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1.
W. Schmidt Th. Scheper Prof. Dr. K. Schügerl 《Bioprocess and biosystems engineering》1988,3(3):129-133
Ethanol was produced with Zymomonas mobilis Z6 (ATCC 29191), in batch culture with synthetic medium on glucose as substrate and in the presence of aspartate. The concentrations of glucose, phosphate, ammonium, ethanol and dissolved O2 and CO2 in the medium and O2 and CO2 in the outlet gas as well as the cell mass by culture fluorescence were measured on-line. Cell mass, glucose and aspartate concentrations were measured off-line. In the presence of a sufficient amount of aspartate, the ethanol inhibition effect can be reduced considerably. However, the improvement with yeast extract is more incisive. The relationship between the intensity of culture fluorescence and cell mass concentration is linear, if sufficient aspartate is present.List of Symbols ASP kg/m3
aspartate concentration
-
CTR kg/(m3 · h)
CO2 transfer rate
- N, NH4 kg/m3
nitrogen concentration from NH
4
+
-
P kg/m3
product (ethanol) concentration
-
p%
product (ethanol) yield
- PO4 kg/m3
phosphate concentration
-
Q
E
kg/(kg · h)
specific ethanol production rate
-
kg/(kg · h)
specific nitrogen uptake rate from NH
4
+
-
Q
P
kg/(kg · h)
specific phosphate uptake rate
-
Q
s
kg/(kg · h)
specific substrate (glucose) uptake rate
-
S kg/m3
glucose concentration
-
S
O
kg/m3
initial glucose concentration
-
Y
x/s
kg/kg
yield coefficient
-
h–1
specific growth rate 相似文献
2.
Summary A mathematical model simulating the behaviour or Streptomyces aureofaciens in batch culture under conditions when tetracyclines are synthesized in excessive amounts has been formulated. The response of the mathematical model to the experimental conditions applied corresponds with data obtained in the experiments. The mathematical model demonstrated that the level of tetracycline production is determined during the period of culture growth beginning with exhaustion of inorganic phosphate from the medium and ending with inhibition of the synthesis of enzymes caused by the synthesized tetracyclines. Further tetracycline synthesis is then proportional to the amount of enzymes synthesized in this interval.List of symbols
E
Activity of ACT-oxygenase (10×nkat/g)
-
P
Product concentration (mg/l)
-
k
1-k
6
Rate constants
-
K
S
Saturation constant (g sugar/l)
-
K
I1
Inhibition constant (mg product/l)
-
K
I2
Inhibition constant (mM phosphate/l)
-
K
I3
Inhibition constant (mg product/l)
-
S
1
Substrate sucrose (g sugar/l)
-
S
2
Substrate concentration — phosphate (mM/l)
-
r
P
Specific rate of product formation (mg product/g · h)
-
r
E
Specific rate of enzyme synthesis (10×nkat/g2 · h), Expressed by activity units
-
t
Cultivation time (hour)
-
X
Biomass dry weight (g/l)
-
Y
S/X
Yield coefficient
-
Specific growth rate (h-1) 相似文献
3.
Summary The performance ofZymomonas mobilis strains ATCC 31821 and ATCC 31823 was assessed in batch and continuous culture. In batch culture using a medium containing 250 g/l glucose, identical maximum specific growth rates of 0.16/h were found, though final biomass concentration and growth yield were significantly lower for ATCC 31 823 than for ATCC 31 821. Final ethanol concentrations in this medium were about 110 g/l vor both organisms. In continuous culture at increasing dilution rates using a medium containing 100 g/l glucose, no significant differences were seen between the two strains with respect to the fermentation parameters studied. For ATCC 31 821, maximum rates of glucose uptake (Qs) and ethanol produktion (Qp) of 8.7 g glu/g/h and 4.4 g eth/g/h, respectively, were found. Both strains showed a similar performance at a fixed dilution rate of 0.1/h, where maximum ethanol concentrations of about 68 g/l were reached at a feed glucose concentration of about 139 g/l. At this dilution rate the maximum values of Qs and Qp were about 5.8 g glu/g/h and 2.8 g eth/g/h, respectively. Test tube experiments showed that growth, measured as optical density, decreased with increasing concentrations of exogenous ethanol with complete inhibition of growth at ethanol concentrations >8% (v/v). As evidenced by the results presented here, we have been unable to practice the invention as described in U.S. Patent 4,403,034 (Rogers and Tribe 1983).Nomenclature D
Dilution rate, 1/h
- max
maximum specific growth rate, 1/h
- SR
Initial substrate concentration, g glucose/1
- S
Residual substrate concentration, g glucose/1
- S0
Effluent substrate concentration, g glucose/1
- X
Blomass concentration; g cells/l
- OD620
Optical density at 620 nm, dimensionless
- [P]
Product concentration, g ethanol/1
- Yx/s
Growth yield, g cells/g glucose used
- Yp/s
Product yield, g ethanol/g glucose used
- %, Yield
Percentage yield, Yp/sx100/Y
p
s/max
=Yp/sx100/0.51
- Qs
Specific rate of glucose uptake, g glucose/g cells/h
- Qp
Specific rate of ethanol formation, g ethanol/g cells/h
- me
Maintenance energy coefficient, g glucose/g cells/h
- VP
Volumetric productivity, g ethanol/l/h
- t
Fermentation time, h 相似文献
4.
