Culture Salinity Research Articles

Growth and Development of Stadia Artemia salina in Culture with Different Concentration of Bran Suspension

The annual need for Artemia in Indonesia reaches 40-60 tons, but up to now 100% of this need is still imported. Various efforts have been made to produce Artemia cysts, but the main obstacle in cultivating Artemia to produce cysts is the availability of natural food, namely phytoplankton which can survive in high salinity. The use of organic materials such as bran can be a solution for feeding and can increase the density of Artemia, but excessive use of bran suspension in Artemia cultivation ponds can trigger a decrease in the quality of the water for the growth of Artemia. This research was conducted to determine the optimal concentration of bran feed for the growth and development of Artemia salina without compromising the water quality of the cultivation. The Artemia feed used in this study was a bran suspension enriched with lemuru fish oil (12 ml/L bran suspension). The bran feed concentration treatments in this study were 5 treatments sequentially, namely P1 to P5 with feed concentrations of 11, 18, 26.34, and 41 mg/L. Artemia salina cultivation in this study was carried out at an initial density of 50 ind/L with a salinity of 30 pptl. The research results showed that cultivating Artemia salina using bran suspension feed with different concentrations had an effect on the growth and development of Artemia salina. The best growth and development of Artemia results from cultivation using bran suspension feed with a concentration of 41 mg/L.

Культивирование Dunaliella salina на питательной среде из нейтрально-сульфитных щелоков

The effectiveness of cultivation of microalgae Dunaliella salina in the nutrient medium from neutral-sulfite alkalis obtained during the production of cellulose from birch wood, with additional sodium chloride addition was established. D. salina microalgae were isolated from the bottom sediment of the Koyash Lake of the Kerch Peninsula. It was shown that the physiological activity of microalgae was affected by the amount of sodium chloride introduced into the nutrient medium. When up to 5 % sodium chloride is added to the nutrient medium. D. salina microalgae exhibit halotolerant properties when up to 5 % of sodium chloride is added to the nutrient medium. With an increase in the amount of sodium chloride introduced up to 30 %, D. salina culture exhibits halophilic properties. The best kinetic characteristics of the growth of D. salina when cultivated in the nutrient medium from neutral sulfite alkalis were observed at halophilic physiological activity. The yield of biomass of D. salina microalgae when cultivated in the nutrient medium without and when 5 % sodium chloride was added to the nutrient medium from neutral-sulfite alkalis is higher compared to the addition of 15 and 30 % sodium chloride to the nutrient medium. However, the accumulation of protein has an opposite dependence, in particular, the protein content of the culture fluid, in which 15 and 30 % sodium chloride was applied is higher than that when 5 % sodium chloride was applied. With an increase in the duration of cultivation up to 240 hours, a decrease in the pH of the nutrient medium from 7.04 to 4.70 was observed, this was due to the assimilation by microalgae of mineral and organic-bound nitrogen present in the nutrient medium from neutral-sulfite alkalis. It was established that during cultivation microalgae assimilate both reducing substances and coloring substances present in the nutrient medium, which results in intensive cell growth. With an increase in the duration of cultivation of microalgae, an increase in the number of cells in the culture fluid to 4 ⋅ 106 cl/ml was observed, which at the same time synthesize the extracellular enzyme xylanase, which contributes to the additional formation of reducing substances in the nutrient medium due to the enzymatic hydrolysis of xylan. The obtained research results show the prospects of using neutral-sulfite alkalis in biotechnology in the cultivation of D. salina microalgae for the production of biological products. For citation: Iksanov R.A., Kanarsky A.V., Kanarskaya Z.A., Gеmatdinova V.M. Cultivation of Dunaliella salina Microalgae in the Nutrient Medium from Neutral-Sulfite Alkalis. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 6, pp. 162–175. (In Russ.). https://doi.org/10.37482/0536-1036-2023-6-162-175

Learning from fluorescence: A tool for online multiparameter monitoring of a microalgae culture

