共查询到20条相似文献,搜索用时 46 毫秒
1.
Luiza Moraes Gabriel M. da Rosa Lucielen O. Santos Jorge A. V. Costa 《Biotechnology progress》2020,36(4):e2987
The present study was aimed to develop a membrane sparger (MS) integrated into a tubular photobioreactor to promote the increase of the carbon dioxide (CO2) fixation by Spirulina sp. LEB 18 cultures. The use of MS for the CO2 supply in Spirulina cultures resulted not only in the increase of DIC concentrations but also in the highest accumulated DIC concentration in the liquid medium (127.4 mg L−1 d−1). The highest values of biomass concentration (1.98 g L−1), biomass productivity (131.8 mg L−1 d−1), carbon in biomass (47.9% w w−1), CO2 fixation rate (231.6 mg L−1 d−1), and CO2 use efficiency (80.5% w w−1) by Spirulina were verified with MS, compared to the culture with conventional sparger for CO2 supply. Spirulina biomass in both culture conditions had high protein contents varying from 64.9 to 69% (w w−1). MS can be considered an innovative system for the supply of carbon for the microalgae cultivation and biomass production. Moreover, the use of membrane system might contribute to increased process efficiency with a reduced cost of biomass production. 相似文献
2.
Viola Pooth Kathrin van Gaalen Sandra Trenkamp Wolfgang Wiechert Marco Oldiges 《Biotechnology progress》2020,36(1):e2917
Nowadays, chemical production of 1,4-butanediol is supplemented by biotechnological processes using a genetically modified Escherichia coli strain, which is an industrial showcase of successful application of metabolic engineering. However, large scale bioprocess performance can be affected by presence of physical and chemical gradients in bioreactors which are a consequence of imperfect mixing and limited oxygen transfer. Hence, upscaling comes along with local and time dependent fluctuations of cultivation conditions. This study emphasizes on scale-up related effects of microbial 1,4-butanediol production by comprehensive bioprocess characterization in lab scale. Due to metabolic network constraints 1,4-butanediol formation takes place under oxygen limited microaerobic conditions, which can be hardly realized in large scale bioreactor. The purpose of this study was to assess the extent to which substrate and oxygen availability influence the productivity. It was found, that the substrate specific product yield and the production rate are higher under substrate excess than under substrate limitation. Furthermore, the level of oxygen supply within microaerobic conditions revealed strong effects on product and by-product formation. Under strong oxygen deprivation nearly 30% of the consumed carbon is converted into 1,4-butanediol, whereas an increase in oxygen supply results in 1,4-butanediol reduction of 77%. Strikingly, increasing oxygen availability leads to strong increase of main by-product acetate as well as doubled carbon dioxide formation. The study provides clear evidence that scale-up of microaerobic bioprocesses constitute a substantial challenge. Although oxygen is strictly required for product formation, the data give clear evidence that terms of anaerobic and especially aerobic conditions strongly interfere with 1,4-butanediol production. 相似文献
3.
Christina Schädel Andreas Richter Andreas Blöchl Günter Hoch 《Physiologia plantarum》2010,139(3):241-255
Hemicelluloses account for one‐quarter of the global dry plant biomass and therefore are the second most abundant biomass fraction after cellulose. Despite their quantitative significance, the responsiveness of hemicelluloses to atmospheric carbon oversupply is still largely unknown, although hemicelluloses could serve as carbon sinks with increasing CO2 concentrations. This study aimed at clarifying the role hemicelluloses play as carbon sinks, analogous to non‐structural carbohydrates (NSC), by experimentally manipulating the plants' carbon supply. Sixteen plant species from four different plant functional types (grasses, herbs, seedlings of broad‐leaved trees and conifers) were grown for 2 months in greenhouses at either extremely low (140 ppm), medium (280 ppm) or high (560 ppm) atmospheric CO2 concentrations, thus inducing situations of massive C‐limitation or ‐oversupply. Above and belowground biomass as well as NSC significantly increased in all species and tissues with increasing CO2 concentrations. Increasing CO2 concentrations had no significant effect on total hemicellulose concentrations in leaves and woody tissues in all species, except for two out of four grass species, where hemicellulose concentrations increased with atmospheric CO2 supply. Despite the overall stable total hemicellulose concentrations, the monosaccharide spectra of hemicelluloses showed a significant increase in glucose monomers in leaves of woody species as C‐supply increased. In summary, total hemicellulose concentrations in de novo built biomass seem to be largely unaffected by changed atmospheric CO2 concentrations, while significant increases of hemicellulose‐derived glucose with increasing CO2 concentrations in leaves of broad‐leaved and conifer tree seedlings showed differential responses among the different hemicellulose classes in response to varying CO2 concentrations. 相似文献
4.
