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1.
《Journal of Fermentation Technology》1988,66(1):123-126
The effect of Eh on the methanogenesis of methanol by Methanosarcina barkeri strain Fusaro was studied in pH-controlled anaerobic batch cultures at 37°C, in which the Eh of the culture medium was controlled by the addition of Ti(III)-citrate at values ranging from −340 to −520 mV. The changes in Eh revealed that the specific growth rate, μ, specific methane production rate, QCH4 and growth yield, YX/S were optimum under an Eh between −430 and −520 mV, while they decreased at the higher Eh of −340 mV. The maximum values of QCH4 and μ under the optimum Eh condition were 210 ml CH4/g dry cell weight·h−1 and 0.11 h−1, respectively. 相似文献
2.
Ordered substrate binding and evidence for a thermally induced change in mechanism for E. coli aspartate transcarbamylase 总被引:3,自引:0,他引:3
Isotopic exchange kinetics at equilibrium for E. coli native aspartate transcarbamylase at pH 7.8, 30 °C, are consistent with an ordered BiBi substrate binding mechanism. Carbamyl phosphate binds before l-Asp, and carbamyl-aspartate is released before inorganic phosphate. The rate of [14C]Asp C-Asp exchange is much faster than [32P]carbamyl phosphate Pi exchange. Phosphate, and perhaps carbamyl phosphate, appears to bind at a separate modifier site and prevent dissociation of active-site bound Pi or carbamyl phosphate. Initial velocity studies in the range of 0–40 °C reveal a biphasic Arrhenius plot for native enzyme: Ea (>15 °C) = 6.3 kcal/ mole and Ea (<15 °C) = 22.1 kcal/mole. Catalytic subunits show a monophasic plot with Ea ? 20.2 kcal/mole. This, with other data, suggests that with native enzyme a conformational change accompanying aspartate association contributes significantly to rate limitation at t > 15 °C, but that catalytic steps become definitively slower below 15 °C. Model kinetics are derived to show that this change in mechanism at low temperature can force an ordered substrate binding system to produce exchange-rate patterns consistent with a random binding system with all exchange rates equal. The nonlinear Arrhenius plot also has important consequences for current theories of catalytic and regulatory mechanisms for this enzyme. 相似文献
3.
King-Thom Chung Edgar H. Nilson Marilyn J. Case Allen G. Marr Robert E. Hungate 《Applied microbiology》1973,25(5):778-780
The growth rate of a eukaryotic population dividing at a constant rate can be estimated from the equation, tm/g ln 2 = ln (1 + R), in which tm is the time required for mitosis, g is the generation time, and R is the fraction of cells undergoing mitosis. Values for tm and R can be determined by direct microscope examination of the population. The validity of the derived equation has been checked with an exponentially growing culture of a prokaryote, Escherichia coli, in which chloramphenicol was administered to inhibit protein synthesis. Cells having enough protein completed the division process whereas the rest of the population was inhibited. From the plot of the growth curve before and after administration of chloramphenicol, tm and R were estimated. The calculated and actual growth rates were almost identical. 相似文献
4.
5.
The ferrous iron oxidation kinetics of Thiobacillus ferrooxidans in batch cultures was examined, using on-line off-gas analyses to measure the oxygen and carbon dioxide consumption rates
continuously. A cell suspension from continuous cultures at steady state was used as the inoculum. It was observed that a
dynamic phase occurred in the initial phase of the experiment. In this phase the bacterial ferrous iron oxidation and growth
were uncoupled. After about 16 h the bacteria were adapted and achieved a pseudo-steady state, in which the specific growth
rate and oxygen consumption rate were coupled and their relationship was described by the Pirt equation. In pseudo-steady
state, the growth and oxidation kinetics were accurately described by the rate equation for competitive product inhibition.
