共查询到20条相似文献,搜索用时 15 毫秒
1.
Life cycle assessment (LCA) of indigenous freshwater microalgae, Scenedesmus dimorphus, cultivation in open raceway pond and its conversion to biodiesel and biogas were carried out. The LCA inventory inputs for the biogas scenario was entirely based on primary data obtained from algal cultivation (in pilot scale raceway pond), harvesting, and biogas production; while only the downstream processing involved in biodiesel production namely drying, reaction and purification were based on secondary data. Overall, eight scenarios were modeled for the integrated process involving: algae-based CO2 capture and downstream processing scenarios for biodiesel and biogas along with impact assessment of nutrient addition and extent of recycling in a life cycle perspective. The LCA results indicated a huge energy deficit and net CO2 negative in terms of CO2 capture for both the biodiesel and biogas scenarios, majorly due to lower algal biomass productivity and higher energy requirements for culture mixing. The sensitivity analysis indicated that variability in the biomass productivity has predominant effect on the primary energy demand and global warming potential (GWP, kg CO2 eq.) followed by specific energy consumption for mixing algal culture. Furthermore, the LCA results indicated that biogas conversion route from microalgae was more energy efficient and sustainable than the biodiesel route. The overall findings of the study suggested that microalgae-mediated CO2 capture and conversion to biodiesel and biogas production can be energy efficient at higher biomass productivity (> 10 g m−2 day−1) and via employing energy-efficient systems for culture mixing (< 2 W m−3). 相似文献
2.
In the view of the facts that algal extracts have been used in agriculture asa source of plant growth stimulating agents and IAA has been shown to bepresent in the extracts, a study was planned to establish whether or notaxenic algae can produce IAA. Evidence is provided for extracellular IAAproduction during culture of two axenic green microalgae. IAAidentification was based on co-chromatography with the standard, analysisof UV and fluorescent spectra, and gas chromatography – selectedion-monitoring mass spectrometry. HPLC analyses showed that underthe experimental conditions the amounts of IAA released to the mediumby Scenedesmus armatus and Chlorella pyrenoidosa weregenerally low. IAA tended to occur in Scenedesmus armatus culturemedium at higher concentrations than in that of Chlorellapyrenoidosa. In fast-growing cultures of Scenedesmus armatus,constantly aerated with CO 2/air mixture, the concentration of IAAcalculated per cell was less than in the slow-growing cultures. 相似文献
3.
Ubiquinone (Coenzyme Q10, CoQ10), a yellow-to-orange-colored lipophilic substance having nutraceutical value, was extracted
from dried biomass of Pseudomonas diminuta using supercritical carbon dioxide (SC-CO 2). The effect of different operational parameters (temperature, pressure, and extraction time) and addition of co-solvent
on SC-CO 2 extraction of CoQ10 was studied in detail. The solubility parameter of CoQ10, CO 2, and CO 2 with ethanol and methanol as co-solvents was calculated and validated with experimental results. Theoretically, ethanol and
methanol had significant effect as co-solvent, and the difference between the two was only marginal. A maximum recovery of
22.33% was obtained using pure SC-CO 2 at 40 °C, 150 bar, and run time of 60 min. Ethanol as co-solvent at 3 mL/g of dried biomass at 40 °C and 150 bar increased
the recovery from 22.33 to 68.57%. Further optimization of the extraction conditions by Box–Behnken design effectively increased
the recovery to 96.2%. The optimized conditions were a temperature of 38 °C, pressure of 215 bar, and run time of 58 min. 相似文献
4.
