共查询到20条相似文献,搜索用时 15 毫秒
1.
The present research is focused on cultivation of microalgae strain Chlorella vulgaris for bio-fixation of CO 2 coupled with biomass production. In this regard, a single semi-batch vertical tubular photobioreactor and four similar photobioreactors in series have been employed. The concentration of CO 2 in the feed stream was varied from 2 to 12 % (v/v) by adjusting CO 2 to air ratio. The amount of CO 2 capture and algae growth were monitored by measuring decrease of CO 2 concentration in the gas phase, microalgal cell density, and algal biomass production rate. The results show that 4 % CO 2 gives maximum amount of biomass (0.9 g L ?1) and productivity (0.118 g L ?1 day ?1) of C. vulgaris in a single reactor. In series reactors, average productivity per reactor found to be 0.078 g L ?1 day ?1. The maximum CO 2 uptake for single reactor also found with 4 % CO 2, and it is around 0.2 g L ?1 day ?1. In series reactors, average CO 2 uptake is 0.13 g L ?1 day ?1 per reactor. TOC analysis shows that the carbon content of the produced biomass is around 40.67 % of total weight. The thermochemical characteristics of the cultivated C. vulgaris samples were analyzed in the presence of air. All samples burn above 200 °C and the combustion rate become faster at around 600 °C. Almost 98 wt% of the produced biomass is combustible in this range. 相似文献
2.
Soybean ( Glycine max L. Merrill cv `Bragg') plants were grown in pots at six elevated atmospheric CO 2 concentrations and two watering regimes in open top field chambers to characterize leaf xylem potential, stomatal resistance and conductance, transpiration, and carbohydrate contents of the leaves in response to CO 2 enrichment and water stress conditions. Groups of plants at each CO 2 concentration were subjected to water stress by withholding irrigation for 4 days during the pod-filling stage. Under well watered conditions, the stomatal conductance of the plants decreased with increasing CO2 concentration. Therefore, although leaf area per plant was greater in the high CO2 treatments, the rate of water loss per plant decreased with CO2 enrichment. After 4 days without irrigation, plants in lower CO2 treatments showed greater leaf tissue damage, lower leaf water potential, and higher stomatal resistance than high CO2 plants. Stomatal closure occurred at lower leaf water potentials for the low CO2 grown plants than the high CO2 grown plants. Significantly greater starch concentrations were found in leaves of high CO2 plants, and the reductions in leaf starch and increases in soluble sugars due to water stress were greater for low CO2 plants. The results showed that even though greater growth was observed at high atmospheric CO2 concentrations, lower rates of water use delayed and, thereby, prevented the onset of severe water stress under conditions of low moisture availability. 相似文献
3.
Microalgae systems are currently being researched due to their ability to mitigate carbon dioxide emissions while obtaining a value-added product in the form of biomass. This paper elucidates the ability of microalgal–bacteria consortia for the conversion of organic matter contained in anaerobically digested swine slurry into biomass organic carbon via CO 2 uptake. In this context, the configuration of the reactor, different nitrogen availabilities and different microalgal communities developed in the evaluated reactors (open pond and enclosed tubular photobioreactor) were inferred as a possible reason for the different conversion efficiencies found. The biomass quality in terms of macromolecular cell component obtained under the two different reactors did not show any clear difference. The high efficiency in biomass nitrogen uptake resulted in biomass mainly composed of carbohydrates and proteins. Finally, the photosynthetic efficiency of the two reactor types showed high values which indicated the high efficiency of converting irradiance supplied to the systems into energy stored in biomass. 相似文献
4.
Similar to other photosynthetic microorganisms, the cyanobacterium Arthrospira platensis can be used to produce pigments, single cell proteins, fatty acids (which can be used for bioenergy), food and feed supplements, and biofixation of CO 2. Cultivation in a specifically designed tubular photobioreactor is suitable for photosynthetic biomass production, because the cultivation area can be reduced by distributing the microbial cells vertically, thus avoiding loss of ammonia and CO 2. The aim of this study was to investigate the influence of light intensity and dilution rate on the photosynthetic efficiency and CO 2 assimilation efficiency of A. platensis cultured in a tubular photobioreactor in a continuous process. Urea was used as a nitrogen source and CO 2 as carbon source and for pH control. Steady‐state conditions were achieved in most of the runs, indicating that continuous cultivation of this cyanobacterium in a tubular photobioreactor could be an interesting alternative for the large‐scale fixation of CO 2 to mitigate the greenhouse effect while producing high protein content biomass. 相似文献
5.
