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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 24 (1986), S. 47-50 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The results of a whole year experiment on the outdoor mass culture of Spirulina maxima strain 4Mx on fertilized sea-water are reported. Carbonate and phosphate precipitation in the sea-water media was prevented by maintaining a low concentration of phosphate and by controlling the pH in the range of 8.0–8.3. The mean annual yield of biomass on sea-water plus urea as nitrogen source was 7.35 g (dry weight) m-2· day-1, a value slightly lower than that obtained on the standard bicarbonate medium (8.14 g · m-2 · day-1). On sea-water plus nitrate the yield was only 5.2 g·m-2·day-1. The nitrogen content of the biomass was higher in summer and lower in winter. The seasonal effect was more evident when nitrate was the nitrogen source.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 187-197 
    ISSN: 0006-3592
    Keywords: algal cultures ; photosynthetic efficiency ; light saturation effect ; spatial dilution of light ; Arthrospira (Spirulina) platensis ; tubular and flat photobioreactors ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The light saturation effect imposes a serious limitation on the efficiency with which solar energy can be utilized in outdoor algal cultures. One solution proposed to reduce the intensity of incident solar radiation and overcome the light saturation effect is “spatial dilution of light” (i.e., distribution of the impinging photon flux on a greater photosynthetic surface area), but consistent experimental data supporting a significant positive influence of spatial light dilution on the productivity and the photosynthetic efficiency of outdoor algal cultures have never been reported. We used a coiled tubular reactor and compared a near-horizontal straight tubular reactor and a near-horizontal flat panel in outdoor cultivation of the cyanobacterium Arthrospira (Spirulina) platensis under defined operating conditions for optimum productivity. The photosynthetic efficiency achieved in the tubular systems was significantly higher because their curved surface “diluted” the impinging solar radiation and thus reduced the light saturation effect. This interpretation was supported by the results of experiments carried out in the laboratory under continuous artificial illumination using both a flat and a curved chamber reactor. The study also showed that, when the effect of light saturation is eliminated or reduced, productivity and solar irradiance are linearly correlated even at very high diurnal irradiance values, and supported findings that outdoor algal cultures are light-limited even during bright summer days. It was also observed that, besides improving the photosynthetic efficiency of the culture, spatial dilution of light also leads to higher growth rates and lowers the cellular content of accessory pigments; that is, it reduces mutual shading in the culture. The inadequacy of using volumetric productivity as the sole criterion for comparing reactors of different surface-to-volume ratio and of the areal productivity for evaluating the performance of elevated photobioreactors operated outdoors is stressed; it is furthermore suggested that the photosynthetic efficiency achieved by the culture also be calculated to provide a suitable parameter for comparison of different algal cultivation systems operated under similar climatic conditions. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 187-197, 1998.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5176
    Keywords: Arthrospira platensis ; Spirulina ; tubular photobioreactors ; outdoor culture ; aeration rate ; cell density ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Arthrospira (Spirulina) platensis M2 was grown outdoors in 50-mm diameter tubular reactors under the climatic conditions of central Italy (Florence) from September to December 1995 and in March 1996. Except for September, the cultures temperature was regulated. Mean productivities of 0.83, 0.44 and 0.61 g dry wt L−1 d−1 were achieved in autumn (September–October), winter (November–December) and March, respectively. In autumn and winter, the photosynthetic efficiency of the cultures and the degree of correlation between productivity and solar irradiance were significantly greater than in summer. The effect of cell density and aeration rate on productivity was evaluated in September. The productivity of cultures operated at high supra-optimal population density was about 30% less at high aeration rate (1.0 LL−1 min−1), and 50% less at standard aeration rate (0.17 LL−1 min−1), than that of control cultures kept at optimal population density and standard aeration rate. The reduction of productivity in high-density cultures was due to lower daylight output rates and higher night biomass losses (the latter were particularly relevant under standard aeration conditions). The main factor limiting productivity in closed reactors during autumn was the night temperature. Heating the cultures during daylight hours on sunny days did not cause any significant increase of the yields, since under sunlight the unheated cultures also reached the optimal temperature for growth early in the morning. On cloudy days, the day-time temperature of the unheated cultures remained well below the optimum, however this had only a limited effect on productivity since algal growth was mainly light-limited.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied phycology 12 (2000), S. 543-547 
    ISSN: 1573-5176
