No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Effects of carbon dioxide feeding rate and light intensity on the fed-batch pulse-feeding cultivation of Spirulina platensis in helical photobioreactor
Abstract
The behavior of S. platensis was investigated in this study through fed-batch pulse-feeding cultures performed at different carbon dioxide feeding rates (F = 0.44–1.03 g L−1 d−1) and photosynthetic photon flux density (PPFD = 80–250 μmol photons m−2 s−1) in a bench-scale helical photobioreactor. To achieve this purpose, an inorganic medium lacking the carbon source was enriched by gaseous carbon dioxide from a cylinder. The maximum cell concentration achieved was 12.8 g L−1 at PPFD = 166 μmol photons m−2 s−1 and F = 0.44 g L−1 d−1 of CO2. At PPFD = 80 and 125 μmol photons m−2 s−1, the carbon utilization efficiency (CUE) reached maximum values of 50 and 69%, respectively, after about 20 days, and then it decreased, thus highlighting a photolimitation effect. At PPFD = 166 μmol photons m−2 s−1, CUE was ≥90% between 20 and 50 days. The photosynthetic efficiency reached its maximum value (9.4%) at PPFD = 125 μmol photons m−2 s−1. The photoinhibition threshold appeared to strongly depend on the feeding rate: at high PPFD, an increase in the amount of fed CO2 delayed the inhibitory effect on biomass growth, whereas at low PPFD, excess CO2 addition caused the microalga to stop growing.
... In all of the above-mentioned studies, high concentrations of CO 2 have been examined. Industrial flue gas has high concentrations of CO 2 (4-14% v/v or more) along with toxic gases such as SO 2 , NO x , and heavy metals with high temperatures [25,26]. High concentrations of CO 2 inhibit the growth of microalgae [27]. ...
... Spirulina cultivation was performed by air injection in two neutral and alkaline medium separately. Initial pH of the growth medium was adjusted to 9.5 by adding a few milliliter of NaOH 1.0N [26]. Concentration of algal biomass at the beginning of each test run was 20 mg/L. ...
... Air was injected in control photo-bioreactor. Light exposure with the intensity of 10 Klux was in intermittent (14 h on / 10 h off) and continuous mode [26]. Flow rate of combustion gas into the photo-bioreactor was set at 1.5 L/min. ...
Introduction: Global warming and the need to reduce greenhouse gas emissions from various emission sectors are not hidden from anyone. The aim of this study was to determine Carbon dioxide (CO2)capture
from combustion gases of methane for cultivation of microalgae spirulina platensis.
Materials and methods: Microalgae culture medium was added in two photobioreactor. Air and combustion gas was injected into control and test reactors respectively. Artificial light with 10 Klux intensity was used and
operated in continuous and intermittent (14 h ON and 8 h OFF) modes. Inlet concentration of carbon dioxide in to the test photobiorector was set in the range of 2000 to 6000 ppm and was measured in the inlet and outlet of
photo-bioreactor by ND-IR CO2 analyzer.
Results: In the control photo-bioreactor, the average removal of CO2 from the air was 42%. In the test reactor with an inlet CO2 concentration of 4100 ppm, the average removal of CO2 from the combustion gas was 23%. After 9 days of cultivation, the amount of carbon dioxide stabilized by microalgae was 0.528 and 1.14 g/L (dry weight) in the control and experimental photobioreactors respectively. The CO2 bio-fixation rate was in the range of 2.2% and 4.0% at different runs. After 9.0 days of cultivation concentration of microalgae was 0.25 and 1.0 g/L in the control and test reactors respectively. Algae productivity with intermittent light was 35% less than continuous light exposure.
Conclusion: It is possible to use CO2 capture from combustion gases of commercial heater for cultivation of microalgae spirulina.
... Environmental factors such as light intensity and photoperiod are essential for microalgal growth, however, their impact on growth is species-specific and depends on the product examined (Chen and Chen 2006;Engin et al. 2018). Some microalgae perform well under low light intensity such as T. suecica (Grabowski 2017), whereas the growth of some other microalgae such as Spirulina platensis is inhibited under high light intensity (Soletto et al. 2008). However, the light inhibitory effect in microalgal species can be overcome by the addition of organic carbon substrate (Alkhamis and Qin 2013). ...
... Microalgal species able to grow under mixotrophy normally require a low light but can tolerate high light photoinhibition (Soletto et al. 2008;Grabowski 2017). In this study, dry weight biomass and optical density of P. lutheri were significantly affected by the intensity of light. ...
... Ogawa and Aiba (1981) observed a photoinhibition of Scenedesmus acutus and C. vulgaris under mixotrophy at a light intensity of > 80 μmol photons m −2 s −1 . In contrast, S. platensis showed an enhanced growth rate at high light intensity and no photoinhibition was detected in mixotrophy; however, the growth was inhibited in phototrophy with the increase in light intensity (Soletto et al. 2008;Alkhamis and Qin 2013). The present study demonstrates that in mixotrophic cultures high light intensity may result in photoinhibition of P. lutheri, however, high cell density can be attained by culturing P. lutheri mixotrophically at a moderate light, which can even reduce production cost. ...
The present study aimed to investigate the effects of organic carbon sources, cultivation methods, and environmental factors on growth and lipid content of Pavlova lutheri for biodiesel production. In the 250-mL flask bioreactors, P. lutheri was cultivated in the modified artificial seawater (ASW) medium containing glucose, glycerol, sodium acetate, or sucrose as an organic carbon substrate. The effects of different growth conditions (phototrophic, mixotrophic, and heterotrophic) and environmental factors such as photoperiod, light intensity, and salinity were evaluated. Growth of P. lutheri was inhibited under heterotrophy but was enhanced in mixotrophy as compared to phototrophy. Biomass and lipid content of P. lutheri were significantly (p < 0.05) affected by changing photoperiod, light intensity, and salinity. Higher biomass concentration and lipid content were observed at a light intensity of 100 ± 2 μmol photons m⁻² s⁻¹, 18 h photoperiod, and 30% salinity, in a modified ASW medium supplemented with 10 mmol sucrose. An increase in biomass concentration from 320 ± 25.53 to 1106 ± 18.52 mg L⁻¹ and high lipid content of 31.11 ± 1.65% (w/w) were observed with the optimized culture conditions, demonstrating a significant (p < 0.05) enhancement in biomass and lipid content due to the improved culture conditions. The present study emphasizes the possible use of sucrose for biomass and lipid production with P. lutheri under the optimized culture conditions. Using low-cost and relatively easy accessible feedstock such as sucrose would be a valuable alternative for growing microalgae with enhanced lipid content.
... El problema de acumulación de oxígeno aumenta cuando un fotobiorreactor tubular helicoidal sufre escalamiento en el sistema de iluminación. Por lo tanto, es necesario tener una unidad separada de desgasificación, en muchas oportunidades esta unidad puede estar acoplado con el sistema de inyección airlift (Soletto et al., 2008), ya que la inyección de gas desde el fondo del fotobiorreactor favorece el mezclado, suministra suficiente CO 2 y dependiendo de la altura del fotobiorreactor, se logra una eficiente remoción de oxígeno disuelto en el medio. La remoción de exceso de oxígeno es un problema de transferencia de masa parecido al de suministro de CO 2 , las principales formas de controlar este fenómeno son: Disminuir la presión de oxígeno, mayor agitación y altas temperaturas. ...
... Lograron resultados satisfactorios en el crecimiento de Spirulina platensis, con productividades de 0.40 g L -1 d -1 sin daños celulares. Soletto et al. (2008) evaluaron un fotobiorreactor helicoidal a escala de laboratorio con alimentación semicontinua en cultivo de Spirulina platensis bajo diferentes condiciones de intensidad de luz y velocidad de alimentación de CO 2 , para evitar la adición en exceso del CO 2 al comienzo del cultivo que podría causar una inhibición por saturación de sustrato. La óptima velocidad de alimentación de CO 2 para el crecimiento celular, se correlacionó con la intensidad de luz a la cual fue expuesta. ...
Las cianobactérias son organismos eficientes en la conversión de energía solar y producen una gran variedad de metabolitos. En la actualidad son el centro de atención para la producción de biocombustible, son usadas como biofertilizantes, control de contaminación ambiental y como fuente de nutrientes en alimentación humana y animal. Con el fin de proporcionar crecimiento y aprovechar el potencial de las cianobacterias, se requieren fotobiorreactores eficientes. Aunque se han propuesto muchos tipos de fotobiorreactores, no existe un reactor ideal, solo unos pocos pueden utilizarse para la producción de biomasa de cianobacterias. De hecho, la elección del fotobiorreactor más adecuado depende de la situación, ya que tanto las especies de algas disponibles y el destino final jugarán un papel importante. Uno de los principales factores que limita su aplicación práctica en cultivos de biomasa es la transferencia de masa. Por esto, entender el coeficiente de transferencia de masa en los fotobiorreactores es necesario para una operación eficiente del cultivo de biomasa en cianobacterias. En esta revisión, se discuten varios tipos de fotobiorreactores muy promisorios para la producción de biomasa de cianobacterias.
... Ce cas particulier montre que moins de 40 % du CO 2 est transmis aux algues. Il faut toutefois faire attention à ne pas injecter du dioxyde de carbone en excès, car une trop forte concentration peut inhiber les algues (Soletto et al. 2008). La littérature rapporte des optimums très variables entre 5 et 100 % de CO 2 dans le gaz (Olaizola 2003;Tang et al. 2011 De plus, cette inhibition est liée à la lumière fournie ; si le flux de photon est insuffisant, un ajout excédentaire de CO 2 sera plus délétère que si l'on soumet les algues à un fort flux de photon. ...
... Dans ces études, le pH est souvent non régulé. L'inhibition des algues par les forts ajouts de CO 2 pourrait donc être plutôt due à l'acidification du milieu selon Soletto et al. (2008) et Olaizola (2003. Hors, il est largement accepté que le CO 2 diffuse sans contrainte au travers de la membrane cellulaire (Amoroso et al. 1998 ;Badger and Price 2003 ;Giordano et al. 2005). ...
Les conditions de culture de microalgues autotrophes en système ouvert associant microalgues/bactéries ont été étudiées au cours de ce travail de thèse. L’objectif était de développer un procédé de valorisation des nutriments (N, P) contenus dans la phase liquide des digestats issus de méthanisation agricole. Dans un premier temps, une synthèse sur les filières de méthanisation suivi d’un état de l’art sur les microalgues et leurs conditions de culture ont permis de mettre en évidence les principaux paramètres d’influence spécifiques à l’influent étudié, tels que la coloration, et les interactions avec les processus de nitrification/dénitrification. Ainsi, dans le but de mieux comprendre les mécanismes et d’évaluer les impacts des paramètres principaux, un pilote de laboratoire composé de 6 réacteurs de 2,5 litres a été conçu et des analyses spécifiques ont été développées au laboratoire. A partir de ces outils, l’effet de la couleur et de la lumière sur la pénétration de la lumière et sur la croissance algale a été quantifié. L’impact positif de la lumière s’est révélé d’importance équivalente à l’impact négatif de la couleur sur la croissance. Au cours de la culture, la concentration en algues augmente jusqu’à rendre la pénétration de la lumière dans le milieu faible, exacerbant le poids de la lumière. Ensuite, l’influence du ratio N/P du milieu a été testée, ce qui a permis de mettre en exergue le stockage du phosphore par les microalgues, leur permettant de continuer leur croissance lorsque le phosphore du milieu est épuisé. En outre, le taux et la vitesse d’élimination de l’azote ne sont pas impactés, tandis que celle celui du phosphore augmente avec la concentration en P du milieu. Par la suite, le transfert du dioxyde de carbone et son impact sur la croissance des microalgues ont été étudiés. La productivité algale est fonction de la quantité de CO2 fournie à la culture et chute à 0 sans injection. Le transfert en condition de culture est optimal lorsque la croissance des microalgues est forte, c’est-à-dire lorsque la concentration en carbone inorganique du milieu est plus faible et que la consommation algale est élevée. Enfin, l’étude du temps de séjour des solides et de leur fréquence d’extraction a révélé que la nitrification-dénitrification est un mécanisme important d’élimination de l’azote dans une culture algale en continu et en système ouvert. Il peut même s’avérer prédominant par rapport à l’assimilation de l’azote par les microalgues dans certaines conditions. La proportion de chacun de ces processus peut néanmoins être contrôlée par ces paramètres. Ces expérimentations ont par ailleurs permis de mieux comprendre les interactions entre microalgues et bactéries nitrifiantes ainsi que la prédominance des genres d’algues en fonction des conditions de culture. Les microalgues sont de meilleures compétitrices sur le phosphore que les bactéries nitrifiantes. De plus, lorsque le phosphore n’est pas limitant, la nitrification est réduite en proportion de la productivité algale. En cas de limitation en phosphore et avec une faible lumière disponible, les genres d’algues qui se sont montrés dominants sont Scenedesmus sp. et Chlorella sp. respectivement. Les essais expérimentaux ont été complétés par le développement ou l’adaptation de modèles biocinétiques capables de représenter la croissance algale et l’épuration assez fidèlement. A partir de cette modélisation, différentes configurations ont été simulées pour dimensionner un lagunage algal à haut rendement et ainsi mieux comprendre et apprécier la faisabilité d’une culture algale pour extraire les nutriments des digestats.