The denitrifying marine bacterium, Pseudomonas nautica 617, can grow on lactate aerobically or anaerobically in presence of nitrate with generation times of 1.5 and 3 h respectively. The growth on heptadecane occurs only in presence of oxygen whatever its concentration with a genrration time of 8.5 h. The influence of oxygen, carbon sources (lactate or heptadecane) and nitrate was examined on O2, NO3
-, NO2
- consumption, on nitrate and nitrite reductases activities, on cell yields, and on the ratio of CO2 produced per unit of biomass. Pseudomonas nautica metabolizes hydrocarbons under denitrifying conditions in the presence of oxygen. Nitrate and nitrite are used during growth on lactate and heptadecane up to oxygen concentrations corresponding to 50 and 30% of air-saturation, respectively. When growth on n-alkane was not oxygen-limited (above 50% of air-saturation) the catabolism decreases in favour of carbon incorporation into the cell. Nitrate and nitrite reductases were strongly inhibited after 20% of airsaturation in the presence of lactate as growth substrate. With n-alkane, only the nitrate reductase activity was greatly reduced. 相似文献
5.
CO2 fixation by a hydrogen-oxidizing bacterium, Cupriavidus necator, was evaluated in a packed bed bioreactor under a constant flow rate of gas mixtures (H2, O2, CO2). The overall energy efficiency depends on the efficiencies of CO2 fixation into carbohydrate and the reduced carbon into biomass and bioproducts, respectively. The efficiencies varied with the limiting gas substrate. Under O2 limitation, the efficiency (20–30%) of CO2 fixation increased with time and was higher than the overall efficiency (12–18%). Under H2 limitation, the efficiency of CO2 fixation declined with time while the biomass yield was quite similar to that under O2 limitation. A cellular metabolic model was suggested for the lithoautotrophic growth of C. necator, including CO2 fixation into carbohydrate followed by the main metabolic pathway of reduced carbon. Under CO2 limitation, most H2 energy was wasted, resulting in a very low biomass yield. Under a dual limitation of O2 and nitrogen, biosynthesis of poly(3-hydroxybutyrate) was triggered, and the energy efficiency or yield of biopolyester was lower than those of microbial cell mass. Compared with a green microalga Neochloris oleoabundans that produces lipid under nutrient limitation, C. necator exhibited a much higher (3–6 times) energy efficiency in producing biomass and bioproducts from CO2. 相似文献
6.
Our previous work indicated that salinity caused a shift in the predominant site of nitrate reduction and assimilation from the shoot to the root in tomato plants. In the present work we tested whether an enhanced supply of dissolved inorganic carbon (DIC, CO2+ HCO3) to the root solution could increase anaplerotic provision of carbon compounds for the increased nitrogen assimilation in the root of salinity-stressed Lycopersicon esculentum (L.) Mill. cv. F144. The seedlings were grown in hydroponic culture with 0 or 100mM NaCl and aeration of the root solution with either ambient or CO2-enriched air (5000 μmol mol?1). The salinity-treated plants accumulated more dry weight and higher total N when the roots were supplied with CO2-enriched aeration than when aerated with ambient air. Plants grown with salinity and enriched DIC also had higher rates of NO?3 uptake and translocated more NO?3 and reduced N in the xylem sap than did equivalent plants grown with ambient DIC. Incorporation of DIC was measured by supplying a 1 -h pulse of H14CO?3 to the roots followed by extraction with 80% ethanol. Enriched DIC increased root incorporation of DIC 10-fold in both salinized and non-salinized plants. In salinity-stressed plants, the products of dissolved inorganic 14C were preferentially diverted into amino acid synthesis to a greater extent than in non-salinized plants in which label was accumulated in organic acids. It was concluded that enriched DIC can increase the supply of N and anaplerotic carbon for amino acid synthesis in roots of salinized plants. Thus enriched DIC could relieve the limitation of carbon supply for ammonium assimilation and thus ameliorate the influence of salinity on NO?3 uptake and assimilation as well as on plant growth. 相似文献
7.
