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1.
Aims: The objective of this study is to develop kinetic models based on batch experiments describing the growth, CO2 consumption, and H2 production of Anabaena variabilis ATCC 29413-UTM as functions of irradiance and CO2 concentration.
Methods and Results: A parametric experimental study is performed for irradiances from 1120 to 16100 lux and for initial CO2 mole fractions from 0·03 to 0·20 in argon at pH 7·0 ± 0·4 with nitrate in the medium. Kinetic models are successfully developed based on the Monod model and on a novel scaling analysis employing the CO2 consumption half-time as the time scale.
Conclusions: Monod models predict the growth, CO2 consumption and O2 production within 30%. Moreover, the CO2 consumption half-time is an appropriate time scale for analysing all experimental data. In addition, the optimum initial CO2 mole fraction is 0·05 for maximum growth and CO2 consumption rates. Finally, the saturation irradiance is determined to be 5170 lux for CO2 consumption and growth whereas, the maximum H2 production rate occurs around 10 000 lux.
Significance and Impact of the Study: The study presents kinetic models predicting the growth, CO2 consumption and H2 production of A. variabilis . The experimental and scaling analysis methods can be generalized to other micro-organisms. 相似文献
Methods and Results: A parametric experimental study is performed for irradiances from 1120 to 16100 lux and for initial CO
Conclusions: Monod models predict the growth, CO
Significance and Impact of the Study: The study presents kinetic models predicting the growth, CO
2.
Clostridium pasteurianum fermented glucose to acetate, butyrate, CO2 and H2 . In batch cultures the fermentation pattern was only slightly affected by culture pH over the range 8·0 to 5·5. The acetate/butyrate ratio was always higher than or equal to one. Between 2·14 and 2·33 mol H2 was produced per mol glucose fermented. At unregulated pH, more butanol and less butyrate was formed. In a carbon-limited chemostat, the steady-state acetate/butyrate ratio was always lower than one. H2 production was approximately 1·70 mol per mol glucose consumed. Substantial amounts of extracellular protein were formed. With decreasing pH, acetate and formate production decreased, while H2 production was highest at pH 6.0. With increasing dilution rate ( D ), the product spectrum hardly changed, but more biomass was formed. Y glucose max and Y ATP max were 55·97 and 31·48 g dry weight per mol glucose or ATP respectively. With increasing glucose input the formation of fatty acids and H2 slightly decreased.
Continuous cultures fermented mannitol to acetate, butyrate, butanol, CO2 and H2 . With acetate as co-substrate, butanol production and molar growth yields, Y mannitol and Y ATP , markedly decreased, while the butyrate and H2 production increased. The latter reached a value of 2·21 mol H2 per mol mannitol consumed. 相似文献
Continuous cultures fermented mannitol to acetate, butyrate, butanol, CO
3.
SUMMARY: Sterilized raw sewage sludge enriched with sulphate and inoculated with pure strains of Desulphovibrio desulphuricans produced negligible sulphide. Unsterilized sludge supplemented with 7% (w/v) CaSO4 .2H2 O and inoculated with crude cultures of sulphate-reducing bacteria obtained from sewage yielded 1·0% S2- (wt S2- produced as H2 S/vol. of raw sludge) in 6 months at 30°. By repeated subculture more active cultures developed which produced 1% S2- in 7 days and 1·2–1·9% in 28 days. Digested sludge yielded only 0·1% S2- . In semicontinuous fermentations at 30°, raw sludge without added sulphate produced 20 times its own volume of gas containing 70% CH4 and 30% CO2 . When 5% CaSO4 .2H2 O and an active crude culture of sulphate reducers were added, gas production decreased steadily to zero. There were no differences in pH, temperature and redox potential in sludges producing methane or sulphide. The chief cause of inhibition appeared to be the action of sulphide: 0·02% soluble sulphide (S2- ) totally inhibited methane formation; 0·01% S2- initially decreased gas production by one-quarter but there was a slow recovery to normal, suggesting acclimatization of the methane-producing organisms to sulphide.
