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1.
Open ponds are the preferred cultivation system for large-scale microalgal biomass production. To be more sustainable, commercial scale biomass production should rely on seawater, as freshwater is a limiting resource, especially in places with high irradiance. If seawater is used for both pond fill and evaporative volume makeup, salinity of the growth media will rise over time. It is not possible for any species to achieve optimum growth over the whole saline spectrum (from seawater salinity level up to salt saturation state). In this study, we investigated the effects of gradual salinity increase (between 35 and 233 ppt) on biomass productivity and biochemical composition (lipid and carbohydrate) of six marine, two halotolerant, and a halophilic microalgae. A gradual and slow stepped salinity increase was found to expand the salinity tolerance range of tested species. A gradual reduction in biomass productivity and maximum photochemical efficiency was observed as a consequence of increased salinity in all tested species. Among the marine microalgae, Tetraselmis showed highest biomass productivity (32 mg L?1 day?1) with widest salinity tolerance range (35 to 109 ppt). Halotolerant Amphora and Navicula were able to grow from 35 ppt to 129 ppt salinity. Halophilic Dunaliella was the only species capable of growing between 35 and 233 ppt and showed highest lipid content (56.2%) among all tested species. This study showed that it should be possible to maintain high biomass in open outdoor cultivation utilizing seawater by growing Tetraselmis, Amphora, and Dunaliella one after another as salinity increases in the cultivation system.  相似文献   

2.
Photosynthetic and respiratory responses (P–E curves) of Gracilaria parvispora from the southeast Gulf of California were studied at four temperatures (20, 25, 30, 35 °C) and salinity (25, 30, 35, 40 psu) combinations. The alga showed acclimation in its photosynthetic and respiratory responses to tropical temperature as well as to oceanic salinity. A positive effect of temperature on photosynthetic rate (P max) was observed for all salinities. Photosynthetic rates for treatments at 20 and 25 °C were lower (<9.2 mg O2?g dry weight (dw)?1?h?1) than for treatments at 30 and 35 °C (>12 mg O2 g dw?1?h?1). G. parvispora showed limited tolerance to low salinities (25 psu) and low temperatures (20 °C) and the interaction between temperature and salinity was significant (analysis of variance, P?<?0.05). Responses to salinity indicated adaptation to oceanic salinity. Photosynthetic responses were lower at 25 psu than at higher salinities. The lowest P max values (6.2–8.2 mg O2?g dw?1?h?1) were observed at the lowest salinity (25 psu) regardless of temperature. Compensation and saturation irradiances (26–170 and 57–149 μmol photons m?2?s?1, respectively) indicate adaptation to lower irradiances in shallow (1–2 m depth) habitats, where turbidity can be high, and the capacity of shade adaptation has been developed. Results suggest distribution of this species is mainly related to salinity or temperature. The potential mariculture efforts of G. parvispora would be limited by low temperatures in winter, and indicate that this species will probably not be able to spread further due to low temperatures (<15 °C) in the upper part of the Gulf of California.  相似文献   