N. Stevnsborg H. G. Lawford N. Martin T. Beveridge 《Applied microbiology and biotechnology》1986,25(2):116-123
Summary Increasing the temperature in chemostat culture ofZymomonas mobilis ATCC 29 191 with low and high glucose concentrations was found to result in a decreasing frequency of septation leading to the formation of long filaments and in increasing outer membrane blebbing. Whether this effect is strain specific or universal inZymomonas is, unknown. Improvements in the fermentation kinetics could be achieved at elevated temperatures, with an optimum at 33°C. Temperatures >30°C induced uncoupled growth in chemostat cultures ofZ. mobilis ATCC 29 191. The results of this study emphasize the importance of temperature regulation in optimizing the performance of continuous fermentations withZymomonas.Nomenclature
D
Dilution rate, 1/h
- max
Maximum specific growth rate, 1/h
-
S
R
Initial substrate concentration, g glucose/1
- S
Amount of glucose consumed, g glucose/1
-
S
0
Effluent substrate concentration, g glucose/1
-
X
Biomass concentration
- g
cells/1
- [P]
Amount of product formed, g ethanol/1
- [P]
Product concentrations, g ethanol/l
-
Y
x/s
Growth yield, g cells/g glucose used
-
Y
p/s
Product yield, g ethanol/g glucose used
-
O
s
Specific rate of glucose uptake, g glucose/g cells/h
-
Q
p
Specific rate of ethanol formation, g ethanol/g cells/h
-
VP
Volumetric productivity, g ethanol/1/h
-
t
Fermentation time, h
Corresponding author 相似文献
5.
Growth yields and growth rates of Desulfovibrio vulgaris (Marburg) growing on hydrogen plus sulfate and hydrogen plus thiosulfate as the sole energy sources 总被引:13,自引:0,他引:13
Desulfovibrio vulgaris (Marburg) was grown on H2 plus sulfate and H2 plus thiosulfate as the sole energy sources and acetate plus CO2 as the sole carbon sources. Conditions are described under which the bacteria grew exponentially. Specific growth rates () and molar growth yields (Y) at different pH were determined. and Y were found to be strongly dependent on the pH. Highest growth rates and molar growth yields were observed for growth on H2 plus sulfate at pH 6.5 (=0.15h-1; Y
SO
4
2-
=8.3g·mol-1) and for growth on H2 plus thiosulfate at pH 6.8 (=0.21h-1; Y
S
2O
3
2
=16.9g·mol-1).The growth yields were found to increase with increasing growth rates: plots of 1/Y versus 1/ were linear. Via extrapolation to infinite growth rates a Y
SO4
2-
/max of 12.2g·mol-1 and a YS2O
3
2-
/max of 33.5g·mol-1 was obtained.The growth yield data are interpred to indicate that dissimilatory sulfate reduction to sulfide is associated with a net synthesis of 1 mol of ATP and that near to 3 mol of ATP are formed during dissimilatory sulfite reduction to sulfide. 相似文献
6.