We propose a systematic approach for monitoring important productivity parameters in a Dunaliella salina culture using 2D fluorescence data. For this purpose, a methodology based on Machine Learning algorithm Projection to Latent Structures Regression (PLSR) coupled with variable selection strategies was used. Additionally, a robustness analysis is proposed to support the validation of the yielded models and provide a measure of their reliability. Robust (i.e., Q2≥ 0.5) and parsimonious (i.e., selecting down to 3 % of the fluorescence variables present in a 250–700 nm wavelength excitation-emission matrix) models were obtained for monitoring cell count, chlorophyll b, total carotenoids and β-carotene culture concentration, and the ratio between total carotenoids and total chlorophylls, all of which were validated with a left-out batch performing with R2 higher than 0.7 except for β-carotene (R2 = 0.54).

The Effect of Sodium Chloride on Biomass Growth and Protein Synthesis during Cultivation of Dunaliella salina Microalgae on a Nutrient Medium from Beet Molasses

Introduction. Currently, the applications of halophiles of the genus Halobacteriaceae are mainly limited to the use of β-carotene and hydrolases in the food and cosmetic industries. The expansion of halophile applications in biotechnology is based on the synthesis of effective and highly specific biocatalysts that can meet industrial needs. Halophiles are excellent sources of enzymes that are not only resistant to salt, but can also be effective in other extreme conditions. The resistance of halophiles to external factors is of increasing interest to them from biotechnologists, because they are the source of many BAS, and their habitat allows cultivation in non-sterile conditions. In this regard, it is of scientific and practical interest to determine the possibility of using D. salina bacteria in industry, which are recommended for wastewater treatment, expression of recombinant proteins, production of biofuels, production of natural polymer materials.Purpose. To study the effectiveness of cultivation of microalgae Dunaliella salina (D. salina) on a nutrient medium from molasses, experiments with additional addition of sodium chloride were carried out in this work.Materials and Methods. The review includes foreign articles published in English for the period 2010-2023. Search for scientific articles on suitable topics in the bibliographic databases Google Scholar, Scopus, Web of Science. When selecting publications for review, priority was given to highly cited sourcesResults. It was found that an increase in the cultivation temperature of microalgae from 5 to 25℃ favorably affects the growth characteristics of D. Salina culture: the specific growth rate increases, and the cell generation time decreases. When the content of sodium chloride in the nutrient medium is up to 5%, D. salina microalgae exhibit halotolerant properties. With an increase in the NaCl content in the nutrient medium up to 30%, D. salina culture exhibits halophilic properties. The best kinetic characteristics of the growth of D. salina culture are manifested with halophilic physiological activity. The yield of biomass of D. salina microalgae during cultivation on a nutrient medium without application and when introducing 5% sodium chloride into the nutrient medium from molasses is higher compared to the introduction of 15 and 30% sodium chloride into the nutrient medium. According to the results obtained, it can be said that an increase in the content of sodium chloride leads to an increase in the growth rate of the culture and the generation time, also in the values of 30% NaCl, a higher content of protein and β-fructosidase is manifested. With an increase in the duration of cultivation up to 240 h, a decrease in the pH of the nutrient medium from 7.04 to 4.70 is observed, which is due to the assimilation of mineral and organic nitrogen by microalgae. With an increase in the duration of cultivation of microalgae, there is an increase in the number of cells in the culture fluid up to 4 × 107 cl /ml, which at the same time synthesize the extracellular enzyme β-fructosidase, hydrolyzing sucrose.Conclusions. In view of the studies obtained, it is possible to indicate the possibility of using beet molasses as a source of carbon and substances that stimulate the growth of D.salina to produce biomass, protein substances and the enzyme β-fructosidase.

