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Implementation of outdoor photobioreactors has been challenged by an extremely oversaturated daily peak of solar irradiance. This study aims to understand the role of column size and paranet shading as well as to investigate the most convenient light control in outdoor cyanobacterial culture. The photobioreactor (PBR) consisted of plastic columns with a diameter of 12.74 cm (PBRd-20) and 31.85 cm (PBRd-50) laid outdoors and inclined at 158.22° upwards against solar radiation, while paranet shading was provided at 0%, 50%, 70%, and 90% shading capacity. A semi-continuous culture of cyanobacterium Arthrospira (Spirulina) platensis was conducted for 6 weeks with weekly monitoring of the growth parameter as well as the proximate and pigments content, while the daily irradiance and culture maximum temperature were recorded. The result shows that the column diameter of 12.74 cm had a lethal risk of 44.7% and this decreased to 10.5% by widening the column diameter to 31.85 cm. This lethal risk can be eliminated by the application of a paranet at a 50% reduction level for the column diameter of 31.85 cm and a 70% reduction level for the column diameter of 12.74 cm. The highest culture productivity of 149.03 mg/(L·day) was achieved with a PBRd-20 with 50% shading treatment, but a PBRd-50 with 90% shading treatment led to an increase in the protein and phycocyanin content by 66.7% and 14.91%, respectively. [ABSTRACT FROM AUTHOR]

Seaweed aquaculture is affected by natural and anthropogenic stressors, which put the biomass productivity of the cultures at risk. Seaweed biomass for commercial purposes, principally in pharmaceutical and/or nutraceutical applications, needs to be free of pollutants; therefore, controlled cultures have relevance in regulating the quality of biomass. The aim of this work was to demonstrate the successful utilization of controlled outdoor cultures to remove excess heavy metal accumulation in Gracilaria chilensis, an important commercial seaweed farming model. Specifically, we designed a simple and operational heavy metal depuration protocol, utilizing seawater and tap water removal, which permitted the concentration reduction of 10 heavy metals, including As, Cu, and Cd but not Zn, from the biomass at 7 days of culture. The percentage of depuration of the heavy metals ranged from 32 to 92% at 7 days, which was maintained throughout 21 days of culture. During the culture period, the monitored physicochemical parameters (temperature, salinity, and dissolved oxygen, among others) remained stable, with an increase in the daily growth rate (DGR% d−1) of the biomass recorded after 14 days of culture. Consequently, the experimental setup was successful for heavy metal depuration, which highlights the importance of controlled outdoor cultures as important tools of sustainability. [ABSTRACT FROM AUTHOR]

Botryococcus braunii CCAP 807/2 has been studied intensively for biofuel production due to its high hydrocarbon content. This strain is also capable of producing high value carotenoids. The aim of the study was to analyse the carotenoid production of B.braunii 807/2 under different growing conditions, first, by using different media and light intensities in indoors, and next, to examine the carotenoid composition between green, intermediately pigmented and red B. braunii grown in indoors and outdoors. The alga was cultured indoors under two different light intensities (100 and 500 μmol photons m−2 s−1) using three different media: a control with complete modified CHU 13 medium, modified CHU 13 without N and modified CHU13 without N + 2Fe. All cultures were grown at 25 °C with 12:12 h light:dark cycle and were mixed with magnetic stirrers. For the determination of carotenoid composition at different stages, the green, intermediately pigmented and red cells were collected from indoor and outdoor cultures and analysed for their carotenoid composition using HPLC. The cultures grown at high light intensity reached the highest biomass yield at 0.6 g L−1 on day 16, whereas their counterparts at low light intensity took 30 days to reach the same biomass yield. The carotenoid production of B. braunii 807/2 at high light intensity increased up to twofold in 2 days compared to the ones grown at low light. Botryococcus braunii 807/2 accumulates lutein, canthaxanthin and astaxanthin and β,β-carotene as the main carotenoids. Whilst lutein was the major carotenoids of the green/intermediate cells, canthaxanthin and astaxanthin were the predominant carotenoids of the red cells under indoor and outdoor culture, respectively. This study suggests that Botryococcus braunii 807/2 is a potential candidate for the production of lutein and/or astaxanthin. It accumulates a high amount of lutein when grown under optimum conditions and a high amount of astaxanthin when grown under sub-optimum conditions outdoors. [ABSTRACT FROM AUTHOR]