Summary Three yeasts of the genus Candida (Candida intermedia, candida lipolytica and Candida tropicalis) were cultivated batchwise on three different carbon sources: glucose, acetate, and hexadecane. Growth curves, oxygen uptake rates, CO2 evolution rates and the amount of oxygen required for biomass production were determined. The data were compared and discussed from the point of maximum specific growth rate, maximum oxygen uptake rate, carbon conversion into CO2 and biomass, consumption of oxygen and available energy for cell synthesis. The results indicated a relationship between m
m, Ys, YO, and for different carbon sources. YO and were in the same order of magnitude for acetate (0.58 and 0.38 respectively) and hexadecane (0.45 and 0.40 respectively). These values were remarkably lower than those for glucose (1.26 and 0.54 respectively).Symbols av e–
Available electrons per mol of substrate (dimensionless)
- Eav
Energy available per mol of substrate (dimensionless)
- Cd
Dissimilated carbon (%)
-
m
Maximum specific rate of oxygen uptake (mMO2 h–1 g–1)
- RQ
CO2 evolved per O2 consumed
- mol. wt.
Molecular weight
- YATP
Biomass mass yield based on mol of ATP generated (g)
-
Biomass mass yield based on available energy (g)
- YM
Biomass mass yield based on mol of organic substrate (g)
- YO
Biomass mass yield based on oxygen consumed (gg–1)
- 1/YO
Oxygen consumed for one gram of biomass produced (gg–1)
- Ys
Biomass mass yield based on organic substrate (dimensionless)
- b
Reductance degree of biomass (equiv. available electrons/g atom carbon)
- s
Reductance degree of organic substrate (equiv. available electrons/g atom carbon)
-
Fraction of energy in organic substrate which is converted to biomass
- b
Weight fraction carbon in biomass (dimensionless)
- s
Weight fraction carbon in organic substrate (dimensionless)
- m
Maximum specific growth rate (h–1) 相似文献
7.
S. N. Mukhopadhyay A. Ornelas Vale E. Camargo Rubio G. Cassarubias Arcos 《Applied microbiology and biotechnology》1978,6(1):55-66
Summary Submerged batch cultivation under controlled environmental conditions of pH 3.8, temperature 30°C, and KLa200 h–1 (above 180 mMO2
l
–1 h–1 oxygen supply rate) produced a maximum (12.0 g·l
–1) SCP (Candida utilis) yield on the deseeded nopal fruit juice medium containing C/N ratio of 7.0 (initial sugar concentration 25 g·l
–1) with a yield coefficient of 0.52 g cells/g sugar. In continuous cultivation, 19.9 g·l
–1 cell mass could be obtained at a dilution rate (D) of 0.36 h–1 under identical environmental conditions, showing a productivity of 7.2 g·l
–1·h–1. This corresponded to a gain of 9.0 in productivity in continuous culture over batch culture. Starting with steady state values of state variables, cell mass (CX–19.9 g·l
–1), limiting nutrient concentration (Cln–2.5 g·l
–1) and sugar concentration (CS–1.5 g·l
–1) at control variable conditions of pH 3.8, 30°C, and KLa 200 h–1 keeping D=0.36 h–1 as reference, transient response studies by step changes of these control variables also showed that this pH, temperature and KLa conditions are most suitable for SCP cultivation on nopal fruit juice. Kinetic equations obtained from experimental data were analysed and kinetic parameters determined graphically. Results of SCP production from nopal fruit juice are described.Nomenclature Cln
concentration of ammonium sulfate (g·l
–1)
- CS
concentration of total sugar (g·l
–1)
- CX
cell concentration (g·l
–1)
- D
dilution rate (h–1)
- Kln
Monod's constant (g·l
–1)
- m
maintenance coefficient (g ammonium sulfate cell–1 h–1)
- m(S)
maintenance coefficient (g sugar g cell–1 h–1)
- t
time, h
- Y
yield coefficient (g cells/g ammonium sulfate)
- Ym
maximum of Y
- YS
yield coefficient based on sugar consumed (g cells · g sugar–1)
- YS(m)
maximum value of YS
-
µm
maximum specific growth rate constant (h–1) 相似文献
8.