... El problema de acumulación de oxígeno aumenta cuando un fotobiorreactor tubular helicoidal sufre escalamiento en el sistema de iluminación. Por lo tanto, es necesario tener una unidad separada de desgasificación, en muchas oportunidades esta unidad puede estar acoplado con el sistema de inyección airlift (Soletto et al., 2008), ya que la inyección de gas desde el fondo del fotobiorreactor favorece el mezclado, suministra suficiente CO 2 y dependiendo de la altura del fotobiorreactor, se logra una eficiente remoción de oxígeno disuelto en el medio. La remoción de exceso de oxígeno es un problema de transferencia de masa parecido al de suministro de CO 2 , las principales formas de controlar este fenómeno son: Disminuir la presión de oxígeno, mayor agitación y altas temperaturas. ...
... Lograron resultados satisfactorios en el crecimiento de Spirulina platensis, con productividades de 0.40 g L -1 d -1 sin daños celulares. Soletto et al. (2008) evaluaron un fotobiorreactor helicoidal a escala de laboratorio con alimentación semicontinua en cultivo de Spirulina platensis bajo diferentes condiciones de intensidad de luz y velocidad de alimentación de CO 2 , para evitar la adición en exceso del CO 2 al comienzo del cultivo que podría causar una inhibición por saturación de sustrato. La óptima velocidad de alimentación de CO 2 para el crecimiento celular, se correlacionó con la intensidad de luz a la cual fue expuesta. ...
La evaluación del análisis de las tasas de crecimiento de las especies forestales Myroxylon balsamum (L.) Harms (Bálsamo) y Minquartia guianensis Aubl. (Guayacán negro) y Otoba parvifolia (Doncel) establecidas en rodales de investigación en la Estación Científica Jatun Sacha (ECJS), con una edad de 20 años, fue el motivo principal de esta investigación. De acuerdo a los resultados obtenidos se encontró que el Bálsamo necesita 59 años para alcanzar los 60 centímetros de Diámetro Mínimo de Corta (DMC), que está determinado por el Acuerdo Ministerial 039 del Ministerio del Ambiente, el Guayacán negro Huambula, necesita 69 años para llegar a los 40 centímetros de diámetro, mientras que el Doncel necesita 27 años para obtener 50 cm de diámetro.
... El problema de acumulación de oxígeno aumenta cuando un fotobiorreactor tubular helicoidal sufre escalamiento en el sistema de iluminación. Por lo tanto, es necesario tener una unidad separada de desgasificación, en muchas oportunidades esta unidad puede estar acoplado con el sistema de inyección airlift (Soletto et al., 2008), ya que la inyección de gas desde el fondo del fotobiorreactor favorece el mezclado, suministra suficiente CO 2 y dependiendo de la altura del fotobiorreactor, se logra una eficiente remoción de oxígeno disuelto en el medio. La remoción de exceso de oxígeno es un problema de transferencia de masa parecido al de suministro de CO 2 , las principales formas de controlar este fenómeno son: Disminuir la presión de oxígeno, mayor agitación y altas temperaturas. ...
... Lograron resultados satisfactorios en el crecimiento de Spirulina platensis, con productividades de 0.40 g L -1 d -1 sin daños celulares. Soletto et al. (2008) evaluaron un fotobiorreactor helicoidal a escala de laboratorio con alimentación semicontinua en cultivo de Spirulina platensis bajo diferentes condiciones de intensidad de luz y velocidad de alimentación de CO 2 , para evitar la adición en exceso del CO 2 al comienzo del cultivo que podría causar una inhibición por saturación de sustrato. La óptima velocidad de alimentación de CO 2 para el crecimiento celular, se correlacionó con la intensidad de luz a la cual fue expuesta. ...
Las cianobactérias son organismos eficientes en la conversión de energía solar y producen una gran variedad de metabolitos. En la actualidad son el centro de atención para la producción de biocombustible, son usadas como biofertilizantes, control de contaminación ambiental y como fuente de nutrientes en alimentación humana y animal. Con el fin de proporcionar crecimiento y aprovechar el potencial de las cianobacterias, se requieren fotobiorreactores eficientes. Aunque se han propuesto muchos tipos de fotobiorreactores, no existe un reactor ideal, solo unos pocos pueden utilizarse para la producción de biomasa de cianobacterias. De hecho, la elección del fotobiorreactor más adecuado depende de la situación, ya que tanto las especies de algas disponibles y el destino final jugarán un papel importante. Uno de los principales factores que limita su aplicación práctica en cultivos de biomasa es la transferencia de masa. Por esto, entender el coeficiente de transferencia de masa en los fotobiorreactores es necesario para una operación eficiente del cultivo de biomasa en cianobacterias. En esta revisión, se discuten varios tipos de fotobiorreactores muy promisorios para la producción de biomasa de cianobacterias.
... Helical PBRs is a promising design as it allows a larger ratio of surface area for the culture volume to receive illumination effectively, and thus the incident light energy input per unit of volume is high [9], [10]. Helical PBRs has been used in literature as an experimental PBR for microalgae culture evaluation given its high yield [11], [12]. However, since curvature affects energy uptake, it is important to obtain an efficient helical PBR design to assess an appropriate curvature that can minimize the energy consumption in the PBR. ...
In this paper we present the design problem of helical tubular PhotoBioReactors (PBR) based on energy consumption minimization, using the radius of curvature for the cultivation of microalgae. Computational Fluid Dynamics (CFD) is used to design a configuration of the helical pipeline with minimum energy consumption. We determined how flow direction changes affect energy consumption. Additionally, it was found that the radius of curvature affects the pressure drop in the PBR’s pipe, so a cost function has been developed to solve an optimization problem seeking to obtain the optimum radius of curvature and a helical tubular PBR design with low pumping rates.
... It is interesting to note that the quickest CO 2 drop (Figure 14b) was detected in the 4L-PBR illuminated by the highest power (28.8 W) yellow LED. This result parallels the fact that increased energy intensity rapidly activates photosynthetic production of microalgae before saturation [59]. Meanwhile, one may assume that the 7-L PBR should have showed better CO 2 mitigation during the early stage, since the cell's vital response is generally the most sensitive at red LED wavelengths of 640-700 nm [60]. ...
Microalgae-based photobioreactors (PBRs) have gained attention as a sustainable solution for indoor air quality (IAQ) control. This study investigates indoor CO2 absorption performance of Spirulina maxima (S. maxima) in NaHCO3-limited cultivation (standard: NaHCO3-free medium = 1:1 v/v%) of a lab-scale PBR system. Cultivation performance of three medium amendments (standard, 50% NaHCO3, and NaHCO3-free) was compared by observing cell growth for 30 days in a controlled environment. Empirical examinations were conducted to evaluate the algal CO2 uptake, and overall system performance in the culture volumes of 2, 4, and 7 L and natural indoor CO2 concentration of ~1100 ppm. We found CO2 was reduced by ~55%, in an air chamber of 0.064 m³, showing the greatest mitigation rate (~20%) on Day 4. Under a high concentration of CO2 (10,000 ppm), the CO2 levels were decreased up to ~90% before saturation. This research provides valuable insights into the development of S. maxima-activated IAQ control systems for airtight buildings.
... The light intensity was 150 µmol photons m −2 s −1 with a 12:12 light-dark (LD) cycle, and the temperature was 30 ± 1 • C [15,34]. The pH of the culture medium was adjusted to 9.5 ± 0.02 using 6 M NaOH [19,35]. The pH was measured using a pH meter (Metrohm 827 pH Lab meter). ...
The rise of CO2 concentration on Earth is a major environmental problem that causes global warming. To solve this issue, carbon capture and sequestration technologies are becoming more and more popular. Among them, cyanobacteria can efficiently sequestrate CO2, which is an eco-friendly and cost-effective way of reducing carbon dioxide, and algal biomass can be harvested as valuable products. In this study, the hydrodynamic parameters of an airlift photobioreactor such as gas holdup, mean bubble diameter and liquid circulation velocity were measured to investigate CO2 biofixation by Spirulina sp. The total gas holdup was found to increase linearly with the increase in the gas velocity from 0.185 to 1.936 cm/s. The mean bubble velocities in distilled water only and in the cyanobacterial culture on the first and sixth days of cultivation were 109.97, 87.98, and 65.89 cm/s, respectively. It was found that shear stress at gas velocities greater than 0.857 cm/s led to cyanobacterial death. After 7 days of batch culture, the maximum dry cell weight reached 1.62 g/L at the gas velocity of 0.524 cm/s, whereas the highest carbon dioxide removal efficiency by Spirulina sp. was 55.48% at a gas velocity of 0.185 cm/s, demonstrating that hydrodynamic parameters applied in this study were suitable to grow Spirulina sp. in the airlift photobioreactor and remove CO2.
... 0.0494; and pH was initially adjusted to 7.4 (Chang and Yang 2003;Richmond 2006). As the aim was investigation of different CO2 concentrations effect on C. vulgaris growth, used modified BG-11 medium without carbon source, NaHCO3 (Soletto et al. 2008). ...
Despite the numerous and variety of experimental studies on high-quality microalgal species for sequestrating of CO2, recorded cases are rare and not characterized well. The growth response of a green unicellular microalgae, Chlorella vulgaris, was studied under varying concentrations of carbon dioxide (ranging from 0.036 to 8%) and flue gas in a bench-scale system. The highest biomass production potential of algae recorded at 6% CO2 (v/v). ability of growth under flue gas was proved, though biomass production decreased fairly. Interestingly, total lipid content of algae enhanced with increasing CO2 levels from ambient air to 6% and ranged from 30 to 45.5 wt.% respectively. Therefore, the present results suggested that understudied C. vulgaris is appropriate for mitigating CO2, due to its high biomass productivity and C-fixation ability, also is good candidate for producing biodiesel, due to its high lipid content.
... The microalgae Spirulina platensis has previously been identified as a most popular microalgae strain that has been shown to be effective in the biofixation of carbon dioxide (Carvalho et al., 2004;Zeng et al., 2012;Soletto et al., 2008). Furthermore, Spirulina is widely regarded as one of the most important sources of commercially viable renewable feedstock for the production of single cell protein and other high-value metabolites, the most notable of which is phycocyanin, which is found in high concentrations in the microalgae (Leema et al., 2010). ...
Due to the limited availability of fresh water and the high cost of land for plant culture, microalgae cultivation has attracted significant attention in recent years and has been shown to be the best option for CO2 bio-sequestration. Bio-sequestration of CO2 through algae bioreactors has been hailed as one of the most promising and ecologically benign methods available. This research study was taken up to alleviate certain limitations associated with the technology such as low CO2 sequestration efficiency and low biomass yields. In this study three distinct cyanobacterial strains, Chlorella sp., Synechococcus sp., and Spirulina sp., were tested in 10 litre raceway ponds for their capacity for CO2 bioconversion and high biomass production under various CO2 concentrations at different EC. The highest growth rate of all tested cyanobacterial strains was observed during the first 4 days of cultivation under CO2 5% to 10%. Additionally, all these cyanobacterial strains were explored for their bioremediation capabilities. The results showed that the Chlorella sp., Synechococcus sp., and Spirulina sp. were able to remove COD of the wastewater by 56%, 48% and 77% respectively and the BOD removal efficiency was 48%, 30% and 52% respectively. The primary results indicated that the Spirulina sp. was to be the best cynobacteria studied in terms of biomass production, CO2 bioconversion, and bioremediation capacities. Therefore, the Spirulina sp. was further scaled up in 1500 litre raceway pond for CO2 bio-sequestration and biomass production. The biomass collected was utilised to extract biomolecules such as protein, carbohydrate and lipids.
... This value for irradiance is about one order of magnitude less than recorded outdoors in summer days (1850-2000 m mol photon m 2 s −1 ). Chen et al. [45] observed that the maximum biomass production and biomass productivity of Arthrospira platensis increased with increasing light intensity from 100 to 700 μmol photons m -2 s −1 while they remained nearly unchanged when the light intensity was higher than 900 μmol photons m -2 s −1 , which may be related to excessive illumination that would inhibit the biomass production and CO2 fixation efficiency [46]. Indeed, photoinhibition is defined as a loss of photosynthetic capacity due to damage caused by photon flux densities (PFD) in excess of that required to saturate photosynthesis. ...
In recent decades and to deal with the scarcity of fossil fuels, many studies have been developed in order to set up a sustainable biofuel production sector. This new sector must be efficient (high productivity), economically profitable (low production costs and therefore acceptable fuel prices), and ethical (low carbon balance, no competition with food resources). The production of bioethanol is based on the fermentation of reserve sugars, accumulated in the form of starch in microalgae and glycogen in cyanobacteria. The advantage of this bioenergy production route lies in the fact that the post-crop fermentation process is at the industrial stage since it has already been tested for many years for the production of bioethanol from agricultural resources. One of the most cultivated cyanobacteria is Arthrospira (“Spirulina”) and its production is also already at industrial scale. Depending on the cultivation conditions, this cyanobacteria is able to accumulate up to 65% DW (dry weight) of glycogen, making it a feasible feedstock for bioethanol production. The aim of this review is to provide a clear overview of these operating conditions for glycogen accumulation.
... where r G is the maximum daily growth rate (g DM ·d −1 ) and H G = 21.01 kJ·g DM −1 dry biomass enthalpy [30]. ...