Bacterial substrate consumption is regarded as the primary process, which is described by the equation for competitive product
inhibition. Subsequently the kinetic equation for the specific growth rate, μ, is derived by applying the Pirt equation for bacterial substrate consumption and growth. The maximum specific growth rate,
μ
max, measured in the batch culture agrees with the dilution rate at which washout occurs in continuous cultures. The maximum
oxygen consumption rate, q
O2,max, of the cell suspension in the batch culture was determined by respiration measurements in a biological oxygen monitor at
excess ferrous iron, and showed changes of up to 20% during the course of the experiment. The kinetic constants determined
in the batch culture slightly differ from those in continuous cultures, such that, at equal ferric to ferrous iron concentration
ratios, biomass-specific rates are up to 1.3 times higher in continuous cultures.
Received: 8 February 1999 / Accepted: 17 February 1999 相似文献
6.
In an isometric tetanus in frog's sartorius muscle tension approaches the plateau exponentially with rate constant α. α a depends on sarcomere length, s, and temperature, T, according to the Arrhenius equation See PDF for Equation for temperatures between 1 and 20°C and for sarcomere lengths 2.0–2.8 µm. The energy of activation, E, does not vary significantly with s; E = 13.9 ± 2.4 kcal/mole. A(s) decreases monotonically with s; A(2.1 µm) is about three times greater than A(2.8 µm). Late in relaxation active tension approaches zero exponentially with rate constant r. r decreases exponentially with increasing duration of tetanus, D, from r0 in a twitch to r∞ for large D. The rate constant for decrease of r with D increases with s and with T. r0 and r∞ obey the Arrhenius equation and decrease with increasing s. 相似文献
7.
MYERS J 《The Journal of general physiology》1946,29(6):429-440
1. Chlorella pyrenoidosa has been grown in a continuous-culture apparatus under various light intensities provided by incandescent lamps, other conditions of culture being maintained constant. Light intensity curves for cells immersed in the No. 11 Warburg buffer and in Knop''s solution + 4.4 per cent CO2 at a saturating light intensity were determined as characteristics of the photosynthetic mechanism. These characteristics were referred to the centrifuged cell volume as an index of quantity of cellular material. 2. Cells grown at intensities in the range of about 35 f.-c. develop a capacity for a high rate of photosynthesis (c.mm. O2/hour/c.mm. cells). At culture intensities above or below this range the cells produced have a lower capacity for photosynthesis. A similar effect is observed for rate of photosynthesis per unit dry weight or rate per unit cell nitrogen. 3. The rate of photosynthesis per cell or rate per unit chlorophyll shows no maximum at any light intensity of culture but increases continuously throughout the range of light intensities studied. 4. Maximum rate of growth is attained at a light intensity of about 100 f.-c. The hypothesis is advanced that at culture intensities above that needed to give maximum rate of growth (100 f.-c.) a mechanism is developed which opposes the photosynthetic process and removes the photosynthetic products. 5. The low capacity for photosynthesis shown by cells grown at culture intensities below 35 f.-c. finds no immediate explanation. 6. The shape of the light intensity curve is markedly affected by the light intensity at which the cells have been cultured. Cells grown at lower intensities give light intensity curves approaching the Blackman type with a short transitional region between light limitation and light saturation. 相似文献
8.
The effect of cultivation temperature on the ATP pool and adenylate energy charge (EC) in Escherichia coli has been studied in both batch and continuous cultures. In batch culture, μmax and the ATP pool increased with increasing growth temperatures between 27–42°C (from 0.26 to 0.62 h−1, and from 5.1 to 8.2 nmol/mg dry wt., respectively). In continuous culture at a constant dilution rate (D = 0.2 h−1), with increasing growth temperatures between 28–43°C, the ATP pool increased about 2-fold (from 4.2 to 8.1 nmol/mg dry wt) and the EC from 0.80 to 0.99. 相似文献
9.
