• Journal of Microbiology and Biotechnology
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• v.18 no.5
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• pp.821-827
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• 2008

The unicellular green alga Dunaliella salina is a halotolerant eukaryotic organism. Its halophytic properties provide an important advantage for open pond mass cultivation, since D. salina can be grown selectively. D. salina was originally described by E. C. Teodoresco in 1905. Since that time, numerous isolates of D. salina have been identified from hypersaline environments on different continents. The new Dunaliella strain used for this study was isolated from the salt farm area of the west coastal side of South Korea. Cells of the new strain were approximately oval- or pear-shaped (approximately $16-24\;{\mu}m$ long and $10-15\;{\mu}m$ wide), and contained one pyrenoid, cytoplasmatic granules, and no visible eyespot. Although levels of $\beta$-carotene per cell were relatively low in cells grown at salinities between 0.5 to 2.5 M NaCl, cells grown at 4.5 M NaCl contained about a ten-fold increase in cellular levels of $\beta$-carotene, which demonstrated that cells of the new Korean strain of Dunaliella can overaccumulate $\beta$-carotene in response to salt stress. Analysis of the ITS1 and ITS2 regions of the new Korean isolate showed that it is in the same clade as D. salina. Consequently, based on comparative cell morphology, biochemistry, and molecular phylogeny, the new Dunaliella isolate from South Korea was classified as D. salina KCTC10654BP.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.953-954
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• 2012

• Journal of Microbiology
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• v.45 no.2
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• pp.153-157
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• 2007

5-enolpyruvylshikimate-3-phosphate synthase (EPSP synthase, EC 2.5.1.19) is the sixth enzyme in the shikimate pathway which is essential for the synthesis of aromatic amino acids and many secondary metabolites. The enzyme is widely involved in glyphosate tolerant transgenic plants because it is the primary target of the nonselective herbicide glyphosate. In this study, the Dunaliella salina EPSP synthase gene was cloned by RT-PCR approach. It contains an open reading frame encoding a protein of 514 amino acids with a calculated molecular weight of 54.6 KDa. The derived amino acid sequence showed high homology with other EPSP synthases. The Dunaliella salina EPSP synthase gene was expressed in Escherichia coli and the recombinant EPSP synthase were identified by functional complementation assay.

• Microbiology and Biotechnology Letters
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• v.21 no.4
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• pp.342-347
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• 1993

It was proved that the cell growth followed a photo-inhibition model in light-limited turbidostat cultivation, having 1.06 (1/h) of maximum specific growth rate and 0.00094(kcal/$cm^2$/h) and 0.063 (kcal/$cm^2$/h) as half saturation and light inhibition constants, repectively. ${\beta}$-carotene production showed a growth related porcess. And the activation energy of Dunaliella salina was roughly estimated as 12.36 (kcal/mole) in employing Arrhenius relationship. It should also point out that relatively much porduction of ${\beta}$-carotene was observed at hight light intensity with yieding 1.04 (mg-carotene/g-dry cell/day) of specific product production rate while the cell growth was decreased. The optimal conditions of producing ${\beta}$-carotene in turbiodostat cultivation were as follows: $7.5{\times}10^{-3}$(kcal/$cm^2$/h)of light intensity, 2 (mM) and 50(mM) of nitrate and sodium bicarbonate concentrations and 100(ml/h) of $CO_2$ flow rate.

• ALGAE
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• v.21 no.3
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• pp.333-341
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• 2006

The productivities of Chlorella ovalis and Dunaliella parva were influenced by the rates of medium compositions obtained from the fermented animal wastewater (BM: bacteria mineral water) including a natural substitute chelator for EDTA (etylenediaminetetraacetic acid). The most favorable medium was -E+50 adding 50% BM in f/2 medium instead of EDTA, a chemical chelator, which increased more 19-fold of cell density in C. ovalis and 7-fold in D. parva than cells cultured on f/2 medium as well as the enhancements of chlorophyll a (f/2-E: 0.26 g L–1, -E+50: 1.5 g L–1 in C. ovalis; f/2-E: 2.7 g L–1, -E+50: 15 g L–1 in D. parva) and the increase of maximal PSII quantum yields. These results were verified that the BM could play an important part as a natural chelator substituted for EDTA. In the fields of biotechnology, food organisms in fishery and eco-industries of CO2 sequestration in air and nutrient removal in water, the natural chelator of BM could be applied to enhance the biomass of the other microalgae.