The microalgae Scenedesmus abundans cultivated in five identical airlift photobioreactors (PBRs) in batch and fed-batch modes at the outdoor tropical condition. The microalgae strain S. abundans was found to tolerate high temperature (35–45 °C) and high light intensity (770–1690 µmol m− 2 s− 1). The highest biomass productivities were 152.5–162.5 mg L− 1 day− 1 for fed-batch strategy. The biomass productivity was drastically reduced due to photoinhibition effect at a culture temperature of > 45 °C. The lipid compositions showed fatty acids mainly in the form of saturated and monounsaturated fatty acids (> 80%) in all PBRs with Cetane number more than 51. The fed-batch strategies efficiently produced higher biomass and lipid productivities at harsh outdoor conditions. Furthermore, the microalgae also accumulated omega-3 fatty acid (C18:3) up to 14% (w/w) of total fatty acid at given outdoor condition. 相似文献
5.
ABSTRACTIn the present paper recent investigations on the applications of supercritical fluid extraction (SCE) from post fermentation biomass or in situ extraction of inhibitory fermentation products as a promising method for increasing the yield of extraction have been reviewed. Although supercritical CO 2 (SC-CO 2) is unfriendly, or even toxic, for some living cells and precludes direct fermentation in dense CO 2, it does not rule out other useful applications for in situ extraction of inhibitory fermentation products and fractional extraction of biomass constituents. This technique is a highly desirable method for fractional extraction of biomass constituents, and intracellular metabolites due to the potential of system modification by physical parameters and addition of co-solvents to selectively extract compounds of different polarity, volatility and hydrophilicity without any contamination. 相似文献
6.
The objective of this study was to investigate the extraction of lipids, for example, mono‐ and polyunsaturated fatty acids (PUFA) as well as carotenoids, from wet microalgae biomass using pressurized subcritical extraction solvents, which meet the requirements of food and feed applications. To demonstrate the effect of the solvent and temperature on the lipid yield, we chose two microalgae species, viz. Chlorella vulgaris and Phaeodactylum tricornutum, differing in their biochemical composition fundamentally. In case of P. tricornutum, ethanol showed the highest fatty acid yield of 85.9% w/w. In addition to eicosapentaenoic acid (EPA), the ethanolic extracts contained exceptional amounts of fucoxanthin (up to 26.1 mg/g d. w.), which can be beneficial to protect unsaturated fatty acids from oxidation processes and in terms of human nutrition. For C. vulgaris, a fatty acid yield of 76.5% w/w was achieved from wet biomass using ethyl acetate at 150°C. In general, an increase in the extraction temperature up to 150°C was found to be important in terms of fatty acid yield when extracting wet microalgae biomass. The results suggest that it is possible to efficiently extract both fatty acids and carotenoids from wet microalgae by selecting suitable solvents and thus circumvent energy‐intensive drying of the biomass. 相似文献
7.
The present study describes the chemical composition and the antibacterial activity of extracts from Cordia verbenacea DC (Borraginaceae), a traditional medicinal plant that grows widely along the southeastern coast of Brazil. The extracts were obtained using different extraction techniques: high-pressure operations and low-pressure methods. The high-pressure technique was applied to obtain C. verbenacea extracts using pure CO 2 and CO 2 with co-solvent at pressures up to 30 MPa and temperatures of 30, 40 and 50 °C. Organic solvents such as n-hexane, ethyl acetate, ethanol, acetone and dichloromethane were used to obtain extracts by low-pressure processes. The antibacterial activity of the extracts was also subjected to screening against four strains of bacteria using the agar dilution method. The extraction yields were up to 5.0% w/w and up to 8.6% w/w for supercritical fluid extraction with pure CO 2 and with ethyl acetate as co-solvent, respectively, while the low-pressure extraction indicates yields up to 24.0% w/w in the soxhlet extraction using water and aqueous mixture with 50% ethanol as solvents. The inhibitory activity of the extracts in Gram-positive bacteria was significantly higher than in Gram-negative. The quantification and the identification of the extracts recovered were accomplished using GC/MS analysis. The most important components identified in the extract were artemetin, β-sitosterol, α-humulene and β-caryophyllene, among others. 相似文献
8.
