation time (average of the experimental values)
- Tc
calculated value of T
- Te
experimental value of T
- TRS
total reducing sugars calculated as glucose
- Uo
initial urea concentration
- Um
urea concentration of the feeding mash
- V
reactor working volume
- Vi
volume of the inoculum
-
volume fraction of inoculum=Vi/V 相似文献
4.
Walter Borzani 《Biotechnology letters》1995,17(12):1295-1298
Summary The following equations represent the influence of the ethanol concentration (E) on the specific growth rate of the yeast cells () and on the specific production rate of ethanol () during the reactor filling phase in fed-batch fermentation of sugar-cane blackstrap molasses: =
0 - k · E and v = v
0
· K/(K +E)
Nomenclature E
ethanol concentration in the aqueous phase of the fermenting medium (g.L–1)
- Em
value of E when = 0 or = 0 (g.L–1)
- F
medium feeding rate (L.h–1)
- k
empirical constant (L.g–1.h–1)
- K
empirical constant (g.L–1)
- Mas
mass of TRS added to the, reactor (g)
- Mcs
mass of consumed TRS (g)
- Me
mass of ethanol in the aqueous phase of the fermenting medium (g)
- Ms
mass of TRS in the aqueous phase of the fermenting medium (g)
- Mx
mass of yeast cells (dry matter) in the fermenting medium (g)
- r
correlation coefficient
- S
TRS concentration in the aqueous phase of the fermenting medium (g.L–1)
- Sm
TRS concentration of the feeding medium (g.L–1)
- t
time (h)
- T
temperature (° C)
- TRS
total reducing sugars calculated as glucose
- V
volume of the fermenting medium (L)
- V0
volume of the inoculum (L)
- X
yeast cells concentration (dry matter) in the fermenting medium (g.L–1)
-
filling-up time (h)
-
specific growth rate of the yeast cells (h–1)
- 0
value of when E=0
-
specific production rate of ethanol (h–1)
- 0
value of when E=0
-
density of the yeast cells (g.L–1)
-
dry matter content of the yeast cells 相似文献
5.
W. Borzani 《Biotechnology letters》1986,8(3):187-190
Summary A method is proposed to program the addition of disinfectants to the mash in order to assure maximum yield in repeated batch ethanol fermentations of unsterilized molasses media.Nomenclature A
total acidity of the fermented mash (calculated as H2SO4)
- C
concentration of the bacterial contaminants
- Co
empirical coefficient
- C1
arbitrary value of Cmax
- CN
value of C at the end of fermentation cycle number N
- Cmax
maximum value of C that does not affect the fermentation yield
- K,K
empirical constants
- N
number of a given fermentation cycle in a series of repeated batch fermentations
- N1
number of fermentation cycles leading to a reduction of C from Cmax to C1
- N2
number of fermentation cycles leading to an increasing of C from C1 to Cmax
- TRS
total reducing sugars (calculated as glucose)
-
fermentation yield (% of the theoretical value) 相似文献
6.
Borzani W 《Biotechnology and bioengineering》1987,29(7):844-849
During the fermentor feeding phase in constant fed-batch ethanol fermentation of molasses, the ethanol production rates are constant and are correlated to the sugar feeding rates by a Monod-like equation. The parameters of this Monod-like correlation depend on the sugars concentration of the feeding mash. A model is proposed to explain the constancy of the ethanol production rate experimentally observed. From the Monod-like correlation it is possible to evaluate the maximum value of the mash feeding rate to be used in order to have a completely fermented medium just at the end of the feeding phase. 相似文献
7.
Summary The highest values of the specific growth rate at the exponential phase (0.144 h-1) and of the yeast cells productivity (0.80 g.L-1.h-1) were obtained at 34°C and 30°C, respectively. The cells yield factor decreased from 0.495 to 0.275 when the temperature was increased from 26°C to 42°C.Nomenclature P
yeast cells productivity
- P
yeast cells productivity
- r
correlation coefficient
- S
glycerol concentration
- t
time
- tf
duration of the test
- T
temperature
- X
yeast cells concentration, dry matter
- X0
initial value of X
- Xf
final value of X
- Yx/s
yeast cells yield
- t
duration of the exponential phase
- m
specific growth rate at the exponential phase 相似文献
8.