• KSBB Journal
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• v.14 no.2
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• pp.160-166
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• 1999

High cell density cultivation of microalga Dunaliella bardawil using nitrogen fed-batch cultures was studied in batch flask. Optimum environmental conditions include concentrated nutrients except NaCl and carbon sources, carbon sources, pH, light, agitation, nitrate and phosphate ions. Cell growth, consumption rates of nitrate and phosphate ions were monitored. Optimal conditions for higher cell density were found to be(in the range tested): 5 times concentrated media(1 times-10 times concentrated media) pH 8.0 (7.0-9.0) white light(blue and red light) 15mM of nitrate (0.94-15mM) 250mM $NaHCO_3$ and $CO_2$ gas. However, the addition of phosphate ions did not enhance the algal maximum cell density and specific growth rate. Nitrate was found to be effective for the cell growth. The maximum cell density of fed-batch culture using nitrate ions in $8.955{\times}106$cells/ml after 189hr incubation.

• Journal of Microbiology and Biotechnology
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• v.26 no.5
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• pp.854-866
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• 2016

The production cost of biodiesel from microalgae is still not competitive, compared with that of petroleum fuels. The genetic improvement of microalgal strains to increase triacylglycerol (TAG) accumulation is one way to reduce production costs. One of the most promising approaches is the isolation of starch-deficient mutants, which have been reported to successfully increase TAG yields. To date, such a stable mutant is not available in an oleaginous marine microalga, despite several advantages of using marine species for biodiesel production. Algae in the genus Dunaliella are known to tolerate high salt concentration and other environmental stresses. In addition, the cultivation processes for large-scale outdoor commercialization have been well established for this genus. In this study, Dunaliella tertiolecta was used to screen for starch-deficient mutants, using an iodine vapor-staining method. Four out of 20,016 UV-mutagenized strains showed a substantial reduction of starch content. A significantly higher TAG content, up to 3-fold of the wild-type level, was observed in three of the mutants upon induction by nitrogen depletion. The carotenoid production and growth characteristics of these mutants, under both normal and oxidative stress conditions, were not compromised, suggesting that these processes are not necessarily affected by starch deficiency. The results from this work open up new possibilities for exploring Dunaliella for biodiesel production.

• Microbiology and Biotechnology Letters
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• v.40 no.3
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• pp.282-285
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• 2012

In this study, the ability of Chlorella vulgaris and Dunaliella salina to use biomass resources for anaerobic digestive biogas production was examined. The differences in cell wall structure pretreatments affecting the yield of soluble products showed that D. salina is a better candidate for biogas production than C. vulgaris. There was no significant difference between pretreated and non-pretreated D. salina in terms of methane production yield by inocula obtained from anaerobic digestion systems. Therefore, D. salina is a suitable algal biomass for biogas production due to its high biomass productivity, simple pretreatment needs, and easy conversion to biogas.

• Journal of Marine Bioscience and Biotechnology
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• v.6 no.2
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• pp.68-75
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• 2014

This study investigated the potential use of various organic carbon sources (glucose, glycerol and acetate) and different concentrations of $CO_2$ for culturing marine microalga Dunaliella tertiolecta. Cell growth and lipid production were monitored under heterotrophic, mixotrophic and photoautotrophic modes of cultivation. D. tertiolecta showed the ability to grow under mixotrophic (acetate and glucose), heterotrophic (glucose) and photoautotrophic condition under high $CO_2$ concentration (15%). With all the organic carbon sources (glucose, glycerol and acetate) tested in this study, 1~5% acetate enhanced cell growth rate and lipid content, while higher concentrations of acetate (10% and 15%) were inhibitory and resulted in cell death.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.186-191
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• 1999

The three speices of miroalgae (Chlorella vulgaris, Dunaliella salina and Porphyridium purpureum) were immobilized in Ca-alginate capsules as a basic study for development of economic cultivation process, and then were cultivated in an air-bubble column bioreactor. Under the batch culture of aerobic conditions, the thickness of the capsule membrane and $CO_2$ supply did not affect the growth of the immobilized microalga, Chlorella vulgaris. Cell concentration of immobilized microalgae in the capsule was higher than those of imobilized microalgae in beads and free cells. The cell concentration of microencapsulated Dunaliella salina was greater about 5 times than that of free cells. Based on these results, it is concluded that the application of microencapsulation technology to the culture of microalgae was an effective method for high-density cultivation.