Linked fermentations, in which gas from a methane fermentation swept H2 S from a sulphide fermentation, gave a final gas mixture of about 60% CH4 , 30% CO2 and 5–10% H2 S. The yield of sulphide depended on the rate of sweeping. 相似文献
Linked fermentations, in which gas from a methane fermentation swept H
4.
Effects of gaseous environment and temperature on the storage behaviour of Listeria monocytogenes on chicken breast meat 总被引:1,自引:0,他引:1
Portions of skinless chicken breast meat (pH 5·8) were inoculated with a strain of Listeria monocytogenes and stored at 1, 6 or 15°C in (1) aerobic conditions; (2) 30% CO2 + air; (3) 30% CO2 + N2 ; and (4) 100% CO2 . When samples were held at 1°C the organism failed to grow under any of the test conditions, despite marked differences between treatments in spoilage rate and ultimate microflora. At 6°C counts of L. monocytogenes increased ca 10-fold in aerobic conditions before spoilage of the meat, but only when the inoculum culture was incubated at 1°C rather than 37°C. In CO2 atmospheres growth of L. monocytogenes was inhibited on meat held at 6°C, especially under 100% CO2 . By contrast, storage at 15°C led to spoilage of the meat within 2 d, in all gaseous environments, and listeria levels increased up to 100-fold. Differences in the behaviour of L. monocytogenes on poultry and red meats are discussed. 相似文献
5.
The growth behaviour of the thermophilic anaerobic bacterium Thermoanaerobium brockii for the production of its intracellular secondary alcohol dehydrogenase (sADH) has been studied in batch cultures as well as in continuous cultivation with complete cell recycling. In batch culture the maximum specific growth rate, μMAX , was 0·5 h−1 , resulting in a cell density of 1·2 g l−1 and an sADH activity of 1·3 units ml−1 . Higher glucose concentrations resulted in a decrease in ep cf7 max rs, enzyme productivity as well as biomass yield although an increase in total biomass was achieved. To improve cell density and productivity, continuous culture with complete cell recycling was used, resulting in an increase in cell density by 5 times and in productivity of the sADH by 3 times in comparison to those obtained in batch culture. 相似文献
6.
Aims: To investigate the effect of pH, water activity ( a w ) and temperature on the growth of Weissella cibaria DBPZ1006, a lactic acid bacterium isolated from sourdoughs.
Methods and Results: The kinetics of growth of W. cibaria DBPZ1006 was investigated during batch fermentations as a function of pH (4·0–8·0), aw (0·935–0·994) and temperature (10–45°C) in a rich medium. The growth curve parameters (lag time, growth rate and asymptote) were estimated using the dynamic model of Baranyi and Roberts (1994. A dynamic approach to predicting bacterial growth in food. Int J Food Microbiol 23, 277–294). The effect of pH, a w and temperature on maximum specific growth rate (μmax ) were estimated by fitting a cardinal model. μmax under optimal conditions (pH = 6·6, a w = 0·994, T = 36·3°C) was estimated to be 0·93 h−1 . Minimum and maximum estimated pH and temperature for growth were 3·6 and 8·15, and 9·0°C and 47·8°C, respectively, while minimum a w was 0·918 (equivalent to 12·2% w/v NaCl).
Conclusions: Weissella cibaria DBPZ1006 is a fast-growing heterofermentative strain, which could be used in a mixed starter culture for making bread.
Significance and Impact of the Study: This is the first study reporting the modelling of the growth of W. cibaria , a species that is increasingly being used as a starter in sourdough and vegetable fermentations. 相似文献
Methods and Results: The kinetics of growth of W. cibaria DBPZ1006 was investigated during batch fermentations as a function of pH (4·0–8·0), a
Conclusions: Weissella cibaria DBPZ1006 is a fast-growing heterofermentative strain, which could be used in a mixed starter culture for making bread.
Significance and Impact of the Study: This is the first study reporting the modelling of the growth of W. cibaria , a species that is increasingly being used as a starter in sourdough and vegetable fermentations. 相似文献
7.
