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1.
O. D. Teniola W. H. Holzapfel S. A. Odunfa 《World journal of microbiology & biotechnology》2005,21(1):39-43
Ogiis processed traditionally by the use of uncontrolled spontaneous fermentation of maize, sorghum and millet. In this study, traditionally applied spontaneous fermentation was compared with accelerated batch fermentation (or back-slopping) and the use of starter cultures to initiate fermentation. Lactic acid bacteria populations comprised 95 of the total viable bacteria and remained prominent throughout the fermentations, while number of moulds and coliform bacteria declined as the fermentation progressed. The fermentation method involving the application of starter culture helps most to control the prevalence of coliforms and moulds. Lactic acid bacteria, such as Lactococcus raffinolactis, Pediococcussp.,Pediococcus pentosaceus, Lactobacillus plantarum, Lb. suebicus and Lb. brevis,were isolated at different processing stages of ogi using accelerated batch fermentation (back-slopping) technique. Highest increase in acidity was observed immediately after wet-milling and sieving fermenting maize grains at 28 and 48 h. Sharp increases in the reducing sugar levels were noted between 24 and 28 h of fermentations during wet-milling and sieving processes. 相似文献
2.
Summary A criterion is proposed to plot concentration-time curves in fed-batch fermentations when the reactor filling stage is followed by a batch phase.Nomenclature F
mash feeding rate
- R
cells growth rate
- S
TRS concentration in the feeding mash
- t
time
- T
time measured from the beginning of the feeding phase until to the end of the fermentation
- TRS
total reducing sugars, calculated as glucose
- X
cells concentration (dry matter)
-
fermentor filling-up time 相似文献
3.
The possibility of solving the mass balances to a multiplicity of substrates within a CSTR in the presence of a chemical reaction following Michaelis-Menten kinetics using the assumption that the discrete distribution of said substrates is well approximated by an equivalent continuous distribution on the molecular weight is explored. The applicability of such reasoning is tested with a convenient numerical example. In addition to providing the limiting behavior of the discrete formulation as the number of homologous substrates increases, the continuous formulation yields in general simpler functional forms for the final distribution of substrates than the discrete counterpart due to the recursive nature of the solution in the latter case.List of Symbols
C{N. M} mol/m3
concentration of substrate containing N monomer residues each with molecular weight M
-
{N, M}
normalized value of C{N. M}
-
C
{M} mol/m3 da
concentration of substrate of molecular weight M
-
in
normalized value of C
{M} at the i-th iteration of a finite difference method
-
{M}
normalized value of C
{M}
-
C
0{N.M} mol/m3
inlet concentration of substrate containing N monomer residues each with molecular weight M
-
{N ·M}
normalized value of C0{N. M}
-
0
i
normalized value of C
0
{M} at the i-th iteration of a finite difference method
-
C
0
{M} mol/m3
da initial concentration of substrate of molecular weight M
-
C
tot mol/m3
(constant) overall concentration of substrates (discrete model)
-
C
tot
mol/m3
(constant) overall concentration of substrates (continuous model)
-
D
deviation of the continuous approach relative to the discrete approach
-
i
dummy integer variable
-
I
arbitrary integration constant
-
j
dummy integer variable
-
k
dummy integer variable
-
K
m
mol/m3
Michaëlis-Menten constant for the substrates
-
l
dummy integer variable
-
M da
molecular weight of substrate
-
M
normalized value of M
-
M
da
maximum molecular weight of a reacting substrate
-
N
number of monomer residues of a reacting substrate
-
N
maximum number of monomer residues of a reacting substrate
-
N
total number of increments for the finite difference method
-
Q m3/s
volumetric flow rate of liquid through the reactor
-
S
inert product molecule
-
S
i
substrate containing i monomer residues
-
V m3
volume of the reactor
-
v
max mol/m3 s
reaction rate under saturating conditions of the enzyme active site with substrate
-
v
max{N. M} mol/m3 s
reaction rate under saturating conditions of the enzyme active site with substrate containing N monomer residues with molecular weight M
-
max{N · M}
dimensionless value of vmax{N. M} (discrete model)
-
max{M}
dimensionless value of v
max
{M} (continuous model)
-
mol/m3 s
molecular weight-averaged value of vmax (discrete model)
-
mol.da/m3s
molecular weight-averaged value of vmax (continuous model)
-
v
max
{M} mol.da/m3s
reaction rate under saturating conditions of the enzyme active site with substrate with molecular weight M
-
max
{M}
dimensionless value of vmax{M}
-
max, (i)
dimensionless value of vmax{M} at the i-th iteration of a finite difference method
-
v
max
mol/m3 s
reference constant value of v
max
Greek Symbols
dimensionless operating parameter (discrete distribution)
-
dimensionless operating parameter (continuous distribution)
-
M da
(average) molecular weight of a monomeric subunit
-
M
selected increment for the finite difference method
-
auxiliary corrective factor (discrete model) 相似文献
4.