Seaweed aquaculture is affected by natural and anthropogenic stressors, which put the biomass productivity of the cultures at risk. Seaweed biomass for commercial purposes, principally in pharmaceutical and/or nutraceutical applications, needs to be free of pollutants; therefore, controlled cultures have relevance in regulating the quality of biomass. The aim of this work was to demonstrate the successful utilization of controlled outdoor cultures to remove excess heavy metal accumulation in Gracilaria chilensis, an important commercial seaweed farming model. Specifically, we designed a simple and operational heavy metal depuration protocol, utilizing seawater and tap water removal, which permitted the concentration reduction of 10 heavy metals, including As, Cu, and Cd but not Zn, from the biomass at 7 days of culture. The percentage of depuration of the heavy metals ranged from 32 to 92% at 7 days, which was maintained throughout 21 days of culture. During the culture period, the monitored physicochemical parameters (temperature, salinity, and dissolved oxygen, among others) remained stable, with an increase in the daily growth rate (DGR% d−1) of the biomass recorded after 14 days of culture. Consequently, the experimental setup was successful for heavy metal depuration, which highlights the importance of controlled outdoor cultures as important tools of sustainability.

This study aimed to evaluate the influence of a magnetic field (MF) intensity of 25 mT on Chlorella fusca cultivation in outdoor and indoor conditions, and evaluate the changes in the macromolecules, pigment content and protein profile. C. fusca was cultivated for 15 d in raceway photobioreactor. MF was applied for 24 h d−1 and 1 h d−1. In outdoor cultivation, MF applied for 24 h d−1 increased 23% in the biomass concentration, while indoor assays resulted in an increase in both modes, with biomass production increasing between 70 and 85%. Biomass composition was altered when MF was applied for 1 h d−1 in indoor assays; the highest protein content was achieved (32.7%). Nitrate consumption was higher in outdoor assays, while MF application did not alter the protein profile. The results showed that combining the outdoor conditions with MF is advantageous, as higher biomass concentration can be achieved with lower energy expenditure. [ABSTRACT FROM AUTHOR]