Using two mouse-mouse hybridoma cell lines, the response to ammonia step and serial changes was investigated in batch and continuous cultures with serum-free medium. The inhibitory effect of ammonia on cell growth depended on the cultivation mode, and differed markedly between cell lines. The cell line, 4C10B6 producing IgG monoclonal antibody against Pseudomonas, showed a high adaptation ability to ammonia. The 4C10B6 cells could grow under ammonia concentration as high as 21 mmol/l NH4Cl with a viability of 80% in the continuous culture with serial increase in ammonia concentration. Whereas, in the batch culture with ammonia step change the cell growth completely ceased at 12 mmol/l NH4Cl. The other cell line, TO-405 producing IgG monoclonal antibody against hepatitis B surface antigen, could not adapt to ammonia, and the cell growth did not occur at 9 mmol/l NH4Cl even under the ammonia serial change.List of symbols DFeed
d-1 Dilution rate of fresh feed medium (=Fo/V)
- DOut
d-1 Dilution rate of cell suspension (=F1/V)
- F1
ml·d-1 Volumetric discharge rate of cell suspension
- F0
ml·d-1 Volumetric flow rate of fresh feed medium
- kD
h-1 Specific death rate
- P
mmol·l-1 Product concentration
- S
mmol·l-1 Substrate concentration in culture broth
- S0
mmol·l-1 Substrate concentration in feed medium
- t
d Cultivation time
- V
ml Working volume of reactor
- X0
cells·ml-1 Total cell density
- XV
cells·ml-1 Viable cell density
- YP/S
mmol·mmol-1 Yield of product from substrate
- YX/S
cells·mmol-1 Yield of cells from substrate
-
mmol·cell-1·h-1 Specific production rate
-
h-1 Specific growth rate
-
mmol·cell-1·h-1 Specific consumption rate of substrate 相似文献
9.
José Humberto de Queiroz Jean-Louis Uribelarrea Alain Pareilleux 《Applied microbiology and biotechnology》1993,39(4-5):609-614
The energetics of growth of the fission yeast Schizosaccharomyces pombe was studied in continuous high-cell concentration cultures using a cell-recycle fermentor. Under non-O2-limited conditions, steady-states were obtained at various specific growth rates (partial cell-recycle) with purely oxidative (glucose limitation) or respiro-fermentative (glucose excess) metabolic behaviour. The stoichiometry of biomass synthesis was established from the elemental composition of the cells and measurements of all the specific metabolic rates, i.e. consumption of glucose and O2 and production of CO2, ethanol and other products. The theoretical yield factor for biomass on glucose was YG,X = 0.85 C-mol·C-mol–1 and maintenance requirements were negligible. Assuming a constant coupling between energy generation and biomass formation for both respirative and respiro-fermentative breakdown of glucose, the biomass yield from ATP (YATP) and the efficiency of oxidative phosphorylation (P/O ratio) could be determined as 9.8 g biomass·mol ATP and 1.28 mol ATP·atom of O2, respectively.
Correspondence to: A. Pareilleux 相似文献
10.
Summary Growth and ethanol production by three strains (MSN77, thermotolerant, SBE15, osmotolerant and wild type ZM4) of the bacterium Zymomonas mobilis were tested in a rich medium containing the hexose fraction from a cellulose hydrolysate (Aspen wood). The variations of yield and kinetic parameters with fermentation time revealed an inhibition of growth by the ethanol produced. This inhibition may result from the increase in medium osmolality due to ethanol formation from glucose.Nomenclature S
glucose concentration (g/L)
- C
conversion of glucose (%)
- t
fermentation time (h)
- qS
specific glucose uptake rate (g/g.h)
- qp
specific ethanol productivity (g/g.h)
- Qp
volumetric ethanol productivity (g/L.h)
- QX
volumetric biomass productivity (g/L.h)
- YX/S
biomass yield (g/g)
- Yp/S
ethanol yield (g/g)
-
specific growth rate (h-1) 相似文献
11.