The influence of phosphorus (P) and nitrogen (N) supply on biomass, leaf area, photon saturated photosynthetic rate (Pmax), quantum yield efficiency (), intercellular CO2 concentration (Ci), and carboxylation efficiency (CE) was investigated in Vicia faba. The influence of P on N accumulation, biomass, and leaf area production was also investigated. An increase in P supply was consistently associated with an increase in N accumulation and N productivity in terms of biomass and leaf area production. Furthermore, P increased the photosynthetic N use efficiency (NUE) in terms of Pmax and . An increase in P supply was also associated with an increase in CE and a decrease in Ci. Under variable daily meteorological conditions specific leaf nitrogen content (NL), specific leaf phosphorus content (PL), specific leaf area (L), root mass fraction (Rf), Pmax, and remained constant for a given N and P supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. L increased with increasing N supply or with increasing NL. We tested also the hypothesis that P supply positively affects both N demand and photosynthetic NUE by influencing the upper limit of the asymptotic values for Pmax and CE, and the lower limit for Ci in response to increasing N.This revised version was published online in March 2005 with corrections to the page numbers. 相似文献
5.
R. D. Tanner D. Hunkeler N. Qureshi I. S. Maddox 《Bioprocess and biosystems engineering》1996,14(4):177-181
A published process for the fermentative production and recovery of acetone-butanol-ethanol (ABE) has been modelled and analysed. Postulation of a Variable Yield Function has led to an unexpected Value Function. Given a desired ABE production range of 1.6×106 kg per year to 32×106 kg per year, and a typical fixed (or variable) cost term, , of $0.4 per kg ABE, the process has been shown to be unprofitable in the range 2×106 kg per year to 18 × 106 kg per year. Profitability is achieved at low production values (less than 2×106 kg per year), and at high production values (greater than 18×106 kg per year). Conversely, profitability is achieved for the comparable fixed yield case, for=$0.4 per kg ABE, for all production values, with the profitability increasing linearly with production.List of Symbols
N
ABE production, kg/yr,N
1 andN
2 for capacity 1 and 2, respectively
-
N
min
Minimum value ofN. ABE production, kg/yr
-
P
ABE concentration in a batch fermentation system, kg/l
-
p
ABE price, $/kg
-
p
1
p-, $/kg
-
S
Amount of raw material, kg or kg/yr
-
S
1
Substrate concentration in a batch fermentation system, kg/l
-
s
Price of raw material, $/kg
-
V
Value function, $/yr
-
V(N)
Value function for production capacityN, $/yr
-
Y
Continuous/fed batch fermentation yield, kg ABE/Kg whey permeate lactose.Y
1 andY
2 refer to yield for capacity 1 and 2, respectively
-
y
Batch fermentation traditional yield, kg ABE/Kg whey permeate lactose
-
Average value ofY, kg ABE/Kg whey permeate lactose
-
Y
min
Minimum Yield for continuous/fed batch fermentation, kg ABE/Kg whey permeate lactose
-
Y(N)
Continuous/fed batch fermentation yield function, kg ABE/Kg whey permeate lactose
Greek Letters
Proportionality constant, yr/kg ABE
-
Proportionality constant, kg ABE/yr
-
Fixed costs (fermentation equipment, reverse osmosis and pervaporation equipment) + variable costs (energy, steam and labour + pervaporation membrane cost to remove ABE and recycle unused sugar), $/kg ABE
-
Exponent ofN in a generalized yield function
We thank Tricia A. Doak (Department of Chemical Engineering, Vanderbilt University) for generating Figs. 2–5 on the computer. 相似文献
6.