This work dealt with the study of growth parameters, pigments production, and bioenergetic aspects of the microalga Dunaliella tertiolecta in different culture media. For this purpose, cultures were carried out in Erlenmeyer flasks containing F/2 medium, Bold’s Basal medium, or an alternative medium made up of the same constituents of the Bold’s Basal medium dissolved in natural seawater instead of distilled water. D. tertiolecta reached the highest dry cell concentration (Xmax = 1223 mgDM·L⁻¹), specific growth rate (µmax = 0.535 d⁻¹), cell productivity (PX = 102 mgDM·L⁻¹·d⁻¹), and photosynthetic efficiency (PE = 14.54%) in the alternative medium, while the highest contents of carotenoids (52.0 mg·g⁻¹) and chlorophyll (108.0 mg·g⁻¹) in the biomass were obtained in Bold’s Basal medium. As for the bioenergetic parameters, the biomass yield on Gibbs energy dissipation was higher and comparable in both seawater-based media. However, the F/2 medium led to the highest values of moles of photons absorbed to produce 1 C-mol of biomass (nPh), total Gibbs energy absorbed by the photosynthesis (ΔGa) and released heat (Q), as well as the lowest cell concentration, thus proving to be the least suitable medium for D. tertiolecta growth. On the other hand, the highest values of molar development of O2 and consumption of H⁺ and H2O were obtained in the alternative medium, which also ensured the best kinetic parameters, thereby allowing for the best energy exploitation for cell growth. These results demonstrate that composition of culture medium for microalgae cultivation has different effects on pigments production, growth kinetics, and bioenergetics parameters, which should be taken into consideration for any use of biomass, including as raw material for biofuels production.
... In addition, the specific maximum growth rate found in the present study was slightly higher than those reported by Soletto et al. [42] and Caixeta et al. [43] for A. platensis cultured in various standard and economic mineral media. ...
Proteases are industrially important catalysts. They belong to a complex family of enzymes that perform highly
focused proteolysis functions. Given their potential use, there has been renewed interest in the discovery of proteases with novel properties and a constant thrust to optimize the enzyme production. In the present study, a
novel extracellular neutral protease produced from Arthrospira platensis was detected and characterized. Its proteolytic activity was strongly activated by β-mercaptoethanol, 5,5-dithio-bis-(2-nitrobenzoic acid) and highly
inhibited by Hg2+ and Zn2+ metal ions which support the fact that the studied protease belongs to the cysteine
protease family. Using statistical modelling methodology, the logistic model has been selected to predict
A. platensis growth-kinetic values. The optimal culture conditions for neutral protease production were found
using Box-Behnken Design. The maximum experimental protease activities (159.79 U/mL) was achieved after
13 days of culture in an optimized Zarrouk medium containing 0.625 g/L NaCl, 0.625 g/L K2HPO4 and set on 9.5
initial pH.
The extracellular protease of A. platensis can easily be used in the food industry for its important activity at neutral
pH and its low production cost since it is a valuation of the residual culture medium after biomass recovery
... However some species are able to use organic compounds in presence or absence of carbon dioxide. Moreover, environmental parameters such as pH, temperature, light and concentrations of carbon dioxide and nutrients strongly affect microalgae growth and biomass productivity (Li et al. 2004;Mata et al., 2010;Olaizola, 2003;Ras et al., 2013;Soletto et al., 2008;Sorokin and Krauss, 1958). ...
Advanced control strategies proved to be promising tools to improve the performances of microalgae production systems, especially in the perspective of large scale cultivation plants. This paper proposes the validation of a nonlinear control strategy with experimental results. Additionally, the on-line estimation of the biomass concentration in a photobioreactor is presented. The proposed control law maintains the biomass concentration at a targeted level. This is achieved by a state feedback linearizing control law in an inner loop, in addition to a Proportional Integral regulator with an anti-windup compensation in an outer loop. To cope with the lack of on-line biomass concentration measurements, this variable is estimated on-line by an Extended Kalman Filter, based on available on-line measurements (pH, incident light intensity and dissolved carbon dioxide concentration). Performance and robustness of the proposed control strategy are assessed through experimental results obtained with cultures of the microalgae Porphyridium purpureum in a laboratory-scale continuous photobioreactor.
... [1] Light radiation, temperature, and pH value will most directly affect productivity. [2][3][4] The light intensity and photoperiod are the critical components in determining the biomass production of algae cultivation. [5] Maximal photosynthetic efficiency is required to attain high biomass production. ...
Marine microalga Isochrysis sp. contains omega-3 fatty acids like eicosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA). Environmental factors play a major role in PUFA biosynthesis. Hence,
the study focused to optimize factors such as temperature, pH, and photoperiod by response sur-
face methodology (RSM). RSM results showed that the model is significant (p � 0.05) with a high
correlation coefficient (R2 ¼ 0.908). The optimum conditions showed that maximum biomass
(327 mg/L) at the temperature of 30 �C, pH of 7.5 and 16:8 (Light: Dark cycle), whereas the higher
amount of DHA (13.3%) and EPA (9.0%) was observed in the conditions of 18 �C, pH of 7.5 and
16:8 (Light: Dark cycle). The biomass content was directly proportional to the temperature whereas
DHA content was inversely proportional. It was revealed that the mRNA expression of EPA and
DHA specific desaturases (5Des & 4Des) were significantly elevated in low temperature (20 �C) con-
ditions. The results were highly correlated with the fatty acid profile of Isochrysis sp. grown under
low temperature (20 �C) conditions which enhanced the EPA and DHA levels. This study suggests
that the temperature is the most influencing factor which can be exploited in the industrial appli-
cation of DHA and EPA production from Isochrysis s
... The microalga group, Chlorophyta, was widely used in the phycoremediation of industrial, municipal, and domestic wastewaters , whereas Scenedesmus sp. were utilized for treating specific wastewaters (Mata et al. 2012;Girard et al. 2014). Many researchers reported the growth potential of Spirulina sp. for treating the wastewaters in different modes (Samson and Leduy 1985;Travieso et al. 2001;Soletto et al. 2008). Mathematical optimization is required to identify the optimum operational condition of microalgal growth in PSWW. ...
Phycoremediation encompasses microalgae as a sustainable treatment system by integrating the wastewater treatment with bioenergy recovery. However, transforming this technology to real time from lab scale is limited due to temperature and cell volume (inoculum size). Thus, the present study aims to investigate the influence of inoculum size (10%–30% v/v) and temperature condition (25°C–35°C) for the growth of five microalgal species in paddy-soaked wastewater (PSWW), using response surface methodology (RSM). The optimal conditions for better biomass production and wastewater treatment were found to be at 25°C and 30% inoculum size. Among five selected microalgae, Chlorella pyrenoidosa exhibited maximum dry biomass content (831 mg/L) with greater (>90%) removal on ammonical nitrogen (NH3-N) and phosphates (PO4-P) at a rate of 0.025 and 0.006 mg P/mg of dry biomass, respectively, with significant p value (p<0.05). Similar results were obtained for Chlorella vulgaris and Scenedesmus obliquus (an indigenous sp.) with more than 80% removal efficiency. However, at higher temperatures, Chlorella pyrenoidosa exhibited better results when other strains failed to maintain biomass production and removal on NH3-N and PO4-P. This study demonstrated that phycoremediation is a viable option upon selecting appropriate strains and conditions imminent for scale-up applications.
... Pure CO 2 must be avoided during sparging due to the higher power requirement and low productivity, increasing the overall operating cost of the process. Moreover, it must be considered that every algae species has its toleration limit for flue gases, which must be regulated and supplied per the toleration limit of the species (Soletto et al., 2008;Zhao and Su, 2014). Process integration of anaerobic digestion coupled with microalgae has become a critical process for sustainable development of the process. ...
... Los factores ambientales tienen un efecto significativo en la biomasa de microalgas, las condiciones ambientales, como la radiación de luz, la temperatura y el valor del pH causan diversos comportamientos sobre la producción de biomasa de diferentes especies de microalgas (Li et al., 2011), más directamente afecta la productividad (Soletto et al., 2008;Mata et al., 2010;Xenopoulos et al., 2002). Otros factores como la concentración de nutrientes afectan el crecimiento, consumo de nutrientes y propiedades y acumulación de lípidos (Aslan y Kapdan, 2006;Goldberg y Cohen, 2006;Rodolfi et al., 2009). ...
The microalgae are photosynthetic microorganisms recognized for their production of vitamins, carbohydrates, pigments, and lipids. However, this production is affected by the composition of micro and macronutrients in the culture system, which in some cases constitute high costs, 70% in the production of microalgae. The objective of this study was to evaluate a commercial edaphic fertilizer as a culture medium for the microalgae Desmodesmus opoliensis and its effect on cell kinetics. For this, Remital® was used as a commercial medium in static cultures, evaluating a total of four concentrations (0.5, 1.0, 1.5 and 2.0 gr/l of distilled water), this culture medium was purchased with the Guillard F/2 medium (1 ml/l) in triplicate for each culture medium (n= 3). To determine the kinetic curve and its behavior, the cell density (cel/ml) was carried out by means of cell count in Neubauer chamber and total chlorophylls (μg/ml) by spectrophotometry, at a culture temperature of 24 ± 2 °C and a photoperiod of 12:12 (light:dark) for 14 days. The Guillard F/2 reached a maximum cell density of 4.33±1.96 (106 cells/ml). The treatment with concentrations of 2 g/l, showed the highest growth with an average of 2.9x106 cel/ml, without significant statistical differences when compared with the different concentrations of the commercial fertilizer Remital® (P>0.05). These results confirm and allow the use of unconventional fertilizers such as Remital® in the production of Desmodesmus opolienis.
... Los factores ambientales tienen un efecto significativo en la biomasa de microalgas, las condiciones ambientales, como la radiación de luz, la temperatura y el valor del pH causan diversos comportamientos sobre la producción de biomasa de diferentes especies de microalgas (Li et al., 2011), más directamente afecta la productividad (Soletto et al., 2008;Mata et al., 2010;Xenopoulos et al., 2002). Otros factores como la concentración de nutrientes afectan el crecimiento, consumo de nutrientes y propiedades y acumulación de lípidos (Aslan y Kapdan, 2006;Goldberg y Cohen, 2006;Rodolfi et al., 2009). ...
Las microalgas son microorganismos fotosintéticos reconocidos por su producción de vitaminas, carbohidratos, pigmentos y lípidos. Sin embargo, esta producción es afectada por la composición de nutrientes micro y macrominerales en el sistema de cultivo, que para algunos casos constituyen altos costos, un 70% en la producción de microalgas. El objetivo de este estudio fue evaluar un fertilizante edáfico comercial como medio de cultivo para la microalga Desmodesmus opoliensis y su efecto en la cinética celular. Para esto, se utilizó como medio comercial Remital® en cultivos estáticos, evaluando un total de cuatro concentraciones (0.5; 1.0; 1.5 y 2.0 gr/l de agua destilada), este medio de cultivo fue comprando con el medio F/2 Guillard (1 ml/l) por triplicado para cada medio de cultivo (n=3). Para determinar la curva cinética y su comportamiento, la densidad celular (cel/ml) se llevó a cabo por medio de conteo celular en cámara de Neubauer y las clorofilas totales (μg/ml) por espectrofotometría, a una tempertura de cultivo de 242 °C y un fotoperiodo de 12:12 (Luz:Oscuridad) durante 14 días. El F/2 Guillard alcanzó una densidad celular máxima de 4.33±1.96 (106 cel/ml). El tratamiento con concentraciones de 2 g/l, mostró el mayor crecimiento con un promedio de 2.9x106 cel/m, sin diferencias estadísticas significativas al ser comparado con las diferentes concentraciones del fertilizante comercial Remital® (P>0.05). Estos resultados confirman y permiten el uso de fertilizantes no convencionales como el Remital® en la producción de Desmodesmus opolienis.
... Such systems if developed on larger volumes can generate ample amounts of heat which needs to be abated by providing temperature control systems (Richmond 1987). Tubular reactors can be several meters long and can be arranged in different patterns like vertically coiled (Rorrer and Mullikin 1999;Travieso et al. 2001;Oncel and Kose 2014), horizontally coiled (Campo et al. 2001;Adessi et al. 2012), conical (Watanabe and Hall 1996;Morita et al. 2001), helical (Soletto et al. 2008), or 3D mesh layout . A schematic diagram of vertically coiled, horizontally coiled, conical, and helical type tubular reactors is shown in Figs. 4, 5, 6, and 7, respectively. ...
The application of microalgae for wastewater treatment is attracting increasing attention of researchers because of the added potential of harvesting the generated algal biomass for deriving numerous useful products. The conventional systems, viz., algal ponds, are historically used for both wastewater treatment and biomass production at field scale. However, such systems are dependent on the prevalent environmental conditions and do not provide a sufficient level of control over the process, thus achieving a sub-optimal performance. Photobioreactors provide a better process control and optimization due to their design. However, their large-scale application is constrained by the overall economics, in addition to the increased complexity of the operation. The recent advancement in the technology, however, has addressed many of the associated difficulties in the large-scale photobioreactor application. This chapter provides an overview of the photobioreactor technology, the inherent complexity of their application, and the current technical advances leading to their large-scale application.
... Such systems if developed on larger volumes can generate ample amounts of heat which needs to be abated by providing temperature control systems (Richmond 1987). Tubular reactors can be several meters long and can be arranged in different patterns like vertically coiled (Rorrer and Mullikin 1999;Travieso et al. 2001;Oncel and Kose 2014), horizontally coiled (Campo et al. 2001;Adessi et al. 2012), conical (Watanabe and Hall 1996;Morita et al. 2001), helical (Soletto et al. 2008), or 3D mesh layout . A schematic diagram of vertically coiled, horizontally coiled, conical, and helical type tubular reactors is shown in Figs. 4, 5, 6, and 7, respectively. ...