    Keywords: antifungal and antibacterial compounds ; bioactivity ; cyanobacteria ; cytotoxicity ; Nostoc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fifty cyanobacterial strains from different habitats(symbioses, soil, fresh and marine waters) belongingto the genus Nostoc were cultured and tested forbioactivity. Thirty-seven strains were isolated in ourlaboratory, the remaining were supplied by officialculture collections. All the organisms were grownunder controlled laboratory conditions. The biomasseswere lyophilised and extracted with ethanol:water toobtain a hydrophilic extract and then withdichloromethane:isopropanol to obtain a lipophilicextract. Both crude extracts were tested forantifungal (against Penicillium expansum andRhizoctonia solani) and antibacterial activity(against Agrobacterium vitis, Escherichiacoli and Staphylococcus epidermidis), and fortoxicity against Artemia salina nauplii.Twenty-four strains showed activity against at leastone of the target organisms. Bioactivity was equallydistributed between lipophilic and hydrophilicextracts, and was mostly directed against fungi (15strains) and Artemia nauplii (12 strains);antibacterial activity was less frequent (8 strains).The presence of bioactivity was independent of thestrain origin.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5176
    Keywords: Arthrospira (Spirulina) platensis ; integrated culture system ; raceway pond ; photobioreactor ; alveolar panel ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cultivation of microalgae in closed photobioreactors suffers from high temperatures, whereas in open raceway ponds the optimal temperature is seldom reached. With an integrated device coupling a raceway pond with a suitably sized and positioned closed system (alveolar panel), the heat accumulated in the panel was efficiently transferred to the pond and a near-optimum temperature regimen for Arthrospira platensis was maintained, with no need for any additional cooling device. The productivity obtained in the integrated system was higher than the sum of the productivities (g reactor−1 day−1) of the pond and panel systems operating separately.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5176
    Keywords: eicosapentaenoic acid ; fatty acid profile ; Modular Flat Panel Photobioreactor ; Nannochloropsis sp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nannochloropsis sp. was grown in a Modular FlatPanel Photobioreactor (MFPP) consisting of sixalveolar panels each with 20.5 L culture volume and3.4 m2 illuminated surface area. The panelsformed a closely-packed unit with illuminationprovided by banks of fluorescent tubes placed betweenthe panels. The whole unit was contained in athermoregulated cabinet. Continuous illumination ofone side of the panels with 115 μmolphoton m-2 s-1 attained a mean volumetricproductivity of 0.61 g (d. wt) L-1 24 h-1,increasing to 0.97 g (d. wt) L-1 24 h-1 whenthe same irradiance was provided on both sides of thepanels. With 230 μmol photon m-2 s-1 onone side of the panel, a mean productivity of 0.85 g(d. wt) L-1 24 h-1 was achieved, whichreached 1.45 g (d. wt) L-1 24 h-1 when bothsides were illuminated. Increasing the amount of lightprovided to the culture (either by increasingirradiance or the illuminated surface area) decreasedpigment and enhanced the total fatty acid content, butdid not change significantly the content ofeicosapentaenoic acid. A MFPP of the presentdimensions could produce sufficient microalgae tosupport a hatchery producing 6 million sea breamfingerlings annually.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5176
    Keywords: Euglena gracilis ; fatty acids ; non-photosynthetic mutant ; WZSL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of growth conditions on fatty acid profilewere examined in the photosynthetic wild type and inthe spontaneous non-photosynthetic WZSL mutant of theunicellular flagellate Euglena gracilis. Inthe light, the amount of polyunsaturated fatty acids(PUFAs) is higher in the wild type than in the mutant,independent of the carbon source. Among importantPUFAs, linolenic acid (18:3 ω3) is present inhigh amount only in wild type cells grown in the lightwith any of the tested carbon sources. The content ofother PUFAs, such as arachidonic acid (20:4ω6), EPA (20:5 ω3) and DHA (22:6ω3), is not correlated with the presence oflight or chloroplasts.The main effect of the dark in both strains is tolower the content of PUFAs and mono-unsaturated fattyacids and to increase the content of saturated fattyacids with all the carbon sources.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied phycology 12 (2000), S. 493-498 
    ISSN: 1573-5176
    Keywords: Arthrospira ; Chad ; dihé ; Kanembu ; Lake Kossorom ; Spirulina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In 1997 a survey was conducted among the Kanembu whoharvest Arthrospira (Spirulina) from LakeKossorom in the Prefecture of Lac (Chad). Informationon the amount of Arthrospira harvested and thepreparation and use of dihé was obtained byinterviewing the women who daily gather around thelake for the harvesting. Dihé is obtained byfiltering and sun drying the algal biomass on thesandy shores of the lake. The semi-dried dihé is then cut into small squares and taken tothe villages, where the drying is completed on mats inthe sun. Dihé is mainly used to prepare la souce, a kind of fish or meat and vegetable broth.Part of the harvest is sold to local consumers or towholesalers, who trade the product in the markets ofMassakori, Massaquet and N'Djamena and also across theborder of the country. The local trading valueof the dihé annually harvested from LakeKossorom (about 40 t) amounts to more than US$100,000, which represents an important contributionto the economy of the area.
    Type of Medium: Electronic Resource
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