S. E. Vecht M. W. Platt Z. Er-El I. Goldberg 《Applied microbiology and biotechnology》1988,27(5-6):587-592
Summary The present study describes the growth of Pseudomonas putida cells (ATCC 33015) in batch and continuous cultures on two toxic substrates; toluene and m-toluic acid as sole carbon and energy sources. In fed-batch cultures on m-toluic acid up to 3.55 g cell dry weight/1 were achieved with a maximal specific growth rate (max) of 0.1 h-1. The average cellular yield was 1.42 g cell dry weight/g m-toluic acid utilized. When liquid toluene was added to shake-flask cultures in the presence of 0.7 g/1 m-toluic acid, the average cellular yield obtained was 1.3 g cell dry weight/g toluene utilized and the max was 0.13 h-1. Growth on toluene vapour in the presence of 0.7 g/l m-toluic acid in batch cultures resulted in a cellular yield of 1.28 g cell dry weight/g toluene utilized, with growth kinetics almost identical to those with liquid toluene (max liquid=0.13 h-1, max vapour=0.12 h-1). The maximal biomass concentration was 3.8 g cell dry weight/l, obtained in both cases after 100 h of incubation. Pseudomonas putida was grown in a chemostat initially on 0.7 g/l m-toluic acid and vapour toluene and then in the steady state on toluene as the sole source of carbon and energy. Toluene was added continuously to the culture as vapour with the inflowing airstream. Chemostat cultures could be maintained at steady state for several months on toluene. The maximal biomass concentration obtained in the chemostat culture was 3.2 g cell dry weight/l. The maximum specific growth rate was 0.13 h-1, with a cellular yield of 1.05 g cell dry weight/g toluene utilized. Approximately 70% of the toluene consumed was converted into biomass, and the remainder was converted to CO2 and unidentified byproducts. 相似文献
7.
Masset J Calusinska M Hamilton C Hiligsmann S Joris B Wilmotte A Thonart P 《Biotechnology for biofuels》2012,5(1):35-15
Background
Pure bacterial strains give better yields when producing H2 than mixed, natural communities. However the main drawback with the pure cultures is the need to perform the fermentations under sterile conditions. Therefore, H2 production using artificial co-cultures, composed of well characterized strains, is one of the directions currently undertaken in the field of biohydrogen research.Results
Four pure Clostridium cultures, including C. butyricum CWBI1009, C. pasteurianum DSM525, C. beijerinckii DSM1820 and C. felsineum DSM749, and three different co-cultures composed of (1) C. pasteurianum and C. felsineum, (2) C. butyricum and C. felsineum, (3) C. butyricum and C. pasteurianum, were grown in 20?L batch bioreactors. In the first part of the study a strategy composed of three-culture sequences was developed to determine the optimal pH for H2 production (sequence 1); and the H2-producing potential of each pure strain and co-culture, during glucose (sequence 2) and starch (sequence 3) fermentations at the optimal pH. The best H2 yields were obtained for starch fermentations, and the highest yield of 2.91?mol?H2/ mol hexose was reported for C. butyricum. By contrast, the biogas production rates were higher for glucose fermentations and the highest value of 1.5?L biogas/ h was observed for the co-culture (1). In general co-cultures produced H2 at higher rates than the pure Clostridium cultures, without negatively affecting the H2 yields. Interestingly, all the Clostridium strains and co-cultures were shown to utilize lactate (present in a starch-containing medium), and C. beijerinckii was able to re-consume formate producing additional H2. In the second part of the study the co-culture (3) was used to produce H2 during 13?days of glucose fermentation in a sequencing batch reactor (SBR). In addition, the species dynamics, as monitored by qPCR (quantitative real-time PCR), showed a stable coexistence of C. pasteurianum and C. butyricum during this fermentation.Conclusions
The four pure Clostridium strains and the artificial co-cultures tested in this study were shown to efficiently produce H2 using glucose and starch as carbon sources. The artificial co-cultures produced H2 at higher rates than the pure strains, while the H2 yields were only slightly affected. 相似文献8.