The current study demonstrates the nutrient removal efficiency of algal-bacterial photobioreactors in the semi-batch mode for secondary treated domestic wastewater. The experiments were conducted to predict the optimum conditions for running a photobioreactor at a comparatively larger scale. The main focus was on optimizing illumination costs and nutrient removal efficiency to make reactor construction and operation economically viable. Chlorella vulgaris and Chlamydomonas reinhardtii were used for the experiments. Various input parameters were varied, and nutrient removal efficiencies along with biomass, chlorophyll-a content, temperature, pH, alkalinity, dissolved organic carbon, and dissolved oxygen were monitored. Model simulations were also run to confirm optimum performance. A maximum of ~25 mg l⁻¹ N and ~10 mg l⁻¹ P were found to be efficiently removed within 2 days hydraulic retention time (HRT), 9 h:3 h light: dark condition and 1543 μmol photons m² s⁻¹ light intensity. The results demonstrate superior nutrient removal efficiency than similar to previous studies.
... Their beneficial potential was experimentally proved in vitro and in vivo to treat some pathologies and in the prevention of the hyper cholesterol level, certain inflammatory diseases, allergies, cancer, toxicity inferred by the certain medicine, the viral infections, the cardiovascular diseases, the diabetes and other pathologies (Costa et al., 2007 andAssimakopoulos, 2008). Spirulina growth was found in a wide range of habitats, like open and closed ponds (Soletto et al., 2008), photo bioreactors (Volkmann et al., 2007), sewage and wastewater (Mary et al., 2010), desert, marine and seawater (Hiri et al.,2011). In Algeria, Spirulina platensis is founded in Guelta (point of mountain water) in Tamanras set that resembles to the Paracas strain (Doumandji et al., 2009). ...
An experiment was conducted on culture and growth performance of Spirulina platensis in various concentrations of rotten apple medium (RAM) and Kosaric Medium (KM). The observation was conducted for three months from March to May at the Live Food Culture Laboratory, Department of Aquaculture, Faculty of Fisheries, Bangladesh Agricultural University. Culture of S. platensis was performed in 1.0L glass flasks in three different media such as 2.5, 5.0 and 10% and KM with three replications under fluorescent light in light : dark (12 hr : 12 hr) condition of a period of 14 days. Growth performances of S. platensis varied from one medium to another. The initial cell weight of S. platensis was 0.0023 mg/L and a maximum cell weight of 12.44 mg/L was found in KM and 10.468 mg/L in RAM on 10 th day of culture. It was also observed that, the initial chlorophyll a content of S. platensis was 0.0015 mg/L which was attained at a highest content of 10.54 mg/L in KM and 12.35 mg/L in RAM on 10 th day of culture. A decreasing trend of cell weight was observed from 10 th day of culture. The growth of S. platensis was significantly (p<0.05) better in 5.0% Digested Rotten Apple Medium (DRAM) than other concentrations 2.5% DRAM and 10% DRAM. From the results obtained in the present study, it was summarized that the growth of S. platensis was better in the concentrations of 5.0% DRAM than other concentrations of RAM. Thus, the concentration of 5.0% DRAM is most suitable for S. platensis culture compare with standard KM. These media are easily available and most inexpensive in contrast of Bangladesh. So digested rotten apple can be used for commercially and economically viable mass culture of S. platensis.
... Otros metabolitos sintetizados por Spirulina son los pigmentos (Khazi, Demirel, & Dalay, 2018;Murugan & Rajesh, 2014), los cuales, al igual que el resto de la composición química, están influenciados por los parámetros físico-químicos que interactúan en cultivos, a saber: temperatura (Lee, Chen, & Peng, 2012;Pandey & Tiwari, 2010;Uslu, Isik, Koc, & Goksan, 2011), aireación (Ravelonandro et al., 2011), concentración de dióxido de carbono (Soletto et al., 2008), fuentes de carbono (Soundarapandian & Vasanthi, 2010), intensidad de luz (Lee et al., 2012;Pandey & Tiwari, 2010;Ravelonandro et al., 2011), pH (Pandey & Tiwari, 2010) Uslu et al., 2011) o fósforo (Markou, 2012;Markou, Chatzipavlidis, & Georgakakis, 2012;Ravelonandro et al., 2011;Uslu et al., 2011;Yuan, Kumar, Sahu, & Ergas, 2011). ...
El objetivo de la presente investigación fue evaluar el crecimiento y el contenido de pigmentos de un nuevo aislado de Spirulina subsalsa cultivada en agua mar a diferentes salinidades y concentraciones de nitrógeno. La nueva cepa de S. subsalsa se aisló a partir de muestras de agua procedentes del embalse de Clavellino, estado Sucre, Venezuela, y fue identificada haciendo uso de la clave taxonómica propuesta por Aguiar (2013). El medio de cultivo ensayado fue el f/2, modificando las concentraciones de nitrato (14,5; 29 y 58 mmol/L) y cloruro de sodio (0, 9 y 18 ‰ por adición de agua de mar). Los cultivos se realizaron por triplicado, de forma discontinua, bajo condiciones de medio ambiente controlado (T: 30±1 ºC; iluminación: 3.000 lux; agitación manual, fotoperiodo 12:12), durante 21 días. Los resultados obtenidos evidenciaron que la salinidad de 9 ‰ y la concentración de nitrato de 14 mmol/L fueron los parámetros que propiciaron los mayores contenidos de biomasa; mientras que la clorofila a y la ficocianina mostraron mayores valores en la misma concentración de nitrógeno, pero a 0 ‰. Estos hallazgos indican que la salinidad y la concentración de nitrógeno afectan el crecimiento y los pigmentos del nuevo aislado de S. subsalsa y además sugieren que esta cepa posee potencial para su aprovechamiento biotecnológico con miras a obtener metabolitos valiosos en las industrias alimenticias y farmacológicas.
... Sensors in a tube reactor are usually mounted in a fixed place, although parameters may vary over the length of the tube. For instance, if tube bioreactors are used to cultivate algae, a comprehensive data set on oxygen accumulation and CO 2 depletion can help to find the optimal parameter settings to control aeration and CO 2 supply [12,39]. In such situations, a mobile sensor that moves with the fluid may be better as it can provide measurements of the entire reactor volume. ...
The application of standard sensor electrodes is often limited to stirred tank reactors due to their wired nature and their large space requirement. For other cultivation systems, sensors require a great technical effort to be implemented. Here we propose a new concept of sensors: miniaturized, mobile, wireless, and self-contained spherical sensors with diameters of only 7.9 mm. The micro-probes send their data wirelessly at a frequency band of about 433 MHz to a base station during the process run and are easily deployable for many biotechnological applications and reactor types, without any need to modify the cultivation system, as the probes are nearly non-invasive due to their small size. The system consists of a platform that can accommodate various sensor types, e.g., temperature as shown in this work. The sensor spheres are reusable and can be charged by induction before being deployed in a biotechnological application. Furthermore, redundancy can easily be realized by adding several sensors into a single reactor, since each base station can coordinate up to 24 spheres. From computational fluid dynamics (CFD) simulations we could infer the maximum allowable density of spheres that would still enable them to be homogeneously distributed within a reactor as 1.1 g/cm³. We could demonstrate the practical applicability of our concept by deploying the spheres in shaking flasks, lab-scale stirred tank reactors, and tube reactors in typical lab environments. In all cases, the spheres showed reliable data transmission despite the potentially shielding technical environment.
... This effect can be diminished by substantially increasing the amount of accessible inorganic carbon. In this case, inhibition delays and the return of Spirulina culture to normal state occur faster and with minimal consequences (Soletto et al., 2008). Decrease in light intensity from 5 to 2 klx on Spirulina is associated with a significant increase in the amount of chlorophyll to ca. 30% (Danesi et al., 2004). ...
This present chapter emphasizes the data on environmental and technological stresses in cyanobacteria (namely Arthrospira platensis (Spirulina) and Nostoc linckia). The factors investigated were: light, temperature, salinity, and chemical stimulants. Common elements have been established for cyanobacterial response to the stress caused by various factors, as well as specific elements depending on the culture and type of stress. Changes in phycobilins, proteins, carbohydrates, and lipids content, as well as in the activity of antioxidant enzymes in cyanobacteria under stress conditions are presented. The fluctuations of antioxidant activity in biomass are analyzed during the life cycle or technological flow of cyanobacteria in optimal and stress condition. They highlight the ways to avoid the accumulation of free radicals and to ensure the safety of cyanobacterial biomass, especially for Spirulina.
... Previous studies conducted under outdoor conditions showed reduced growth rate, photosynthetic efficiency, and chlorophyll content during such peak hours mainly due to photoinhibition (Vonshak et al., 2014;Torzillo et al., 1998;Chanawongse et al., 1994). Photoinhibition is light-induced photo-oxidative stress occurring at light intensities above the saturation of the photosynthetic rate, which causes severe photo-damage to photosynthetic pigments and, in extreme cases, a total loss of the algal culture (Soletto et al., 2008;Jensen and Knutsen, 1993). Moreover, the culture temperature between 35 °C and 37 °C was found to be optimum for microalgal biomass productivity (Richmond, 1988) while, a further increase in temperature was observed to hinder the growth rate due to inactivation of PSII activity (Chaiklahan et al., 2007). ...
There is no virtual report on the commercial cultivation of Arthrospira in Malaysia beyond the laboratory scale probably because of the high costs of production and the lower yield which are highly interconnected with the algal cultivation techniques. One way to alleviate the production cost is through outdoor mass cultivation under natural conditions using all available resources. Therefore, the present study was conducted to investigate the prospects of the production of Arthrospira platensis under Malaysian tropical climate using enhanced cultivation techniques to reach a maximum yield. In this study, the growth and yield of A. platensis were investigated under three different cultivation conditions: laboratory (control), outdoor shaded (greenhouse, T1), and outdoor non-shaded (field, T2). The algal growth was measured through optical density, biomass dry weight, and chlorophyll a content. The algal yield was determined by calculating its productivity and specific growth rate. The A. platensis cultivation under outdoor non-shaded conditions achieved significantly higher growth (p < 0.05) with 1.62 ± 0.038 ABS of maximum optical density, 0.88 ± 0.020 g L-1 of maximum biomass dry weight, 8.77 ± 0.219 mg L-1 of maximum chlorophyll a content, 0.091 ± 0.0022 g L-1 d-1 of productivity and 0.220 ± 0.0017 µ d-1 of specific growth rate over a cultivation period of eight days. The present finding showed that the Malaysian climate is suitable for a satisfactory A. platensis productivity with proper cultivation techniques such as the pre-adaptation of the algal culture, inoculation in the late evening, continuous agitation and compensation of the evaporated culture medium.
... Cells were cultivated in the modified culture medium including BG-11 and ASN-III with ratio 1:1 (v/v) (17). As the aim was investigation of different CO 2 concentrations effect on S. platensis growth, modified medium without carbon source, NaHCO 3 , was used (18). ...
Introduction: Because their ability to capture CO2, photosynthetical microorganisms have some advantages to CO2 mitigation from high CO2 streams such as flue gases and they can use CO2 as carbon source. Recently, experts have made efforts to exploit microorganisms intended for recovering CO2 from power plants.
Materials and methods: To achieve this purpose, we studied the growth response of the cyanobacterium Spirulina platensis PCC9108 under different concentrations of carbon dioxide (ranging from 0.036% to 10%) and flue gas in a bench-scale system. Preparation of different concentrations of CO2 and injection into Erlenmeyer flasks was performed by a system including air compressor, CO2 capsule, pressure gauge and flow meter.
Results: The main goal of studying this paper is a survey of organism's potential to grow by generated CO2 from flue gas of power plant. It already had the potential and highest biomass production recorded at 8% CO2 (v/v). Also we proved that S.platensis PCC9108 can be grown under flue gas, although biomass production decreased fairly. Total lipid content of algae interestingly enhanced with elevated CO2 levels from ambient air to 4% and 6% which ranged from 14.5 to 15.8 and 16 dry weight (wt.) % respectively. In contrast, total protein content illustrated no difference between all treatment and its value was about 46 wt.%.
Discussion and conclusion: The results of present study suggested that understudied S.platensis PCC9108 is appropriate for mitigating CO2 because of its carbon fixation ability. Also due to its high protein content, this cyanobacterium is a good candidate to produce SCP (single cell protein).
... The results were statistically (Tukey test) the same, in 5% level. Similar results were found by Borges et al. [38], Soletto et al. [39] and Madkour et al. [24], showing that this specific maximum growth rate found in this study indicates good results. which are similar to those found in this work. ...
Arthrospira platensis is a rich source of essential amino acids, vitamins and it is used as a feedstock for energy sources. The high cost of the growth medium used in its cultivation is a problem for increasing the production viability. The present study aimed to compare the technical viability and the cost elementsin different growth medium for A. platensis cultivation. For that purpose, it was proposed the use of three different growth medium, named as M1, M2 and M3 in a lab scale. The growth of the treatments presented a microbial process with characteristic phases. M1, M2 and M3 maximum concentration (Xmax), productivity (Px) and the maximum specific growth rate (μmax) showed no significant difference among treatments. However, M3 presented the lowest cost element, about 45.75% less than the M1 and 38.92% lower than M2. Therefore, the comparison enabled the result that M3 presented the best performance to be used, thus increasing profitability of this production in a lab-scale analysis.
... The photosynthetic efficiency (PE) was calculated using Equation (7) (Soletto et al., 2008): ...