A general understanding of the links between atmospheric CO 2 concentration and the functioning of the terrestrial biosphere requires not only an understanding of plant trait responses to the ongoing transition to higher CO 2 but also the legacy effects of past low CO 2. An interesting question is whether the transition from current to higher CO 2 can be thought of as a continuation of the past trajectory of low to current CO 2 levels. Determining this trajectory requires quantifying the effect sizes of plant response to low CO 2. We performed a meta‐analysis of low CO 2 growth experiments on 34 studies with 54 species. We quantified how plant traits vary at reduced CO 2 levels and whether C 3 versus C 4 and woody versus herbaceous plant species respond differently. At low CO 2, plant functioning changed drastically: on average across all species, a 50% reduction in current atmospheric CO 2 reduced net photosynthesis by 38%; increased stomatal conductance by 60% and decreased intrinsic water use efficiency by 48%. Total plant dry biomass decreased by 47%, while specific leaf area increased by 17%. Plant types responded similarly: the only significant differences being no increase in SLA for C 4 species and a 16% smaller decrease in biomass for woody C 3 species at glacial CO 2. Quantitative comparison of low CO 2 effect sizes to those from high CO 2 studies showed that the magnitude of response of stomatal conductance, water use efficiency and SLA to increased CO 2 can be thought of as continued shifts along the same line. However, net photosynthesis and dry weight responses to low CO 2 were greater in magnitude than to high CO 2. Understanding the causes for this discrepancy can lead to a general understanding of the links between atmospheric CO 2 and plant responses with relevance for both the past and the future. 相似文献
6.
The present study was aimed to develop a membrane sparger (MS) integrated into a tubular photobioreactor to promote the increase of the carbon dioxide (CO 2) fixation by Spirulina sp. LEB 18 cultures. The use of MS for the CO 2 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), CO 2 fixation rate (231.6 mg L −1 d −1), and CO 2 use efficiency (80.5% w w −1) by Spirulina were verified with MS, compared to the culture with conventional sparger for CO 2 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
7.
Plant responses to increasing atmospheric CO 2 concentrations have received considerable interest. However, major uncertainties in relation to interactive effects of CO 2 with above- and below-ground conditions remain. This microcosm study investigated the impacts of CO 2 concentration on plant growth, dry matter partitioning and rhizodeposition as affected by: (i) photon flux density (PFD), and (ii) growth matrix. Plants were grown in a sandy loam soil for 28 d under two photon flux densities: 350 (low PFD) and 1000 μmol m –2 s –1 (high PFD) and two CO 2 concentrations: 450 (low CO 2) and 720 μmol mol –1 (high CO 2). Partitioning of recent assimilate amongst plant and rhizosphere C-pools was determined by use of 14CO 2 pulse-labelling. In treatments with high PFD and/or high CO 2, significant ( P < 0.05) increases in dry matter production were found in comparison with the low PFD/low CO 2 treatment. In addition, significant ( P < 0.05) reductions in shoot %N and SLA were found in treatments imposing high PFD and/or high CO 2. Root weight ratio (RWR) was unaffected by CO 2 concentration, however, partitioning of 14C to below ground pools was significantly ( P < 0.05) increased. In a separate study, L. perenne was grown for 28 d in microcosms percolated with nutrient solution, in either a sterile sand matrix or nonsterile soil, under high or low CO 2. Dry matter production was significantly ( P < 0.01) increased for both sand and soil grown seedlings. Dry matter partitioning was affected by matrix type. 14C-allocation below ground was increased for sand grown plants. Rhizodeposition was affected by CO 2 concentration for growth in each matrix, but was increased for plants grown in the soil matrix, and decreased for those in sand. The results illustrate that plant responses to CO 2 are potentially affected by (i) PFD, and (ii) by feedbacks from the growth matrix. Such feedbacks are discussed in relation to soil nutrient status and interactions with the rhizosphere microbial biomass. 相似文献
8.