Summary The fermentation by Candida shehatae and Pichia stipitis of xylitol and the various sugars which are liberated upon hydrolysis of lignocellulosic biomass was investigated. Both yeasts produced ethanol from d-glucose, d-mannose, d-galactose and d-xylose. Only P. stipitis fermented d-cellobiose, producing 6.5 g·l-1 ethanol from 20 g·l-1 cellobiose within 48 h. No ethanol was produced from l-arabinose, l-rhamnose or xylitol. Diauxie was evident during the fermentation of a sugar mixture. Following the depletion of glucose, P. stipitis fermented galactose, mannose, xylose and cellobiose simultaneously with no noticeable preceding lag period. A similar fermentation pattern was observed with C. shehatae, except that it failed to utilize cellobiose even though it grew on cellobiose when supplied as the sole sugar. P. stipitis produced considerably more ethanol from the sugar mixture than C. shehatae, primarily due to its ability to ferment cellobiose. In general P. stipitis exhibited a higher volumetric rate and yield of ethanol production. This yeast fermented glucose 30–50% more rapidly than xylose, whereas the rates of ethanol production from these two sugars by C. shehatae were similar. P. stipitis had no absolute vitamin requirement for xylose fermentation, but biotin and thiamine enhanced the rate and yield of ethanol production significantly.Nomenclature max
Maximum specific growth rate, h-1
-
Q
p
Maximum volumetric rate of ethanol production, calculated from the slope of the ethanol vs. time curve, g·(l·h)-1
-
q
p
Maximum specific rate of ethanol production, g·(g cells·h)
-
Y
p/s
Ethanol yield coefficient, g ethanol·(g substrate utilized)-1
-
Y
x/s
Cell yield coefficient, g biomass·(g substrate utilized)-1
-
E
Efficiency of substrate utilization, g substrate consumed·(g initial substrate)-1·100 相似文献
12.
Roland H. Müller Oleg V. Sysoev Wolfgang Babel 《Applied microbiology and biotechnology》1986,25(3):238-244
Summary Investigations were made into the improvement of growth yield (Y) of Pichia pinus MH 4 growing continuously on methanol by feeding formate so as to create an increasing concentration gradient (transient state). Under particular formate supply conditions, Y could be increased from 0.37 g·g-1 on methanol alone to 0.55 and 0.47 g·g-1 in the presence of formate at dilution rates (D) of 0.045 and 0.075 h-1, respectively. These differences could be explained as being due to a limiting formate consumption rate of 50–60 nmol·min-1·g-1 dry wt., coupled to a net-energy generation independent of D. Any further formate oxidation proceeded without energy gain. Deviations from optimum conditions of biomass increase are discussed in terms of different formate oxidizing systems and uncoupling properties of formate itself. These results are compared to and confirmed by steady-state considerations.Abbreviations a
steepness of the formate gradient (g·l-1·h-1)
- a
acceleration of change of formate concentration in the fermenter (g·l-1·h-2)
- D
dilution rate (h-1)
- Ft
formate
- S1 and S2
initial and final formate concentration of the gradient (g·l-1)
- Y
growth yield in g·g-1 methanol 相似文献
13.
Summary An algorithm for the optimization of a fermentation process was studied using the combination of dynamic programming and linear predictive procedure by regression analysis. It was applied to the fed-batch culture for glutamic acid production with ethanol feeding, the results of which proved that it was effective for the optimization problems.Nomenclature
a
i
, b
i
, c
i
, d
i
;i = 1 2 or 3:
Partial regression coefficients derived by multiple regression analysis ( - )
-
E :
Euclid distance ( - )
-
F :
Volumetric feed rate (l/hr)
-
f :
Defined by Eq. (13) (g-glutamic acid)
-
G :
Concentration of glutamic acid (g/l)
-
G* :
Aeration rate (l/hr)
-
J :
Objective function defined by Eq. (12) (g-glutamic acid)
-
N :
Number of stage ( - )
-
P :
Defined by Eq. (14) (g-glutamic acid)
-
Q :
Metabolic activity of the culture, in this case Q = Q
CO
2 (mole CO2/g-cell hr)
-
S :
Ethanol concentration in culture broth (g/l)
-
S
Q
:
Ethanol concentration in feed (g/l)
-
S* :
Ethanol concentration in effluent gas (g/l)
-
t :
Culture time (hr)
-
t
o
:
Initial culture time (hr)
-
V :
Volume of culture broth (l)
-
X :
Cell concentration (g/l)
-
X :
State vector (X, S, Q, V)
- :
Rate of Q
CO
2 change (mole CO2/g-cell·h2)
- :
Specific growth rate of microorganisms (hr–1)
- :
Specific production rate of glutamic acid (g-glutamic acid/g-cell·hr)
- :
Specific consumption rate of ethanol (g-ethanol/g-cell·hr)
- :
Standard deviation ( - )
This optimization procedure was presented in preliminary form at the 45th Annual Meeting of the Soc. of Chem. Engrs., Japan, Osaka, C105 (1980). 相似文献
14.