In experiments with the unicellular green algae Scenedesmus obliquus a correlation was found between the presence of the CO 2-accumulating mechanism and the appearance of polyphasic luminescence decay kinetics. A potentiometric titration method was used to measure and calculate photosynthetic carbon uptake.Polyphasic luminescence decay kinetics was found when the algae showed photosynthetic characteristics typical of algae adapted to low-CO 2 conditions. When high-CO 2 grown algae were transferred to low-CO 2 conditions they gradually developed polyphasic decay kinetics during the first 25–30 minutes. When low-CO 2 grown algae were transferred to high-CO 2 conditions the polyphasic decay kinetics disappeared. To account for these results a working hypothesis is presented on the basis of the energy requirement for a CO 2-accumulating mechanism. 相似文献
9.
Mass culture of microalgae is a potential alternative to cultivation of terrestrial crops for bioenergy production. However, microalgae require nitrogen fertiliser in quantities much higher than plants, and this has important consequences for the energy balance of these systems. The effect of nitrogen fertiliser supplied to microalgal bubble-column photobioreactor cultures was investigated using different nitrogen sources (nitrate, urea, ammonium) and culture conditions (air, 12% CO 2). In 20 L cultivations, maximum biomass productivity for Chlorella vulgaris cultivated using nitrate and urea was 0.046 and 0.053 g L −1 day −1, respectively. Maximum biomass productivity for Dunaliella tertiolecta cultivated using nitrate, urea and ammonium was 0.033, 0.038 and 0.038 g L −1 day −1, respectively. In intensive bubble-column photobioreactors using 12% CO 2, maximum productivity reached 0.60 and 0.83 g L −1 day −1 for C. vulgaris and D. tertiolecta, respectively. Recycling of nitrogen within the photobioreactor system via algal exudation of nitrogenous compounds and bacterial activity was identified as a potentially important process. The energetic penalty incurred by supply of artificial nitrogen fertilisers, phosphorus, power and CO 2 to microalgal photobioreactors was investigated, although analysis of all energy burdens from biomass production to usable energy carriers was not conducted. After subtraction of the power, nitrogen and phosphorus energy burdens, maximum net energy ratios for C. vulgaris and D. tertiolecta cultivated in bubble columns were 1.82 and 2.10. Assuming CO 2 was also required from a manufactured source, the net energy ratio decreased to 0.09 and 0.11 for C. vulgaris and D. tertiolecta, so that biomass production in this scenario was unsustainable. Although supply of nitrogen is unlikely to be the most energetically costly factor in sparged photobioreactor designs, it is still a very significant penalty. There is a need to optimise both cultivation strategies and recycling of nitrogen in order to improve performance. Data are supported by measurements including biochemical properties (lipid, protein, heating value) and bacterial number by epifluorescence microscopy. 相似文献
10.
CO 2 at different concentrations were added to cultures of the eukaryotic microalgae, Chlorella kessleri, C. vulgaris and Scenedesmus obliquus, and the prokaryotic cyanobacterium, Spirulina sp., growing in flasks and in a photobioreactor. In each case, the best kinetics and carbon fixation rate were with a vertical
tubular photobioreactor. Overall, Spirulina sp. had the highest rates. Spirulina sp., Sc. obliquus and C. vulgaris could grow with up to 18% CO 2. 相似文献
11.
A culture method was developed for photoautotrophic culture of Haematococcus pluvialis, Chlorella vulgaris, Scenedesmus obliquus, Spirulina platensis, Nostoc and Stigonema in a two-tier flask consisting of nutrient media in the upper chamber and CO 2 generating buffer mixture (KHCO 3/K 2CO 3) in the lower chamber. The concentration of buffer mixture was varied to obtain desired levels of CO 2. CO 2 at 2.0% (v/v) level enhanced growth and chlorophyll content over control cultures (without CO 2 supplementation) in all microalgal species. Haematococcus pluvialis culture in BBM and KM1 media showed 6.71- and 2.07-fold increase in biomass yields with astaxanthin productivity at 7.26 and 7.48 mg l –1 level respectively. CO 2 supplementation to C. vulgaris and S. obliquus cultures resulted in 5.97- and 7.30-folds increase in biomass with 2–3 fold increase in chlorophyll and carotenoid contents over their respective controls. Similarly 2–3 fold increase in chlorophyll and carotenoid contents were observed in Sp. platensis, Nostoc and Stigonema spp. This culture methodology will provide information on CO 2 requirement for growth of algae and metabolite production and also facilitates studies on the influence of light and temperature conditions. 相似文献
12.