A fixed bed perfusion system for hybridoma cell immobilization is presented. The system consists of a culturing vessel (300 ml total volume) in which polyurethane (PU) sponges in the form of small cubes of about 5 mm sides are packed. Cells are immobilized by physical entrapment in the foam matrix. By entrapment of the cells in the pores of the matrix high cell concentration can be maintained in a mechanically protected environment. Medium is continuously circulated by an airlift pump mounted in the cell-free chamber (700 ml total volume).Medium flow rate, feeding rate, dissolved oxygen, pH, nutrient uptake and waste product formation can be easily monitored and controlled. Steady state conditions are established with medium dilution rates of 1.0–1.5 reactor volume per day. The steady state is characterized by a constant cell density, constant culture volume and constant glucose and lactate levels. Cell-free supernatant is collected continuously in a cold room adjacent to the 37°C culture room. Monoclonal antibodies (MAb) are produced at a concentration of 150–200 g/ml for several weeks. An important feature of the system is the capacity to maintain a population of cells after the growth phase in a non-proliferating state for extended time periods expressing high titers of MAb.Abbreviations DO
Dissolved Oxygen
- FBS
Fetal Bovine Serum
- FBR
Fixed Bed Reactor
- MAb
Monoclonal Antibody
- PU
polyurethane 相似文献
9.
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
10.
A. O. Ejiofor C. H. Posten B. O. Solomon W. -D. Deckwer 《Bioprocess and biosystems engineering》1994,11(4):135-144
Parameter identification of structured models is often a problem in biotechnology, because the poor data situation and the number of unknown parameters only allow for inaccurate estimates. But often only a subset of all kinetic parameters of the model are of interest for production purposes, e.g. for fed-batch cultivation. These parameters should be estimated with a given accuracy. In addition, the experiments for information acquisition with respect to these parameters should be as simple as possible and should consider some practical restrictions. In this contribution a fed-batch feeding strategy is proposed to allow for an accurate estimation of yield and of critical growth rate of baker's yeast. The feeding also allows for economic and stereotyped use of staff and equipment and is therefore suitable for routine use in screening of strains and media. The overall pattern is similar to that one, usually used in production scale to minimize errors by limited model validity. After an initial phase for achieving a reproducible state three different growth rates are adjusted to cover the range of possible critical growth rates. From biomass and ethanol measurements yield and critical growth rate can be estimated with an accuracy of about 2.1%. The fermentation pattern ends up with a constant feeding rate to simulate a limited oxygen transfer rate and to allow for an uptake of residual sugar and ethanol before a dough test can be carried out. Beside experimental results simulations and sensitivity analyses are shown.List of Symbols
P
ethanol concentration
-
S
substrate concentration
-
S
f
substrate concentration in feed
-
T
fermentation time
-
V
fermenter volume
-
X
biomass concentration
- C
measurement error covariance matrix
- F
Fisher information matrix
- X
state variables
- Y
output variables
- X
p
state sensitivity functions with respect to parameters
- Y
p
output sensitivity functions
-
e
eigenvectors
-
k
vector of limitation and inhibition parameters
-
n
number of observations
-
q
in
feeding stream
-
q
b
stream for samples and ammonia feed
-
r
vector of specific turnover rates
-
y
vector of yields
-
specific weight
-
eigenvalues
-
specific growth rate
-
set
exponent in exponential feeding
-
standard deviation
Dedicated to the 65th birthday of Professor Fritz Wagner.A. O. Ejiofor and B. O. Solomon are grateful to the Alexander von Humboldt Stiftung for granting them fellowships and to GBF for providing all the materials necessary for their successful research stay in Germany. 相似文献
11.
Dialysis cultures with immobilized hybridoma cells for effective production of monoclonal antibodies
An industrial scale reactor concept for continuous cultivation of immobilized animal cells (e.g. hybridoma cells) in a radial-flow fixed bed is presented, where low molecular weight metabolites are removed via dialysis membrane and high molecular products (e.g. monoclonal antibodies) are enriched. In a new nutrient-split feeding strategy concentrated medium is fed directly to the fixed bed unit, whereas a buffer solution is used as dialysis fluid. This feeding strategy was investigated in a laboratory scale reactor with hybridoma cells for production of monoclonal antibodies. A steady state monoclonal antibody concentration of 478 mg l-1 was reached, appr. 15 times more compared to the concentration reached in chemostat cultures with suspended cells. Glucose and glutamine were used up to 98%. The experiments were described successfully with a kinetic model for immobilized growing cells. Conclusions were drawn for scale-up and design of the large scale system.Abbreviations: cGlc – glucose concentration, mmol l-1; cGln – glutamine concentration, mmol l-1; cAmm – ammonia concentration, mmol l-1; cLac – lactate concentration, mmol l-1; cMAb – MAb concentration, mg l-1; D – dilution rate, d-1; Di – dilution rate in the inner chamber of the membrane dialysis reactor, d-1; D0 – dilution rate in the outer chamber of the membrane dialysis reactor, d-1; q*FB,Glc – volume specific glucose uptake rate related to the fixed bed volume, mmol lFB
-1 h-1; q*FB,Gln – volume specific glutamine uptake rate related to the fixed bed volume, mmol lFB
-1 h-1. 相似文献
12.