Controlling the nitrogen environment for optimal Rhodomonas salina production

AbstractThe microalga Rhodomonas salina is a widely used species for rearing live feed organisms in the aquaculture feed market. A species-specific medium is an essential step towards enhancing productivity and decreasing production costs for microalgae cultivation. However, relevant aspects of medium composition such as nitrogen source and elemental ratio have not yet been characterized for this alga. This study aimed to optimize the following three aspects of culture media: 1) optimal ratio between nitrogen and phosphorus (N:P ratio); 2) preferred source of nitrogen; and 3) tolerance of R. salina towards free ammonia. To investigate this, we conducted a series of controlled laboratory experiments in shake flasks. Our experiments revealed a 45% increase in growth rate when an N:P ratio of 15:1 was used compared to the standard ratio of 25:1. Ammonium and nitrate were equally well accepted as a nitrogen source, however, a mix of ammonium and nitrate resulted in significant growth reduction. Free ammonia did not affect growth of the alga at the tested concentrations of up to 5 mg ammonia–nitrogen L−1. We conclude that for optimal R. salina cultivation, an N:P ratio of 15:1 is strongly preferred, as it leads to a significant increase in growth rate. Further, media with a single source of nitrogen promote faster growth over media with mixed sources, and ammonium may safely be used as a nitrogen source, since R. salina tolerates certain levels of free ammonia. Overall, this work provides insights into the optimal cultivation conditions for R. salina, allowing for more efficient and reliable production of this relevant species.

Appropriate carbon–nitrogen ratio is beneficial to the accumulation of 9-cis-β-carotene during Dunaliella salina cultivation

Appropriate carbon–nitrogen ratio is beneficial to the accumulation of 9-cis-β-carotene during Dunaliella salina cultivation

Storage and Algal Association of Bacteria That Protect Microchloropsis salina from Grazing by Brachionus plicatilis.

Loss of algal production from the crashes of algal mass cultivation systems represents a significant barrier to the economic production of microalgal-based biofuels. Current strategies for crash prevention can be too costly to apply broadly as prophylaxis. Bacteria are ubiquitous in microalgal mass production cultures, however few studies investigate their role and possible significance in this particular environment. Previously, we demonstrated the success of selected protective bacterial communities to save Microchloropsis salina cultures from grazing by the rotifer Brachionus plicatilis. In the current study, these protective bacterial communities were further characterized by fractionation into rotifer-associated, algal-associated, and free-floating bacterial fractions. Small subunit ribosomal RNA amplicon sequencing was used to identify the bacterial genera present in each of the fractions. Here, we show that Marinobacter, Ruegeria, and Boseongicola in algae and rotifer fractions from rotifer-infected cultures likely play key roles in protecting algae from rotifers. Several other identified taxa likely play lesser roles in protective capability. The identification of bacterial community members demonstrating protective qualities will allow for the rational design of microbial communities grown in stable co-cultures with algal production strains in mass cultivation systems. Such a system would reduce the frequency of culture crashes and represent an essentially zero-cost form of algal crop protection.

Study on high-CO2 tolerant Dunaliella salina and its mechanism via transcriptomic analysis.

Microalgae has been regarded as a promising method for reducing CO2 emission. High CO2 concentration generally inhibits algal growth, and previous studies have mostly focused on breeding freshwater algae with high CO2 tolerance. In this study, one marine algal strain Dunaliella salina (D. salina) was grown under 0.03%-30 % CO2 and 3% NaCl conditions, and was evaluated to determine its potential for CO2 assimilation. The results showed that D. salina could tolerate 30% CO2 , and its maximum biomass concentration could reach 1.13g·L-1 after 8days incubation, which was 1.85 times higher than that of incubation in air (0.03%). The phenomenon of high-CO2 tolerance in D. salina culture was discussed basing on transcriptome analysis. The results showed that D. salina was subjected to oxidative stress under 30% CO2 conditions, and the majority genes involving in antioxidant system, such as SOD, CAT, and APX genes were up-regulated to scavenge ROS. In addition, most of the key enzyme genes related to photosynthesis, carbon fixation and metabolism were up-regulated, which are consistent with the higher physiological and biochemical values for D. salina incubation under 30% CO2 .