We examined how the freely floating macrophyte, Stratiotes aloides L., sampled from a CO 2-supersaturated pond, changes leaf morphology, photosynthesis and inorganic carbon acquisition during its different submerged and emerged life stages in order to evaluate whether S. aloides requires consistently supersaturated CO 2 conditions to grow and complete its life cycle. Submerged rosettes formed from over-wintering turions had typical traits of submerged plants with high specific leaf area and low chlorophyll a concentrations. Emergent leaf parts of mature, floating specimens had typical terrestrial traits with stomata, low specific leaf area and high chlorophyll a content, while offsets formed vegetatively and basal, submerged parts of mature plants showed traits in between. All submerged leaf types exhibited some ability to use HCO 3− but only rosettes formed from turions had efficient HCO 3− use. Rosettes also had the highest CO 2 affinity and maximum CO 2-saturated photosynthesis in water. Half-saturation constants for CO 2 (21–74 μM CO 2) were for all submerged leaf parts 5–140 times lower than the concentrations of free CO 2 in the pond (350–2800 μM CO 2). Emergent leaves were less efficient in water but had significantly higher photosynthesis than submerged, mature leaf parts in air, and rates of photosynthesis of emergent leaves in air were three to five times higher than rates of CO 2-saturated photosynthesis of the three submerged leaf types in water. Underwater photosynthetic rates estimated at CO 2 concentrations corresponding to air equilibrium were not sufficiently high to support any noticeable growth except for rosettes, in which bicarbonate utilization combined with high CO 2 affinity resulted in photosynthetic rates corresponding to almost 34% of maximum rates at high free CO 2. We conclude that S. aloides requires consistently high CO 2-supersaturation to support high growth and to complete its life cycle, and we infer that this requirement explains why S. aloides mainly grows in ponds, ditches and reed zones that are characterized by strong CO 2-supersaturation. 相似文献
9.
The apparent affinity of photosynthesis for inorganic carbon in Anabaena variabilis strain M-3 increased during the course of adaptation from high to low CO 2 concentration (5% and 0.03% v/v CO 2 in air, respectively). This was attributed to an increased ability of the cells to accumulate inorganic carbon during the course of adaptation to low CO 2 conditions. The release of phycobiliproteins was used to evaluate the sensitivity of the cells to lysozyme treatment followed by osmotic shock. High CO 2-grown cells were more sensitive to this treatment than were low CO 2 ones. The efflux of inorganic carbon from cells preloaded with radioactive bicarbonate is faster in high than it is in low CO 2-adapted cells. It is postulated that the cell wall or membrane components undergo changes during the course of adaptation to low CO 2 conditions. This is supported by electron micrographs showing differences in the cell wall appearance between high and low CO 2-grown cells. The increasing ability to accumulate HCO 3− and the lessened sensitivity to lysozyme during adaptation to low CO 2 conditions depends on protein synthesis. The increase in affinity for inorganic carbon during the adaptation to low CO 2 conditions is severely inhibited by the presence of spectinomycin. Incubation in the light significantly lessens the time required for the adaptation to low CO 2 conditions. 相似文献
11.
We examined how the freely floating macrophyte, Stratiotes aloides L., sampled from a CO 2-supersaturated pond, changes leaf morphology, photosynthesis and inorganic carbon acquisition during its different submerged and emerged life stages in order to evaluate whether S. aloides requires consistently supersaturated CO 2 conditions to grow and complete its life cycle. Submerged rosettes formed from over-wintering turions had typical traits of submerged plants with high specific leaf area and low chlorophyll a concentrations. Emergent leaf parts of mature, floating specimens had typical terrestrial traits with stomata, low specific leaf area and high chlorophyll a content, while offsets formed vegetatively and basal, submerged parts of mature plants showed traits in between. All submerged leaf types exhibited some ability to use HCO 3− but only rosettes formed from turions had efficient HCO 3− use. Rosettes also had the highest CO 2 affinity and maximum CO 2-saturated photosynthesis in water. Half-saturation constants for CO 2 (21–74 μM CO 2) were for all submerged leaf parts 5–140 times lower than the concentrations of free CO 2 in the pond (350–2800 μM CO 2). Emergent leaves were less efficient in water but had significantly higher photosynthesis than submerged, mature leaf parts in air, and rates of photosynthesis of emergent leaves in air were three to five times higher than rates of CO 2-saturated photosynthesis of the three submerged leaf types in water. Underwater photosynthetic rates estimated at CO 2 concentrations corresponding to air equilibrium were not sufficiently high to support any noticeable growth except for rosettes, in which bicarbonate utilization combined with high CO 2 affinity resulted in photosynthetic rates corresponding to almost 34% of maximum rates at high free CO 2. We conclude that S. aloides requires consistently high CO 2-supersaturation to support high growth and to complete its life cycle, and we infer that this requirement explains why S. aloides mainly grows in ponds, ditches and reed zones that are characterized by strong CO 2-supersaturation. 相似文献
12.