The objective of this work was to evaluate the performance of a pilot scale membrane photobioreactor (MPBR) for treating the effluent of an anaerobic membrane bioreactor (AnMBR) system. In particular, new experimental data on microalgae productivity, nutrient recovery, CO2 biofixation and energy recovery potential was obtained under different operating conditions, which would facilitate moving towards cost-effective microalgae cultivation on wastewater. To this aim, a 2.2-m³ MPBR equipped with two commercial-scale hollow-fibre ultrafiltration membrane modules was operated treating the nutrient-loaded effluent from an AnMBR for sewage treatment. The influence of several design, environmental and operating parameters on MPBR performance was studied. Among the conditions evaluated, variations in solar irradiance significantly affected the nutrient recovery rate (NRR). Operating at temperatures above 25 °C and high biomass concentrations, which increased light shading effect, negatively affected biomass production and NRR. Maximum biomass productivity of 66 mg VSS L⁻¹ d⁻¹ (areal productivity of 15.78 g VSS m⁻² d⁻¹) and NRR of 7.68 mg N L⁻¹ d⁻¹ and 1.17 mg P L⁻¹ d⁻¹ were achieved when operating at 4.5 days of biomass retention time. These results would outcome maximum theoretical energy recoveries and CO2 biofixations of about 0.43 kWh and 0.51 kg CO2 per m³ of treated water, respectively. Moreover, the excellent quality permeate that was produced (i.e. negligible levels of pathogens and suspended solids) represents a reclaimed water source.
... 2.3.1. Measurement of microalgae growth Microalgae biomass concentration was determined by UV-Spectrophotometry (TU-1901, Puxi Instrument Company, Beijing China) and relationship curve between Spirulina platensis dry weight and the absorbance was measured by measuring OD 560nm of microalgae and dry weight in various biomass concentrations (Soletto et al., 2008). As Eq. (1), a good linear relation was established when OD 560nm less than 1. ...
To improve the microalgae production in batch cultivation, a cultivation mode that continuously pre-harvesting Spirulina platensis from photobioreactor (PBR) with culture medium recycling was proposed. For realizing the continuously pre-harvesting cultivation mode, a Spirulina platensis culture column PBR with overflowing device was designed, which could adjust pre-harvesting rate through the overflowing device. By adjusting the pre-harvesting rate, the biomass concentration could be kept when biomass accumulation and pre-harvesting biomass were equal. Hence, the meridional light attenuation could be reduced by controlling biomass concentration in PBR. The maximum microalgae production were 44.6%, 10.98% higher in total production than that cultivated in batch cultivation without pre-harvesting and periodically pre-harvesting cultivation mode respectively, which was realized in pre-harvesting rate 0.228 mL min-1 and biomass concentration 1.8 g L-1. Besides, a model was built by mass balance and polynomial fitting for evaluating the continuously pre-harvesting cultivation mode.
... Light intensity and photoperiod are vital parameters for the cultivation of microalgae (Soletto et al. 2008). Microalgae use light as their source of energy for synthesizing the cell protoplasm, and light intensity clearly affects microalgal growth (Richmond 2004;Borowitzka 2016). ...
Microalgae are considered as the future source of biofuels because of their high biomass productivity and neutral lipid content as triacylglycerides (TAG). Microalgae have high photosynthetic efficiency and the possibility of being cultivated in different wastewaters. The isolation of potential microalgae followed by the optimization of cultivation conditions is prerequisite for successful cultivation and accumulation of high lipid content. In the present work, a three-layer artificial neural network (ANN) model is developed to predict the essential parameters (such as pH, temperature, light intensity, photoperiod, and medium composition) based on 156 sets of laboratory experiments for achieving maximum biomass from Euglena sp. The independent parameters (viz., temperature, light intensity, photoperiod and number of days at fixed pH, and media composition) were fed as input to the ANN, and biomass yield was investigated. The comparison of the simulated environmental conditions using the ANN model and experimental results are found to have an excellent correlation coefficient of about 0.97 for the model variables used in this study. The model results established that artificial neural network design may be judiciously employed for optimization of different environmental conditions for this isolated microalga.
... Una de las cianobacterias más cultivada en fotobiorreactores es Arthrospira (A. maxima y A. platensis), anteriormente llamada Spirulina; y la producción de su biomasa o metabolitos dependerá de diversos factores tales como la temperatura (Pandey & Tiwari, 2010;Colla et al., 2007a;Colla et al., 2007b;Ogbonda et al., 2007), tasa de aireación (Ravelonandro et al., 2011), concentración de CO 2 (Soletto et al., 2008;Ravelonandro et al., 2011), fuentes de carbono (Soundarapandian & Vasanthi, 2010), fuentes de nitrógeno (Colla et al., 2007a;Colla et al., 2007b;Uslu et al., 2011;Yuan et al., 2011), fosfato y fase de crecimiento (Ravelonandro et al., 2011;Yuan et al., 2011). ...
El cultivo de cianobacterias, como Arthrospira, puede realizarse en sistemas abiertos y sistemas cerrados o fotobiorreactores. El objetivo de la presente investigación fue evaluar la producción de pigmentos de Arthrospira maxima cultivada en dos tipos de fotobiorreactores. El cultivo se realizó de forma discontinua (Batch) bajo ambiente controlado, en fotobiorreactores helicoidales y cilíndricos, durante 30 días, en medio Zarrouk. La determinación de los pigmentos se realizó en las fases de crecimiento exponencial y estacionario. Para los pigmentos liposolubles, la biomasa se sometió a extracción con acetona 90%, y posterior determinación por Cromatografía Líquida de Alta Eficiencia, y para la extracción de los pigmentos ficobiliproteínicos se ensayaron cuatro métodos: 1. regulador de fosfatos/enzimas; 2. solución alcalina, previo tratamiento con CaCl2; 3. buffer de fosfato, previo tratamiento con hielo seco y 4. agua (4ºC), y posterior determinación por Espectrofotometría UV-Visible. Los mayores valores de pigmentos liposolubles fueron obtenidos en los cultivos realizados en fotobiorreactor helicoidal durante la fase exponencial (clorofila a 11,08±0,006 µg mL-1; β-caroteno 1,82±0,003 µg mL-1; zeaxantina 0,72±0,002 µg mL-1); mientras que los mayores contenidos de los pigmentos ficobiliproteínicos se obtuvieron en fotobiorreactor cilíndrico, durante la fase estacionaria, utilizando el buffer de fosfato tratado con hielo seco para la extracción. Dentro de las ficobiliproteínas, fue la ficocianina la que se encontró en mayor proporción (FC = 77,74±0,767 mg L-1), seguido por la aloficocianina y ficoeritrina. Se concluye que la biomasa de Arthrospira maxima presenta potencial biotecnológico por sus altos contenidos de pigmentos.
... Autotrophic cultivation of photosynthetic microorganism is increasing quickly, mainly in large-scale production in order to harvest enough biomass to obtain useful biomolecules. Microalgae cultivation has been developed in open ponds and photobioreactors, such as horizontal, vertical or helicoidal tubular reactors, flat-plate reactors, and membrane photobioreactors [23][24][25][26]. Tubular reactors with airlift systems are among the most popular types to enhance biomass composition for novel uses. ...
Algae (macroalgae and microalgae) are aquatic photosynthetic organisms largely used due to the variety of bioactive compounds in their composition. Macroalgae have caught the attention of the food, cosmetic, pharmaceutical, and nutraceutical industries. The food industry has recently used microalgae biomass, and several others have used it as biofuel source in wastewater treatments, for example. Many algae-derived secondary metabolites are known for their skin benefits, which include protection from UV radiations and prevention of rough texture, wrinkles, and skin flaccidity. It also avoids skin aging due to the presence of antioxidant compounds. The variety of cosmetic formulations using biocompounds or algae extracts is increasing since they also provide the desired safe materials from environmental resources. Although the cosmetic effects of some of these compounds were described in recent publications, the majority of biomolecules in algae species have not yet been studied and, therefore, are not be used for cosmetic purposed. Besides that, the majority of algae effects in cosmetics are described in patents without considerable explanation about the type of biocompounds or the mechanisms responsible for each cosmetic performance. Thus, this review aimed at a better understanding of the recent uses of algae in cosmetic formulations with potential applications for new researches.
As a green process, microalgal-bacterial granular sludge (MBGS) process shows talents in achieving pollutant removal, resource recovery and carbon neutralization. However, when it comes to application, the adequate mixing of MBGS and substrate should be adopted theoretically. Therefore, this study devoted to address the necessity of stirring for MBGS in municipal wastewater treatment. Outdoor performances showed that stirring significantly enhanced both of the photosynthetic efficiency and biomass productivity of MBGS with almost 2-fold increase as compared to non-stirred MBGS, while the average pore size and microalgae-to-bacteria ratio also increased. Consequently, stirring acted as a pivotal role in accelerating pollutants removal, with removals of organics (89.89% COD) and nutrients (99.22% NH4+-N, 92.15% PO43--P) reaching peak levels at 2 h and 6 h, respectively, while removals of organics (87.50% COD) and nutrients (86.11% NH4+-N, 86.76% PO43--P) removal peaked at 8 h for non-stirred MBGS. The improved granule characteristics and microbial compositions due to the stirring were found to be favorable for MBGS to adapting to the changeable weather. Based on the above results, the possible underlying mechanisms of stirring for improving MBGS were illustrated. Overall, stirring positively impacted the photosynthetic efficiency, biomass productivity, pollutant removal and microbial structure for MBGS. This study gains knowledge on stirred MBGS process under outdoor conditions for its future practical application.
Phycobiliproteins are photosynthetic light-harvesting pigments isolated from microalgae with fluorescent, colorimetric and biological properties, making them a potential commodity in the pharmaceutical, cosmetic and food industries. Hence, improving their metabolic yield is of great interest. In this regard, the present review aimed, first, to provide a detailed and thorough overview of the optimization of culture media elements, as well as various physical parameters, to improve the large-scale manufacturing of such bioactive molecules. The second section of the review offers systematic, deep and detailed data about the current main features of phycobiliproteins. In the ultimate section, the health and nutritional claims related to these bioactive pigments, explaining their noticeable potential for biotechnological uses in various fields, are examined.
In this study, the light factors and nitrogen availability effect on Thermosynechococcus sp. CL-1 (TCL-1) productivity of biomass and C-phycocyanin were observed. The variation of light factors (intensity, color and arrangement) and concentration of dissolved inorganic nitrogen (DIN) from 2.9 to 116.7 mM were applied in the TCL-1 cultivation with 3 g/L initial biomass concentration. Moreover, extended cultivation using two DIN concentrations with better results and various lighting arrangements were conducted. Additionally, the malondialdehyde (MDA) content in the biomass was also measured as the indicator of oxidative stress. The double-side lighting arrangement with the intensity of 500 and 1000 μmole m⁻² s⁻¹ reach better biomass productivity while the mixed lighting with red LED enhances C-phycocyanin productivity. Outstanding C-phycocyanin productivity of 281.4 ± 10 mg L⁻¹ day⁻¹ is achieved by the application of double side mixed color lighting and the intensity of 250 μmole m⁻² s⁻¹ on each side. Application of 2.9 mM DIN in the TCL-1 culture gains the highest biomass productivity recorded as 2022 ± 162 mg L⁻¹day⁻¹. Otherwise, highest C-phycocyanin productivity is 201.6 ± 40.4 mg L⁻¹day⁻¹ with 14.6 mM DIN. The higher concentration of MDA, which indicates the larger amount of free radical in the FPBR, is produced in the cultivation using 2.9 mM DIN.
CO2 bio-fixation by photosynthetic microorganisms not only offer high efficiency on its process, but also produce valuable byproducts. Carotenoids are one of the interesting byproducts of the photosynthetic microorganism cultivation due to its wide application in industries. Isolated cyanobacterium, Thermosynechococcus sp. CL-1 (TCL-1), was assessed for its theoretical feasibility of performance on biomass productivity, carotenoid (zeaxanthin, β-carotene) productivity and CO2 fixation rate. The cultivation carried out under various growth factors including light intensity, concentration of nitrogen supply and salinity.
Cultivation with the addition of 5.8 mM nitrogen supply under light intensity of 1000 μE/m²/s and 0.14 M salinity gained the best results on biomass productivity (90.3 mg/L/h) and CO2 fixation rate (129.1 ± 5.5 mg/L/h) at the 8th hour of cultivation. This results related with the highest zeaxanthin productivity which reached 0.074 ± 0.004 mg/L/h and β-carotene productivity of 0.39 ± 0.03 mg/L/h. The results indicated that TCL-1 is the potential source to efficiently produce carotenoid compounds.
In this paper, an optimal minimal variation control in the fed-batch fermentation of glycerol bioconversion to 1,3-propanediol (1,3-PD) caused by Klebsiella pneumonia (K. pneumonia) is considered. In fed-batch process, it is required for the concentration of 1,3-PD to satisfy a quality constraint (i.e., the concentration of 1,3-PD at the terminal time is to reach a critical value), and furthermore, the cost associated with the change of the control signal must also be taken into account. It is formulated as an optimal control problem in which the total variation of the control signal is taken as the cost function, while the feeding rates of glycerol and alkali and the switching instants are taken as decision variables. The optimal control problem is subject to the quality constraint and certain continuous state inequality constraints. To handle the continuous state inequality constraints, the optimal control problem is approximated as a sequence of nonlinear programming subproblems. Because of the nature of the optimal control problem, which is highly complicated, a parallel algorithm is proposed to solve these subproblems based on genetic algorithm and the gradients of the constraint functions with respect to decision variables. From extensive simulation studies, it is observed that the obtained optimal feeding rates and switching instants are highly satisfactory.