Dagmar Vran 《Biotechnology and bioengineering》1976,18(3):297-309
Cells of Candida utilis grown in a single-stage chemostat at D = 0.05, 0.1, 0.25, and 0.35 hr?l were separated into a fraction of scar-bearing mother cells and a fraction of scar-free daughter cells. The scar-free cells were transferred into small batch cultures where the length of the maturation phase, changes in length and width of cells, specific growth rate, and specific rate of RNA and protein synthesis were examined for 5 hr. The daughter cells grown at D = 0.05 hr?1 were very small at the moment of separation from the mother cells (about one-third of the mother cell). Their maturation phase (in a batch culture), at the beginning of which they attain the specific growth rate approaching the μmax of the strain used, lasts for 3 hr. On the other hand, daughter cells grown at D = 0.35 hr?1 are almost the same size as the mother cells at the moment of separation. After transfer to a batch culture they begin to bud almost immediately. Similarly, in their other morphological and physiological parameters they differ strikingly from immature daughter cells which are formed at low specific growth rates. The importance of these differences from the point of view of mathematical modeling of growth processes is discussed. 相似文献
10.
H. S. Lokesha K. R. Nagabhushana S. H. Tatumi R. R. Rocca Fouran Singh 《Luminescence》2023,38(3):326-333
Zr1−xCexO2 with x = 0.005, 0.01, 0.02, and 0.03 samples were synthesized using a combustion technique. The X-ray diffraction results revealed that Ce-doped ZrO2 nanoparticles were in a monoclinic structure up to 1 mol% Ce concentration. The increase in the Ce concentration caused more distortion in the monoclinic structure of zirconia. The samples showed a mixed phase (monoclinic + tetragonal) beyond 1 mol% Ce content. The crystallite size (D) and strain (ε) were calculated from the Williamson–Hall equation. The D decreased from 25 ± 1 to 20 ± 1 nm and ε increased from 0.03 to 0.28% with an increase in Ce concentration. Photoluminescence (PL) spectra of Zr1−xCexO2 showed emission in the blue region under an excitation wavelength of 290 nm. Zr0.995Ce0.005O2 showed the highest PL intensity with an average lifetime of 0.93 μs, and the PL intensity decreased with the increase in the Ce concentration. Thermoluminescence (TL) glow curves of Zr1−xCexO2 were measured after gamma irradiation (500 Gy) with a heating rate of 5 K s−1. The TL curve of Zr0.995Ce0.005O2 showed two prominent peaks at 412 K (peak 1) and 600 K (peak 2). The first TL glow peak was shifted towards a higher temperature at 440 K above 1 mol% Ce concentration. Repetitive TL measurements on the same aliquot exhibited excellent repeatability. Kinetic parameters associated with the TL peaks were calculated using the curve fitting method. Peak 1 followed non-first-order kinetics. The value of the activation energy of the 440 K peak was found to be 0.95 ± 0.01 eV for Zr0.99Ce0.01O2. These findings showed that Zr1−xCexO2 might be used in lighting and radiation dosimeter applications. 相似文献
11.
This paper theoretically analyses the relationship between surplus energy, which is available for either somatic growth or reproduction, and body weight. From the data of metabolism and growth of the biwamasu, Oncorhynchus rhodurus, obtained by Miura et al., a Bernoulli's differential equation is induced to represent the relationship between body weight and the sum of surplus energy and active metabolic rate. Solving this equation gives the amount of surplus energy, f(Wx), as follows:f(Wx) = (αWx1−γ+β1−γ)1/(1−γ)−Wx, in which α, β and γ are constants and Wx is body weight at age x. The function is applied to ten fish populations and consequently it is found to be useful for a wider age range and a wider variety of fishes than the conventional function. 相似文献
12.