Influence of culture conditions on exopolysaccharide production by Lactobacillus rhamnosus strain C83 总被引:6,自引:1,他引:5
The influence of culture conditions on growth and exopolysaccharide (EPS) production by Lactobacillus rhamnosus strain C83 was investigated using fermentor batch cultures. A temperature shift (from 37 to 25 °C) at the beginning of the exponential growth phase (0–5 h) enhanced EPS production. Furthermore, an optimal environmental pH of 6·2–7·2 improved the performance of strain C83 and partially anaerobic culture conditions (pO2 from 0 to 10%) triggered EPS over-production by the cells. The sugar composition of this polymer was independent of culture conditions, such as carbon source, medium composition, temperature, pH, pO2 and growth phases. In all cases, galactose and glucose were the principal components. 相似文献
8.
Effects of carbon dioxide in anther cultures 总被引:1,自引:0,他引:1
In anther cultures of Anemone canadensis L., Anemone dichotoma L., Anemone hupehensis Lemoine, Clematis viticella L. and Papaver setigerum DC. a positive relationship between incubation in 2% CO2 and the production of microspore-derived embryos was observed. In anther cultures of Nicotiana tabacum L., Anemone hupehensis and Clematis viticella a combination of cold treatment (7°C) and incubation in 2% CO2 increased embryo production. In Anemone canadensis cold treatment increased the number of proembryos, whereas incubation in 2% CO2 had no effect. In Anemone hupehensis 5% CO2 increased embryo production by more than 2%. In Anemone dichotoma and Papaver setigerum 2% CO2 was the more efficient level. CO2 had no significant effect on pH in the culture medium in anther cultures of Anemone canadensis. 相似文献
9.
SUMMARY: A filamentous mould was cultured by the continuous flow method in which medium is supplied at a constant rate and the culture volume is kept constant. Flow rates up to 0·1 culture volumes/hr were used. The mycelial dry weight concentration and the yield of mycelium/g of carbon source used were equal to or slightly greater than the maximum obtained in batch culture. With glucose concentrations up to 80 g/1. at a flow rate of 0·05 culture volumes/hr, about 45% of the substrate carbon was converted into mycelial carbon and the remainder oxidized to CO2 .
With unlimited amounts of all nutrients available growth of the mould followed the exponential law, as does bacterial growth, and therefore the mould had a constant doubling time.
The oxygen demand of the mould as function of growth rate was determined.
Conditions were found under which the rate of penicillin production/g of mycelium remained at its maximum value for 1000 hr. 相似文献
With unlimited amounts of all nutrients available growth of the mould followed the exponential law, as does bacterial growth, and therefore the mould had a constant doubling time.
The oxygen demand of the mould as function of growth rate was determined.
Conditions were found under which the rate of penicillin production/g of mycelium remained at its maximum value for 1000 hr. 相似文献
10.
Steelhead trout Oncorhynchus mykiss sperm held in seminal plasma or sperm-immobilizing buffer (pH 8·6) at 10° C consumed O2 at the rate of c . 2 nmol O2 min−1 10−9 sperm; the rate of O2 consumption was not different in sperm held for 4 or 24 h. Decreasing the extracellular pH from 8·5 to 7·5 either by diluting semen with buffer titrated with HCl or by increasing the partial pressure of CO2 in the incubation atmosphere resulted in c . a 40% decrease in the rate of sperm respiration. The data did not, however, support the hypothesis that the precipitous reduction in the capacity for sperm motility that occurs as external pH is reduced is a result of a decrease in cellular metabolism. The rate of O2 consumption of freshly collected semen from different males was not correlated to cellular ATP content or to the proportion of sperm that were motile upon activation; the initial ATP content and sperm motility were positively correlated. The rate of O2 consumption was not significantly increased following sperm activation or by the addition of an uncoupler of oxidative phosphorylation, carbonyl cyanide p -trifluoromethoxyphenylhydrazone, suggesting that these sperm have little, if any, capacity for increased oxidative metabolism. 相似文献
11.