BACKGROUND: Recently, wastewater effluents from animal farms have been treated using microalgae for the removal of organic and inorganic compounds. Swine wastewater (SW) and wastewater treated by anaerobic digestion (TW) were used as culture media for a wild strain of microalga, Chlorella sp. (Chlorophyta), previously isolated for our research group. This was cultivated under laboratory conditions in a batch culture, and then inoculated in a cascade thin‐layer reactor under outdoor conditions. The kinetic behavior, nutrient removal (COD, NH4+‐N, NO3−‐N and PO34−‐P) efficiency and biochemical composition of the microalga biomass were evaluated. RESULTS: SW supported the highest growth (339 × 106 cells mL−1 and μ = 0.42 d−1) and the maximal removal of COD (91%), nitrates (87%), ammonium (45%) and phosphate (70%) in a batch culture. Whereas, in continuous cultivation, an adequate operation was achieved at temperatures up to 42 °C, with removals greater than 80% of COD, 70% of nitrates, 90% of ammonium and 60% of phosphates. Also, the produced biomass achieved the highest content of proteins (386 mg g−1 dry weight), carbohydrates (291.49 mg g−1 dry weight) and saturated and monounsaturated fatty acids, reaching 74.76% of total fatty acids. CONCLUSIONS: The SW medium showed greater growth of Chlorella than TW using the outdoor thin‐layer cascade reactor. This is an opportunity to use wastewater as nutrient to obtain biomass enriched in compounds with various possibilities for application. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In the present study, the mass production of the rotifer species Brachionus plicatilis was evaluated using closed outdoor algae culture systems in 450- and 1000-L polyethylene bags fed with the microalgae Nannochloropsis gaditana and supplemented with probiotic bacteria Pseudoalteromonas sp. (SLP1). These bacteria were previously isolated from the digestive tract of the commercially important fish Yellowtail kingfish (Seriola lalandi, Family: Carangidae) and their stimulatory activity on growth in the microalga N. gaditana was verified. In each treatment, a significantly greater production of organisms (P < 0.05) was shown when fed with the microalgae and supplemented with beneficial bacteria over 9 days compared to control treatments without the addition of beneficial bacteria. Using denaturing gradient gel rlectrophoresis analysis (DGGE), the permanence of the SPL1 bacteria was demonstrated in a B. plicatilis culture in a 1000-L outdoor system when they were incorporated into the diet. With these results, it is shown that the use of this microalgae-bacteria mixture is feasible to improve rotifer production in outdoor batch culture systems. This is a potential input vector for beneficial bacteria as well as nutritional elements into the digestive tract of larval and juvenile stages of fish of economic importance, especially S. lalandi. [ABSTRACT FROM AUTHOR]

Various configurations and modes of airlift photobioreactors were examined in the cultivation of Chaetoceros gracilis. Internal loop and external loop airlifts were cultivated in a batch mode in a controlled indoor environment. The external loop system provided a better performance than the internal loop system due to better light exposure. A continuous operation was conducted in an internal loop airlift photobioreactors-inseri es. This was designed to minimise the effect of light blocking due to overgrown cells as the high-density culture was, in this configuration, only limited to the last airlift column in the series. Outdoor large-scale operation was conducted in a flat-panel airlift photobioreactor. Due to uneven light availability, the outdoor culture could not perform as well as the indoor one in terms of growth rate. Among the four systems investigated, the continuous culture in airlift photobioreactors-in-series provided the best performance with the highest cell density of 12.12 × 106 cells mL-1. Cost analysis based on the maximum number of reactors that can be installed in one square metre indicates that the indoor system requires lowest operating cost per unit cultivation area, whereas the outdoor system provides highest profit as a result of the inherited large productivity.

This work is the last of a series of three papers. The previous ones were performed in tubular photobioreactors and raceways. In the present work, the outdoor continuous production of Nannochloropsis gaditana in flat-panel reactors is studied over a two-year period, analysing the influence of the dilution rate imposed in addition to the nitrate and phosphate supplied. Maximum biomass and lipid yields of 0.19 g/l day and 38.0 mg/l day were obtained when operating at a dilution rate of 0.35 1/day and concentrations of 10.0 mM NO 3 − and 0.8 mM PO 4 3 − in the culture medium. By decreasing the specific nitrate input (below 2 mmol N/g day), and exposing the culture to moderate light availability and temperature, the volumetric productivity of saturated and monounsaturated fatty acids increased to 10.0 mg/l day. The specific nitrate input, together with other important parameters such as the average irradiance, temperature and dilution rate were used to develop a model describing this species' behaviour. The model is a powerful tool for further improvement and scaling-up of this technology. [ABSTRACT FROM AUTHOR]

Diatoms are very diverse and highly productive organisms, found in a wide variety of environments. This study aims to analyze the growth and lipid composition of Phaeodactylum tricornutum, cultured in an outdoor pilot-scale bubble column photobioreactor under natural conditions in Chile for biodiesel production. Results showed that P. tricornutum cultures reached their highest biomass concentration (0.96 ± 0.04 kg m−3) after 14 days of culturing, at the stationary phase, with a volumetric productivity of 0.13 kg m−3 d−1. Biomass samples showed a total lipid content of 9.08 ± 0.38 wt %. The fatty acid methyl ester analysis revealed a composition of 24.39% C16-C18 fatty acids, 42.34% saturated fatty acids, 21.91% monounsaturated fatty acids and 31.41% polyunsaturated fatty acids. These findings suggest that P. tricornutum oil can be used as an alternative raw material for the production of biodiesel capable of meeting international quality standards.