3.
There has been considerable interest in cultivation of green microalgae (Chlorophyta) as a source of lipid that can alternatively be converted to biodiesel. However, almost all mass cultures of algae are carbon-limited. Therefore, to reach a high biomass and oil productivities, the ideal selected microalgae will most likely need a source of inorganic carbon. Here, growth and lipid productivities of Tetraselmis suecica CS-187 and Chlorella sp were tested under various ranges of pH and different sources of inorganic carbon (untreated flue gas from coal-fired power plant, pure industrial CO2, pH-adjusted using HCl and sodium bicarbonate). Biomass and lipid productivities were highest at pH 7.5 (320?±?29.9 mg biomass L?1 day?1and 92?±?13.1 mg lipid L?1 day?1) and pH 7 (407?±?5.5 mg biomass L?1 day?1 and 99?±?17.2 mg lipid L?1 day?1) for T. suecica CS-187 and Chlorella sp, respectively. In general, biomass and lipid productivities were pH 7.5?>?pH 7?>?pH 8?>?pH 6.5 and pH 7?>?pH 7.5?=?pH 8?>?pH 6.5?>?pH 6?>?pH 5.5 for T. suecica CS-187 and Chlorella sp, respectively. The effect of various inorganic carbon on growth and productivities of T. suecica (regulated at pH?=?7.5) and Chlorella sp (regulated at pH?=?7) grown in bag photobioreactors was also examined outdoor at the International Power Hazelwood, Gippsland, Victoria, Australia. The highest biomass and lipid productivities of T. suecica (51.45?±?2.67 mg biomass L?1 day?1 and 14.8?±?2.46 mg lipid L?1 day?1) and Chlorella sp (60.00?±?2.4 mg biomass L?1 day?1 and 13.70?±?1.35 mg lipid L?1 day?1) were achieved when grown using CO2 as inorganic carbon source. No significant differences were found between CO2 and flue gas biomass and lipid productivities. While grown using CO2 and flue gas, biomass productivities were 10, 13 and 18 %, and 7, 14 and 19 % higher than NaHCO3, HCl and unregulated pH for T. suecica and Chlorella sp, respectively. Addition of inorganic carbon increased specific growth rate and lipid content but reduced biomass yield and cell weight of T. suecica. Addition of inorganic carbon increased yield but did not change specific growth rate, cell weight or content of the cell weight of Chlorella sp. Both strains showed significantly higher maximum quantum yield (Fv/Fm) when grown under optimum pH.  相似文献   

4.
Microalgae cultivation systems can be divided broadly into open ponds and closed photobioreactors. This study investigated the growth and biomass productivity of the halophilic green alga Tetraselmis sp. MUR-233, grown outdoors in paddle wheel-driven open raceway ponds and in a tubular closed photobioreactor (Biocoil) at a salinity of 7 % NaCl (w/v) between mid-March and June 2010 (austral autumn/winter). Volumetric productivity in the Biocoil averaged 67 mg ash-free dry weight (AFDW) L?1 day?1 when the culture was grown without CO2 addition. This productivity was 86 % greater, although less stable, than that achieved in the open raceway pond (36 mg L?1 day?1) grown at the same time in the autumn period. The Tetraselmis culture in the open raceway pond could be maintained in semi-continuous culture for the whole experimental period of 3 months without an additional CO2 supply, whereas in the Biocoil, under the same conditions, reliable semi-continuous culture was only achievable for a period of 38 days. However, stable semi-continuous culture was achieved in the Biocoil by the addition of CO2 at a controlled pH of ~7.5. With CO2 addition, the volumetric biomass productivity in the Biocoil was 85 mg AFDW L?1 day?1 which was 5.5 times higher than the productivity achieved in the open raceway pond (15 mg AFDW L?1 day?1) with CO2 addition and 8 times higher compared to the productivity in the open raceway pond without CO2 addition (11 mg AFDW L?1 day?1), when cultures were grown in winter. The illuminated area productivities highlight an alternative story and showed that the open raceway pond had a three times higher productivity (3,000 mg AFDW m?2 day?1) compared to the Biocoil (850 mg AFDW m?2 day?1). Although significant differences were found between treatments and cultivation systems, the overall average lipid content for Tetraselmis sp. MUR-233 was 50 % in exponential phase during semi-continuous cultivation.  相似文献   

