In this paper, the biomass and lutein productivity of the lutein-rich new strain Scenedesmus almeriensis is modelled versus irradiance and temperature. The results demonstrate that S. almeriensis is ...a mesophile microorganism with an optimal growth temperature of 35°C, and capable of withstanding up to 48°C, which caused culture death. This strain is also tolerant to high irradiances, showing no signs of photoinhibition even at the maximum irradiance essayed of 1625 μE m⁻² s⁻¹ accumulating up to 0.55% dry weight (d.wt.) of lutein. The optimal conditions that maximise the biomass productivity also favour the lutein productivity, lutein being a primary metabolite. Maximal biomass and lutein productivities of 0.87 g l⁻¹ day⁻¹ and 4.77 mg l⁻¹ day⁻¹, respectively, were measured. The analysis of light availability inside the cultures, quantified as average irradiance, demonstrates that the cultures were mainly photo-limited, although photosaturation also took place at high external irradiances. The effect of temperature was also investigated finding that the specific maximal growth rate is modified by the temperature according to the Arrhenius equation. The influence of both light availability and temperature was included in an overall growth model, which showed, as a result, capable of fitting the whole set of experimental data. An overall lutein accumulation rate model was also proposed and used in a regression analysis. Simulations performed using the proposed models show that under outdoor conditions a biomass productivity of 0.95 g l⁻¹ day⁻¹ can be expected, with a lutein productivity up to 5.31 mg l⁻¹ day⁻¹. These models may be useful to assist the design and operation optimisation of outdoor cultures of this strain.
Different pilot-scale outdoor photobioreactors using medium recycling were operated in a greenhouse under different environmental conditions and the growth rates (0.1 to 0.5 day⁻¹) obtained evaluated ...in order to compare them with traditional systems used in aquaculture. The annualized volumetric growth rate for Nannochloropsis gaditana was 0.26 g l⁻¹ day⁻¹ (peak 0.4 g l⁻¹ day⁻¹) at 0.4 day⁻¹ in a 5-cm wide flat-panel bioreactor (FP-PBR). The biomass productivity achieved in this reactor was 10-fold higher than in traditional reactors, reaching values of 28 % and 45 % dry weight (d.w.) of lipids and proteins, respectively, with a 4.3 % (d.w.) content of eicosapentaenoic acid (EPA). A model for predicting EPA productivity from N. gaditana cultures that takes into account the existence of photolimitation and photoinhibition of growth under outdoor conditions is presented. The effect of temperature and average irradiance on EPA content is also studied. The maximum EPA productivity attained is 30 mg l⁻¹ day⁻¹.
•How temperature and KOH concentration influence on the carotenoids extraction.•How different polarity solvents influence on the recovery.•To establish a standard method for all microalgae is not ...possible.
Microalgae are an interesting source of natural pigments that have valuable applications. However, further research is necessary to develop processes that allow us to achieve high levels of carotenoid recovery while avoiding degradation. This work presents a comprehensive study on the recovery of carotenoids from several microalgae genera, optimizing carotenoid extraction using alkaline saponification at various temperatures and KOH concentrations. Results show that I. galbana requires a temperature of 60 °C and <10% KOH, N. gaditana and K. veneficum require 60 °C and no saponification, P. reticulatum requires 40 °C and 10% KOH, T. suecica and H. pluvialis require 25 °C and 40% KOH while C. sp. and S. almeriensis require 80 °C and 40% KOH. The influence of the solvent on carotenoid recovery was also studied. In general terms, an ethanol:hexane:water (77:17:6 v/v/v) mixture results in good yields.
► A methodology to recirculate medium in microalgae cultures is developed. ► The most adequate sterilization method is established. ► The recirculation reduces the demand of nutrients cutting costs ...in the process. ► N. gaditana continuous cultures were maintained using the recirculated medium. ► The biomass biochemical composition resulted of high interest for aquaculture.
Nannochloropsis gaditana is a good producer of proteins and valuable fatty acids for aquaculture. Recycling of culture medium is interesting for microalgae commercial production as it cuts costs and prevents environmental contamination. The recycled medium must be sterilized to prevent the buildup of unwanted metabolites and microorganisms. We tested several sterilization methods: filtration, ozonation, chlorination, addition of hydrogen peroxide and heating. Results showed that the most successful method is ozonation lowering the bacterial load to 1.9103CFUs/mL, which is 1000-fold and 10-fold lower than the supernatant obtained after harvesting and the initial filtered medium, respectively. Continuous cultures of N. gaditana were grown using this recirculated supernatant. A maximum biomass productivity of 0.8g/L/d composed of ∼50% proteins and 40% lipids with more than 3%d.w. EPA was obtained making this biomass very interesting for aquaculture.
•A low-cost medium for Nannochloropsis gaditana culture is developed.•Agricultural fertilizers are used as alternative nutrient sources.•A reduction in the amount of nutrients needed to prepare the ...medium was achieved.•A high-quality biomass, suitable for aquaculture applications is produced.