Juliane Kellner Tobias Houska Remy Manderscheid Hans‐Joachim Weigel Lutz Breuer Philipp Kraft 《Global Change Biology》2019,25(9):2947-2957
The rising concentration of atmospheric carbon dioxide (CO2) is known to increase the total aboveground biomass of several C3 crops, whereas C4 crops are reported to be hardly affected when water supply is sufficient. However, a free‐air carbon enrichment (FACE) experiment in Braunschweig, Germany, in 2007 and 2008 resulted in a 25% increased biomass of the C4 crop maize under restricted water conditions and elevated CO2 (550 ppm). To project future yields of maize under climate change, an accurate representation of the effects of eCO2 and drought on biomass and soil water conditions is essential. Current crop growth models reveal limitations in simulations of maize biomass under eCO2 and limited water supply. We use the coupled process‐based hydrological‐plant growth model Catchment Modeling Framework‐Plant growth Modeling Framework to overcome this limitation. We apply the coupled model to the maize‐based FACE experiment in Braunschweig that provides robust data for the investigation of combined CO2 and drought effects. We approve hypothesis I that CO2 enrichment has a small direct‐fertilizing effect with regard to the total aboveground biomass of maize and hypothesis II that CO2 enrichment decreases water stress and leads to higher yields of maize under restricted water conditions. Hypothesis III could partly be approved showing that CO2 enrichment decreases the transpiration of maize, but does not raise soil moisture, while increasing evaporation. We emphasize the importance of plant‐specific CO2 response factors derived by use of comprehensive FACE data. By now, only one FACE experiment on maize is accomplished applying different water levels. For the rigorous testing of plant growth models and their applicability in climate change studies, we call for datasets that go beyond single criteria (only yield response) and single effects (only elevated CO2). 相似文献
8.
W. -H. Schunck S. Mauersberger E. Kärgel J. Huth H. -G. Müller 《Archives of microbiology》1987,147(3):245-248
Transition of n-hexadecane utilizing cultures of Candida maltosa to oxygen-limited growth caused an up to 6-fold increase of the cellular cytochrome P-450 content. Enhanced cytochrome P-450 formation required protein de novo synthesis and was not due to a change of the apo/holo-enzyme ratio as demonstrated by cycloheximide inhibition and immunological quantitation. The effect of low oxygen concentration (pO2=3–5%) was simulated by selective inhibition of alkane hydroxylation with carbon monoxide (at a pO2 of 70–75%). Enhanced cytochrome P-450 formation occurred even when a constant growth rate was maintained through utilization of a second non-repressive growth substrate. However, the presence of n-alkanes was an essential precondition. It was concluded, that the cytochrome P-450 formation was mainly regulated by the intracellular inducer concentration which depends on the relative rates of alkane transport into the cell and the actual alkane hydroxylating activity of the enzyme system.Abbreviation cyt
cytochrome 相似文献
9.
JOHN E. ERICKSON J. PATRICK MEGONIGAL GARY PERESTA BERT G. DRAKE 《Global Change Biology》2007,13(1):202-215
Elevated atmospheric carbon dioxide concentrations ([CO2]) generally increase plant photosynthesis in C3 species, but not in C4 species, and reduce stomatal conductance in both C3 and C4 plants. In addition, tissue nitrogen concentration ([N]) often fails to keep pace with enhanced carbon gain under elevated CO2, particularly in C3 species. While these responses are well documented in many species, implications for plant growth and nutrient cycling in native ecosystems are not clear. Here we present data on 18 years of measurement of above and belowground biomass, tissue [N] and total standing crop of N for a Scirpus olneyi‐dominated (C3 sedge) community, a Spartina patens‐dominated (C4 grass) community and a C3–C4‐mixed species community exposed to ambient and elevated (ambient +340 ppm) atmospheric [CO2] in natural salinity and sea level conditions of a Chesapeake Bay wetland. Increased biomass production (shoots plus roots) under elevated [CO2] in the S. olneyi‐dominated community was sustained throughout the study, averaging approximately 35%, while no significant effect of elevated [CO2] was found for total biomass in the C4‐dominated community. We found a significant decline in C4 biomass (correlated with rising sea level) and a concomitant increase in C3 biomass in the mixed community. This shift from C4 to C3 was accelerated by the elevated [CO2] treatment. The elevated [CO2] stimulation of total biomass accumulation was greatest during rainy, low salinity years: the average increase above the ambient treatment during the three wettest years (1994, 1996, 2003) was 2.9 t ha−1 but in the three driest years (1995, 1999, 2002), it was 1.2 t ha−1. Elevated [CO2] depressed tissue [N] in both species, but especially in the S. olneyi where the relative depression was positively correlated with salinity and negatively related with the relative enhancement of total biomass production. Thus, the greatest amount of carbon was added to the S. olneyi‐dominated community during years when shoot [N] was reduced the most, suggesting that the availability of N was not the most or even the main limitation to elevated [CO2] stimulation of carbon accumulation in this ecosystem. 相似文献
10.