5.
The high cost of aeration needed to tumble culture macroalgae is a limiting factor for integration with land-based finfish culture. Toward reducing this electricity cost, we compared intermittent aeration (16 h on:8 h off) with continuous aeration (24 h on) on the productivity of two strains of Chondrus crispus (Basin Head and Charlesville) and Palmaria palmata from Atlantic Canada between May and June 2011. Algal fronds were cultured under a 16:8-h light/dark photoperiod in 50-L tanks supplied with finfish effluent (49 μmol L?1 of ammonium and 11 μmol L?1 of phosphate) at a mean water flow rate of 0.4 L min?1. Nitrogen (N) influx was 1.8 gN m?2 day?1, and phosphorus (P) influx was 0.9 gP m?2 day?1, with uptake rates ranging from 0.02 to 2.4 gN m?2 day?1 and ?0.2 to 0.4 gP m?2 day?1. On average, the macroalgae culture system (algae and biofilms) removed 1.0 gN m?2 day?1 (51.9 %). The growth of macroalgae (pooled across treatment and strain) ranged from 0.5 to 1.6 % day?1, which accounted for a yield of 2.2 to 5.4 g DW m?2 day?1. Switching off aeration at night improved the growth rate of Basin Head Chondrus by 146 % and had no effect on growth rate or nitrogen and carbon removal by P. palmata and Charlesville Chondrus. Growth and yield of Basin Head Chondrus under intermittent aeration were over two times greater than both Charlesville Chondrus treatments.  相似文献   

6.
Cultivation of seaweeds on a commercial scale requires a large number of propagules with desirable phenotypic traits which include high growth rates and resistance to diseases. Seaweed micropropagation can be considered as one of the best methods to provide a large amount of seedlings for commercial cultivation. This study was carried out to optimize the parameters known to affect the growth of Kappaphycus alvarezii in vitro and subsequently improve the production of seedlings through micropropagation. Suitability of media, concentration of phytoregulators, types and concentration of fertilizers, culture density, light intensity, interval of aeration activity, salinity, and pH were found to be critical factors for the growth of K. alvarezii. The optimum condition for direct regeneration of K. alvarezii in a culture vessel was found to be cultivation of explants in Provasoli's enriched seawater (PES) media supplemented with 2.5 mg L?1 6-benzylaminopurine (BAP), 1.0 mg L?1 indole-3-acetic acid (IAA), and 3.0 mg L?1 natural seaweed extract (NSE) with culture density of 0.4 %?w/v, under light intensity of 75 μmol photons m?2 s?1, continuous aeration of 30.0 L h?1, salinity of 30.0 ppt, and pH 7.5. An airlift photobioreactor was constructed for the mass propagation of K. alvarezii explants with optimum culture conditions obtained from the study. The optimum growth rates of the K. alvarezii explants in culture vessels (5.5 % day?1) and photobioreactor (6.5 % day?1) were found to be higher than the growth rate observed in field trials in the open sea (3.5 % day?1). The information compiled during the course of this study will be of utility to commercial seaweed cultivators.  相似文献   

7.
In this study, hypersaline media were used for ocean cultivation of the marine microalga Tetraselmis sp. KCTC12432BP for enhanced biomass and fatty acid (FA) productivity. Hypersaline media (55, 80, and 105 PSU) were prepared without sterilization by addition of NaCl to seawater obtained from Incheon, Korea. The highest biomass productivity was obtained at 55 PSU (0.16 g L?1 day?1) followed by 80 PSU (0.15 g L?1 day?1). Although the specific growth rate of Tetraselmis decreased at salinities higher than 55 PSU, prevention of contamination led to higher biomass productivity at 80 PSU than at 30 PSU (0.03 g L?1 day?1). FA content of algal biomass increased as salinity increased to 80 PSU, above which it declined, and FA productivity was highest at 80 PSU. Ocean cultivation of Tetraselmis was performed using 50-L tubular module photobioreactors and 2.5-kL square basic ponds, closed- and open-type ocean culture systems, respectively. Culturing microalgae in hypersaline medium (80 PSU) improved biomass productivities by 89 and 152% in closed and open cultures, respectively, compared with cultures with regular salinity. FA productivity was greatly improved by 369% in the closed cultures. The efficacy of salinity shift and N-deficiency to enhance FA productivity was also investigated. Lowering salinity to 30 PSU with N-starvation following cultivation at 80 PSU improved FA productivity by 19% in comparison with single-stage culture without N-deficiency at 30 PSU. The results show that salinity manipulation could be an effective strategy to improve biomass and FA productivity in ocean cultivation of Tetraselmis sp.  相似文献   