A. Prell J. Lasík J. Koníček M. Sobotka J. Sys 《Bioprocess and biosystems engineering》1995,13(6):289-292
Growth of X. campestris and production of xanthan were studied in several batch fermentations with different starting concentrations of N-source. The dependencies of growth, productivity and yields on initial N-source concentration were observed. The maximum yields in the course of cultivations were identified.List of Symbols
Y
e
economical yield coefficient
-
Y
P/sc
product yield coefficient related to C-source
-
r
N
specific growth rate related to cell number (h–1)
-
Y
exp
experimental yield coefficient
-
Y
T
theoretical yield coefficient
-
c(Sn)
concentration of N-source (mg/l)
-
c(Sc)
concentration of C-source (g/l)
-
c(P)
concentration of product (g/l)
-
N
cell number (l–1)
-
thermodynamic efficiency
We are grateful to Mrs. B. Bhalová, PhD, for chemical analyses of the medium. 相似文献
9.
Emma Dixon Tatiana Schweibenz Alison Hight Brian Kang Allyson Dailey Sarah Kim Meng-Yang Chen Yura Kim Sarah Neale Ashley Groth Trish Ike Sarah Khan Brandon Schweibenz David Lieu David Stone Tania Orellana Robin D. Couch 《Journal of industrial microbiology & biotechnology》2011,38(5):607-615
Cyathin A3, produced by the fungus Cyathus helenae, is a member of the cyathane family of diterpene natural products. While many of the cyathanes display antibacterial/antimicrobial activity or have cytotoxic activity against human cancer cell lines, their most exciting therapeutic potential is derived from their ability to induce nerve growth factor (NGF) release from glial cells, making the cyathanes attractive lead molecules for the development of neuroprotective therapeutics to prevent/treat Alzheimer’s disease. To investigate if cyathin A3 has NGF-inducing activity, we set out to obtain it using published C. helenae bench-scale fungal fermentations. However, to overcome nonproducing fermentations, we developed an alternative, bacteria-induced static batch fermentation approach to the production of cyathin A3, as described in this report. HPLC, UV absorption spectra, and mass spectrometry identify cyathin A3 in fungal fermentations induced by the timely addition of Escherichia coli K12 or Bacillus megabacterium. Pre-filtration of the bacterial culture abolishes cyathin A3 induction, suggesting that bacteria-associated media changes or physical interaction between the fungus and bacteria underlie the induction mechanism. Through alteration of incubation conditions, including agitation, the timing of induction, and media composition, we optimized the fermentation to yield nearly 1 mg cyathin A3/ml media, a sixfold increase over previously described yields. Additionally, by comparison of fermentation profiles, we reveal that cyathin A3 biosynthesis is regulated by carbon catabolite repression. We have used an enzyme-linked immunosorbent assay to illustrate that cyathin A3 induces NGF release from cultured glial cells, and therefore cyathin A3 warrants further examination in the development of neuroprotective therapeutics. 相似文献
10.