Aquatic and aerial respiration of the amphibious fishes Lipophrys pholis and Periophthalmus barbarus were examined using a newly designed flow-through respirometer system. The system allowed long-term measurements of oxygen consumption and carbon dioxide release during periods of aquatic and aerial respiration. The M o 2 of L. pholis , measured at 15° C, was 2·1 μmol O2 g–1 h–1 during aquatic and 1·99 μmol O2 g–1 h–1 during aerial exposure. The corresponding values of the M co2 were 1.67 and 1.59 μmol O2 g–1 h–1 respectively, giving an aquatic respiratory exchange ratio (RER) of 0·80 and an aerial RER of 0·79. The M o2 of P. barbarus , measured at 28°C, was 4·05 μmol O2 g–1 h–1 during aquatic and 3·44 μmol O2 g–1 h–1 during aerial exposure. The corresponding values of the Mco2 were 3·29 μmol CO2 g–1 h–1 and 2·63 μmol CO2 g–1 h–1 respectively, giving an aquatic RER of 0·81 and an aerial RER of 0·77. While exposed to air for at least 10 h, both species showed no decrease in metabolic rate or carbon dioxide release. The RER of these fishes equalled their respiratory quotient. After re-immersion an increased oxygen consumption, due to the payment of an oxygen debt, could not be detected. 相似文献
12.
The optimum temperature for multiplication of legionella strains in culture media is around 37°C. The effect of high temperatures on the growth of strains isolated from various environments is poorly known. We studied the growth (cell multiplication, respiration) of clinical and environmental Legionella pneumophila strains in liquid media at intervals of 0.5°C in the temperature range from 41.6 to 51.6°C using a temperature gradient incubator. Cell multiplication and CO2 production decreased markedly with all the strains at temperatures above 44–45°C. CO2 continued to be produced up to 51.6C even if cell multiplication generally stopped at around 48.4–50.0C. Thus, legionella retained its metabolic activity beyond the maximum temperature for cell multiplication. The CO2 production per bacterial cell (metabolic quotient, qCO2 ) increased with increasing temperature up to 45°C, whereafter it decreased, the turning point being almost at the same at which the rate of cell multiplication decreased. The difference in qCO2 between the strains may reflect their different physiological capacities for tolerating high temperatures. 相似文献
13.
We investigated the thermal acclimation of photosynthesis and respiration in black spruce seedlings [ Picea mariana (Mill.) B.S.P.] grown at 22/14 °C [low temperature (LT)] or 30/22 °C [high temperature (HT)] day/night temperatures. Net CO2 assimilation rates ( A net ) were greater in LT than in HT seedlings below 30 °C, but were greater in HT seedlings above 30 °C. Dark and day respiration rates were similar between treatments at the respective growth temperatures. When respiration was factored out of the photosynthesis response to temperature, the resulting gross CO2 assimilation rates ( A gross ) was lower in HT than in LT seedlings below 30 °C, but was similar above 30 °C. The reduced A gross of HT seedlings was associated with lower needle nitrogen content, lower ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) maximum carboxylation rates ( V cmax ) and lower maximum electron transport rates ( J max ). Growth treatment did not affect V cmax : J max . Modelling of the CO2 response of photosynthesis indicated that LT seedlings at 40 °C might have been limited by heat lability of Rubisco activase, but that in HT seedlings, Rubisco capacity was limiting. In sum, thermal acclimation of A net was largely caused by reduced respiration and lower nitrogen investments in needles from HT seedlings. At 40 °C, photosynthesis in LT seedlings might be limited by Rubisco activase capacity, while in HT seedlings, acclimation removed this limitation. 相似文献
14.
Dry weight (DW) and nitrogen (N) accumulation and allocation were measured in isolated plants of Danthonia richardsonii (Wallaby Grass) for 37 d following seed imbibition. Plants were grown at ≈ 365 or 735 μ L L–1 CO2 with N supply of 0·05, 0·2 or 0·5 mg N plant–1 d–1 . Elevated CO2 increased DW accumulation by 28% (low-N) to 103% (high-N), following an initial stimulation of relative growth rate. Net assimilation rate and leaf nitrogen productivity were increased by elevated CO2 , while N concentration was reduced. N uptake per unit root surface area was unaffected by CO2 enrichment. The ratio of leaf area to root surface area was decreased by CO2 enrichment. Allometric analysis revealed a decrease in the shoot-N to root-N ratio at elevated CO2 , while the shoot-DW to root-DW ratio was unchanged. Allometric analysis showed leaf area was reduced, while root surface area was unchanged by elevated CO2 , indicating a down-regulation of total plant capacity for carbon gain rather than a stimulation of mineral nutrient acquisition capacity. Overall, growth in elevated CO2 resulted in changes in plant morphology and nitrogen use, other than those associated simply with changing plant size and non-structural carbohydrate content. 相似文献
15.