C. F. M. Kingdon 《Applied microbiology and biotechnology》1985,22(3):165-168
Summary Immobilized and free bacterial cells stored at 4° C in substrate free buffer were found to exhibit two phases of oxygen uptake on resuspension in an oxygen rich growth medium in the well of a standard polarographic Clarke electrode. A rapid oxygen uptake phase 1, followed by a stower, phase 2 associated with cellular division. The duration (mV) and rate of phase 1 oxygen uptake (mV min-1) was a linear function of cell concentration. Phase 1 duration was sensitive to the presence of the aminoglycoside antibiotic gentamycin. For a fixed cell concentration the inhibition of phase 1 was a direct function of gentamycin concentration. Whole cells stored at 4° retained phase 1 activity for at least one month. 相似文献
13.
Takahiro Suzuki Tsuneo Yamane Shoichi Shimizu 《Applied microbiology and biotechnology》1986,24(5):366-369
Summary A kinetic study of the production of poly--hydroxybutyric acid (PHB) by a fed-batch culture of Protomonas extorquens showed that a nitrogen source was necessary even in the PHB production phase. The effect of ammonia feeding on PHB production was consequently investigated. The nitrogen source (ammonia water) was supplied at a low constant feeding rate after the growth phase in which cell mass concentration reached 60 g/l. Feeding with a small quantity of ammonia resulted in a more rapid increase in intracellular PHB content than was the case without ammonia feeding. Excessive feeding of ammonia, however, caused not only degradation of accumulated PHB but also reduction of microbial PHB synthetic activity. 相似文献
14.
Shuwen Liu Yong Liang Qian Liu Tongtong Tao Shujuan Lai Ning Chen Tingyi Wen 《Applied microbiology and biotechnology》2013,97(2):573-583
Fed-batch fermentation is the predominant method for industrial production of amino acids. In this study, we comprehensively investigated the effects of four kinds of feeding nutrients and developed an accurate optimization strategy for fed-batch production of l-threonine. The production of l-threonine was severely inhibited when cell growth ceased in the bath culture. Similarly, l-threonine production was also associated with cell growth in the carbon-, phosphate-, and sulfate-limited fed-batch cultures, but the accumulation of l-threonine was markedly increased because of the extended production time in the growth stage. Interestingly, auxotrophic amino acid (l-isoleucine)-limited feeding promoted l-threonine production over the non-growth phase. Metabolite analysis indicates that substantial production of acetate and glutamate and the resulting accumulation of ammonium may lead to the inhibition of l-threonine production. During the growth phase, the levels of l-isoleucine were accurately optimized by balancing cell growth and production with Pontryagin’s maximum principle, basing on the relationship between the specific growth rate μ and specific production rate ρ. Furthermore, the depletion of l-isoleucine and phosphate at the end of the growth phase favored the synthesis of l-threonine in the subsequent non-growth phase. Combining the two-stage feeding profiles, the final l-threonine concentration and conversion rate were increased by 5.9- and 2.1-fold, respectively, compared to batch processes without feeding control. The identification of efficient feeding nutrient and the development of accurate feeding strategies provide potential guidelines for microbial production of amino acids. 相似文献
15.
Under seminatural conditions feeding and postfeeding behaviors of individual apple maggot flies, Rhagoletis pomonella(Diptera: Tephritidae), were recorded after flies were presented with yeast hydrolysate or sucrose droplets, varying in either concentration, amount of food solute, or total droplet volume. The objectives were (a) to establish, at a constant level of previous food deprivation, food ingestion thresholds in relation to food quality and quantity and (b) to study the effect of initial food quantity and quality on food handling time and subsequent food foraging behavior. For both carbohydrate and protein substrates, fly foraging time after feeding on a tree branchlet was positively related to total amount of food solute previously encountered on a leaf surface, though largely independent of food volume or concentration. The volume and concentration of food presented, however, significantly affected food handling and processing time and therefore foraging time. In fact, total branchlet residence time was more closely linked to food handling and processing time than to foraging time. Less time was needed for uptake of liquid than dry food, the latter requiring liquification by salivary secretion and eliciting considerable intermittent cleaning of mouthparts by feeding flies. Similar to the situation in other fluid feeders, uptake time in R. pomonelladecreased with increasing dilution, although below a threshold of a 30% concentration of solute, the rate of nutrient intake decreased rapidly. When the level of dilution and total volume of food ingested were great enough, engorged flies entered extended quiescent postfeeding periods during which they extrude orally droplets of liquid crop contents (bubbling). After this they reinitiated feeding, followed by more bubbling and feeding bouts. Multivariate logistic regression analysis suggested that bubbling behavior is determined by liquid food volume and degree of dilution, hunger, and temperature. Although thresholds triggering bubbling decreased with increasing temperature, higher temperature by itself did not result in bubbling behavior. This suggests that bubbling is not primarily a mechanism to achieve evaporative cooling as has been suggested but, rather, a behavior to eliminate excess water, thereby enabling engorged flies to continue feeding on diluted food sources. 相似文献
16.