Chlorella vulgaris is used for food and feed applications due to its nutraceutical, antioxidant and anticancer properties. An airlift photobioreactor comprising transparent draft tube was used for C. vulgaris cultivation. The effect of reactor parameters like hydrodynamics (0.3–1.5 vvm), light intensity (85–400 μmol m⁻² s⁻¹), photoperiod (12–24 h) and gas-phase carbon dioxide (CO2) concentration (5–15% v/v) were evaluated on microalgae and associated bacterial growth, biochemical profile; with special emphasis on ω-3, ω-6 fatty acids, and vitamin B12. The optimal growth of C. vulgaris without CO2 supplementation was observed at 1.2 vvm, which was associated with higher algal productivity, chlorophyll, vitamin B12 content, and bacterial load along with 72% of nitrate removal. The higher light intensity (400 μmol m⁻² s⁻¹) and photoperiod (24:0) increased biomass productivity and ω-3 fatty acid content (in lipid) up to 2–3 fold. The elevated levels of gas-phase CO2 concentration (15% v/v) enhanced EPA content up to 7% and biomass productivity up to 171 mg L⁻¹ day⁻¹. However, the increase in CO2 concentration lowered vitamin B12 content (up to 30%) and bacterial load (2–3 log). Also, all the cultivation conditions favoured desirable ω-6/ω-3 ratio(in the range of 1–2).
Phycobiliproteins are a group of water soluble proteins with an associated chromophore, responsible for the light-harvesting in cyanobacteria. They are divided in four main types: phycoerythrin, phycocyanin, phycoerythrocyanin and allophycocyanin, and they are characterized according to their structure and light quality absorption. Phycobiliproteins from cyanobacteria have been described as potential bioactive compounds, and recognized as high-valued natural products for biotechnological applications. Moreover, phycobiliproteins have been associated to antioxidant, anticancer and anti-inflammatory capacities among others. Thus, in order to produce phycobiliproteins from cyanobacteria for industrial application, it is necessary to optimize the whole bioprocess, including the processing parameters (such as light, nitrogen and carbon source, pH, temperature and salinity) that affects the growth and phycobiliprotein accumulation, as well as the optimization of phycobiliproteins extraction and purification. The aim of this review is to give an overview of phycobiliproteins not only in terms of their chemistry, but also in terms of their biotechnological applicability and the advances and challenges in the production of such compounds.
This research aimed to study factors suitable for cultivation of Spirulina platensis in a greenhouse including its preliminary economic analysis. The growth rate of algae was divided into 2 experiments. The first experiment studied effects of type and duration of light emitted diode (LED) illumination on cultivation of algae. The second experiment studied the photo flux density (PFD) affecting the cultured algae and its specific growth rate models. It was found that the controlled cultivation of algae in a greenhouse yielded better growth rate than that of algae cultivated in natural system. The LED illumination with the ratio of red and blue as 3:1 with lighting period of 16 hours per day at 350 μmol/m 2 s yielded the best growth of Spirulina platensis. From economic analysis, the development of smart algae farming by LED electric solar cell was found to have breakeven point of 2.03 years.
Magnetic cobalt ferrite/silica nanoparticles (MSNs) and methyl functionalized MSNs (methyl‐MSNs) were used to enhance lipid production in Chlorella vulgaris culture through enhancement of gas‐water mass transfer and increased dissolved concentration of CO2. Methyl‐MSNs enhanced CO2–water mass transfer rate better than MSNs, and 0.3 wt% methyl‐MSNs are more effective than 0.1 wt% MSNs. In the cultivation experiment, 0.3 wt% methyl‐MSNs yielded the highest dry cell weight and subsequently, the highest mass transfer rate. However, enhancement of mass transfer rate did not increase lipid content. The volumetric lipid productivity in C. vulgaris culture depends not only on intracellular lipid content but also on the cell mass concentration. Consequently, 0.1 wt% methyl‐MSNs yielded the highest volumetric lipid productivity in C. vulgaris cultivation. This article is protected by copyright. All rights reserved.
In order to shift the world to a more sustainable future, it is necessary to phase out the use of fossil fuels and focus on the development of low-carbon alternatives. However, this transition is slow so there still exists a large dependence on fossil-derived power and therefore CO2 release. Owing to the potential for assimilating and utilizing CO2 to generate carbon neutral products such as biodiesel, the application of microalgae technology to capture CO2 from flue gases has gained significant attention over the past decade. Microalgae offer a more sustainable source of biomass energy over conventional fuel crops since they grow more quickly and do not adversely affect food supply. This review focuses on the technical feasibility of combined carbon fixation and microalgae cultivation for carbon reuse. We appraise a range of different C metabolisms and the impact of flue gas compounds on microalgae. Fixation of flue gas CO2 is found to be dependent on the selected microalgae strain and on flue gas compounds/concentrations. Additionally, we assess current pilot-scale demonstrations of microalgae technology for CO2 capture as well as discuss its future prospects. Practical implementation of this technology at an industrial-scale still requires significant research, necessitating multidiscipline R&D to demonstrate its viability for CO2 capture from flue gases at the commercial level.
A photobioreactor in the form of a 245-m-long loop made of plexiglass tubes having an inner diameter of 2.6 cm was designed and constructed for outdoor culture of Spirulina. The loop was arranged in two planes, with 15 8-m-long tubes in each plane. In the upper plane, the tubes were placed in the vacant space between the ones of the lower plane. The culture recycle was performed either with two airlifts, one per plane, or with two peristaltic pumps. The power required for water recycle in the tubular photobioreactor, with a Reynolds number of 4000, was 3.93 × 10−2 W m−2. The photobioreactor contained 145 L of culture and covered an overall area of 7.8 m2. The photobioreactor operation was computer controlled. Viscosity measurements performed on Spirulina cultures having different biomass concentrations showed non-Newtonian behavior displaying decreasing viscosity with an increasing shear rate. The performance of the two-plane photobioreactor was tested under the climatic conditions of central Italy (latitude 43.8° N, longitude 11.3° E). A biomass concentration of 3.5 g L−1 was found to be adequate for outdoor culture of Spirulina. With a biomass concentration of 6.3 g L−1, the biomass output rate significantly decreased. The net biomass output rate reached a mean value of 27.8 g m−2 d−1 in July; this corresponded to a net photosynthetic efficiency of 6.6% (based on visible irradiance). © 1993 John Wiley & Sons, Inc.
The heterotrophic marine microalga Crypthecodinium cohnii produces docosahexaenoic acid (DHA), a polyunsaturated fatty acid with food and pharmaceutical applications. So far, DHA production has been studied with glucose and acetic acid as carbon sources. This study investigates the potential of ethanol as an alternative carbon source for DHA production by C. cohnii. In shake-flask cultures, the alga was able to grow on ethanol. The specific growth rate was optimal with 5 g l-1 ethanol and growth did not occur at 0 g l-1 and above 15 g l-1. By contrast, in fed-batch cultivations with a controlled feed of pure ethanol, cumulative ethanol addition could be much higher than 15 g l-1, thus enabling a high final cell density and DHA production. In a representative fed-batch cultivation of C. cohnii with pure ethanol as feed, 83 g dry biomass l-1, 35 g total lipid l-1 and 11.7 g DHA l-1 were produced in 220 h. The overall volumetric productivity of DHA was 53 mg l-1 h-1, which is the highest value reported so far for this alga.
Progress has been made in the past decade in developing appropriate technology for microalgal mass cultivation. This review details basic requirements required in order to achieve high productivity and low cost of production. There is a need for a wide variety of algal species and strains that will favorably respond to the varying environmental conditions existing outdoors. Another essential requirement is for better bioreactors, either by improving existing open raceway types or developing tubular closed systems. The latter solution seems more promising. These developments must overcome the main limitation confronting the industry today which is the overall low areal yields which fall too short of the theoretical maximum and which are associated with scaling up microalgal culture to commercial size.
It is well known that plants vary in the sensitivity of the photosynthetic apparatus to radiation of different wavelengths (Rabinowitch 1951). This would seem to eliminate any possibility of a unique definition of photosynthetically active radiation (PAR) for use in ecophysiology. Gabrielsen (1960), in his review of photosynthetic action spectra for the original edition of this encyclopedia, gave two basic reasons why this is not so: the variations in spectral response become important only when (1) the spectrum of the radiation is changing, and (2) the photosynthetic rate is limited by the amount of radiation available.
The light assimilation curves of 10 Cuban macroscopic marine plants presented assimilation plateaus except for those few cases with photoinhibition due to excess light, high temperature, or water stagnation inside unshaken incubation bottles.The studied brown algae had an average compensation irradiance (Ik) value lower than the Ik for both green algae and seagrasses.As bottles cannot be adequately agitated during in situ experiments at different depths, this type of field work should be designed only to determine relative photosynthesis values. Because of temperature increments due to artificial lighting, laboratory experiments should provide temperature control during incubations.
Spirulina sp. was able to grow photoautotrophically (in the light), heterotrophically (on glucose) and mixotrophically (simultaneously in the light and on glucose). The highest specific growth rate was reached in mixotrophic culture (0.055h−1, above I=30Wm−2, CGl=0.5gl−1). The specific growth rate of the alga on 2.5gl−1 glucose was markedly increased with increasing light intensity up to 30Wm−2. In photoautotrophic culture at a light intensity above 50Wm−2 photoinhibition occurred.Unstructured kinetic models to describe microalgal culture system including photoautotrophic, heterotrophic and mixotrophic specific growth rate as a function of light intensity and glucose concentration were proposed. The models demonstrated that the light intensity for autotrophic culture was 30–50Wm−2, glucose concentration for heterotrophic growth was >0.5gl−1 and for mixotrophic growth of Spirulina sp. in batch culture using 1l photobioreactor was >30Wm−2 and glucose concentration >0.5gl−1.
Photosynthetic CO2 fixation was investigated in a cylindrical shaped helical tubular photobioreactor incorporating the filamentous cyanobacterium Spirulina platensis. A laboratory scale photobioreactor was constructed with a 0.25 m2 basal area in a cylindrical shape(0.9 m high × 0.57 m diameter). The photostage comprised transparent polyvinyl chloride tubing (60 m in length and 1.6 cm internal diameter with 0.3 cm wall thickness, total volume=12.1 litre). The inner surface of the photostage (1.32 m2) was illuminated with cool white fluorescent lamps; the photosynthetically active radiation(PAR, 400–700 nm) energy input into the bioreactor was 2920 kJ per day. The operation of the air-lift photobioreactor with CO2 enriched air(4%) at a flow rate of 0.3 litre min−1 showed a maximum daily photosynthetic efficiency of 5.45 % (PAR) under batch culture conditions. This corresponded to a production rate of 30.2 g dry weight (14.6 gC) m−2 (basal area) day−1.
The relationship between the tilt angle of a flat-plate photobioreactor and productivity of Spirulina platensis was evaluated along with the annual seasons under the climatic conditions of south Israel (latitude approx. 31°). The reactor tilt angle exerted a significant effect on the optimal population density and thus on the productivity of cell mass, owing to its control over the amount of solar radiation entering the reactor. A direct relationship between solar energy and productivity was observed: the higher the amount of solar energy that was admitted by varying the reactor tilt angle according to season, the higher was the productivity that could be sustained in the culture. Small tilt angles of 10° to 30° in summer and larger angles in the vicinity of 60° in winter resulted in maximal productivities for these seasons. Photosynthetic efficiency was calculated for the different tilt angles for all seasons. Efficiency was low in the winter due to temperature limitations. In summer it was highest in the 90° reactors, indicating that for optimal tilt angles in this season (in regards to productivity) a significant amount of radiation could not be effectively used by the culture. The results suggest a potential benefit in orientating and tilting reactors at various appropriate angles to the sun on a seasonal basis: up to 35% enhancement in annual output rate is estimated to be achievable.
This preliminary study aims at evaluating the efficiency of a bench-scale tubular photobioreactor by means of batch cultivations of Spirulina platensis under light-limited conditions. The most interesting feature of this plant configuration is the use of an airlift system for biomass re-cycling instead of traditional pumps to avoid the well-known problems of trichome damage owing to mechanical stress. A maximum cell concentration of 10.6gl−1 was attained after 15 days of cultivation using a photosynthetic active radiation of 120μmolphotonsm−2s−1. Although the system operated in laminar flow under all the conditions investigated in this study, excess thricome stress was prevented only at relatively low air flow rates (
The ability of Spirulina platensis LB2340 to grow on carbon dioxide and mixtures of bicarbonate/carbonate was compared under light irradiation conditions simulating those naturally present in temperate latitudes. Batch tests performed at 25 °C in open tanks suggested that inorganic carbon is preferentially assimilated in the form of bicarbonate and that its utilization efficiency depends either on pH or final biomass level. The efficiencies of photosynthesis (PE) and carbon utilization (CUE) on carbon dioxide reached maximum values (>6 and 38%) after 4 and ≥7 days, respectively. They then progressively decreased. Fed-batch tests performed on carbon dioxide showed the highest values of biomass concentration (1.50 g l−1) and PE (1.1%) under pseudo steady-state conditions at 0.25 l per day feeding rate.