Ammonium ion affecting tylosin production by Streptomyces fradiae NRRL 2702 in continuous culture 总被引:1,自引:0,他引:1
S.H. Lee 《Letters in applied microbiology》1997,25(5):349-352
Nitrogen regulation in tylosin production by Streptomyces fradiae NRRL 2702 was studied in chemostat culture using a soluble synthetic medium. The maximum value of specific tylosin formation rate ( q TYL ) was 1·13 mg g−1 h−1 at the specific growth rate (μ) of 0·05 h−1 , and q TYL decreased with increasing levels of the specific growth rate after reaching a rate of 0·1 h−1 . The optimum conditions for tylosin formation were that the specific ammonium ion uptake rate ( q N ) and μ were 0·13 mmol g−1 h−1 and 0·05 h−1 , respectively. The specific formation rates of threonine dehydratase (TDT) and tylosin were repressed by high levels of specific ammonium ion uptake rate. This study showed the adaptation to chemostat cultures of the nitrogen regulation of tylosin fermentations. 相似文献
16.
The von Bertalanffy growth parameters for common wolf–fish Anarhichas lupus in the North Sea were: male: L ∞=111·2 cm, t 0 =–0·43 and K =0·12; and female: L ∞=115·1 cm, t 0 =–0·39 and K =0·11, making this the fastest growing stock reported. Resting metabolic rates (RMR±S.E.) and maximum metabolic rates (MMR±S.E.) for six adult common wolf–fish (mean weight, 1·39 kg) at 5° C were 12·18±1·6 mg O2 kg–1 h–1 and 70·65±7·63 mg O2 kg–1 h–1 respectively, and at 10° C were 25·43±1·31 mg O2 kg–1 h–1 and 113·84±16·26 mg O2 kg–1 h–1 . Absolute metabolic scope was 53% greater at 10° C than at 5° C. The diet was dominated by Decapoda (39% overall by relative occurrence), Bivalvia (20%) and Gastropoda (12%). Sea urchins, typically of low energy value, occupied only 7% of the diet. The fast growth probably resulted from summer temperatures approximating to the optimum for food processing and growth, but may have been influenced by diet, and reduced competition following high fishing intensity. 相似文献
17.
Abstract. Cyperus longus L. , which has a widespread but disjunct distribution throughout Europe and extends northwards into Britain, was found to be a C4 species based upon its Kranz leaf anatomy, low CO2 compensation point and the labelling of malate as an early product of 14 CO2 fixation. The photosynthetic characteristics of C. longus are similar to many other C4 species with a high maximum rate of photosynthesis (> 1.5 mg CO2 m −2 s −1 ) and a relatively high temperature optimum (30–35°C), but unlike many C4 species the rate of photosynthesis does not decline rapidly below the optimum temperature and a substantial rate (0.6 mgCO2 m−2 s−1 )occursat 15°C. Leaf extension is very slow at 15°C and shows a curvilinear response to temperatures between 15 and 25°C. Leaves extend at a rate of almost 4 cm d−1 at 25°C. 相似文献
18.
Symbiotic N2 fixation in a high Alpine grassland: effects of four growing seasons of elevated CO2 总被引:1,自引:0,他引:1
J. A. Arnone Iii 《Functional ecology》1999,13(3):383-387
1. Increasing carbon dioxide concentration (E: 680 μl CO2 litre–1 vs ambient, A: 355 μl CO2 litre–1 ) around late-successional Alpine sedge communities of the Swiss Central Alps (2450 m) for four growing seasons (1992–1995) had no detectable effect on symbiotic N2 fixation in Trifolium alpinum —the sole N2 -fixing plant species in these communities (74 ± 30 mg N m–2 year–1 , A and E plots pooled).