Summary Fed-batch fermentation of non-supplemented concentrated whey permeate resulted in high ethanol productivity for feeds of lactose for which batch fermentation had a poor performance. At an initial lactose concentration of 100 g/L and a constant lactose feeding rate of 18 g/h we have obtained: ethanol concentration 64 g/L, ethanol productivity 3.3 g/Lh, lactose consumption 100%, ethanol yield 0.47 g/g, and biomass yield 0.058 g/g.Nomenclature St
total lactose fed per medium volume in the bioreactor, g/L
- Si
initial lactose concentration, g/L
- F
lactpse feeding rate, g/h
- P
final ethanol concentration, g/L
- Yp/s
ethanol yield, g ethanol/g lactose
- Yx/s
biomass yield, g biomass/g lactose
- XS
lactose consumption, %
- Qp
overall ethanol volumetric productivity, g/Lh
- m
maximum specific growth rate, h
- qsm
maximum specific lactose consumption rate, g/gh
- qpm
maximum specific ethanol production rate, g/gh 相似文献
17.
Kirsten Brandt 《Plant Cell, Tissue and Organ Culture》1991,26(3):195-201
A method for estimating the oxygen availability in plant cell cultures grown in stationary liquid media (e.g. many protoplast cultures) was developed. The method is based on short-term measurements of respiration rate versus oxygen concentration on a sample of cells, suspended in liquid media. From such data it is possible to estimate the oxygen concentration at the bottom of a stagnant liquid culture, by calculating the amount of oxygen reaching the cells by diffusion. As an example, rape (Brassica napus L. cv. Omega) hypocotyl protoplasts were grown with different oxygen concentrations at the site of the cells, obtained by varying the cell density, the height of the liquid layer and the oxygen content of the gas phase. The number of surviving calli was positively correlated with the estimated oxygen availability in the range between 60 and 350 M O2, below 60 M all cells died. This indicates that oxygen availability can be a limiting factor in the range usually encountered in protoplast cultures, and that the method can be useful when designing optimal growth conditions for stationary cultures of plant cells.Abbreviations C1
bulk oxygen concentration in agitated medium
- Co
oxygen concentration in medium at the gas-liquid interface, in equilibrium with the gas
- Cx
oxygen concentration at cell level
- D
diffusion constant of oxygen in water
- KLa
oxygen transfer rate
- l
height of liquid above cells
- n
number of cells per ml
- Rx
respiration rate per cell 相似文献
18.
B. Sonnleitner E. Heinzle G. Braunegg R. M. Lafferty 《Applied microbiology and biotechnology》1979,7(1):1-10
Summary Under chemolithoautotrophic growth conditions with the organism Alcaligenes eutrophus H16 the exponential growth phase is characterized by two different growth rates, each associated with different specific rates of ammonium consumption. On the basis of the analytical determination of Poly--hydroxybutyric acid (PHB), it can be conclusively shown that PHB is synthesized even during the exponential growth phase at a specific rate proportional to the specific growth rates of total biomass. After complete consumption of ammonium, the increase of biomass is exclusively due to PHB synthesis, whereas protein and rest biomass (cell dry weight minus PHB) remain constant. After an extended period of fermentation, the PHB content reaches a saturation value. The transient phase between the growth and the storage phase is very short in comparison to the duration of the whole fermentation. In the case of Alcaligenes eutrophus, strain H 16, high concentrations of dissolved oxygen strongly influence growth as well as PHB synthesis.Abbrevations
cO2,L
concentration of oxygen in the liquid phase (dissolved oxygen tension: d.o.t)
-
cH2,L
concentration of hydrogen in the liquid phase
-
cCO2,L
concentration of carbon dioxide in the liquid phase
- S
limiting substrate, concentration of
- X
total biomass, concentration of; total cell dry weight
- P
product; PHB, concentration of
- R
rest biomass: X-P, concentration of
-
rX
dX/dt growth rate
-
rP
dP/dt rate of PHB synthesis
-
rR
dR/dt rate of rest biomass production
-
r0
dcO2,L/dt rate of oxygen consumption
-
X
dX/dt·1/X=rX·1/X specific growth rate
-
P
dP/dt·1/P=rP·1/P specific rate of product formation
-
R
dR/dt·1/R=rR·1/R specific rate of rest biomass formation
- r0/R
specific respiration rate 相似文献
19.