The photoinhibition of photosynthesis was investigated in two morphotypes of the red alga Corallina elongata, i.e. sun and shade types, using pulse amplitude modulated (PAM) chlorophyll fluorescence and oxygen evolution. The contents of chlorophyll, phycoerythrin, phycocyanin and soluble protein were analysed. Exposure to solar radiation caused a strong decrease in the effective photosynthetic quantum yield. This decline was more pronounced in the shade than in the sun morphotype. The plants partially recovered from this effect, indicating that it was mainly due to reversible photoinhibition and, to a smaller extent, non-reversible photodamage. Photoinhibition occurred in this alga even in its natural habitat when the sun was at high angles. Recovery from photoinhibition was higher in algae grown in the sun than in the shade. The net photosynthetic oxygen production was higher in the shade than in the sun morphotype. A decrease in oxygen evolution was observed at about noon, recovering at dusk. The concentrations of chlorophyll a (Chl a) and phycoerythrin were higher in the shade than in the sun morphotype. The Chl a and phycocyanin contents did not change significantly throughout the day. However, a clear daily variation in phycoerythrin content was observed with a strong decrease around noon. The soluble protein concentration decreased around noon, but only in the sun morphotype. The relationship between the photosynthetic quantum yield, oxygen evolution and pigment concentration is discussed, together with photoinhibition.
The commercial culture of microalgae is now over 30 years old with the main microalgal species grown being Chlorella and Spirulina for health food, Dunaliella salina for β-carotene, Haematococcus pluvialis for astaxanthin and several species for aquaculture. The culture systems currently used to grow these algae are generally fairly unsophisticated. For example, Dunaliella salina is cultured in large (up to approx. 250 ha) shallow open-air ponds with no artificial mixing. Similarly, Chlorella and Spirulina also are grown outdoors in either paddle-wheel mixed ponds or circular ponds with a rotating mixing arm of up to about 1 ha in area per pond. The production of microalgae for aquaculture is generally on a much smaller scale, and in many cases is carried out indoors in 20–40 1 carboys or in large plastic bags of up to approximately 1000 1 in volume. More recently, a helical tubular photobioreactor system, the BIOCOIL™, has been developed which allows these algae to be grown reliably outdoors at high cell densities in semi-continuous culture. Other closed photobioreactors such as fiat panels are also being developed. The main problem facing the commercialisation of new microalgae and microalgal products is the need for closed culture systems and the fact that these are very capital intensive. The high cost of microalgal culture systems relates to the need for light and the relatively slow growth rate of the algae. Although this problem has been avoided in some instances by growing the algae heterotrophically, not all algae or algal products can be produced this way.
Spirulina (Arthrospira) platensis (Nordstedt) Geitler cells grown under mixotrophic conditions exhibit a modified response to light. The maximal photosynthetic rate and the light saturation value of mixotrophic cultures were higher than those of the photoautotrophic cultures. Dark respiration and light compensation point were also significantly higher in the mixotrophically grown cells. As expected, the mixotrophic cultures grew faster and achieved a higher biomass concentration than the photoautotrophic cultures. In contrast, the growth rate of the photoautotrophic cultures was more sensitive to light. The differences between the two cultures were also apparent in their responses to exposure to high photon flux density of 3000 μmol·m−2·s−1. The light-dependent O2 evolution rate and the maximal efficiency of photosystem II photochemistry declined more rapidly in photoautotrophically grown than in mixotrophically grown cells as a result of exposure to high photon flux density. Although both cultures recovered from the high photon flux density stress, the mixotrophic culture recovered faster and to a higher extent. Based on the above results, growth of S. platensis with a fixed carbon source has a significant effect on photosynthetic activity.
In crop ecology, the two most popular definitions of photosynthetically active radiation are the irradiance (radiant power flux density) in the waveband 400 to 700 nm, and the quantum flux density in the same waveband. Instruments calibrated in either of these two units are available. Calculations show that the quantum flux measurement is less subject to the systematic error caused by the spectral response not matching the action spectrum for photosynthesis in an “average crop plant” (11) than is the irradiance measurement. The range of errors is ±6 and ±16 per cent, respectively, for the 9 natural and artificial light sources examined. The imperfections of the instruments themselves are not included.
Since microalgae have a high photosynthetic capability, solar energy-driven CO2 fixation technologies using microalgae have the potential to convert CO2 in the stack gas from a thermal power station into energy-rich biomass. We investigated a new design of photobioreactor in order to achieve efficient photosynthetic performance. The system has several advantages over the conventional mass culture system of microalgae. We have investigated the energy and material balances of microalgal biomass production in a photobioreactor system both theoretically and experimentally. CO2 conversion to microalgal biomass in the laboratory scale conical-shaped helical tubular photobioreactor incorporating Spirulina platensis was investigated. The photobioreactor system was constructed with a basal area of 0.255 m2. The total volume of photostage was 6.23 litre with 0.651 m2 light absorbing area (inner surface of cone). The photostage was illuminated with cool white fluorescent lamps, the daily energy input of the photosynthetic active radiation (PAR, 400–700nm) into the photobioreactor was 1249 kJ. The productivity of Spirulina platensis of this photobioreactor was 15.9 g dry biomass per m2 (basal area) per day, or 0.51 g dry biomass litre−1 day−1. This corresponded to a photosynthetic efficiency of 6.83 % (PAR). According to these results, a large scale microalgal production using a unit basic type photobioreactor (1 m2 basal area) is discussed.
A preliminary attempt is presented to remove glucose, acetate and propionate, selected as model organic pollutants, by fed-batch Arthrospira platensis mixotrophic cultivation. Cultures performed at 30 °C by pulse feeding glucose under conditions of con-tinuous 2.0 klux light were shown to ensure a final biomass concentration (1.3 g l -1) about 40% higher than alternating 12 h light and 12 h darkness. Additional tests, carried out using continuous illumination, demonstrated that the average specific growth rate of A. platensis, calculated during the start-up, was on glucose (0.096 d -1) higher than on acetate (0.074 d -1), propionate (0.068 d -1) or a bicarbonate/carbonate solution taken as a reference of autotrophic metabolism (0.072 d -1). Nitrate and phosphate removals, either exper-imentally determined or theoretically estimated by material balances, evidenced the biotic nature of both phenomena.
Arthrospira (Spirulina) platensis (Nordstedt) Gomont was cultivated under light-limited conditions in 5-L open tanks by daily supplying NH4Cl as nitrogen source. Exponentially increasing feeding rates were adopted to prevent ammonia toxicity. The total feeding time (T) was varied between 12 and 20 days, and the starting (m0) and total (mT) quantities of the nitrogen source per unit reactor volume were varied in the ranges 0.19–1.7 mM and 2.3–23.1 mM, respectively. This intermittent addition of the nitrogen source prevented ammonia from reaching inhibitory levels and ensured final cell concentrations (Xm) and cell productivities (Px) comparable with those of batch runs with KNO3. Moreover, the lower nitrogen addition due to the use of NH4Cl rather than KNO3 allowed for higher nitrogen-to-cell conversions (Yx/n). These results were evaluated using three-factor, five-level, central composite experimental planning, combined with the response surface methodology, selecting T, m0, and mT as the independent variables and Xm, Px, and Yx/n as the response variables. This approach allowed us to identify, through the simultaneous optimization of the variables, T=16 days, m0=1.7 mM, and mT=21.5 mM as the best conditions for A. platensis cultivation at 72 μmol photons·m−2·s−1. Under these conditions, a maximum cell concentration of 1239 mg ·L−1 was obtained, which is a value comparable with that obtained using KNO3 as nitrogen source and nearly coincident with the theoretical one estimated by the response surface methodology.
The effects of solar radiation on photosynthetic oxygen production and pulse amplitude modulated (PAM) fluorescence were measured in the marine brown macroalga Padina pavonia harvested from different depths from the Greek coast near Korinth. In fluence rate-response curves the light compensation point for photosynthetic oxygen production increased and the saturation level decreased with increasing exposure time to solar radiation. Cutting off the UV-B wavelength range (280–315 nm) from solar radiation reduced the inhibition of photosynthesis, and the organisms were less affected when all of the UV radiation was filtered out. Algae collected from 7 m depth were much more prone to photoinhibition than those harvested from rock pools exposed to unfiltered solar radiation. During continuous exposure to solar radiation, rock pool algae showed photoinhibition after longer periods of time than specimens from 7 m or from dark adapted habitats. When subjected to unfiltered solar radiation the ratio of the variable fluorescence to the maximal fluorescence (Fv = Fm− Fo) rapidly declined with increasing exposure time. However, again algae from 7 m depth were more prone to photoinhibition than rock pool algae. The differences between the two ecological strains were less obvious when UV-B or total UV was removed from solar radiation. Only in the latter case a complete recovery was observed after 2 h while, when exposed to unifiltered sunlight, only the rock pool algae recovered completely within that time.
This article focuses on the recent world-wide advances of the biotechnology of the increasingly important fed-batch (or semi-batch) cultivation technique used in microbial processes. The history and characteristics of the fed-batch technique in microbial reactions are reviewed and examples of those fed-batch operations are cited which have greatly increased the productivity of microbial conversions in comparison to conventional batch operation; the various fed-batch techniques will be classified according to the mode of nutrient-feeding. Theoretical mathematical models are compared with experimental results. Fed-batch cultures with automatic feedback control are discussed in detail. Cultivation of high microbial cell concentrations, repeated fed-batch operations, and the start-up of microbial processes are described and, finally, some future prospects of fed-batch techniques in microbial processes are discussed.
The mixotrophic growth of the diatom Phaeodactylum tricornutum UTEX-640 was studied using diverse substrates at different concentrations in discontinuous and fed-batch modes. The nutrients used were acetate (0.005–0.1 M), starch (0.5–5 g l−1), lactic acid (0.005–0.1 M), glycine (0.005–0.02 M), glucose (0.5–5 g l−1) and glycerol (0.005–0.1 M). Biomass concentration and biochemical profile were monitored. The capacity of the different nutrients to promote mixotrophic growth varied not only with its nature, but also with the concentration used for the experiment, showing how comparisons at the same concentration may be misleading. Subsequent fed-batch cultures using glycerol (0.1 M), and supplemented urea (0.01 M) and sodium nitrate (1 g l−1) as nitrogen sources, showed that repeated additions of organic substrate can sustain mixotrophic growth at very high density cultures. The best results were obtained using with urea (0.01 M), which resulted in maximum biomass and eicosapentaenoic acid productivities that were, respectively, 1.52 g l−1 per day and 43.13 mg l−1 per day, significantly higher than those obtained for the photoautotrophic control. Although the results reported here were obtained in flask cultures of only 1 l working volume and under low irradiance (165 μEm−2 s−1), similar data were reported for photoautotrophic growth on glycerol of this same strain in outdoor pilot-scale tubular photobioreactors (tube diameter 3 and 6 cm and to 50 and 200 l working volume, respectively), which suggest the possibility of using mixotrophy for the mass production of microalgae.
Chlorophyll is a pigment used as colorant in the food, pharmaceutical and cosmetic industries. It can be obtained in considerable quantities from Spirulina platensis biomass. In this work, the cultivation of the microalga was done using urea as the nitrogen source by a fed-batch process. The addition of urea was done in four different modes: intermittent addition every 24 or , continuous addition by exponentially increasing the added mass, and continuous addition by using a constant mass flow rate. The experiments were carried out at three different temperatures: and and at a constant light intensity of . The results showed a positive influence of urea in the growth of Spirulina but no effect on the final chlorophyll content of the cultures. Best results were obtained by continuous urea addition in exponentially increasing amount, at 30°C.
Spirulina platensis was autotrophically cultivated by fed-batch addition of urea as a nitrogen source. Continuous and pulse feeding regimes of this nitrogen source (time intervals of 24 h) were compared using a constant mass flow rate. Both series of experiments were carried out at three different temperatures (25, 28 and 31 °C) and total times of urea addition (12, 15 and 18 days), according to a 22 simple factorial design, and the effects of these variables on the nitrogen-to-cell conversion factor and cell productivity were verified by analysis of covariance (ANCOVA). The intermittent addition of urea yielded results similar to those obtained by the continuous feeding, therefore, the former operation mode would be preferable to reduce the production costs of this cyanobacterium in large-scale facilities.
Spirulina is one of the most extensively used microalgae for animal and human nutrition; its main interest is centered in its high protein content, 60–65% on a dry weight basis. In this study, Spirulina was grown in open raceway ponds, and several physicochemical (e.g., pH, dissolved oxygen concentration, temperature, conductivity and irradiance) and biological (e.g., biomass concentration and yield) variables were studied. The variables were correlated in order to implement a mathematical model to predict algal yield. Dissolved oxygen concentration in the cultivation ponds ranged between 10 mg l−1 in winter (115% of O2 saturation) and 30 mg l−1 in summer (375% of O2 saturation); a clear decrease of biomass concentration was found when dissolved oxygen was >25 mg l−1. Neither biomass concentration nor productivity was saturated at the maximum temperature achieved in the open pond during this study (approximately 28 °C). The pH seemed to control both the maximal algal density in the pond and the productivity that were found to be maximum at pH values below 10.5. Finally, all the variables were positively correlated with irradiance. Principal component analysis (PCA) allowed recognition of different sets of samples characterized by a combination of temperature, dissolved oxygen concentration, pH, biomass, productivity, irradiance and conductivity. This method helped to predict a significant loss of productivity in the open ponds in mid-summer due to high pH and high-dissolved O2 concentration.