8.
Ulva spp. are used in a wide range of commercial applications, including bioremediation, food, bioenergy, pharmaceuticals, and agriculture. The sulfated polysaccharide ulvan obtained from Ulva spp. is of interest for triggering plant defenses against disease. However, the cultivation of Ulva spp. is still in its infancy. This study verified the feasibility of cultivating Ulva lactuca and Ulva flexuosa at two sites on the tropical Brazilian coast. We investigated the following: (a) methods to induce sporulation, (b) comparison of seeding ropes inoculated in vitro versus seeding at sea over 40 days, (c) production and harvest cycles at 15 and 30 days, (d) growth productivity of U. flexuosa at sea and in outdoor tanks, and (e) comparison of ulvan yields from biomass cultivated in tanks and the sea. High nutrient treatment was the most efficient method to induce sporulation (7,540?±?3,133 spores m?1). Sea-based cultivation of U. flexuosa was only successful at one site. Seeding of ropes in vitro was more efficient than seeding at sea (0.31?±?0.20 g m?2 day?1), and 15-day harvest cycles were most efficient (20.1?±?1.8 % day?1; 0.46?±?0.11 g m?2 day?1). Despite differences in plant growth in tanks (27.9?±?4.4 % day?1) and at sea (20.1?±?1.8 % day?1), the dry biomass and ulvan yields (17.7?±?5.0 %) did not differ between these systems. Cultivation of U. flexuosa was feasible at sea using in vitro seeding with a production cycle of 15 days in Brazilian tropical waters and tanks with high irradiance and enriched seawater.  相似文献   

9.
The high cost of algal cultivation has been a barrier associated with the commercialisation of algal biodiesel. Therefore, this study aimed to enhance lipid production by optimising the nutrient supply to benefit the coexistence of Dunaliella salina and Nannochloropsis gaditana. The effects on biomass and lipid production of using different proportions of D. salina and N. gaditana, urea and NaHCO3 were optimised by response surface method with a 17-run Box–Behnken design. The optimal conditions for the algal growth are 58 % of D. salina in the mixture at OD680, 150 μL day?1 urea (0.0044 g day?1) and no addition of NaHCO3. The biomass concentration and lipid production reached 1.00 and 0.383 g L?1, respectively, which are exceeded by the amount before optimisation, indicating the efficiency of the model obtained by response surface method.  相似文献   

10.
We determined the effects of cultivation conditions (nitrogen source, salinity, light intensity, temperature) on the composition of polyunsaturated fatty acids (PUFAs) and the production of eicosapentaenoic acid (EPA) in the laboratory cultured eustigmatophycean microalga, Trachydiscus minutus. T. minutus was capable of utilizing all nitrogen compounds tested (potassium nitrate, urea, ammonium nitrate, ammonium carbonate) with no differences in growth and only minor differences in fatty acid (FA) compositions. Ammonium carbonate was the least appropriate for lipid content and EPA production, while urea was as suitable as nitrates. Salinity (0.2 % NaCl) slightly stimulated EPA content and inhibited growth. Increasing salinity had a marked inhibitory effect on growth and PUFA composition; salinity at or above 0.8 % NaCl was lethal. Both light intensity and temperature had a distinct effect on growth and FA composition. The microalga grew best at light intensities of 470–1,070 μmol photons m?2 s?1 compared to 100 μmol photons m?2 s?1, and at 28 °C; sub-optimal temperatures (20, 33 °C) strongly inhibited growth. Saturated fatty acids increased with light intensity and temperature, whereas the reverse trend was found for PUFAs. Although the highest level of EPA (as a proportion of total FAs) was achieved at a light intensity of 100 μmol photons m?2 s?1 (51.1?± 2.8 %) and a temperature of 20 °C (50.9?±?0.8 %), the highest EPA productivity of about 30 mg L?1?day?1 was found in microalgae grown at higher light intensities, at 28 °C. Overall, for overproduction of EPA in microalgae, we propose that outdoor cultivation be used under conditions of a temperate climatic zone in summer, using urea as a nitrogen source.  相似文献   

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