A procedure for estimating biomass during batch fermentation from on-line gas analysis is presented. First, the respiratory quotient was used to determine the fraction of the total oxygen utilization rate required for cell maintenance and growth versus product synthesis. The modified oxygen utilization rate was then used to estimate biomass on-line by integrating the oxygen balance for cell synthesis-maintenance. The method is illustrated for the case of L-lysine synthesis by Corynebacterium glutamicum.List of Symbols
CER mmol CO2/l · h
carbon dioxide evolution rate
-
M
O
2/x mmol O2/h · g cells
maintenance coefficient
-
OUR mmol O2/l · h
oxygen utilization rate
-
OUR
X
mmol O2/l · h
OUR fraction for cell maintenance and growth
-
RQ mmol CO2/mmol O2
respiratory quotient(CER/OUR)
-
X g cells/l
biomass concentration
-
Y
X/O2
yield coefficients 相似文献
15.
Summary Optimal growth conditions for Zymomonas mobilis have been established using continuous cultivation methods. Optimal substrate utilization efficiency occurs with 2.5 g l–1 yeast extract, 2.0 g l–1 ammonium sulfate and 6.0 g l–1 magnesium sulfate in the media. Catabolic activity is at its maximum with glucose uptake rates of 16–18 g l–1 h–1 and ethanol production rates of 8–9 g l–1 h–1, Qg values of 22–26 and Qp values between 11 and 13, which results in 40 g l–1 h–1 ethanol yields using a 100 g l–1 substrate feed. Any increase in these parameters goes on cost of substrate utilization efficiency. Calcium pantothenate can not substitute yeast extract.Abbreviations G
Glucose (%)
- Pant
Calcium pantothenate (mg l–1)
- D
Dilution rate (h–1)
- NH4
Ammonium sulfate (%)
- Mg
Magnesium sulfate (%)
- S1
Residual glucose in the fermenter (g l–1)
- S0
Glucose feed (g l–1)
- Eth
Ethanol concentration (g l–1)
- GUR
Glucose uptake rate (g l–1 h–1)
- Qg
Specific glucose uptake rate (g g–1 h–1)
- Qp
Specific ethanol production rate (g g–1 h–1)
- EPR
Ethanol production rate (g l–1 h–1)
- Yg
Yield coefficient for glucose (g g–1)
- Yp
Conversion efficiency (%)
- C
Biomass concentration (g l–1)
Present address: (Until June 1982) Institut für Mikrobiologie, TH Darmstadt, 6100 Darmstdt, Federal Republic of Germany 相似文献
16.
Summary The influence of temperature on the growth of the theromophilic Bacillus caldotenax was investigated using chemostat techniques and a chemically defined minimal medium. All determined growth constants, that is maximal specific growth rate, yield and maintenance, were temperature dependent. It was striking that the very large maintenance requirement was about 10 times higher than for mesophilic cells under equivalent conditions. A death rate, which was very substantial at optimal and supraoptimal growth temperatures, was estimated by comparing the maintenance for substrate and oxygen. There was no indication for a thermoadaptation as postulated by Haberstich and Zuber (1974).Symbols D
Dilution rate (h–1)
- Dc=max
Critical dilution rate (h–1)
- E
Temperature characteristic (J mol–1)
- k
Organism constant
- kd
Death rate coefficient (h–1)
- km
Maintenance substrate coefficient estimated from MO (h–1)
- MO
Maintenance respiration, mmol O2 per g dry biomass and h (mmol g–1h–1)
- MO
Maintenance respiration, taking kd into account
- mS
Maintenance substrate coefficient, g glucose per g dry biomass and h (h–1)
- OD
Optical density at 546 nm
- QO2
Specific O2-uptake rate (mmol g–1h–1)
- Q
O2
V
Specific O2-uptake rate for viable portion of biomass (mmol g–1 h–1)
- QS
Specific glucose uptake rate (h–1)
- Q
S
V
Specific glucose uptake rate for viable portion of biomass (h–1)
- R
Gas constant 8.28 J mol–1K–1
- S
Substrate concentration in reactor (g l–1)
- SO
Influent substrate concentration (g l–1)
- Tmax
Maximal growth temperature (°C)
- Tmin
Minimal growth temperature (°C)
- X
Dry biomass (g l–1)
- XtOt=X
Dry biomass containing dead and viable cells
- Xv
Viable portion of biomass
- Y
O
m
Potential yield for O2 corrected for maintenance respiration (g mol–1)
- Y
S
m
Potential yield for substrate corrected for maintenance requirement, g biomass per g glucose (–)
-
Specific growth rate (h–1)
- max
Maximal specific growth rate (h–1) 相似文献
17.