Microalgae are considered to be efficient bio-resources for biofuels and bio-based chemicals because they generally have high productivity. The filamentous cyanobacterium Arthrospira ( Spirulina) platensis has been widely used for food, feed, and nutrient supplements and is usually cultivated in open ponds. In order to extend the surface area for growing this alga, we designed a pilot-scale floating closed culture system for cultivating A. platensis on open water and compared the growth and quality of the alga harvested at both subtropical and temperate regions. The biomass productivity of A. platensis NIES-39 was ca. 9 g dry biomass m day in summer at Awaji Island (warm temperature region) and ca. 10 and 6 g dry biomass m day in autumn and winter, respectively, at Ishigaki Island, (subtropical region) in Japan. If seawater can be used for culture media, culture cost can be reduced; therefore, we examined the influence of seawater salt concentrations on the growth of A. platensis NIES-39. Growth rates of A. platensis NIES-39 in diluted seawater with enrichment of 2.5 g L NaNO3, 0.01 g L FeSO·7HO, and 0.08 g L NaEDTA were considerably lower than SOT medium, but the biomass productivity (dry weight) was comparable to SOT medium. This is explained by the heavier cell weight of the alga grown in modified seawater media compared to the alga grown in SOT medium. Furthermore, A. platensis grown in modified seawater-based medium exhibited self-flocculation and had more loosely coiled trichomes. [ABSTRACT FROM AUTHOR]

In the present work, a study on the performance, culture parameters and modeling of the growth and lipid productivity of Nannochloropsis gaditana in outdoor pilot-scale raceway ponds is made. During the experiments, modifications to the dilution rate and nutrient supply were performed, with maximum productivities of 0.19 g BIOMASS /l day and 30.4 mg LIPIDS /l day obtained at 0.30–0.36 1/day and 10.5 mM NO 3 − . The impact of average irradiance within the culture (in the range of 280–350 μE/m 2 s) and the specific nitrate input (SNI, below 0.4 mmol N/g day) was correlated with an enhancement of saturated and monounsaturated fatty acid contents, which attained maximum values of 29.5% and 33.0% of total FAs, respectively. The modeling of growth, lipid and fatty acid production rates was developed taking into account the irradiance, dilution rate and SNI, which might prove useful in the scaling-up of raceway ponds with this species. [ABSTRACT FROM AUTHOR]

The industrial use of microalgae as bulk commodities relies on large scale and economical production. We recently reported a flat, open and shallow (FOS) culture method. In the present study, microalgae (Chlorella sorokiniana) were cultivated in various modes to evaluate key parameters and assess biomass and productivity. Using batch mode with 1-5 cm culture depth, the highest volumetric and areal productivity were 0.37 g L−1 d−1 and 9.08 g m−2 d−1, respectively. Using fed-batch mode, the microalgae density reached 6.40 g L−1. The yield remained stable after the microalgae were harvested 11 times in the semi-continuous mode. The system was then upgraded and scaled up to 4000 L for outdoor experiments in autumn, spring and summer, and the productivities were 6.80, 7.20 and 7.60 g m−2 d−1, respectively. Technoeconomic analysis showed that compared with open pond systems, this method is more efficient in terms of investment, water, electricity and operation, thus having great potential for deployment on non-arable land for massive algal production. [Display omitted] • A flat, open and shallow (FOS) microalgal culture method was developed and upgraded. • Under batch mode with 5 cm broth depth, the highest productivity was 9.08 g/m2/d. • The yield under fed-batch reached 6.40 g L−1 and semi-continuous culture was feasible. • In 4000 L outdoor culture experiments, the highest productivity was 7.60 g/m2/d. • The FOS system is efficient in terms of investment, water, electricity and operation. [ABSTRACT FROM AUTHOR]