In-situ recovery of butanol during fermentation 总被引:1,自引:0,他引:1
S. R. Roffler Prof. H. W. Blanch C. R. Wilke 《Bioprocess and biosystems engineering》1987,2(4):181-190
End-product inhibition in the acetone-butanol fermentation was reduced by using extractive fermentation to continuously remove acetone and butanol from the fermentation broth. In situ removal of inhibitory products from Clostridium acetobutylicum resulted in increased reactor productivity; volumetric butanol productivity increased from 0.58 kg/(m3h) in batch fermentation to 1.5 kg/(m3h) in fed-batch extractive fermentation using oleyl alcohol as the extraction solvent. The use of fed-batch operation allowed glucose solutions of up to 500 kg/m3 to be fermented, resulting in a 3.5- to 5-fold decrease in waste water volume. Butanol reached a concentration of 30–35 kg/m3 in the oleyl alcohol extractant at the end of fermentation, a concentration that is 2–3 times higher than is possible in regular batch or fed-batch fermentation. Butanol productivities and glucose conversions in fed-batch extractive fermentation compare favorable with continuous fermentation and in situ product removal fermentations.List of Symbols
C
g kg/m3
concentration of glucose in the feed
-
C
w dm3/m3
concentration of water in the feed
-
F(t) cm3/h
flowrate of feed to the fermentor at time t
-
V(t) dm3
broth volume at time t
-
V
i dm3
initial broth volume
-
V
si dm3
volume of the i-th aqueous phase sample
-
effective fraction of water in the feed
Part 1. Bioprocess Engineering 2 (1987) 1–12 相似文献
11.
Summary The batch fermentation of whey permeate to lactic acid was improved by supplementing the broth with enzyme-hydrolyzed whey protein. A mathematical model based on laboratory results predicts to a 99% confidence limit the kinetics of this fermentation. Cell growth, acid production and protein and sugar use rates are defined in quantifiable terms related to the state of cell metabolism. The model shows that the constants of the Leudeking-Piret model are not true constants, but must vary with the medium composition, and especially the peptide average molecular weight. The kinetic mechanism on which the model is based also is presented.Nomenclature
K
i
lactic acid inhibition constant (g/l)
-
K
pr
protein saturation constant during cell growth (g/l)
-
K
pr
protein saturation constant during maintenance (g/l)
-
K
s
lactose saturation constant (g/l)
- [LA]
lactic acid concentration (g/l)
- [PR]
protein concentration (g/l)
- [S]
lactose concentration (g/l)
-
t
time (h)
- [X]
cell mass concentration (g/l)
- ,
fermentation constants of Leudeking and Piret
-
specific growth rate (l/h)
-
Y
g, LA/S
acid yield during cell growth (g acid/g sugar)
-
Y
m, LA/S
acid yield during maintenance (g acid/g sugar)
-
Y
x/pr
yield (g cells/g protein)
-
specific sugar use rate during cell growth (g sugar/h·g cell)
-
specific sugar use rate during maintenance (g sugar/h·cell) 相似文献
12.
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
13.
《Biochemical Engineering Journal》2000,4(2):121-128
The batch fermentations were conducted using lactose as the substrate at pH 6.5 and temperature 30°C. Average batch kinetic data was eventually used to develop an unstructured mathematical model. The kinetic parameters of the model were determined by non-linear regression technique using the batch experimental results. Parametric sensitivity analysis showed the maximum specific substrate consumption rate (rSmax) and the maintenance energy constant (mS) to be the most sensitive parameters. The experimental observations in batch fermentation were close to the model predictions. The batch model was extrapolated to identify nutrient feeding strategies, which were tested successfully for two different fed-batch fermentations. It demonstrated enhanced propionic acid productivity. The developed model was found suitable for the design of feeding strategies to increase propionic acid production in fed-batch mode of reactor operation. 相似文献
14.