M. L. F. Giuseppin 《Applied microbiology and biotechnology》1984,20(3):161-165
Summary The influence of the concentration of oxygen on lipase production by the fungus Rhizopus delemar was studied in different fermenters. The effect of oxygen limitation ( 47 mol/l) on lipase production by R. delemar is large as could be demonstrated in pellet and filamentous cultures. A model is proposed to describe the extent of oxygen limitation in pellet cultures. Model estimates indicate that oxygen is the limiting substrate in shake flask cultures and that an optimal inoculum size for oxygen-dependent processes can occur.Low oxygen concentrations greatly negatively affect the metabolism of R. delemar, which could be shown by cultivation in continuous cultures in filamentous growth form (Doptimal=0.086 h-1). Continuous cultivations of R. delemar at constant, low-oxygen concentrations are a useful tool to scale down fermentation processes in cases where a transient or local oxygen limitation occurs.Symbols and Abbreviations CO
Oxygen concentration in the gas phase at time = 0 (kg·m-3)
- CO
2i
Oxygen concentration at the pellet liquid interface (kg·m-3)
- CO
2i
Oxygen concentration in the bulk (kg·m-3)
-
D
Dilution rate (h-1)
- IDO
2
Diffusion coefficient for oxygen (m2·s-1)
-
dw
Dry weight of biomass (kg)
-
f
Conversion factor (rs
O
2 to oxygen consumption rate per m3) (-)
-
k
Radial growth rate (m·s-1)
-
K
Constant
-
kla
Volumetric mass transfer coefficient (s-1)
-
klA
Oxygen transfer rate (m-3·s-1)
-
kl
Mass transfer coefficient (m·s-1)
-
K
O
2
Affinity constant for oxygen (mol·m-3)
-
K
w
Cotton plug resistance (m-3·s-1)
-
M
Henry coefficient (-)
-
NV
Number of pellets per volume (m-3)
-
R
Radius (m)
-
RO
Radius of oxygen-deficient core (m)
-
RQ
Respiration quotient (mol CO2/mol O2)
-
rs
O
2
Specific oxygen consumption rate per dry weight biomass (kg O2·s-1[kg dw]-1)
-
rX
Biomass production rate (kg·m-3·s-1)
-
SG
Soytone glucose medium (for shake flask experiments)
-
SG
4
Soytone glucose medium (for tower fermenter and continuous culture experiments)
-
V
Volume of medium (m-3)
-
X
Biomass (dry weight) concentration (kg·m-3)
-
XR
o
Biomass concentration within RO for a given X (kg·m-3)
-
Y
O
2
Biomass yield calculated on oxygen (kg dw/kg O2)
-
Thiele modulus
-
Efficiency factor =1-(RO/R)3 (-)
-
Growth rate (m-1·s-1·kg1/3)
-
Dry weight per volume of pellet (kg·m-3) 相似文献
18.
Bernard Bibal Gérard Goma Yves Vayssier Alain Pareilleux 《Applied microbiology and biotechnology》1988,28(4-5):340-344
Summary The effect of various culture conditions on growth kinetics of an homofermentative strain of the lactic acid bacterium Streptococcus cremoris were investigated in batch cultures, in order to facilitate the production of this organism as a starter culture for the dairy industry. An optimal pH range of 6.3–6.9 was found and a lactose concentration of 37 g·l-1 was shown to be sufficient to cover the energetic demand for biomass formation, using the recommended medium. The study of the effect of lactic acid concentration on growth kinetics revealed that the end-product was not the sole factor affecting growth. The strain was characterized for its tolerance towards lactic acid and a critical concentration of 70 g·l-1 demonstrated. With the product yield of 0.9 g·g-1 at non-lactose limiting conditions the lactic acid concentration of 33 g·l-1 could not explain the low growth rates obtained, implicating a nutritional limitation.Symbols
t
f
fermentation duration (h)
-
X
Biomass concentration (g·l-1)
-
X
m
maximum biomass concentration (g·l-1)
-
S
lactose concentration (g·l-1)
-
S
r
residual lactose concentration (g·l-1)
-
P
produced lactic acid concentration (g·l-1)
-
P
a
added lactic acid concentration (g·l-1)
-
P
c
critical lactic acid concentration (g·l-1)
-
specific growth rate (h-1)
- max
maximum specific growth rate (h-1)
-
R
x/S
biomass yield (g·g-1) calculated when =0
-
R
P/S
product yield (g·g-1) 相似文献
19.