The extent of biological CO 2 fixation was evaluated for outdoor cultures of the cyanobacterium Anabaena sp. ATCC 33047. Culture conditions were optimized indoors in bubble-column photochemostats operating in continuous mode, subjected to irradiance cycles mimicking the light regime outdoors. Highest values achieved for CO 2 fixation rate and biomass productivity were 1 and 0.6 g L −1 day −1 , respectively. The comparison among different reactors operating simultaneously – open pond, horizontal tubular reactor and vertical flat-panel – allowed to assess their relative efficiency for the outdoor development of Anabaena cultures. Despite the higher volumetric CO 2 fixation capacity (and biomass productivity) exhibited by the tubular photobioreactor, yield of the flat-panel reactor was 50% higher than that of the tubular option on a per area basis, reaching values over 35 g CO 2 fixed m −2 d −1 . The flat-panel reactor actually represents a most suitable system for CO 2 capture coupled to the generation of valuable biomass by Anabaena cultures. [ABSTRACT FROM AUTHOR]

This work studied outdoor pilot scale production of Nannochloropsis gaditana in tubular photobioreactors. The growth and biomass composition of the strain were studied under different culture strategies: continuous-mode (varying nutrient supply and dilution rate) and two-stage cultures aiming lipid enhancement. Besides, parameters such as irradiance, specific nitrate input and dilution rate were used to obtain models predicting growth, lipid and fatty acids production rates. The range of optimum dilution rate was 0.31–0.35 1/day with maximum biomass, lipid and fatty acids productivities of 590, 110 and 66.8 mg/l day, respectively. Nitrate limitation led to an increase in lipid and fatty acids contents (from 20.5% to 38.0% and from 16.9% to 23.5%, respectively). Two-stage culture strategy provided similar fatty acids productivities (56.4 mg/l day) but the neutral lipids content was doubled. [ABSTRACT FROM AUTHOR]

Various configurations and modes of airlift photobioreactors were examined in the cultivation of Chaetoceros gracilis. Internal loop and external loop airlifts were cultivated in a batch mode in a controlled indoor environment. The external loop system provided a better performance than the internal loop system due to better light exposure. A continuous operation was conducted in an internal loop airlift photobioreactors-inseries. This was designed to minimise the effect of light blocking due to overgrown cells as the high-density culture was, in this configuration, only limited to the last airlift column in the series. Outdoor large-scale operation was conducted in a flat-panel airlift photobioreactor. Due to uneven light availability, the outdoor culture could not perform as well as the indoor one in terms of growth rate. Among the four systems investigated, the continuous culture in airlift photobioreactors-in-series provided the best performance with the highest cell density of 12.12 × 106 cells mL-1. Cost analysis based on the maximum number of reactors that can be installed in one square metre indicates that the indoor system requires lowest operating cost per unit cultivation area, whereas the outdoor system provides highest profit as a result of the inherited large productivity. [ABSTRACT FROM AUTHOR]