Jasper Kunow Beatrix Schwörer Karl O. Stetter Rudolf K. Thauer 《Archives of microbiology》1993,160(3):199-205
Archaeoglobus fulgidus, a sulfate-reducing Archaeon with a growth temperature optimum of 83°C, uses the 5-deazaflavin coenzyme F420 rather than pyridine nucleotides in catabolic redox processes. The organism does, however, require reduced pyridine nuclcotides for biosynthetic purposes. We describe here that the Archaeon contains a coenzyme F420-dependent NADP reductase which links anabolism to catabolism. The highly thermostable enzyme was purfied 3600-fold by affinity chromatography to apparent homogeneity in a 60% yield. The native enzyme with an apparent molecular mass of 55 kDa was composed of only one type of subunit of apparent molecular mass of 28 kDa. Spectroscopic analysis of the enzyme did not reveal the presence of any chromophoric prosthetic group. The purified enzyme catalyzed the reversible reduction of NADP (apparent K
M 40 M) with reduced F420 (apparent K
M 20M) with a specific activity of 660 U/mg (apparent V
max) at pH 8.0 (pH optimum) and 80°C (temperature optimum). It was specific for both coenzyme F420 and NADP. Sterochemical investigations showed that the F420-dependent NADP reductase was Si face specific with respect to C5 of F420 and Si face specific with respect to C4 of NADP.Abbreviations F420
coenzyme F420
- F420H2
1,5-dihydrocoenzyme F420
- H4MPT
tetrahydromethanopterin
- CH=H4MPT
N5, N10-methylenetetrahydromethanopterin
- MFR
methanofuran
- HPLC
high performance liquid chromatography
- methylene-H4MPT dehydrogenase
N5, N10-methylenetetrahydromethanopterin dehydrogenase
- 1 U =
1 mol/min 相似文献
15.
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
16.
Effective scale-up is essential for successful bioprocessing. While it is desirable to keep as many operating parameters constant as possible during the scale-up, the number of constant parameters realizable is limited by the degrees of freedom in designing the large-scale operation. Scale-up of aerobic fermentations is often carried out on the basis of a constant oxygen transfer coefficient, k
L
a, to ensure the same oxygen supply rate to support normal growth and metabolism of the desired high cell populations. In this paper, it is proposed to replace the scale-up criterion of constant k
L by a more direct and meaningful criterion of equal oxygen transfer rate at a predetermined value of dissolved oxygen concentration. This can be achieved by using different oxygen partial pressures in the influent gas streams for different scales of operation. One more degree of freedom, i.e., gas-phase oxygen partial pressure, is thus added to the process of scale-up. Accordingly, one more operating factor can be maintained constant during scale-up. It can be used to regulate the power consumption in large-scale fermentors for economical considerations or to describe the fluid mixing more precisely. Examples are given to show that the results of optimization achieved in the bench-scale study can be translated to the production-scale fermentor more successfully with only a small change in the gas-phase oxygen partial pressure employed in the bench-scale operation.List of Symbols
a m2/m3
Specific gas/liquid interfacial area
-
C
L mole/m3
Dissolved oxygen concentration in bulk liquid phase
-
C
* mole/m3
Equilibrium oxygen concentration at gas/liquid interface
-
D
i m
Impeller diameter
-
D
T m
Bioreactor diameter
-
H
L mole/m3 · atm
Henry's-law constant
-
k
L m/s
Liquid-phase mass transfer coefficient
-
N 1/s
Impeller agitation speed
-
N
i
Number of impellers
-
OTR mole/s · m3
Oxygen transfer rate per unit volume of the medium
-
P
g kW
Power input in aerated fermentation
-
P
o kW
Power input in non-gassed fermentation
-
p
g atm
Gas-phase oxygen partial pressure
-
Q m3/s
Volumetric gas flow rate
-
Re
i
Impeller Reynolds number
-
T
Q Joule
Torque applied to the mixer shaft
-
V m3
Liquid volume
-
v
s m/s
Superficial gas velocity
-
kg/m · s
Liquid viscosity
-
kg/m3
Liquid density 相似文献
17.
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
18.