Kirsten Kottmeier Carsten Müller Robert Huber Jochen Büchs 《Applied microbiology and biotechnology》2010,86(1):93-101
By the use of directed limitations of secondary substrates, the metabolic flux should be deflected from biomass production
to product formation. In order to study the impact of directed limitations caused by various secondary substrates on the growth
and product formation of the methylotrophic yeast Hansenula polymorpha, the cultivation systems respiration activity monitoring system (RAMOS) and BioLector were used in parallel. While the RAMOS
device allows the online monitoring of the oxygen transfer rate in shake flasks, the BioLector enables in microtiter plates
the monitoring of scattered light and the fluorescence intensity of the green fluorescent protein (GFP). Secondary substrate
limitations of phosphate, potassium, and magnesium were analyzed in batch fermentations. The sole carbon source was either
10 g/L glucose or 10 g/L glycerol. The expression of the GFP gene is controlled by the FMD promoter (formate dehydrogenase). In batch cultures with glucose as carbon source, a directed limitation of phosphate increased
the GFP production 1.87-fold, compared to phosphate unlimited conditions. Under potassium-limited conditions with glycerol
as sole carbon source, the GFP production was 1.41-fold higher compared to unlimited conditions. A limitation of the substrate
magnesium resulted in a 1.22-fold increase GFP formation in the case of glycerol as carbon source. 相似文献
11.
García-Cantizano J Casamayor EO Gasol JM Guerrero R Pedrós-Alió C 《Microbial ecology》2005,50(2):230-241
Partitioning of CO2 incorporation into oxygenic phototrophic, anoxygenic phototrophic, and chemolithoautotrophic guilds was determined in a freshwater
lake (Lake Cisó, Banyoles, Spain). CO2 incorporation into the different types of microorganisms was studied at different depths, during diel cycles, and throughout
the year. During winter holomixis, the whole lake became anoxic and both the anoxygenic and chemolithoautotrophic guilds were
more active at the surface of the lake, whereas the activity of the oxygenic guild was negligible. During stratification,
the latter guild was more active in the upper metalimnion, whereas the anoxygenic guild was more active in the lower metalimnion.
Specific growth rates and doubling times were estimated for the most conspicuous phototrophic microorganisms. Doubling times
for Cryptomonas phaseolus ranged between 0.5 and 192 days, whereas purple sulfur bacteria (Chromatiaceae-like) ranged between 1.5 and 238 days. These growth rates were similar to those calculated with a different approach in previous
papers and indicate slow-growing populations with very large biomass. Overall, the annual total CO2 incorporation in Lake Cisó was 220 g C m−2. Most of the CO2 incorporation, however, was due to the chemolithoautotrophic guild (61% during holomixis and 56% during stratification),
followed by the anoxygenic phototrophic guild (35 and 19%, respectively) and the oxygenic phototrophs (4 and 25%, respectively),
making dark carbon fixation the key process in the autotrophic metabolism of the lake. 相似文献
12.