An immediate, marked response to small amounts of rainfall occurs in Opuntia basilaris, despite previous drought conditions. The effect of rainfall is upon plant water potential, which is the single most important parameter influencing stomatal opening, CO 2 assimilation, and organic acid synthesis. Nocturnal stomatal opening is initiated following rainfall, and stomata remain open during the daytime. Decreasing stomatal and mesophyll resistances correlate with increasing rates of nocturnal assimilation of 14CO 2. Photosynthetic rates of 14CO 2 assimilation are low, despite high plant water potentials and low stomatal diffusion resistances. The decreased mesophyll resistances and increased rates of nocturnal 14CO 2 assimilation correlate with the increases of nocturnal efficiency of water use and CO 2 assimilation. The diurnal efficiency of water use and CO 2 assimilation is lower than the nocturnal gas exchange efficiency values. 相似文献
13.
Thalli of Ulva reticulata Forskaal, Ulva rigida C. Ag., and Ulva pulchra Jaasund were incubated at different concentrations of dissolved CO 2. Incubation at a high CO 2 concentration resulted in decreased oxygen evolution rate and lower affinity for inorganic carbon at high pH conditions, i.e. the ability to use HCO 3– as a carbon source was reduced. This effect was reversible, and plants regained this HCO 3– uptake capacity when transferred to air concentrations of CO 2. The phytosynthetic oxygen evolution rate of plants grown at high CO 2 concentration was reduced by high O 2 concentrations, whereas thalli and protoplasts from cultures grown at air concentration were not affected. This is interpreted as a deactivation of the carbon-concentrating mechanism during conditions of high CO 2 resulting in high photorespiration when plants are exposed to high O 2 concentrations. Protoplasts were not affected by high O 2 to the same extent and were not able to utilize HCO 3– from the medium. The algae were able to grow at very low CO 2 concentrations, but growth was suppressed when an inhibitor of external carbonic anhydrase was present. Assay of carbonic anhydrase activities showed that external and internal CA activities were lower in plants grown at a high CO 2 concentration compared to plants grown at a low concentration of CO 2. Possible mechanisms for HCO 3– utilization in these Ulva species are discussed. 相似文献
14.
Leymus chinensis is a dominant, rhizomatous perennial C 3 species in the grasslands of Songnen Plain of Northern China, and its productivity has decreased year by year. To determine how productivity of this species responds to different precipitation regimes, elevated CO 2 and their interaction in future, we measured photosynthetic parameters, along with the accumulation and partitioning of biomass. Plants were subjected to combinations of three precipitation gradients (normal precipitation, versus normal ± 40%) and two CO 2 levels (380±20 µmol mol -1,760±20 µmol mol -1) in controlled-environment chambers. The net photosynthetic rate, and above-ground and total biomass increased due to both elevated CO 2 and increasing precipitation, but not significantly so when precipitation increased from the normal to high level under CO 2 enrichment. Water use efficiency and the ratio of root: total biomass increased significantly when precipitation was low, but decreased when it was high under CO 2 enrichment. Moreover, high precipitation at the elevated level of CO 2 increased the ratio between stem biomass and total biomass. The effect of elevated CO 2 on photosynthesis and biomass accumulation was higher at the low level of precipitation than with normal or high precipitation. The results suggest that at ambient CO 2 levels, the net photosynthetic rate and biomass of L. chinensis increase with precipitation, but those measures are not further affected by additional precipitation when CO 2 is elevated. Furthermore, CO 2 may partly compensate for the negative effect of low precipitation on the growth and development of L. chinensis. 相似文献
15.