The purpose of this research was to preliminary assess the suitability of a new method for the preparation of a solid formulation
in form of powder composed by β-cyclodextrin and the supercritical extract of Rosa canina hips. The method implies the extraction of carotenoids, in particular β-carotene, from freeze dried fruits of R. canina with supercritical CO 2 at 70 °C and 300 bar, in the presence of varying quantity of ethanol as entrainer. The obtained supercritical solution is
then expanded at ambient conditions into an aqueous solution of β-cyclodextrin to favour the interaction between β-cyclodextrin
and the lipophilic components of the extract. β-carotene solubility (mole fraction) in supercritical CO 2 or in supercritical CO 2/ethanol mixtures were in the order of 1 10 −7. The β-carotene extracted from R. canina fruits (nearly 10 μg/g of dry matrix), interacts almost quantitatively with β-cyclodextrin affording a solid phase, which
presents a low apparent solubility in water. Finally the interaction with β-cyclodextrin results in a higher concentration
of the β-carotene trans- form relative to the cis- form in the extracted product when collected in an aqueous solution of β-cyclodextrin with respect to the extract in n-hexane. 相似文献
13.
Biodiesel is a renewable and environmental friendly energy source that can be produced via tranesterification from various oil crops such as soy bean, sunflower, palm, and algae. In this work, the microalgae Scenedesmus obliquus, S. armatus and S. bernadii, isolated from natural water basins, were enriched in modified Chu 13 medium. Only S. obliquus showed significant oil accumulation and was thus further cultivated in 3 L tubular photo-reactors under mixotrophic conditions (16:8 h light-dark cycle) at room temperature and varying CO 2 (5, 10, and 15%) supply. The results indicated that S. obliquus can be grown under various CO 2 concentrations. A maximum biomass of 2.3 g/L was achieved when 15% CO 2 was used. The effect of salinity on oil storage was also considered, using sodium chloride (NaCl) solutions of varying concentrations (0.05, 0.2, and 0.3 M). Higher lipid contents were found in cells that were subjected to salt stress compared to those in conditions without salt stress. A maximum oil accumulation of 36% was observed within 15 days at 0.3 M NaCl. A biodiesel yield of up to 97.4% was obtained. 相似文献
14.
The prospect of using constructed communities of microalgae in algal cultivation was confirmed in this study. Three different algal communities, constructed of diatoms ( Diatom), green algae ( Green), and cyanobacteria ( Cyano), each mixed with a natural community of microalgae were cultivated in batch and semi‐continuous mode and fed CO 2 or cement flue gas (12–15% CO 2). Diatom had the highest growth rate but Green had the highest yield. Changes in the community composition occurred throughout the experiment. Green algae were the most competitive group, while filamentous cyanobacteria were outcompeted. Euglenoids, recruited from scarce species in the natural community became a large part of the biomass in semi‐steady state in all communities. High temporal and yield stability were demonstrated in all communities during semi‐steady state. Valuable products (lipids, proteins, and carbohydrates) comprised 61.5 ± 5% of ash‐free biomass and were similar for the three communities with lipids ranging 14–26% of dry mass (DM), proteins (15–28% DM) and carbohydrates (9–23% DM). Our results indicate that culture functions (stability, biomass quality) were maintained while dynamic changes occurred in community composition. We propose that a multispecies community approach can aid sustainability in microalgal cultivation, through complementary use of resources and higher culture stability. 相似文献
15.