To model the physiological potential of marine heterotrophic bacteria, their role in the food web, and in the biogeochemical
carbon cycle, we need to know their growth efficiency response within a matrix of different temperatures and degrees of organic
substrate limitation. In this work, we present one part of this matrix, the carbon growth efficiencies of marine bacteria
under different temperatures and nonlimiting organic and inorganic substrate supply. We ran aerobic turbidostats with glucose
enriched seawater, inoculated with natural populations of heterotrophic marine bacteria at 10, 14, 18, 22, and 26°C. The average
cell-specific growth rates increased with temperature from 1.17 to 2.6 h−1. At steady-state total CO2 production, biomass production [particulate organic carbon (POC) and nitrogen (PON)], and viruslike particle abundance was
measured. CO2 production and specific growth rate increased with increasing temperature. Bacterial carbon growth efficiency (BCGE), the
particulate carbon produced per dissolved carbon utilized, varied between 0.12 and 0.70. Maximum BCGE values and decreased
specific respiration rates occurred at higher temperatures (22 and 26°C) and growth rates. This trend was largely attributable
to an increase in POC per cell abundance; when the BCGE was recalculated, parameterizing the biomass as the product of cell
concentration and a constant cellular carbon content, the opposite trend was observed. 相似文献
13.
Bester E Kroukamp O Hausner M Edwards EA Wolfaardt GM 《Journal of applied microbiology》2011,110(2):387-398
Aims: To investigate carbon transformation by biofilms and changes in biofilm architecture, metabolic activity and planktonic cell yield in response to fluctuating carbon availability. Methods and Results: Pseudomonas sp. biofilms were cultured under alternating carbon‐replete and carbon‐limited conditions. A shift to medium without added carbon led to a 90% decrease in biofilm respiration rate and a 40% reduction in planktonic cell yield within 1 h. Attached cell division and progeny release were shown to contribute to planktonic cell numbers during carbon limitation. Development of a significantly enlarged biofilm surface area during carbon limitation facilitated a rapid increase in whole‐biofilm metabolic activity, cell yield and biomass upon the re‐introduction of carbon after 8 days of limitation. The cumulative number of planktonic cells (>1010 CFU) released from the biofilm during the cultivation period contained only 1·0% of the total carbon available to the biofilm, with 6·5% of the carbon retained in the biofilm and 54% mineralized to CO2. Conclusions: Biofilm‐derived planktonic cell yield is a proliferation mechanism. The rapid response of biofilms to environmental perturbations facilitates the optimal utilization of resources to promote both proliferation and survival. Biofilms function as efficient catalysts for environmental carbon transformation and mineralization. Significance and Impact of the study: A greater understanding of the relationship between biofilm form and function can inform strategies intended to control and/or promote biofilm formation. 相似文献
14.
《Journal of Fermentation and Bioengineering》1991,71(5):350-355
The efficiency of the fed-batch cultivation of recombinant Escherichia coli AT2471 for phenylalanine production is highly dependent on the distribution of the carbon flow between the main process products — biomass, phenylalanine, acetic acid and carbon dioxide. In order to enhance the process performance, the effects of several factors, namely glucose feeding, tyrosine feeding and oxygen supply, were investigated experimentally. As a result, a set of control strategies was developed, designed to tolerate phenylalanine synthesis at the expense of the remaining products. The DO was controlled to prevent acetic acid excretion due to oxygen limitation. The total amount of tyrosine fed was used to provide an optimal balance between biomass synthesis and that of phenylalanine. Special algorithms for control of the glucose feed rate were applied to eliminate the threat of acetic acid excretion due to overfeeding, and at the same time, to reduce excessive CO2 evolution caused by unnecessarily severe glucose limitation. The joint application of these strategies resulted in greatly improved efficiency in the phenylalanine production process: the final phenylalanine concentration reached 46 g/l, the yield was above 17%, and the productivity-0.85 g/l·h. In combination, these data exceed the results reported by others, and are much higher than those obtained by use before the implementation of the proposed complex of techniques. 相似文献
15.