Kinetics of cell death and the production of dissolved organic carbon (DOC) were investigated in Anabaena flos-aquae (Lyngb.) Bréb grown on three different N sources (N2nitrate, and ammonium) in a phosphorus (P)-limited chemostat. The fraction of live cells in the total population increased as growth rate increased with decreasing P limitation. Cell death was less in nitrate and ammonium media than in N2. The specific death rate (γ), when calculated as the slope ofv?1x vs. D?1, where vxand D are live cell fraction (or cell viability) and dilution rate, respectively, was 0. 0082 day?1 in N2and 0.0042 day?1 in nitrate. The slope of the plot in ammonium culture was not significant; however, the value of the live cell fraction was within the range for the NO?3culture. The fraction of live vegetative cells in N2 culture was constant at all growth rates and the increase in the overall live cell fraction with growth rate was due entirely to an increase in live heterocysts. Live heterocysts comprised 3.5% of the total cells at a growth rate of 0.25 day?1 and increased to 6.3% at 0.75 day?1 with the ratio of live heterocysts to live vegetative cells linearly increasing with growth rate. The fraction of live vegetative cells was invariant in nitrate cultures us in N2cultures. The live heterocysts fraction also increased with growth rate in nitrate cultures, along with the live heterocysts : live vegetative cells ratio, but the level was lower than in N2cultures. DOC released from dead cells increased inversely with growth rate in N2from 36.4% of the total DOC at a growth rate of 0.75 day?1 to 54.15% at 0.25 day?1. The contribution of cell death to the total DOC production in nitrate and ammonium media was significantly less than that under N2DOC from dead cells consisted mainly of high-molecular-weight compounds, whereas DOC excreted from live cells was largely of low molecular weight. 相似文献
13.
Crude glycerol is a major byproduct of the biodiesel industry; previous research has proved the feasibility of producing docosahexaenoic acid (DHA, 22:6 n − 3) through fermentation of the algae Schizochytrium limacinum on crude glycerol. The objective of this work is to investigate the cell growth kinetics, substrate utilization efficiency, and DHA production of the algae through a continuous culture. Steady-state biomass yield, biomass productivity, growth yield on glycerol, specific glycerol consumption rate, and fatty acid composition were investigated within the range of dilution rate (D) from 0.2 to 0.6 day−1, and the range of feed crude glycerol concentration (S0) from 15 to 120 g/L. The maximum specific growth rate was determined as 0.692 day−1. The cells had a true growth yield of 0.283 g/g but with a relatively high maintenance coefficient (0.2216 day−1). The highest biomass productivity of 3.88 g/L-day was obtained at D = 0.3 day−1 and S0 = 60 g/L, while the highest DHA productivity (0.52 g/L-day) was obtained at D = 0.3 day−1 and S0 = 90 g/L due to the higher DHA content at S0 = 90 g/L. The biomass and DHA productivity of the continuous culture was comparable to those of batch culture, while lower than the fed-batch culture, mainly because of the lower DHA content obtained by the continuous culture. Overall, the results show that continuous culture is a powerful tool to investigate the cell growth kinetics and physiological behaviors of the algae growing on biodiesel-derived crude glycerol. 相似文献
14.
Summary Deficiency of inorganic phosphate caused the hyper production of invertase and the derepression of acid phosphatase in a continuous culture ofSaccharomyces carlsbergensis. The specific invertase activity was 40,000 enzyme units per g dry cell weight at a dilution rate lower than 0.05 h–1 with a synthetic glucose medium of which the molecular ratio of KH2PO4 to glucose was less than 0.006. This activity is eight fold higher than in a batch growth and 1.5 fold as much as the highest enzyme activity observed so far in a glucose-limited continuous culture.For the hyper production of invertase, it is necessary to culture the yeast continuously by keeping the Nyholm's conservative inorganic phosphate concentration at less than 0.2 m mole per g dry weight cell. The derepression of acid phosphatase brought about by phosphate deficiency, was similar in both batch and continuous cultures.Nomenclature D
dilution rate of continuous culture (h–1)
- Ei
invertase concentration in culture (enzyme unit l–1)
- Ep
acid phosphatase concentration in culture (enzyme unit l–1)
- P
inorganic phosphate concentration in culture (mM)
- S
glucose concentration in culture (mM)
- X
cell concentration in culture (g dry weight cell l–1)
Greek Letter
specific rate of growth (h–1)
Suffix f
feed
- 0
initial value 相似文献
15.