Techno-economic strategies for improving economic viability of β-carotene extraction using natural oil and supercritical solvent: A comparative assessment

Dunaliella salina microalgae is a third-generation feedstock that is both thermophilic and halophilic and can be used to produce nutritious food supplements such as β-carotene. Although several techno-economic studies have been carried out to produce the pigment, most of them considered traditional synthetic chemicals such as hexane, acetone, and petroleum ether as solvents for extracting β-carotene from D. salina. In this study, techno-economic assessment is carried out with the aim of producing food-grade products for human consumption via greener methods of D. salina cultivation, harvesting, and extraction. The techno-economic assessment of the extraction of β-carotene and by-products using natural and edible corn oil and supercritical CO2 reveal that the processes are economically feasible, with a payback time of 5.9 y and 2.7 y (for corn oil and SC-CO2 methods), respectively. The ROIs for both methods are also positive, that is, 16.9 % and 37.1 %, respectively and greater than the prevailing interest rates in most countries. Sensitivity analyses show that the payback time is most sensitive to the yield of β-carotene, its production output, and its selling price. This assessment shows that food-grade β-carotene can be produced in bulk quantity from D. salina (as an alternative to other sources such as carrots, tomatoes, pumpkins, etc.) in order to satisfy the growing demands of nutritional markets.

Development of an automatic system for cultivating the bioluminescent heterotrophic dinoflagellate <italic>Noctiluca scintillans</italic> on a 100-liter scale

Noctiluca scintillans is a heterotrophic dinoflagellate that causes red-colored oceans during the day (red tides) and glowing oceans at night (bioluminescence). This species feeds on diverse prey, including phytoplankton, heterotrophic protists, and eggs of metazoans. Thus, many scientists have conducted studies on the ecophysiology of this species. It is easy to cultivate N. scintillans at a scale of <1 L, but it is difficult to cultivate them at a scale of >100 L because N. scintillans cells usually stay near the surface, while prey cells stay below the surface in large water tanks. To obtain mass-cultured N. scintillans cells, we developed an automatic system for cultivating N. scintillans on a scale of 100 L. The system consisted of four tanks containing fresh nutrients, the chlorophyte Dunaliella salina as prey, N. scintillans for growth, and N. scintillans for storage, respectively. The light intensities supporting the high growth rates of D. salina and N. scintillans were 300 and 20 μmol photons m-2 s-1, respectively. Twenty liters of D. salina culture from the prey culture tank were transferred to the predator culture tank, and subsequently 20 L of nutrients from the nutrient tank were transferred to the prey culture tank every 2 d. When the volume of N. scintillans in the predator culture tank reached 90 L 6 d later, 70 L of the culture were transferred to the predator storage tank. To prevent N. scintillans cells from being separated from D. salina cells in the predator culture tank, the culture was mixed using an air pump, a sparger, and a stirrer. The highest abundance of N. scintillans in the predator culture tank was 45 cells mL-1, which was more than twice the highest abundance when this dinoflagellate was cultivated manually. This automatic system supplies 100 L of N. scintillans pure culture with a high density every 10 d for diverse experiments on N. scintillans.

Impact of the microalga Dunaliella salina (Dunal) Teodoresco culture and its β-carotene extract on the development of salt-stressed squash (Cucurbita pepo L. cv. Mabrouka)

Salinity is a major threat to crop production and global food security. Algae and their extracts containing bioactive compounds can enhance the salt tolerance of plants, including the salt-sensitive plants. The current study evaluated the efficacy of Dunaliella salina (Dunal) Teodoresco culture and/or its β-carotene extract in improving the salt tolerance of squash (Cucurbita pepo L. cv. Mabrouka). Amendment of C. pepo with D. salina culture and/or its β-carotene extract was more effective in alleviating the impact of moderate salinity imposed by seawater dilution of 2.5 dS m−1 than either low (0.55 dS m−1) or high (3.5 dS m−1) salinity, with a comparable effect to that of salicylic acid (SA). Plants that received a combination of D. salina culture and its β-carotene extract showed significantly higher growth (total biomass, fruit productivity) and physiological attributes (photosynthetic pigments, nitrogen (N), phosphorus (P), and potassium (K+) contents) than those receiving either amendment alone, reaching up to 80–90% of the SA-treated plants at moderate salinity (2.5 dS m−1). The combination could enhance the antioxidant activity of moderately salt-stressed C. pepo via increasing carotenoids and phenolics contents, suggesting that this combination could enhance the adaptation of C. pepo to the moderate salinity. The present study recommends using the blooms of D. salina and its β-carotene that is naturally secreted in situ in natural or synthetic open systems in improving the salt tolerance of C. pepo instead of using the expensive synthetic hormones.