J. -Q. Yuan Prof. Dr. K. -H. Bellgardt W. -D. Deckwer W. -S. Jiang 《Bioprocess and biosystems engineering》1993,9(4):173-182
The cell cycling model (CCM) for S. cerevisiae proposed earlier is modified and tested with our own experimental data. Although the original CCM was well verified in steady states and exponential growth with data available in literature, some discrepancies between model predictions and experiments were found for the dynamics of fed-batch culture. The redistribution pattern of the age distribution of daughter cells is suggested as cause of the model error. With an exponential type of redistribution, instead of the original linear one, the model behaviour in transients is improved. The modified model was verified with data of fraction of budding cells and cell number for five fed-batch cultivations. The model agreed well with the experimental data. The simulation results suggest that the cell cycling process indeed is essentially in a pseudo-steady state during fed-batch cultivation, as was assumed in the model. Due to the strong correlation between the quality of baker's yeast and the state of the population in the cell cycling process, the model was applied to optimize the feeding rate of a fedbatch process with consideration of final product quality. The optimal feeding was used succesfully in a laboratory experiment, which demonstrates the validity of the model.List of Symbols
B h
length of budding phase
-
C
b1, C
d1, C
p1
parameters in cycling phase equations
-
C
b2, C
d2, C
p2 h
parameters in cycling phase equations
-
d(i)
number of cells in ith cycling interval inU
d
-
E kg m–3
ethanol concentration
-
F m3 h–1
substrate feeding rate
-
F
max and F
min m3 h–1
upper and lower limit of F
-
FBC, FDC, FPC %
fraction of budding cells, unbudded daughter cells and unbudded parent cells
-
K
B1, K
B2, K
B3, K
EG, K
Ad
parameters in the metabolic model
-
m
ATP mol(gh)–1
maintenance coefficient for ATP
-
n
b, n
d, n
p
number of age intervals in the budding phase, daughter phase and parent phase
-
PO
min, PO
max
minimal and maximal effectiveness of oxidative phosphorylation
-
r
Acmax mol(gh)–1
saturation value of the specific acetyl-CoA-reaction rate
-
S kg m–3
concentration of total reduceable sugars
-
S
R kg m–3
substrate concentration in the feed
-
T
cell number doubling time
-
T
fh
fermentation period
-
U
dh
length of unbudded daughter cell cycling phase
-
U
ph
length of unbudded parent cell cycling phase
-
V
cell
m3
average volume of yeast cells
-
V
L m3
liquid volume of the reactor
-
X kg m–3
cell mass concentration
-
X
N cm–3
cell number concentration
-
Y
ATP g molATP
–1
yield coefficient of ATP
-
parameter in the exponential redistribution function
-
h–1
specific growth rate
-
h
length of the discrete age interval of cell cycle phases
- suffix old and new
denote the value before and after increasing of 相似文献
20.
This paper examines the effects of ionic gold on Saccharomyces cerevisiae, as determined by long-term (growth in gold-containing media) and short-term interactions (H+ efflux activity). An increasing gold concentration inhibited growth and at <0.2 mM Au, growth was not observed. Transmission electron microscopy revealed no differences in ultrastructure but fine electron dense particles were observed in unstained preparations from gold-containing medium. After glucose addition (to 10mM) to starved suspensions of S. cerevisiae, glucose-dependent reduction of external pH occurred as the cells extruded protons. In the presence of increasing gold concentrations, the lag time before proton extrusion did not change but the rate and duration decreased significantly with a marked influence on proton efflux rate being observed at 10 M. Extension of preincubation time of yeast cells in gold-containing medium resulted in a decreasing proton efflux rate and colloidal phase formation in the cell suspensions, the time between gold addition and the beginning of colloidal phase formation depending on the gold concentration used. Both Ca and Mg enhanced the inhibitory effect of gold on the yeast cells with Ca showing a stronger inhibitory effect than Mg. 相似文献