Native scrub‐oak communities in Florida were exposed for three seasons in open top chambers to present atmospheric [CO 2] (approx. 350 μmol mol ?1) and to high [CO 2] (increased by 350 μmol mol ?1). Stomatal and photosynthetic acclimation to high [CO 2] of the dominant species Quercus myrtifolia was examined by leaf gas exchange of excised shoots. Stomatal conductance ( gs) was approximately 40% lower in the high‐ compared to low‐[CO 2]‐grown plants when measured at their respective growth concentrations. Reciprocal measurements of gs in both high‐ and low‐[CO 2]‐grown plants showed that there was negative acclimation in the high‐[CO 2]‐grown plants (9–16% reduction in gs when measured at 700 μmol mol ?1), but these were small compared to those for net CO 2 assimilation rate ( A, 21–36%). Stomatal acclimation was more clearly evident in the curve of stomatal response to intercellular [CO 2] ( ci) which showed a reduction in stomatal sensitivity at low ci in the high‐[CO 2]‐grown plants. Stomatal density showed no change in response to growth in high growth [CO 2]. Long‐term stomatal and photosynthetic acclimation to growth in high [CO 2] did not markedly change the 2·5‐ to 3‐fold increase in gas‐exchange‐derived water use efficiency caused by high [CO 2]. 相似文献
16.
Abstract: Lichens, being poikilohydric, have varying thallus water contents (WC) and show a complex interaction between net photosynthesis (NP) and WC. NP can be depressed at low WC (desiccation effects) and, in some species, also at high WC. In the latter case the depression is normally ascribed to increased CO 2 diffusion resistances through water blockage. Recently, an earlier explanation, that the depression at high WC is due to recycling of CO 2 from increased dark respiration processes (DR), has been given renewed prominence. The two explanations were distinguished by the concurrent use of gas exchange and chlorophyll fluorescence techniques to investigate NP: WC relationships in the lichens Peltigera leucophlebia (green algal) and P. neckeri (cyanobacterial). Both species had a distinct optimal WC for NP with depressed values at low and high WC. The maximal quantum yield for both CO 2 fixation (initial slope of light response curves of NP) and photosystem II (fluorescence signals of dark-adapted thalli) was depressed only at low WC and remained high at optimal and greater WC. In contrast, the relative electron transport rate (ETR, derived from fluorescence signals of thalli in the light) tracked NP and was depressed at low and high WC. The depression of both NP and ETR at high WC (not that at low WC) could be prevented by using elevated external CO 2 concentrations. A single, linear relationship was found between all values of gross photosynthesis (NP + DR) and ETR regardless of external CO 2 concentration or WC. Our results show that, for these lichens, the depression in NP at high WC is a real fall in photosynthetic rate of the photobionts and is not due to recycling of CO 2. The removal of the depression in NP and ETR at high WC by using elevated external CO 2 levels allows us to conclude that an additional CO 2 diffusion resistance is present. 相似文献
17.