A Method for Characterizing the Relation between Nutrient Concentration and Flux into Roots of Intact Plants 总被引:31,自引:1,他引:30
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A method based on the rate of depletion of a nutrient from solution was developed to characterize nutrient flux of plant roots. Nutrient concentration of the solution was measured at a series of time intervals to describe the complete depletion curve. An integrated rate equation, based on a Michaelis-Menten model, was developed and fit to the data of the depletion curve using a least-square procedure. The equation contained values for Vmax, the maximum rate of influx; Km, the Michaelis constant; and E, efflux, which were used to describe the relation between solution concentration and net influx rate. Models other than Michaelis-Menten could also be used. The method uses only one plant or group of plants to obtain data over a range of nutrient concentrations, is adapted particularly to the low concentration range, and measures the concentration below which net influx ceases. With this method the plant is in steady state absorption prior to the experiment and continues at this steady state until near the end of the experiment. 相似文献
16.
《Process Biochemistry》1999,34(5):477-481
The effects of initial glucose concentration and light intensity on specific growth rate, phycocyanin concentration and cell dry weight concentration in mixotrophic batch cultivation of Spirulina platensis using both shake flask and fermenter were investigated. Based on experimental results in shake flask culture, a number of mathematical models were constructed, and the optimal initial glucose concentration and the optimal light intensity were calculated to be Sopt=2.4471 g liter−1 and Lopt=3.8632 klx. Finally, a time-dependent kinetic model for mixotrophic batch cultivation of Spirulina platensis in fermenter was also proposed. This was in good agreement with the experimental results and could be employed to predict the production of biomass and phycocyanin, and the consumption of glucose in fermenter culture. 相似文献
17.
《Process Biochemistry》2004,39(11):1341-1345
Batch fermentation of glucose to gluconic acid was conducted using Aspergillus niger under growth and non-growth conditions using pure oxygen and air as a source of oxygen for the fermentation in 2 and 5 l stirred tank reactors (batch reactor). Production of gluconic acid under growth conditions was conducted in a 5 l batch reactor. Production and growth rates were higher during the period of supplying pure oxygen than that during supplying air, and the substrate consumption rate was almost constant. For the production of gluconic acid under non-growth conditions, conducted in the 2 l batch reactor, the effect of the pure oxygen flow rate and the biomass concentration on the gluconic acid production was investigated and an empirical equation suggested to show the dependence of the production rate rp on the biomass concentration Cx and oxygen flow rate Q, at constant operating conditions (30 °C, 300 rpm and pH 5.5). Biomass concentration had a positive effect on the production rate rp, and the effect of Q on rp was positive at high biomass concentrations. 相似文献
18.
In normalyears, eggs and prolarvae of the plaice (Pleuronectes platessa L.) in the southern North Sea develop within the temperature range 6.0–8.5 °C, although the water may at times be some degrees colder or warmer than this. The effect of temperature, t °C, on the embryonic development time, D days, has been investigated within the tolerated range 2.8–10.5 °C. Various models to express the observed curvilinear relationship between t and D have been considered, that giving the closest fit to the data being (t−t0)(D−D0) = k or . A method is given for the calculation of constants k, D0, and t0. The relationship may also be expressed by the equation D = a(t−t0)b where a and b are constants, but t0 must in this case be found by iteration. At investigated temperatures in the range 4.1–10.5 °C the smallest eggs in a batch from a single source hatched first. Within the tolerated range, hatching prolarvae were substantially smaller at 10.5 °C than at the other temperatures. During the period of prolarval yolk utilization, growth is slower at the high temperatures, so that median temperatures of 6.5–8.0 °C are most efficient in terms of the relationship between growth in length and yolk utilization. Toward the end of the yolk-sac phase, the rate of yolk utilization declines unless a suitable external food source (e.g., Artemia nauplii) is provided. 相似文献
19.