The cyanobacterium Spirulina platensis is an attractive source of chlorophyll, a green pigment used in food, pharmaceutical and cosmetic industries, and other high-value cell components. Moreover, it can be easily and cheaply recovered by filtration from the cultivation medium. In this work, the replacement of potassium nitrate with ammonium sulphate (A) and urea (U) as cheaper nitrogen sources has been investigated: previous research work did in fact demonstrate that urea has no effect on the final chlorophyll content of the cultures. Several batch and fed-batch protocols were tested, modelled and compared in this work for the first time. It was demonstrated that the kinetics of S. platensis growth at 30°C, using urea as nitrogen source, can be comparable and even better than the one achievable with the classic nitrate-based culture media. Adoption of an appropriate slowly increasing urea feeding rate prevented the accumulation of ammonia in the medium as well as its well-known inhibition of biomass growth; therefore, the use of urea should be recognized as a possible way to decrease the costs of a large-scale plant for the production of this cyanobacterium.
A mixotrophic culture might be used as an alternative to conventional photoautotrophic mass culture systems for production of high value chemicals and pharmaceuticals by Spirulina platensis. The possibility of using mixotrophic culture to achieve high cell densities and phycocyanin productivities was investigated using fed-batch culture in a 3.7-l fermentor. In fed-batch cultures, the highest cell concentration of 10.24 g l−1 (dry weight) and the highest phycocyanin production of 795 mg l−1 were achieved which were much higher than those reported in the literature. The highest biomass concentration and phycocyanin production in the mixotrophic fed-batch culture were 5.1-fold and 2.8-fold, respectively, of that obtained in the photoautotrophic batch culture using the same fermentor. The cellular phycocyanin content was enhanced with increasing photosynthetic activities. In the photoautotrophic batch culture, the phycocyanin content was constant at approximately 135 mg g−1 dry cells throughout the course of cultivation. In contrast, in the mixotrophic batch culture, the phycocyanin content was not constant. It increased from 54 mg g−1 to 125 g−1 dry cells during the course of cultivation presumably due to the continuous changes of heterotrophic to photoautotrophic domination. These results suggest that the maximum phycocyanin production should occur at the best combination of cell densities and photosynthetic activities in mixotrophic fed-batch cultures of the microalga.
Spirulina platensis cells, growing photoautotrophically in optimal media under 100 or 200 μmol m−2 s−1 photon flux densities (PFD), were exposed to different concentrations of sodium chloride, up to 0.75 M. After an initial acclimation phase, in which growth rate, photosynthetic activity and endogenous respiration were inhibited, a new steady state was established and a recovery in the photosynthetic activity was observed. Furthermore an increase in the respiration rate took place, exceeding the initial rate of the non-stressed cells. Photosynthetic light-response curves (P-I) of stressed cells showed that the light compensation points were increased and light saturation values were decreased under the different salinity-stress conditions. Photoinhibition of photosynthesis was significantly enhanced under salinity-stress. Photosystem II activities of cells substantially decreased after a salt-shock. The results show that, cells grown in higher PFD are less tolerant to salinity-stress than those grown in lower PFD.
The relationship between light intensity, nitrogen availability and pigmentation was investigated in mixotrophic and heterotrophic cultures of the unicellular red alga Galdieria sulphuraria 074G, a potential host for production of the blue pigment, phycocyanin (PC). During the exponential growth phase of batch cultures, G. sulphuraria 074G contained 2–4 mg phycocyanin per g dry weight. In carbon-limited and nitrogen-sufficient batch cultures grown in darkness, this value increased to 8–12 mg g−1 dry weight during the stationary phase, whereas the phycocyanin content in nitrogen-deficient cells decreased to values below 1 mg g−1 dry weight during stationary phase. Light intensities between 0 and 100 μmol photons m−2 s−1 had no influence on phycocyanin accumulation in mixotrophic cultures grown on glucose or fructose, while light stimulated phycocyanin synthesis in cultures grown on glycerol, in which the phycocyanin content in stationary phase was increased from 10 mg g−1 dry weight in darkness to 20 mg g−1 dry weight at a light intensity of 80 μmol photons m−2 s−1. At higher light intensities, less phycocyanin accumulated than at lower intensities, irrespective of the carbon substrate used. In carbon-limited continuous flow cultures grown on glucose or glycerol at a dilution rate of 0.63 day−1, corresponding to 50% of the maximum specific growth rate, the highest steady-state phycocyanin content of 15–28 mg g−1 dry weight was found at 65 μmol photons m−2 s−1. In contrast to the apparent glucose repression of light-induced PC synthesis observed in batch cultures, no glucose repression of the light stimulation was observed in continuous flow cultures because the glucose concentration in the culture supernatant always remained at limiting levels. Despite the fact that G. sulphuraria 074G contains less phycocyanin than some other microalgae and cyanobacteria, the ability of G. sulphuraria 074G to grow and synthesize phycocyanin in heterotrophic or mixotrophic cultures makes it an interesting alternative to the cyanobacterium, Spirulina platensis presently used for synthesis of phycocyanin.
Mixotrophic culture may be used as an efficient means for enhanced production of light-induced pigments in microalgae. The growth and pigments formation of the green microalga Chlorella zofingiensis cultivated at various glucose and nitrate concentrations in mixotrophic culture were investigated. High glucose and low nitrate concentrations favoured the production of astaxanthin in the algal culture. The highest yield of astaxanthin was 12.5 mg l−1, which was obtained in the medium containing 30 g l−1 glucose and 0.55 g l−1 nitrate. The results indicated that supplementation of glucose and nitrate in the culture medium could be effectively manipulated to enhance astaxanthin production by C. zofingiensis in mixotrophic culture.
This paper reviews bioreactor related aspects of large scale plant cell technology for the production of biologically active compounds. Bioreactor designs currently in use are discussed with respect to specific operating parameters that can be varied to modulate cell growth and function in order to optimize product release and separation. Flow and mixing are recognized as key factors responsible for both the direct hydrodynamic effects on cell shape and function and flow induced changes in mass transfer of nutrients and metabolites. The integration of biosynthesis and separation is considered as a possible approach towards more efficient plant cell and tissue culture.
Cell cultures of Beta vulgaris were developed in an air lift bioreactor of 10 dm3. Culture broth rheology exhibited non-Newtonian, shear thinning characteristics. The pseudoplasticity of the broth was governed by the presence of the cells as well as by the proteins secreted by the cells in the medium. The accumulation of extracellular proteins produced an increase in the viscosity and a change in the rheological properties of the cell-free medium. This phenomena may be a response of the cells to hydrodynamic stress. The accumulation of extracellular proteins and the change in the rheology of cell-free medium were discussed with respect to those data reported in literature obtained in shake flasks and stirred tank bioreactor.
Short-term illumination of the green algae, Chlamydobotrys stellata and Chlamydomonas reinhardtii in CO2-depleted cultivation medium under low photon flux density (50 and 150 μmol m−2 s−1, respectively) resulted in an inhibition of Photosystem II electron transport from water to diaminodurene, but only slightly affected the electron flow from water to 2,6-dichlorobenzoquinone. The intermediary fluorescence level, Fi was raised to the maximum level of fluorescence, Fm. The initial level of fluorescence, Fo was considerably enhanced. The development of the Fo rise was facilitated by low pH, but inhibited in the presence of an acceptor, dichlorobenzoquinone, or by chemical cross-linking of proteins with glutaraldehyde. The uninhibited electron transport and the original Fo level were restored by readdition of CO2 or by dark adaptation of algae. The observations suggest that in green alga cells CO2-depletion in the light results in a reversible inhibition of steady-state electron flow between the primary (QA) and secondary quinone electron acceptor (QB). Following the inhibition of electron transport a long-lived but reversible state of singly-reduced and probably protonated QA is formed which manifests itself as an apparent Fo rise. Prolonged photoinhibitory illumination of the CO2-depleted green alga cells resulted in an irreversible loss of variable fluorescence and electron transport. The photoinactivation developed more slowly in the CO2-depleted than in the CO2-containing cells. It is concluded that in the bicarbonate-depleted redox state, which is accompanied with an enhanced Fo level of fluorescence, the Photosystem II reaction center is less susceptible to photoinhibition than in the bicarbonate-containing state.
Principles of fluid mechanics, gas-liquid mass transfer, and irradiance controlled algal growth are integrated into a method for designing tubular photobioreactors in which the culture is circulated by an airlift pump. A 0.2 m(3) photobioreactor designed using the proposed approach was proved in continuous outdoor culture of the microalga Phaeodactylum tricornutum. The culture performance was assessed under various conditions of irradiance, dilution rates and liquid velocities through the tubular solar collector. A biomass productivity of 1.90 g l(-1) d(-1) (or 32 g m(-2) d(-1)) could be obtained at a dilution rate of 0.04 h(-1). Photoinhibition was observed during hours of peak irradiance; the photosynthetic activity of the cells recovered a few hours later. Linear liquid velocities of 0.50 and 0.35 m s(-1) in the solar collector gave similar biomass productivities, but the culture collapsed at lower velocities. The effect of dissolved oxygen concentration on productivity was quantified in indoor conditions; dissolved oxygen levels higher or lower than air saturation values reduced productivity. Under outdoor conditions, for given levels of oxygen supersaturation, the productivity decline was greater outdoors than indoors, suggesting that under intense outdoor illumination photooxidation contributed to loss of productivity in comparison with productivity loss due to oxygen inhibition alone. Dissolved oxygen values at the outlet of solar collector tube were up to 400% of air saturation.
The heterotrophic marine alga Crypthecodinium cohnii is known to produce docosahexaenoic acid (DHA), a polyunsaturated fatty acid with food and pharmaceutical applications, during batch cultivation on complex media containing sea salt, yeast extract, and glucose. In the present study, fed-batch cultivation was studied as an alternative fermentation strategy for DHA production. Glucose and acetic acid were compared as carbon sources. For both substrates, the feed rate was adapted to the maximum specific consumption rate of C. cohnii. In glucose-grown cultures, this was done by maintaining a significant glucose concentration (between 5 and 20 g/L) throughout fermentation. In acetic acid-grown cultures, the medium feed was automatically controlled via the culture pH. A feed consisting of acetic acid (50% w/w) resulted in a higher overall volumetric productivity of DHA (r(DHA)) than a feed consisting of 50% (w/v) glucose (38 and 14 mg/L/h, respectively). The r(DHA) was further increased to 48 mg/L/h using a feed consisting of pure acetic acid. The latter fermentation strategy resulted in final concentrations of 109 g/L dry biomass, 61 g/L lipid, and 19 g/L DHA. These are the highest biomass, lipid, and DHA concentrations reported to date for a heterotrophic alga. Vigorous mixing was required to sustain aerobic conditions during high-cell-density cultivation. This was complicated by culture viscosity, which resulted from the production of viscous extracellular polysaccharides. These may present a problem for large-scale industrial production of DHA. Addition of a commercial polysaccharide-hydrolase preparation could decrease the viscosity of the culture and the required stirring.
Arthrospira platensis was cultivated photoautotrophically at 6.0 klux light intensity in 5.0-L open tanks, using a mineral medium containing urea as nitrogen source. Fed-batch experiments were performed at constant flowrate. A central composite factorial design combined to response surface methodology (RSM) was utilized to determine the relationship between the selected response variables (cell concentration after 10 days, X(m), cell productivity, P(X), and nitrogen-to-cell conversion factor, Y(X/N)) and codified values of the independent variables (pH, temperature, T, and urea flowrate, K). By applying the quadratic regression analysis, the equations describing the behaviors of these responses as simultaneous functions of the selected independent variables were determined, and the conditions for X(m) and P(X) optimization were estimated (pH 9.5, T = 29 degrees C, and K = 0.551 mM/day). The experimental data obtained under these conditions (X(m) = 749 mg/L; P(X) = 69.9 mg/L.day) were very close to the estimated ones (X(m) = 721 mg/L; P(X) = 67.1 mg/L.day). Additional cultivations were carried out under the above best conditions of pH control and urea flowrate at variable temperature. Consistently with the results of RSM, the best growth temperature was 29 degrees C. The maximum specific growth rates at different temperatures were used to estimate the thermodynamic parameters of growth (DeltaH* = 59.3 kJ/mol; DeltaS* = -0.147 kJ/mol.K; DeltaG* = 103 kJ/mol) and its thermal inactivation (DeltaH(D) (o) = 72.0 kJ/mol; DeltaS(D) (o) = 0.144 kJ/mol.K; DeltaG(D) (o) = 29.1 kJ/mol).
Outdoor production of microalgae could be set on a sound industrial basis if solar energy were utilized at a much higher efficiency than presently obtained. Many types of photobioreactors have been developed in the past in an attempt to answer this challenge, but their photosynthetic efficiency has been rather similar to the basically inefficient open raceway commonly used today. Efficient utilization of the oversaturating solar energy flux mandates that reactors should have a narrow lightpath to facilitate ultra-high cell densities, be maximally exposed to sunshine, and have an efficient mixing system to create strong turbulent streaming to affect dark-light cycles of the highest possible frequency.
Quantitative analysis
- W C Pierce
- E L Haenisch
W.C. Pierce, E.L. Haenisch, Quantitative analysis, 3rd edn, John Wiley & Sons, Inc, New York, 1948.
Coltura massiva di Spirulina platensis in sistemi colturali aperti
- Materassi
R. Materassi, W. Balloni, B. Pushparaj, E. Pelosi, C. Sili, Coltura massiva di Spirulina platensis in sistemi colturali aperti, in: R. Materassi (Ed.), Prospettive della Coltura di Spirulina in Italia, Consiglio Nazionale delle Ricerche, Roma, 1980, p. 241 (1980).
Spirulina: growth, physiology and biochemistry
- Vonshak
Fermentação descontínua alimentada
- Carvalho
Mixotrophic growth of the microalga Phaeodactylum tricornutum—Influence of different nitrogen and organic carbon sources on productivity and biomass composition
- Garcia