The use of fossil fuel is predicted to cause an increase of the atmospheric CO2 concentration, which will affect the global pattern of temperature and precipitation. It is therefore essential to incorporate effects of temperature and water supply on the carbon requirement for root respiration of plants to predict effects of elevated [CO2] on the carbon budget of natural and managed systems.There is insufficient information to support the contentention that an increase in the concentration of CO2 in the atmosphere will enhance the CO2 concentration in the soil to an extent that is likely to affect root respiration. Moreover, there is no convincing evidence for a direct effect of elevated atmospheric [CO2] on the rate of root respiration per unit root mass or the fraction of carbon required for root respiration. However, there are likely to be indirect effects of elevated [CO2] on the carbon requirement of plants in natural systems.Firstly, it is very likely that the carbon requirement of root respiration relative to that fixed in photosynthesis will increase when elevated [CO2] induces a decrease in nutrient status of the plants. Although earlier papers have emphasized that elevated [CO2] favours investment of biomass in roots relative to that in leaves, these are in fact indirect effects. The increase in root weight ratio is due to the more rapid depletion of nutrients in the root environment as a consequence of enhanced growth. This will decrease the specific rate of root respiration, but increase the carbon requirement as a fraction of the carbon fixed in photosynthesis. It is likely that these effects will be minor in systems where the nutrient supply is very high, e.g. in many managed arable systems, and increase with decreasing soil fertility, i.e. in many natural systems.Secondly, a decrease in rainfall in some parts of the world may cause a shortage in water supply which favours the carbon partitioning to roots. Water stress is likely to reduce rates of root respiration per unit root mass, but enhance the fraction of total assimilates required for root respiration, due to greater allocation of biomass to roots.Increased temperatures are unlikely to affect the specific rate of root respiration in all species. Broadly generalized, the effect of temperature on biomass allocation is that the relative investment of biomass in roots is lowest at a certain optimum temperature and increases at both higher and lower temperatures. The root respiration of some species acclimates to growth temperature, so that the effect of global temperature rise is entirely accounted for by the effect of temperature on biomass allocation. The specific rate of root respiration of other species will increase with global warming. In response to global warming the carbon requirement of roots is likely to decrease in temperate regions, when temperatures are suboptimal for the roots' capacity to acquire water. Here global warming will induce a smaller biomass allocation to the roots. Conversely, the carbon requirements are more likely to increase in mediterranean environments, where temperatures are often supraoptimal and a rise in temperature will induce greater allocation of biomass to the roots. 相似文献
16.
J. Wolf 《Plant and Soil》1996,185(1):113-123
The effects of increased atmospheric CO2 on crop growth and dry matter allocation may change if nutrient supply becomes insufficient for maximal growth. Increased atmospheric CO2 may also cause changes in minimum nutrient concentration in plant tissue and hence in the nutrient use efficiency or yield-nutrient uptake ratios of crops. To study these effects for spring wheat, pot experiments have been carried out in two glass houses at ambient and doubled CO2 concentration. Wheat plants were grown at different supplies of N, P or K. Doubling of ambient CO2 resulted in a large increase in total biomass (+70%) and grain yield when the nutrient supply was optimum. With strong N and K limitation this CO2 effect was about halved and with strong P limitation it became almost nil. Doubling of ambient CO2 resulted in a 10% lower minimum N concentration in plant tissue and in no change in the minimum P concentration. 相似文献
17.
Carbon dioxide biofixation by Chlorella vulgaris at different CO2 concentrations and light intensities
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Barbara Clément‐Larosière Filipa Lopes Ana Gonçalves Behnam Taidi Marc Benedetti Michel Minier Dominique Pareau 《Engineering in Life Science》2014,14(5):509-519
In order to develop an effective CO2 mitigation process using microalgae for potential industrial application, the growth and physiological activity of Chlorella vulgaris in photobioreactor cultures were studied. C. vulgaris was grown at two CO2 concentrations (2 and 13% of CO2 v/v) and at three incident light intensities (50, 120 and 180 μmol m?2 s?1) for 9 days. The measured specific growth rate was similar under all conditions tested but an increase in light intensity and CO2 concentration affected the biomass and cell concentrations. Although carbon limitation was observed at 2% CO2, similar cellular composition was measured in both conditions. Light limitation induced a net change in the growth behavior of C. vulgaris. Nitrogen limitation seemed to decrease the nitrogen quota of the cells and rise the intracellular carbon:nitrogen ratio. Exopolysaccharide production per cell appeared to be affected by light intensity. In order to avoid underestimation of the CO2 biofixation rate of the microalgae, exopolysaccharide production was taken into account. The maximum CO2 removal rate (0.98 g CO2 L?1 d?1) and the highest biomass concentration (4.14 g DW L?1) were determined at 13% (v/v) CO2 and 180 μmol m?2 s?1. Our results show that C. vulgaris has a real potential for industrial CO2 remediation. 相似文献
18.