Nitrogen availability and cell density each affects growth and cellular astaxanthin content of Haematococcus pluvialis, but possible combined effects of these two factors on the content and productivity of astaxanthin, especially under outdoor culture conditions, is less understood. In this study, the effects of the initial biomass densities IBDs of 0.1, 0.5, 0.8, 1.5, 2.7, 3.5, and 5.0 g L-1 DW and initial nitrogen concentrations of 0, 4.4, 8.8, and 17.6 mM nitrate on growth and cellular astaxanthin content of H. pluvialis Flotow K-0084 were investigated in outdoor glass column photobioreactors in a batch culture mode. A low IBD of 0.1 g L-1 DW led to photo-bleaching of the culture within 1-2 days. When the IBD was 0.5 g L-1 and above, the rate at which the increase in biomass density and the astaxanthin content on a per cell basis was higher at lower IBD. When the IBD was optimal (i.e., 0.8 g L-1), the maximum astaxanthin content of 3.8% of DW was obtained in the absence of nitrogen, whereas the maximum astaxanthin productivity of 16.0 mg L-1 d-1 was obtained in the same IBD culture containing 4.4 mM nitrogen. The strategies for achieving maximum Haematococcus biomass productivity and for maximum cellular astaxanthin content are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Process variables contributing to describe the growth of Spirulina platensis in outdoor cultures were evaluated. Mathematical models of the process using inputs which were simple and easy to collect in any operating plant were developed. Multiple linear regression (MLR) and artificial neural network (ANN) modelling procedures were evaluated. The dataset contributing to the growth prediction model were biomass concentration, nitrate concentration, pH and dissolved oxygen concentration of culture fluid, light intensity and days in culture, measured once a day. Datasets of 12days were sufficient to develop a model to predict the succeeding day’s biomass concentration with a coefficient of determination of greater than 0.98 under outdoor growth conditions. Insufficient number of datasets resulted in overestimation of the predicted output value. [Copyright &y& Elsevier]

To evaluate the potential of the green agla Chlorella zofingiensis as a feedstock for biodiesel production, the effects of nitrogen and phosphate on lipid accumulation and growth of C. zofingiensis were studied. The maximum specific growth rate (μ max) reached 2.15 day−1 when the concentration of NaNO3 and K2HPO4·3H2O was 1.0 g L−1 and 0.01 g L−1, respectively. The lipid contents of C. zofingiensis grown in media deficient of nitrogen (65.1%) or phosphate (44.7%) were both higher than that obtained from cells grown in full medium (33.5%). The highest lipid productivity (87.1 mg L−1 day−1) was also obtained from cells grown in nitrogen deficient media, indicating nitrogen deficiency was more effective than phosphate deficiency for inducing lipid accumulation in C. zofingiensis. In addition, the feasibility of cultivating the alga in 60 L flat plate photobioreactors and 10 L bottles outdoors for biodiesel was also tested. It was found that C. zofingiensis could adapt to fluctuating temperatures and irradiance of outdoors and the highest μ max and lipid productivity could reach 0.362 day−1 and 26.6 mg L−1 day− 1 outdoors, respectively. The lipid production potential of C. zofingiensis is projected to be 31.1 kg ha−1 day−1 in outdoor culture. These results suggested that C. zofingiensis is a promising organism for feedstock production of biofuel and can be used in scaled up culture outdoors. [ABSTRACT FROM AUTHOR]

Abstract: The BOT-22 strain of Botryococcus braunii was cultured under laboratory and outdoor conditions. Medium K was developed, which decreased the cost of medium preparation to 1/30th. A polycarbonate bottle (10 L) was replaced with a polyethylene bag for cost effectiveness. Addition of nitrogen substantially increased biomass of the strain; however, the hydrocarbon content remained unchanged. Growth rates of >10 L scale cultures were much lower than those of <200mL scale flask cultures. BOT-22 grew well in outdoor cultures despite extensive fluctuations in temperature and light conditions during the day from autumn to early winter and at spring. Maximum growth rates obtained using a tube bioreactor were two times higher than those obtained using 10L/30L scale cultures and a dome bioreactor. Thus, the tube bioreactor was more efficient for utilizing the light required for photosynthesis by this strain. [Copyright &y& Elsevier]