Nannochloropsis gaditana is a microalga with a high nutritional value and a protein and polyunsaturated fatty acid (PUFA) content that makes it interesting as a feed in aquaculture. To maximize its productivity and nutritional value in large-scale culture, a well-known commercial medium was optimized to the most favorable nutrient level using commercial fertilizers. Optimal growth conditions were obtained in the alternative fertilizer-based medium at a nitrogen concentration of 11.3mM, a phosphorus concentration of 0.16mM, and a micronutrient concentration of 30μLL−1. This alternative medium allowed to obtain a biomass concentration similar to that achieved when using the commercial formula but with a reduction in Cu, Fe, and Mo content of 71%, 89%, and 99%, respectively. A maximum biomass productivity of 0.51gL−1d−1 was obtained. The eicosapentaenoic acid and protein contents of the biomass were 2.84% and 44% of dry weight, respectively.
The influence of culture conditions on the quality of Haematococcus pluvialis biomass is assessed. Continuously grown cells have been characterised with respect to their astaxanthin, fatty acid ...content, and antioxidant activity and compared with those of non-growing haematocysts. Moderate limitation of nitrate availability (1.7 mM) under continuous growth conditions favoured the production of reddish palmelloid cells whose extracts possessed antioxidant activity equivalent to that of haematocyst extracts, despite the lower astaxanthin content (0.6%d.wt.), which is compensated by a higher fatty acid level (7.6%d.wt.). Green cells produced under nitrate saturation conditions (>4.7 mM) exhibit only 40% antioxidant activity than palmelloid. In addition, the major fatty acid present in palmelloid cells was oleic acid (40%f.a.), whereas, in both green cells and haematocysts, the main fatty acids were myristic, palmitic, and oleic acid (20-30%f.a. each). Biomass extracts were fractionated and analysed. The antioxidant capacity was a function of both the carotenoid and the fatty acid profiles, the antioxidant capacity of astaxanthin diesters fraction being 60% higher than astaxanthin monoesters fraction and twice than free astaxanthin. In such a way, the evaluation of the quality of H. pluvialis biomass must take into account both variables. When considering the production of H. pluvialis biomass for human consumption, special attention should be paid to the one-step continuous system approach for the generation of cells rich in both astaxanthin and fatty acids, as they have high antioxidant activity but without thick hard cell wall.
Biofouling represents an important limitation in photobioreactor cultures. The biofouling propensity of different materials (polystyrene, borosilicate glass, polymethyl methacrylate, and polyethylene ...terephthalate glycol‐modified) and coatings (two spray‐applied and nanoparticle‐based superhydrophobic coatings and a hydrogel‐based fouling release coating) was evaluated by means of a short‐term protein test, using bovine serum albumin (BSA) as a model protein, and by the long‐term culture of the marine microalga Nannochloropsis gaditana under practical conditions. The results from both methods were similar, confirming that the BSA test predicts microalgal biofouling on surfaces exposed to microalgae cultures whose cells secrete macromolecules, such as proteins, with a high capacity for forming a conditioning film before cell adhesion. The hydrogel‐based coating showed significantly reduced BSA and N. gaditana adhesion, whereas the other surfaces failed to control biofouling. Microalgal biofouling was associated with an increased concentration of sticky extracellular proteins at low N/P ratios (below 15).
We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present ...an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift afterglows. The results of a former study, which showed that GRB afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.
In this paper the utilization of the cyanobacteria Anabaena sp. in carbon dioxide removal processes is evaluated. For this, continuous cultures of this strain were performed at different dilution ...rates; alternatives for the recovery of the organic matter produced being also studied. A maximum CO₂ fixation rate of 1.45g CO₂ L⁻¹ day⁻¹ was measured experimentally, but it can be increased up to 3.0g CO₂ L⁻¹ day⁻¹ outdoors. The CO₂ is mainly transformed into exopolysaccharides, biomass representing one third of the total organic matter produced. Organic matter can be recovered by sedimentation with efficiencies higher than 90%, the velocity of sedimentation being 2·10⁻⁴ s⁻¹. The major compounds were carbohydrates and proteins with productivities of 0.70 and 0.12gL⁻¹ day⁻¹, respectively. The behaviour of the cultures of Anabaena sp. has been modelized, also the characteristics parameters requested to design separation units being reported. Finally, to valorizate the organic matter as biofertilizers and biofuels is proposed.
Tourism has complex relationships with weather and climate, and there is consensus that tourism could be substantially affected by climatic change. While considerable research has been presented on ...how climatic change is likely to affect destinations and tourism stakeholders in the future, there remains limited understanding of the weather preferences of tourists. This is a research priority if the implications of climatic change for the temporal and geographic patterns of tourism demand are to be assessed with more relevance. This paper presents the results of a survey (
n
= 1643 respondents) of the weather preferences of French tourists. Results show the ranking of weather and climate as a factor of destination choice and satisfaction. They also indicate the high tolerance of tourists to heat and even to heat waves, whereas rainy conditions appear to be clearly repulsive. The weight of precipitation in indices like the Tourism Comfort Index should therefore be upgraded. The findings are also compared with studies in other countries. Slight differences in similar surveys can lead to a discrepancy in the appreciation of excessive heat and associated thresholds by 2–3 °C, which might limit the possibility to base climate change impact assessment on such fragile data.
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