Kinetic modeling and process analysis for photo-production of \u03b2-carotene in Dunaliella salina

Dunaliella salina is a green microalga with the great potential to generate natural β-carotene. However, the corresponding mathematical models to guide optimized production of β-carotene in Dunaliella salina (D. salina) are not yet available. In this study, dynamic models were proposed to simulate effects of environmental factors on cell growth and β-carotene production in D. salina using online monitoring system. Moreover, the identification model of the parameter variables was established, and an adaptive particle swarm optimization algorithm based on parameter sensitivity analysis was constructed to solve the premature problem of particle swarm algorithm. The proposed kinetic model is characterized by high accuracy and predictability through experimental verification, which indicates its competence for future process design, control, and optimization. Based on the model established in this study, the optimal environmental factors for both β-carotene production and microalgae growth were identified. The approaches created are potentially useful for microalga Dunaliella salina cultivation and high-value β-carotene production.Graphical

Phytohormone supplementation mediated enhanced biomass production, lipid accumulation, and modulation of fatty acid profile in Porphyridium purpureum and Dunaliella salina cultures

An economically feasible and sustainable microalgal biorefinery needs to develop culture strategies to maximize biomass productivity and accumulate important metabolites in select microalgae. The present study evaluated the effect of indole-3-acetic acid (IAA) and diethyl amino ethyl hexanoate (DAH) on two marine microalgae of commercial importance, viz., Porphyridium purpureum and Dunaliella salina. The photosynthetic efficiency, biomass productivity, and accumulation of PUFA rich lipids in P. purpureum and D. salina were studied. The microalgal cultures supplemented with both the phytohormones at lower concentrations (10-7 to 10-8M) showed an enhanced biomass production (2 to 3.5 fold increase), lipid content (up to 1.4 fold increase), and PUFA content (1 to 2 fold enhancement) at p < 0.001, compared to control cultures. The maximum photosynthetic efficiency (Fv/Fm) of IAA and DAH supplemented microalgal cultures increased up to 2.2 fold with up to a two-fold reduction in the average antenna size (ABS/RC) and dissipation energy (DI0/RC). The study suggests that supplementing the P. purpureum and D. salina cultures with phytohormone could effectively enhance the biomass production and accumulation of PUFA rich lipids.

Mitosis Inhibitors Induce Massive Accumulation of Phytoene in the Microalga Dunaliella salina.

Phytoene is a colourless natural carotenoid that absorbs UV light and provides antioxidant and anti-inflammatory activities as well as protection against photodamage. It is therefore valued for its skin health and aesthetic benefits by the cosmetic industry, as well as by the health food sector. The halotolerant green microalga Dunaliella salina is one of the richest sources of natural carotenoids. We have previously investigated the over-production of phytoene in D. salina after cultivation with the well-characterised mitosis inhibitor, chlorpropham. In this study, 15 herbicides with different modes of action were tested for their potential to promote phytoene accumulation. All herbicides showed different levels of capabilities to support phytoene over-production in D. salina. Most significantly, the two mitosis inhibitors tested in this study, propyzamide and chlorpropham, showed similar capacities to support the over-production of phytoene by D. salina cultures as phytoene desaturase inhibitors. The cellular content of phytoene increased by over 10-fold within 48 h of treatment with the mitosis inhibitors compared to untreated cultures. Results indicate a general effect of mitosis inhibitors on phytoene accumulation in D. salina. Furthermore, red light was found to significantly enhance the phytoene yield when used in combination with effective inhibitor treatments. Red light can be applied to maximize the production of phytoene from D. salina.