The influence of phosphorus (P) and nitrogen (N) supply on biomass, leaf area, photon saturated photosynthetic rate (Pmax), quantum yield efficiency (α), intercellular CO2 concentration (Ci), and carboxylation efficiency (CE) was investigated in Vicia faba. The influence of P on N accumulation, biomass, and leaf area production was also investigated. An increase in P supply was consistently associated with an increase in N accumulation and N productivity in terms of biomass and leaf area production. Furthermore, P increased the photosynthetic N use efficiency (NUE) in terms of Pmax and α. An increase in P supply was also associated with an increase in CE and a decrease in Ci. Under variable daily meteorological conditions specific leaf nitrogen content (NL), specific leaf phosphorus content (PL), specific leaf area (δL), root mass fraction (Rf), Pmax, and α remained constant for a given N and P supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. δL increased with increasing N supply or with increasing NL. We tested also the hypothesis that P supply positively affects both N demand and photosynthetic NUE by influencing the upper limit of the asymptotic values for Pmax and CE, and the lower limit for Ci in response to increasing N. 相似文献
19.
Robert Klemps Siegfried M. Schoberth Hermann Sahm 《Applied microbiology and biotechnology》1987,27(3):229-234
Summary The formation of acetic acid by the thermophilic nonsporeforming homoacetogenic bacterium Acetogenium kivui was studied under various conditions. In pH-controlled batch fermentation at pH 6.4 this bacterium was able to produce up to 625 mM of acetic acid from glucose within 50–60 h. The value of
max obtained was about 0.17 h-1, the yield was about 2.55 mol of acetic acid per mol of glucose utilized. In continuous fermentation both substrate concentration and dilution rate (D) influenced the yield of acetate and the stationary concentration: a glucose concentration of 67 mM at D=0.09 h-1 resulted in 2.82 mol acetate/mol glucose and 190 mM acetate at a production rate of 17.1 mM/1 h. When the dilution rate was increased the production rate reached a maximal value of 43.2 mM/1 h at D=0.32 h-1. At a glucose concentration of 195 mM the dependence of yield upon dilution rate followed a similar pattern and an acetate concentration of 420 mM could be obtained. Enzymatic studies indicate that in A. kivui pyruvate ferredoxin-oxidoreductase and acetate kinase are inhibited at acetate concentrations higher than 800 mM. Based on these results a fed-batch fermentation was developed, which allowed to produce more than 700 mM acetic acid within 40–50 h.Dedicated to Prof. Dr. H. J. Rehm on the occasion of his 60th birthday 相似文献
20.
Adam W. Dalziel Gert Lipka Babur Z. Chowdhry Julian M. Sturtevant David E. Schafer 《Molecular and cellular biochemistry》1984,63(1):83-91
Summary The B, or binding, subunit of cholera enterotoxin forms a pentameric ring structure in the intact toxin, and also when the subunit is isolated from the A subunit. The thermal denaturation of the B subunit ring was examined by differential scanning calorimetry in the presence and absence of ganglioside GM1, its natural receptor. In the absence of ganglioside an irreversible endotherm was observed with maximal excess apparent heat capacity, Cmax, at 74.6° C. When the ganglioside was added in increasing amounts, multiple transitions were observed at higher temperatures, the most prominent having a Cmax at 90.8° C. At high ganglioside concentrations, the 74.6° C transition was not observed. In addition to the thermodynamic results a model is proposed for the interaction of GM1 and B subunit pentamer. This model is derived independently of the calorimetric results (but is consistent with such data) and is based upon considerations of the geometry of the GM1 micelle-B subunit pentamer.Abbreviations Mr
molecular weight in daltons
- GM1
H3Neu-AcGgOse4Cer* = Gall 3Ga1NAc1 4Gal-[3 - 2NeuAc]1 4Glc1 1Cer (asterisked form follows the recommendations of the IUPACIUB Commission on Biochemical Nomenclature, Ref. 3)
- R
molar ratio of GM1 to B monomer
- DSC
differential scanning calorimetry
- Cmax
excess apparent heat capacity
- Cmax
maximal value of Cex
- tm
temperature (° C) at Cex = Cmax
- t1/2
peak width in °C at Cex = Cmax/2
- Hcal
calorimetric enthalpy
- C
p
d
van't Hoff enthalpy
- C
p
d
change in specific heat accompanying denaturation 相似文献