Influence of Environmental Factors and Medium Composition on Vibrio gazogenes Growth and Prodigiosin Production 总被引:1,自引:0,他引:1
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Vibrio gazogenes ATCC 29988 growth and prodigiosin synthesis were studied in batch culture on complex and defined media and in chemostat cultures on defined medium. In batch culture on complex medium, a maximum growth rate of 0.75 h−1 and a maximum prodigiosin concentration of 80 ng of prodigiosin · mg of cell protein−1 were observed. In batch culture on defined medium, maximum growth rates were lower (maximum growth rate, 0.40 h−1), and maximum prodigiosin concentrations were higher (1,500 ng · mg of protein−1). In batch culture on either complex or defined medium, growth was characterized by a period of logarithmic growth followed by a period of linear growth; on either medium, prodigiosin biosynthesis was maximum during linear growth. In batch culture on defined medium, the initial concentration of glucose optimal for growth and pigment production was 3.0%; higher levels of glucose suppressed synthesis of the pigment. V. gazogenes had an absolute requirement for Na+; optimal growth occurred in the presence of 100 mM NaCl. Increases in the concentration of Na+ up to 600 mM resulted in further increases in the concentration of pigment in the broth. Prodigiosin was synthesized at a maximum level in the presence of inorganic phosphate concentrations suboptimal for growth. Concentrations of KH2PO4 above 0.4 mM caused decreased pigment synthesis, whereas maximum cell growth occurred at 1.0 mM. Optimal growth and pigment production occurred in the presence of 8 to 16 mg of ferric ion · liter−1, with higher concentrations proving inhibitory to both growth and pigment production. Both growth and pigment production were found to decrease with increased concentrations of p-aminobenzoic acid. The highest specific concentration of prodigiosin (3,480 ng · mg protein−1) was observed in chemostat cultures at a dilution rate of 0.057 h−1. The specific rate of prodigiosin production at this dilution rate was approximately 80% greater than that observed in batch culture on defined medium. At dilution rates greater than 0.057 h−1, the concentration of cells decreased with increasing dilution rate, resulting in a profile comparable to that expected for linear growth kinetics. No explanation could be found for the linear growth profiles obtained for both batch and chemostat cultures. 相似文献
20.
Fermentation of Cellulosic Substrates in Batch and Continuous Culture by Clostridium thermocellum 总被引:1,自引:1,他引:0
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Fermentation of dilute-acid-pretreated mixed hardwood and Avicel by Clostridium thermocellum was compared in batch and continuous cultures. Maximum specific growth rates per hour obtained on cellulosic substrates were 0.1 in batch culture and >0.13 in continuous culture. Cell yields (grams of cells per gram of substrate) in batch culture were 0.17 for pretreated wood and 0.15 for Avicel. Ethanol and acetate were the main products observed under all conditions. Ethanol:acetate ratios (in grams) were approximately 1.8:1 in batch culture and generally slightly less than 1:1 in continuous culture. Utilization of cellulosic substrates was essentially complete in batch culture. A prolonged lag phase was initially observed in batch culture on pretreated wood; the length of the lag phase could be shortened by addition of cell-free spent medium. In continuous culture with ~5 g of glucose equivalent per liter in the feed, substrate conversion relative to theoretical ranged from 0.86 at a dilution rate (D) of 0.05/h to 0.48 at a D of 0.167/h for Avicel and from 0.75 at a D of 0.05/h to 0.43 at a D of 0.11/h for pretreated wood. At feed concentrations of <4.5 g of glucose equivalent per liter, conversion of pretreated wood was 80 to 90% at D = 0.083/h. Lower conversion was obtained at higher feed substrate concentrations, consistent with a limiting factor other than cellulose. Free Avicelase activities of 12 to 84 mU/ml were observed, with activity increasing in this order: batch cellobiose, batch pretreated wood < batch Avicel, continuous pretreated wood < continuous Avicel. Free cellulase activity was higher at increasing extents of substrate utilization for both pretreated wood and Avicel under all conditions tested. The results indicate that fermentation parameters, with the exception of free cellulase activity, are essentially the same for pretreated mixed hardwood and Avicel under a variety of conditions. Hydrolysis yields obtained with C. thermocellum cellulase acting either in vitro or in vivo were comparable to those previously reported for Trichoderma reesei on the same substrates. 相似文献