Jurjen Frankena Gregory M. Koningstein Henk W. van Verseveld Adriaan H. Stouthamer 《Applied microbiology and biotechnology》1986,24(2):106-112
Summary Maximal molar growth yields (Y
sub
max
) and protease production ofBacillus licheniformis S 1684 during NH
4
+
-, O2-, and NH
4
+
+O2-limitation with either glucose or citrate as carbon and energy source and during glucose-, and citratelimitation in chemostat cultures were determined. Protease production was repressed by excess ammonia when glucose served as C/E-source. Glucose and citrate repressed protease production during NH
4
+
-limitation. A low oxygen tension enbanced protease production at low -values. It was concluded that, besides ammonia repression, catabolite flux and oxygen tension influence protease production, indicating that the energy status of the cell is important for the level of protease production.Y
sub
max
-values were high during glucose-limitation and indicate a high efficiency of growth caused by a highY
ATP
max
. During NH
4
+
-, O2-, and NH
4
+
+O2-limitation with glucose as C/E-values were lower than during glucose limitation. The lowerY
sub
max
-values were due to a lower efficiency of energy conservation.Y
sub
max
-values during limitations with citrate as C/E-source were lower than during limitations with glucose as C/E-source.Nomenclature
specific growth rate (h-1)
-
Y
sub
growth yield per mol substrate (g biomass/mol)
-
Y
max
maximal molar growth yield corrected for maintenance requirements (g biomass/mol)
-
Y
max (corr)
Y
max corrected for product formation (g biomass/mol)
-
m
sub
maintenance requirements (mol/g biomass·h)
-
m
sub (corr)
maintenance requirements corrected for product formation (mol/g biomass·h)
-
q
port
max
maximal specific rate of protease production (E440/mg DW·h) 相似文献
20.
A. Sanromán E. Roca M. J. Núñez Professor Dr. J. M. Lema 《Bioprocess and biosystems engineering》1994,10(2):75-81
When the immobilized cells are employed in packed-bed bioreactors several problems appear. To overcome these drawbacks, a new bioreactor based on the use of pulsed systems was developed [1]. In this work, we study the glucose fermentation by immobilized Saccharomyces cerevisiae in a packed-bed bioreactor. A comparative study was then carried out for continuous fermentation in two packed-bed bioreactors, one of them with pulsed flow. The determination of the axial dispersion coefficients indicates that by introducing the pulsation, the hydraulic behaviour is closer to the plug flow model. In both cases, the residence time tested varied from 0.8 to 2.6 h. A higher ethanol concentration and productivity (increases up to 16%) were achieved with the pulsated reactors. The volumes occupied by the CO2 were 5.22% and 9.45% for fermentation with/without pulsation respectively. An activity test of the particles from the different sections revealed that the concentration and viability of bioparticles from the two bioreactors are similar. From the results we conclude that the improvements of the process are attributable to a mechanical effect rather than to physiological changes of microorganisms.List of Symbols
D m2/s
dispersion coefficient
-
K
is l/g
inhibition substrate constant
-
K
ip l/g
inhibition ethanol constant
-
K
s g/l
Apparent affinity constant
-
P g/l
ethanol concentration
-
q
p g/(gh)
specific ethanol productivity
-
Q
p g/(lh)
overall ethanol productivity
-
q
s g/(gh)
specific glucose consumption rate
-
Q
s g/(lh)
glucose consumption rate
-
S g/l
residual glucose concentration
-
S(in0) g/l
initial glucose concentration
-
V
max g/(lh)
maximum rate
-
Y
p/s g/g
yield in product 相似文献