The variation in the content and composition of essential oils of Bidens tripartita L. grown in Lithuania has been studied using supercritical CO 2 extraction followed by GC–MS. Extraction of essential oils was performed at two different pressures (9.1 and 15.1 MPa). Plant
material has been harvested at different phenological stages (from June to September). A total of 26 different compounds were
identified in the essential oils. The highest content and diversity of compounds was determined during the full-flowering
stage. Identified substances were mainly monoterpene hydrocarbons and sesquiterpene hydrocarbons. The main components were
α-pinene, p-cymene, trans-β-ocimene, and β-elemene. Chemometric analysis, including principal component and hierarchical cluster analyses, showed the
dependence of the essential oils qualitative as well as quantitative composition on the phenological stage the plant was collected
at. It also revealed that there was no correlation between age of the plant and quantity of the identified compounds. 相似文献
16.
Oil production in batch photoautotrophic cultures of the following microalgae is reported: the freshwater microalgae Chlorella vulgaris, Choricystis minor, and Neochloris sp.; the marine microalgae Nannochloropsis salina and Cylindrotheca fusiformis; and C. vulgaris grown in a full-strength seawater medium. In all cases, the solvent extraction of lipids from freeze-dried biomass is compared with extraction from the fresh biomass paste. For all algae, the oils could be extracted equally effectively from freeze-dried samples and the paste samples (67–88 % moisture by weight). Moisture content determinations of the biomass using the freeze-drying method and the high-temperature oven drying were found to be equivalent for all algae. The biomass recovered by flocculation with metal salts (aluminum sulfate, ferric chloride) followed by centrifugation had a certain amount of the flocculant irreversibly bound to it. Washing failed to remove the adsorbed flocculants. For all algae, the adsorbed flocculants did not interfere with oil recovery by solvent extraction. The solvent system of chloroform–methanol–water proved highly effective for quantitative extraction of the lipids from all algae. 相似文献
17.
Microalgae perform oxygenic photosynthesis and are capable of taking up a large amount of CO 2, using an inducible CO 2 concentrating mechanism (CCM), and fixing CO 2 into higher compounds. These characteristics make the microalgae potentially useful for removal and utilization of CO 2 emitted from industrial plants and, generally, the usage of photosynthetic microorganisms has increased and significantly
improved as a solution for CO 2 emissions. In this light and based on previous research using Anabaena cylindrica IAM M1 and Spirulina platensis IAM M 135, enhancement was sought for CO 2 fixation and biomass production by Chlorella vulgaris Buitenzorg by increasing the photon flux density concurrent with increases in culture biomass during the cellular growth
phase and was compared to cultures of Chlorella grown at optimal constant illumination, with all cultures grown using Bennick basal medium, 29°C, and a flow of 1.0 atm.
10% CO 2 enriched air delivered to three in serial photobioreactors of 0.200 dm 3 capacity each. The results showed that increasing illumination during culture increased biomass production of Chlorella by ∼60% as well as increased CO 2 fixation ability by ∼7.0%. It was also demonstrated that the non-competitive inhibition of [HCO 3
−] as a carbon source significantly affected the cultivation in both the increasing and constant photon flux density regimes. 相似文献
18.
Flue gas generated by combustion of natural gas in a boiler was used for outdoor cultivation of Chlorella sp. in a 55 m 2 culture area photobioreactor. A 6 mm thick layer of algal suspension continuously running down the inclined lanes of the
bioreactor at 50 cm s −1 was exposed to sunlight. Flue gas containing 6–8% by volume of CO 2 substituted for more costly pure CO 2 as a source of carbon for autotrophic growth of algae. The degree of CO 2 mitigation (flue gas decarbonization) in the algal suspension was 10–50% and decreased with increasing flue gas injection
rate into the culture. A dissolved CO 2 partial pressure ( pCO 2) higher than 0.1 kPa was maintained in the suspension at the end of the 50 m long culture area in order to prevent limitation
of algal growth by CO 2. NO X and CO gases (up to 45 mg m −3 NO X and 3 mg m −3 CO in flue gas) had no negative influence on the growth of the alga. On summer days the following daily net productivities
of algae [g (dry weight) m −2] were attained in comparative parallel cultures: flue gas = 19.4–22.8; pure CO 2 = 19.1–22.6. Net utilization (η) of the photosynthetically active radiant (PAR) energy was: flue gas = 5.58–6.94%; pure CO 2 = 5.49–6.88%. The mass balance of CO 2 obtained for the flue gas stream and for the algal suspension was included in a mathematical model, which permitted the calculation
of optimum flue gas injection rate into the photobioreactor, dependent on the time course of irradiance and culture temperature.