Abstract: Culturing microalgae using natural sunlight is an effective way to reduce the cost of microalgae-based biodiesel production. In order to evaluate the feasibility of culturing Chlorella zofingiensis outdoors for biodiesel production, effects of nitrogen limitation and initial cell concentration on growth and lipid accumulation of this alga were investigated in 60L flat plate photobioreactors outdoors. The highest μ max and biomass productivity obtained was 0.994day−1 and 58.4mgL−1 day−1, respectively. The lipid content was much higher (54.5% of dry weight) under nitrogen limiting condition than under nitrogen sufficient condition (27.3%). With the increasing initial cell concentrations, the lipid contents declined, while lipid concentrations and productivities increased. The highest lipid content, lipid concentration, and lipid productivity obtained was 54.5%, 536mgL−1 and 22.3mgL−1 day−1, respectively. This study demonstrated that it was possible to culture C. zofingiensis under outdoor conditions for producing biodiesel feedstock. [Copyright &y& Elsevier]

Abstract: The effect of operation regime and culture system on carotenoid productivity by the halotolerant alga Dunaliella salina has been analyzed. Operation strategies tested included batch and semi continuous regime, as well as a two-stage approach run simultaneously in both, open tanks and closed reactor. The best results were obtained with the closed tubular photobioreactor. The highest carotenoid production (328.8mgcarotenoidl−1 culture per month) was achieved with this culture system operated following the two-stage strategy. Also, closed tubular photobioreactor provided the highest carotenoid contents (10% of dry weight) in Dunaliella biomass and β-carotene abundance (90% of total carotenoids) as well as the highest 9-cis to all-trans β-carotene isomer ratio (1.5 at sunrise). [ABSTRACT FROM AUTHOR]

The growth performance of the chlorophycean microalga Muriellopsis sp. outdoors in open tanks agitated with a paddlewheel and its ability to accumulate carotenoids have been evaluated throughout the year. The cells grown in the open system had free lutein as the main carotenoid, with violaxanthin, β-carotene, and neoxanthin also present. Lutein content of the dry biomass ranged from 0.4 to 0.6%, depending on the growth and environmental conditions. In addition, the biomass of Muriellopsis sp. had a high content in both protein and lipids with about half of the fatty acids being of the polyunsaturated type, with α-linolenic acid accounting for almost 30% of the total fatty acids. The effect of determinant parameters on the performance of the cultures in open tanks was evaluated. Operating conditions that allow the maintenance of productive cultures were established under semicontinuous regime for 9 months throughout the year. Biomass and lutein yields in the open system were not far from those in closed tubular photobioreactors, and reached productivity values of 20 g dry biomass, containing around 100 mg lutein m−2 day−1 in summer. The outdoor culture of Muriellopsis sp. in open ponds thus represents a real alternative to established systems for the production of lutein. [ABSTRACT FROM AUTHOR]

Abstract: Performance of Dunaliella salina cultures outdoors in a closed tubular photobioreactor has been assessed. Optimization of conditions involved verification of the effect of several determining factors on the yield of both biomass and carotenoids. Maximal biomass productivity (over 2g (dry weight) m−2 d−1 or 80gm−3 d−1) was achieved at 38cms−1, flow rate; 2 × 109 cellsl−1, initial population density; 25°C, temperature; semi-continuous regime, keeping a cell density interval between 2 × 109 and over 4 × 109 cellsl−1. Coverage of the tubular loop with a sunshade screen to avoid light-induced damage of cells was essential to maintain growth performance. The cellular β-carotene level increased significantly during the light period, as also did that of lutein. The rise in the β-carotene level could be accounted by the 9-cis-isomer, with all-trans-β-carotene remaining steady during the light period. By sunset, the ratio between 9-cis- and all-trans-isomers of β-carotene amounted to 1.5, with over 60% of total β-carotene corresponding to the 9-cis-isomer. Removal of sunshade enhanced carotenoid accumulation by cells to reach up to 10% of dry biomass. Cultivation of Dunaliella in closed tubular photobioreactor, thus represents a suitable approach for the production of a high-quality microalgal biomass enriched in the valuable 9-cis-isomer of β-carotene and lutein. [Copyright &y& Elsevier]

