• ALGAE
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• v.28 no.2
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• pp.203-211
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• 2013

Dunaliella salina and Dunaliella bardawil are well known for carotenogenesis, the overproduction of carotenoids, under stress conditions. The effect of high light (HL) and low light (LL) on the growth, morphology, photosynthetic efficiency, and the ${\beta}$-carotene and zeaxanthin production of D. salina CCAP 19/18 and D. bardawil was investigated and compared. Both strains showed similar growth kinetics under LL growth condition, but D. salina CCAP 19/18 was faster. As the light intensity increased, D. salina CCAP 19/18 cells were elongated and D. bardawil cells became larger. Both strains showed decrease of the maximum quantum yield of PSII ($F_v/F_m$) and election transport rate (ETR) under HL growth condition and D. salina CCAP 19/18 was less liable to the light stress. Both strains had about 1.8 and 5 times difference in the $O_2$ evolution rate at LL and HL conditions, respectively. The ${\beta}$-carotene and zeaxanthin production were increased as the light intensity increased in both strains. D. bardawil was more sensitive to light intensity than D. salina CCAP 19/18. The possible application of D. salina CCAP 19/18 as a carotenogenic strain will be discussed.

• 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.

• Korean Journal of Microbiology
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• v.35 no.4
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• pp.289-295
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• 1999

Halotolerant microalga Dunaliella bardawil was reported to massively accumulate the ${\beta}$-carotene, which protects cells from excess light intensity. Maximum specific growth rate of 0.168/hr was achieved when cells were cultivated at 1 N NaCl, pH 8.0, light intensity 80 ${\mu}E/m^{2}/s$, agitation 70rpm. For the effectiv accumulation of ${\beta}$-carotene, ozone ro hydrogen peroxide was added to media which was irradiated with white fuorescent lamps with moderate light intensity of 250 ${\mu}E/m^{2}/s$. As a result, maximum volumetric content of ${\beta}$-carotene was 324 ${\mu}$g/㎖. The ${\beta}$-carotene extraction efficiency of vegetable oils was in the order of olive oil, sesame oil, rice brain oil, corn oil, and soy bean oil. Sonication and warming was effective in ${\mu}$-carotene extraction and finally 96.9% of ${\beta}$ could be extracted using olive oil.

• KSBB Journal
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• v.26 no.5
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• pp.443-452
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• 2011

In this study, inorganic flocculant with biodegradable polymer flocculant was usedfor microalgae harvest. The aim of this study was to optimize the concentration of inorganic flocculant, the concentration of biodegradable polymer flocculant and reaction volume for decreasing the amounts of flocculant and obtaining the suitable pH range for seawater by response surface methodology. The flocculation of three marine microalgae, Chlorella ellipsoidea, Dunaliella bardawil, and Dunaliella tertiolecta, using inorganic flocculants and biodegradable polymer flocculants was investigated. The results indicated that the optimal flocculant quantity showed 0.1 g/L of ferric chloride, 7.5 g/L of chitosan on Chlorella ellipsoidea. In the case of Dunaliella bardawil, the optimal flocculant quantity showed amount of ferric sulfate more than 0.12 g/L and chitosan more than 0.75 g/L. In the case of Dunaliella tertiolecta, the optimal flocculant quantity showed 1.0 g/L of sodium aluminate, 0.75 g/L of chitosan.

• KSBB Journal
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• v.26 no.2
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• pp.143-150
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• 2011

The aim of the study was to optimize harvesting method for concentrating microalgae from microalgae mass culture. It is well known that the mass density of microalgae is usually very low and these are small size (5-20 ${\mu}m$) in the culture medium. It is essential that microalgae is harvested and concentrated economically for economical biodiesel production from microalgae. In this study, to determine optimized conditions for microalgae harvesting by chemical flocculation. Flocculation of three algae, Chlorella ellipsoidea, Dunaliella bardawil, and Dunaliella tertiolecta, was performed using various chemical flocculants, such as inorganic flocculants (aluminium sulfate, aluminium potassium sulfate, ferrous sulfate, ferric sulfate, ferric chloride, calcium hydroxide, sodium carbonate, sodium nitrite, and sodium aluminate), organic flocculant (polyacrylamide), and biopolymer flocculants (chitosan and starch). The results indicated that aluminium based inorganic flocculants is suitable for microalgae harvesting such as Chlorella ellipsoidea, Dunaliella bardawil, and Dunaliella tertiolecta. The results also recommended that flocculant doses, agitation speed, agitation time, sedimentation time for economical microalgae harvesting method using chemical flocculants.