It was estimated that about 50% of flue gas decarbonization can be attained in the photobioreactor and 4.4 kg of CO 2 is needed for production of 1 kg (dry weight) algal biomass. A scheme of a combined process of farm unit size is proposed;
this includes anaerobic digestion of organic agricultural wastes, production and combustion of biogas, and utilization of
flue gas for production of microalgal biomass, which could be used in animal feeds. A preliminary quantitative assessment
of the microalgae production is presented. 相似文献
19.
The atmospheric CO 2 increase is considered the main cause of global warming. Microalgae are photosynthetic microorganisms that can help in CO 2 mitigation and at the same time produce value‐added compounds. In this study, Scenedesmus obliquus , Chlorella vulgaris , and Chlorella protothecoides were cultivated under 0.035 (air), 5 and 10% (v/v) of CO 2 concentrations in air to evaluate the performance of the microalgae in terms of kinetic growth parameters, theoretical CO 2 biofixation rate, and biomass composition. Among the microalgae studied, S. obliquus presented the highest values of specific growth rate ( μ = 1.28 d ?1), maximum productivities ( P max = 0.28 g L ?1d ?1), and theoretical CO 2 biofixation rates (0.56 g L ?1d ?1) at 10% CO 2. The highest oil content was found at 5% CO 2, and the fatty acid profile was not influenced by the concentration of CO 2 in the inflow gas mixture and was in compliance with EN 14214, being suitable for biodiesel purposes. The impact of the CO 2 on S. obliquus cells’ viability/cell membrane integrity evaluated by the in‐line flow cytometry is quite innovative and fast, and revealed that 86.4% of the cells were damaged/permeabilized in cultures without the addition of CO 2. 相似文献
20.
There is worldwide interest in developing algal biofuel. One main reason for the lack of success so far in producing a sustainable transport fuel from microalgae is the high cost of biomass processing, especially dewatering and oil extraction. There is also a significant cost involved in the energy content of the nutrient fertilisers required for biomass production. Non-destructive oil extraction or “milking” from algae biomass has the potential to bypass all of these hurdles. Using a “milking” strategy means that there would be no need for (a) biomass dewatering, (b) breaking cells for oil extraction and (c) addition of nutrients to the culture, resulting in a significant reduction in energy and fertiliser cost involved in production of biofuel from algae. We make use of the natural tendency of Botryococcus to produce external hydrocarbon in the extracellular matrix. In current study, we showed that external hydrocarbon from Botryococcus braunii BOT-22 can be non-destructively extracted using n-heptane (optimum contact time with n-heptane?=?20 min). We were able to recover almost the entire de novo-produced external hydrocarbons at 5- and 11-day intervals when the culture was maintained with or without 1 % CO 2 addition, respectively. This repeated non-destructive extraction of external hydrocarbon of B. braunii was possible for up to 70 days when 1 % CO 2 was supplied to the culture. When CO 2 was limited, a 70 % lower external hydrocarbon productivity was achieved using the same process. Although the productivity of external hydrocarbon of 9.33 mg L ?1 day ?1 of the “milked” culture is low in these un-optimised cultures, it was 1.3?±?0.2-fold higher compared with that of a conventional semicontinuous culture, showing the potential of this method. 相似文献
|