Yilu Bao Ming Liu Xia Wu Wei Cong Zhengxiang Ning 《Biotechnology and Bioprocess Engineering》2012,17(1):93-99
The objective of this study was to estimate the CO2 absorptivity provided by an in situ carbon supply system using a photosynthetic culture of the cyanobacterium Spirulina platensis in an open raceway pond. The effects of initial total carbon concentrations (ranging from 0 to 0.1 mol/L), suspension depths
(ranging from 5 to 20 cm) and pH values (ranging from 8.9 to 11.0) on the CO2 absorptivity were studied. The results indicated that CO2 absorptivity was positively correlated with pH value, negatively correlated with total carbon concentration, and only negligibly
affected by the suspension depth. The optimum total carbon concentration range and pH range were 0.03 ∼ 0.09 mol/L and 9.7
∼ 10.0, respectively. An average CO2 absorptivity of 86.16% and average CO2 utilization efficiency of 79.18% were achieved using this in situ carbon-supply system in large-scale cultivation of Spirulina platensis, with an initial total carbon concentration of 0.06 mol/L and pH value of 9.8. Our results demonstrated that this system
could obtain a favorable CO2 utilization efficiency in outdoor, large-scale cultivation of Spirulina platensis in open raceway ponds. 相似文献
19.
Two serotype 1 strains ofLegionella pneumophila, Phildelphia 2 and Bellingham, were tested for their ability to metabolize five common substrates by measuring14CO2 released and14C-carbon incorporated into macromolecules. No major differences were noted between the two strains or preparations grown in
the yolk sac of chick embryos or agar-broth diphasic medium, following 2 or 14 pasaages on agar. Glutamate was the most actively
metabolized substrate, followed by glutamine. Acetate, glucose, and succinate were utilized at much more moderate rates. Changes
in cell density and substrate concentration altered the channeling of glutamate and glucose into CO2 and macromolecules. Specific CO2 felease from glutamate was greatest at low cell density and high substrate concentration, while carbon incorporation was
increased at high substrate concentration. A reciprocal relationship was noted with glucose: the proportion of carbon incorporation
was enhanced at low substrate concentration, but CO2 release paralleled increases in substrate concentration. The pH optimum for glutamate carbon incorporation and CO2 release was 5.5 and 6.1, respectively, but 25% of both activities were retained at pH 3.1. CO2 release from glucose was maximal at pH 7.5 with negligible activity at pH 3.1. Pathways of glucose metabolism were explored
by employing glucose, glucose-1-phosphate, and glucose-6-phosphate labeled in various carbon positions. The glycolytic pathway
appeared to play a lesser role than the pentose phosphate and/or Entner-Doudoroff pathways. Glucose-1-phosphate was metabolized
at a much higher rate than glucose or glucose-6-phosphate. We conclude that glutamate is utilized primarily as an energy source
while glucose may serve as an important metabolite for the nutrition ofL. pneumophila. 相似文献
20.
Maria Hermann Attila Teleki Sandra Weitz Alexander Niess Andreas Freund Frank R. Bengelsdorf Ralf Takors 《Microbial biotechnology》2020,13(6):1831-1846
Acetogens such as Clostridium ljungdahlii can play a crucial role reducing the human CO2 footprint by converting industrial emissions containing CO2, CO and H2 into valuable products such as organic acids or alcohols. The quantitative understanding of cellular metabolism is a prerequisite to exploit the bacterial endowments and to fine-tune the cells by applying metabolic engineering tools. Studying the three gas mixtures CO2 + H2, CO and CO + CO2 + H2 (syngas) by continuously gassed batch cultivation experiments and applying flux balance analysis, we identified CO as the preferred carbon and electron source for growth and producing alcohols. However, the total yield of moles of carbon (mol-C) per electrons consumed was almost identical in all setups which underlines electron availability as the main factor influencing product formation. The Wood–Ljungdahl pathway (WLP) showed high flexibility by serving as the key NAD+ provider for CO2 + H2, whereas this function was strongly compensated by the transhydrogenase-like Nfn complex when CO was metabolized. Availability of reduced ferredoxin (Fdred) can be considered as a key determinant of metabolic control. Oxidation of CO via carbon monoxide dehydrogenase (CODH) is the main route of Fdred formation when CO is used as substrate, whereas Fdred is mainly regenerated via the methyl branch of WLP and the Nfn complex utilizing CO2 + H2. Consequently, doubled growth rates, highest ATP formation rates and highest amounts of reduced products (ethanol, 2,3-butanediol) were observed when CO was the sole carbon and electron source. 相似文献