Previous studies have shown that in water the affinity of submerged macrophytes for CO 2 is higher for species restricted to CO 2 than for species with an additional ability to use bicarbonate. We measured slopes of CO 2 uptake versus CO 2 concentration in the gas phase in air, nitrogen and helium for pairs of species, having or lacking the ability to use bicarbonate,
but with similar leaf morphology. For species restricted to CO 2, the slope in nitrogen and helium was 1.5 times and 3.2 times greater than in air. The increased slope in nitrogen results
from a suppression of photorespiration. The further increase in helium reflects the increased rate of diffusion of CO 2 and shows that, even in gas, external diffusion through the boundary layer is a significant hindrance to CO 2 uptake. In contrast, in species able to use bicarbonate, the uptake slope was not affected by gas composition, suggesting
that photorespiration is absent or photorespired CO 2 is efficiently trapped and that internal resistance is high relative to external resistance. Elodea canadensis specimens grown under high concentrations of CO 2 de-regulated their ability to use bicarbonate, and slopes of CO 2 uptake in helium were significantly greater than in air or nitrogen. Overall, these results are consistent with the notion
that while a high affinity for CO 2 will maximise carbon uptake in species restricted to CO 2, for species able to use bicarbonate, a high internal resistance would reduce loss of CO 2 and help maintain high concentrations of CO 2 at the site of fixation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
Photorespiration by Chlamydomonas reinhardtii and Anacystis nidulans was measured as the oxygen inhibition of CO 2 uptake and the CO 2 compensation points. Net photosynthesis was oxygen dependent in Chlamydomonas grown in 5% CO 2, but CO 2 insensitive in cultures bubbled with air. Anacystis, even when cultured in 5% CO 2, exhibited an CO 2 insensitive net photosynthesis. The CO 2 compensation point of Chlamydomonas grown in cultures bubbled with air and Anacystis grown in 5% CO 2 enriched air, were reached shortly after the measurement was begun and the values were very low, less than 10 μl CO 2 1 ?1; while Chlamydomonas grown in 5% CO 2 enriched air for 4 days showed a high, but temporary CO 2 compensation point (60 μl CO 2 1 ?1). After a two hour adaptation in low CO 2, a stable, low CO 2 compensation point was reached. It seems that photorespiration can only be detected by the methods used in this study when the algae are cultured in high CO 2, but a mechanism exists which blocks photorespiration when the green algae are adapted to low CO 2 concentrations. When Chlamydomonas was treated with Diamox, an inhibitor of carbonic anhydrase, after cultivation in low CO 2 (air), the cells behaved as if they had been grown in high CO 2. They showed an oxygen sensitive net photosynthesis and a high CO 2 compensation point. This indicates that carbonic anhydrase plays an important role in the regulation of a measurable photorespiration in Chlamydomonas. The results are discussed in relation to previous observations of photorespiration measured by enzyme assay, metabolic products and gas exchange properties. 相似文献
19.
Growth of Spirulina sp. (MCRC-A0003), a cyanobacterium, was evaluated under different concentrations of carbon-dioxide (CO 2) (4–50 %) in a closed glass photobioreactor. Although significant CO 2 utilization by the cyanobacterial strain was observed up to 50 % concentration, complete utilization was observed only at 4, 10 and 20 % concentrations on 3rd, 6th and 8th day respectively. However, considerable reduction was witnessed in reactors containing 30–50 % CO 2 only between 6th and 9th day. A corresponding increase in the biomass and primary metabolites like chlorophyll- a, carbohydrate and protein were observed. Biomass productivity of Spirulina in reactors sparged with 4, 10 and 20 % CO 2 were 13.7, 43 and 44 % more than that in control reactor without CO 2. While CO 2 increased the levels of primary metabolites in the cyanobacterial cells, it was quite prominent in 10 % CO 2 concentration with the chlorophyll- a, carbohydrate and protein contents were 64, 183 and 626 mg g ?1 respectively. While 10 and 6.6 % increase were noticed in chlorophyll- a and protein, 17 % increase in carbohydrate levels was observed in Spirulina cells, which could be attributed to the conversion of CO 2 to carbohydrate by the cyanobacterium. 相似文献
20.
Rational design of electrocatalysts toward efficient CO 2 electroreduction has the potential to reduce carbon emission and produce value‐added chemicals. In this work, a strategy of constructing 2D confined‐space as molecular reactors for enhanced electrocatalytic CO 2 reduction selectivity is demonstrated. Highly ordered 2D nanosheet lamella assemblies are achieved via weak molecular interaction of atomically thin titania nanosheets, a variety of cationic surfactants, and SnO 2 nanoparticles. The interlayer spacings can be tuned from 0.9 to 3.0 nm by using different surfactant molecules. These 2D assemblies of confined‐space catalysts exhibit a strong size dependence of CO 2 electroreduction selectivity, with a peak Faradaic efficiency of 73% for formate production and excellent electrochemical stability at an optimal interspacing of ≈2.0 nm. This work suggests great potential for constructing new molecular‐size reactors, for highly selective electrocatalytic CO 2 reduction. 相似文献
|