2. This result is based on data collected in the fourth growing season showing that elevated CO2 had no effect on Trifolium above-ground biomass (4·4 ± 1·7 g m–2 , A and E plots pooled, n = 24) or N content per unit land area (124 ± 51 mg N m–2 , A and E pooled), or on the percentage of N Trifolium derived from the atmosphere through symbiotic N2 fixation (%Ndfa: 61·0 ± 4·1 across A and E plots) estimated using the 15 N dilution method.
3. Thus, it appears that N inputs to this ecosystem via symbiotic N2 fixation will not be dramatically affected in the foreseeable future even as atmospheric CO2 continues to rise. 相似文献
2. This result is based on data collected in the fourth growing season showing that elevated CO
3. Thus, it appears that N inputs to this ecosystem via symbiotic N
19.
M. Petruccioli L. Brimer A. R. Cicalini F. Federici 《Journal of applied microbiology》1999,86(2):302-310
Mucor circinelloides LU M40 produced 12·2 mU ml−1 of linamarase activity when grown in a 3 l fermenter in the following optimized medium (g l−1 deionized water): pectin, 10·0; (NH4 )2 SO4 ,
1·0; KH2 PO4 , 2·0; Na2 HPO4 , 0·7; MgSO4 .7H2 O, 0·5; yeast extract, 1·0; Tween-80,
1·0, added after 48 h of fermentation. The purified linamarase was a dimeric protein with a molecular mass of 210 kDa; the enzyme showed optimum catalytic activity at pH 5·5 and 40 °C and had a wide range (3·0–7·0) of pH stability. The enzyme substrate specificity on plant cyanogenic glycosides was wide; the Km value for linamarin was 2·93 mmol l−1 . The addition, before processing, of the fungal crude enzyme to cassava roots facilitated and shortened detoxification; after 24 h of fermentation, all cyanogenic glycosides were hydrolysed. 相似文献
1·0; KH
1·0, added after 48 h of fermentation. The purified linamarase was a dimeric protein with a molecular mass of 210 kDa; the enzyme showed optimum catalytic activity at pH 5·5 and 40 °C and had a wide range (3·0–7·0) of pH stability. The enzyme substrate specificity on plant cyanogenic glycosides was wide; the K
20.
Changes in leaf nitrogen and carbohydrates underlie temperature and CO2 acclimation of dark respiration in five boreal tree species 总被引:8,自引:3,他引:5
We tested the hypothesis that acclimation of foliar dark respiration to CO2 concentration and temperature is associated with adjustments in leaf structure and chemistry. Populus tremuloides Michx. , Betula papyrifera Marsh. , Larix laricina (Du Roi) K. Koch , Pinus banksiana Lamb., and Picea mariana (Mill.) B.S.P. were grown from seed in combined CO2 (370 or 580 μ mol mol–1 ) and temperature treatments (18/12, 24/18, or 30/24 °C). Temperature and CO2 effects were predominately independent. Specific respiration rates partially acclimated to warmer thermal environments through downward adjustment in the intercept, but not Q 10 of the temperature–response functions. Temperature acclimation of respiration was larger for conifers than broad-leaved species and was associated with pronounced reductions in leaf nitrogen concentrations in conifers at higher growth temperatures. Short-term increases in CO2 concentration did not inhibit respiration. Growth in the elevated CO2 concentration reduced leaf nitrogen and increased non-structural carbohydrate concentrations. However, for a given nitrogen concentration, respiration was higher in leaves grown in the elevated CO2 concentration, as rates increased with increasing carbohydrates. Across species and treatments, respiration rates were a function of both leaf nitrogen and carbohydrate concentrations ( R 2 = 0·71, P < 0·0001). Long-term acclimation of foliar dark respiration to temperature and CO2 concentration is largely associated with changes in nitrogen and carbohydrate concentrations. 相似文献