Productivity and morphometric parameters of the microalga Dunaliella salina IBSS-2 under pilot cultivation in continental mid-latitude climate in spring

In this study, we aimed to investigate the taxonomy and various characteristics of Dunaliella salina IBSS-2 strain and describe its cultivation potential in mid-latitude climate during springtime. In addition, our analysis confirmed the essentiality of combining morphological, physiological, and other characteristics when identifying new species and strains of the genus Dunaliella, along with the molecular marker (internal transcribed spacer (ITS) of rDNA gene). The pilot cultivation of microalgae during the springtime in the south of Russia demonstrated that the climatic conditions of this region allow D. salina cultivation for biomass accumulation during this season, highlighting light and temperature conditions as the main factors determining the growth rate of D.salina. A two-fold increase in daily insolation and, consequently, in temperature in April resulted in a more than three-fold increase in productivity of D.salina culture. The maximum productivity of D. salina both in April and May was comparable and reached 2gm-2day-1, and the total yield for 8-10days was about 14.5-16gm-2. The additional CO2 supply into the D. salina culture did not show any significant effect on its growth rate; however, it contributed to maintaining the diversity of morphometric characteristics over a longer period of time. Changes in the morphological and morphometric characteristics of algal cells, including size reduction, were observed during the batch cultivation. Thus, the production potential of the green carotenogenic microalga D. salina was determined in the springtime, which allows expanding the seasonal interval of its cultivation in temperate latitudes.

Effects of algal-bacterial ratio on the growth and cadmium accumulation of Chlorella salina-Bacillus subtilis consortia.

Algae-bacteria consortia have been proven effective in the removal of metal pollutants, but the effects of algal-bacterial ratio in the metal accumulation and resistance by this symbiotic system have not been systematically investigated. In this study, we set up consortia with various ratios of Chlorella salina-Bacillus subtilis, determined their growth, Cd accumulation, levels of intracellular glutathione (GSH), extracellular polysaccharide, phosphorus (P) in the culture medium, and functional groups of consortia after Cd treatments (0.1, 0.5, 1 mg L-1 ) for 7 days. With the addition of B. subtilis in the C. salina culture, the dry weight and specific growth rate of the consortia significantly increased compared with C. salina alone, reaching 68.33 mg and 0.382 (mg L-1 ) d-1 respectively at the 1:4 algal-bacterial ratio with 1 mg L-1 Cd treatment. Maximum Cd removal (51.66%) was also observed upon the same Cd exposure and algal-bacterial ratio. Cadmium was mostly taken up into cells at 1 mg L-1 Cd whereas its adsorption dominated the accumulation when Cd was 0.1 and 0.5 mg L-1 . The amounts of extracellular polysaccharides, GSH, and P of the symbiotic system were also increased by the bacterial addition. Besides, Fouriertransform infrared (FTIR) spectroscopy analysis showed that functional groups like N-H, O-H, and P-O-C were involved in the Cd complexation. Taken together, a higher bacterial ratio promoted the Cd accumulation and detoxification by the C. salina-B. subtilis consortia through intra- and extracellular processes.

Light supply and mineral nutrition conditions as optimization factors for outdoor mass culture of carotenogenic microalga Dunaliella salina

The productivity characteristics of green halophilic algae Dunaliella salina during its pilot cultivation were compared between two nutrient media and under different illumination. Cultivation was carried out in ponds located in the greenhouse during summer season. Two main factors that determine rates of growth and pigments synthesis, as well as the pigments ratio in D. salina grown outdoors in summer, are light and temperature conditions. The mean productivity of D. salina culture grown in two nutrient media, differing in nutrients concentration, was the same, and the mean carotenoid accumulation rate was 30% higher when using Ben-Amotz medium (52 mg·m−2·day−1) than Johnson medium. D. salina cell illumination was decreased by pond shading or by doubling their depth. Both these methods allowed reducing the level of the stress impact on algal culture under extreme light and temperature conditions. Shading of the ponds resulted in an increase in biomass and carotenoid productivity by 30% and 50%. However, a two-fold increase in ponds depth proved to be a more effective technological method, which allowed for an increase in D. salina areal productivity both in biomass and carotenoids by a factor of 3.5–3.8. In conclusion, less concentrated medium and increasing culture depth may be recommended as the optimization factors for D. salina outdoor cultivation.