The optimization of the operation, under the climatic conditions of southern Spain, of an experimental plant for β-carotene production by Dunaliella has been pursued. The effects of mixing, culture depth, cell density and dilution cycles on β-carotene and biomass productivity were studied under a semicontinuous culture regime in open tanks outdoors. Using 3 m2-surface containers, the highest productivity values, for both β-carotene and biomass, were recorded with a flow rate of 0.55 m s−1; 10 cm depth; 0.7 − 0.9 × 106cell ml−1, population density; and dilution cycles of two days. An average annual productivity of 1.65 g (dry wt) m−2 d−1 was estimated for Dunaliella biomass, being that for β-carotene of about 0.1 g m−2 d−1. Under these optimized conditions, experiments have been carried out at the Cadiz Bay with 20 m2-surface tanks during a whole-year cycle. The results obtained have validated this location and the operating conditions established as being most appropriate for efficient mass production of β-carotene rich D. salina. [ABSTRACT FROM AUTHOR]

Purple clams (Hiatula rostrata Lighttoot) accumulate paralytic shellfish poisoning (PSP) toxins produced by a toxic strain of the dinoflagellate Alexandrium minutum Halim. The results confirm the data of our previous study concerning the muscle and siphon that were not showing a gradual rise in toxicity when shellfish accumulated more A. minutum. However, muscle and siphon are intermittently toxic both in exposure and depuration period in laboratory cultured purple clams. PSP toxins were detected in outdoor cultured purple clams, whereas no A. minutum were found in the culture pond during most of the survey time. The outdoor cultured purple clams need longer time to decrease toxicity to allowable levels than laboratory cultured purple clams. It was shown that laboratory data may not predict times over which pond-cultured purple clams may prove toxic to consumers. [Copyright &y& Elsevier]

A vertical flat-plate photobioreactor was developed for the outdoor culture of microalgae using sunlight as the light source. The ability for biomass production and CO2 fixation was evaluated by using a cyanobacterium, Synechocystis aquatilis SI-2. The average areal productivity was 31 g biomass m-2 d-1, which corresponded to a CO2 fixation rate of 51 g CO2 m-2 d-1, sustainable in the northern region of Japan during the winter time (January and February). The relationships between the efficiency of solar energy utilization of the reactor and its effect factors (cell concentration and irradiation) were investigated. [ABSTRACT FROM AUTHOR]

Cells of Chlorella regularis (Artan) Oltmanns (S-50) were grown under solar radiation in Tokyo, using a newly constructed outdoor culture system. The maximum specific growth rate (log, unit h-1) was about 0.3. which was a little lower than the highest value reported using artificial light in the laboratory. The near ultraviolet light, consisting mostly of UV-A, inhibited the growth from 10 to 40% in summer mornings: the inhibition was not significant in the afternoon. The percentage inhibition was correlated with the total dose of the ultraviolet radiation. [ABSTRACT FROM AUTHOR]

Chlorella zofingiensis was grown in semi-continuous culture in an outdoor enclosed tubular photobioreactor. At the quasi-steady state, the response of the culture to changes in photosynthetically active radiance (PAR) was studied by following closely the dissolved O2 concentration,biomass concentration and the carbohydrate and protein content of the biomass. Generally, O2 production and the output of carbon and nitrogen of the biomass showed a linear correlation with incident PAR, suggesting that the cultures were light-limited. Photoinhibition was not observed in high light adapted cultures (on a sunny day), but was observed in shade adapted cultures(cloudy days) when there was a sudden four-fold increase in PAR. The output rate of biomass nitrogen observed on sunny days was, however, lower than that measured on cloudy days. On sunny days, a rapid increase in the C/N ratio of the biomass was seen. We attribute the increase in C/N ratio on sunny days to a slower response of protein synthesis to big increases in PAR, compared to carbohydrate synthesis. The possible influence of this C and N response pattern on the productivity of outdoor algal cultures is discussed. [ABSTRACT FROM AUTHOR]