Rice vinasse treatment by immobilized Synechococcus pevalekii and its effect on Dunaliella salina cultivation.

The development of new strategies in microalgal studies represents an outstanding opportunity to mitigate environmental problems coupled with biomass production at a reduced cost. Here we present a combined bioprocess for the treatment of rice vinasse using immobilized cyanobacteria Synechococcus pevalekii in alginate beads followed by the use of the treated vinasse as a culture medium for Dunaliella salina biomass production. Cyanobacterial-alginate beads showed a chlorophyll a production of 0.68 × 10-3mg bead-1 and a total carotenoid production of 0.64 × 10-3mg bead-1. The first step showed a decrease in nitrate (91%), total solids (29%), and ions. Addition of treated vinasse into D. salina cultivation resulted in a significant increase in cell replication of about 175% (optimized cultivation). The use of natural seawater drastically reduced the medium cost to US$4.75 per m3 and the addition of treated vinasse has the potential to reduce it even more (up to 69%). This study not only provides an insight on the use of cyanobacteria for rice vinasse treatment but also demonstrates a promising lower-cost medium for marine microalgal biomass production with biotechnological purposes.

Impact of combined monochromatic light on the biocomponent productivity of Dunaliella salina

Illumination conditions are crucial factors affecting the growth and biosynthesis of microalgae. In this study, monochromatic red, blue, or the combined red and blue light illumination was applied to Dunaliella salina culture to study the effects of illumination on the growth and biocomponents productivity of the microalga D. salina. The monochromatic blue light (peak wavelength, 455 nm) did not significantly enhance D. salina growth but boosted the cellular contents of lipid, protein, and carbohydrate. Both cellular content and productivity of carotenoid produced by D. salina in the white light control were the highest compared to other monochromatic treatments. Interestingly, simultaneous application of red and blue light in various ratios showed a major boost not only on growth but also on cellular lipid content, and resulted in higher lipid productivity. This result is different from many published literatures reporting the enhancement of biomass or cellular lipid content individually. The optimal ratio of red and blue light was 4:3 (4 dose of red light to 3 dose of blue light), which significantly improved lipid productivity by 35.33% compared to the white light control. The result suggested a monochromatic red and blue light combination of illumination could be employed to increase the biomass yield as well as cellular lipid content of D. salina simultaneously for the production of biofuel.

Effects of different culture media on physiological features and laboratory scale production cost of Dunaliella salina

Microalgal cultivation system depends on optimal parameters obtained from laboratory conditions to overcome high-value compounds production and decrease cost. In this study, the laboratory-scale cultivation of Dunaliella salina was performed to explore the cost and biochemical effects on biomass cultivated using F/2, Conway, and Johnson media. D. salina cultivation was monitored by cell counting, dry biomass measurements and biochemical analyses. Photosynthetic pigment profiles were identified and quantified through high-performance liquid chromatography (HPLC) whereas economic evaluation was based on media cost. Cellular growth parameters were significantly improved by Conway medium, whereas maximum accumulation of pigments, especially violaxanthin (0.855 mg g−1) and chlorophyll a (14.255 mg g−1) were observed when Johnson medium was used. Conway-biomass showed 43 % of total lipid content. This value represents 1.5 and 1.4 times higher than lipid content found in Johnson- and F/2-biomass, respectively. Furthermore, media cost presented a variation of US$1.17–49.62 for each 103 L of media mainly due to NaNO3, KNO3, and cyanocobalamin supplementation. Thus, biomass production showed a cost variation of US$4.64–301.61 per kg on a dry weight basis. These outcomes emphasize the suitability of laboratory parameters and cost comparison among biomass produced by different media.