• Journal of Marine Bioscience and Biotechnology
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• v.10 no.1
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• pp.26-33
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• 2018

Fucoxanthin has been reported as bioactive compounds exhibiting strong antioxidant, anticancer and anti-inflammatory activities. Owing to its a wide range of applications and potentials, commercial production of fucoxanthin from algae has been attracted many attentions. Although, most of seaweeds and diatoms contain fucoxanthin as major carotenoid contents, low productivity of fucoxanthin still hinder the industrial application. Here, we newly isolated and identified indigenous marine diatom Odontella sp. BS-003 as a resource of fucoxanthin production. The characterization, optimization and production of the fucoxanthin, along with other bioactive compound omega-3 fatty acid from odontella sp. BS-003 were analyzed in this study, and the results represented optimal culture condition (two-fold silicate containing F/2 medium) significantly enhanced the algal biomass productivity. The maximum biomass (1.83 g/L), fucoxanthin (3.88 mg/g), along with omega-3 fatty acid (10 %, w/w) were obtained from the 10 L of photobioreactor. Based on the results, it is speculated that the microalga Odontella sp. BS-003 can be a promising natural resource for the production of bioactive compounds.

• The Korean Journal of Malacology
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• v.23 no.1
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• pp.51-57
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• 2007

This study examined the possibility on the dietary value and cryopreservation of the marine microalga, Isochrysis galbana. Four cryoprotectants, dimethyl sulfoxide (DMSO), ethylene glycol (EG), glycerol (Gly) and 1.2-propanedial (PD) were tested at the concentrations of 1.0, 1.5, 2.0, 2.5 and 3.0 M respectively. The highest survival rates were obtained with 1.5 and 2.0 M of four cryoprotectants yielding a survival rate of 80%. Cell concentration of $30\;{\times}\;10^4\;cell/ml$ at the initial point of the experiment was increased to $365\;{\times}\;10^4\;cell/ml$ in 1.5 M of dimethyl sulfoxide, $298\;{\times}\;10^4\;cell/ml$ in 1.5 M of ethylene glycol, $512\;{\times}\;10^4\;cell/ml$ in 1.5 M of glycerol, and $385\;{\times}\;10^4\;cell/ml$ in 1.5 M of 1.2-propanedial after five days, respectively. In dietary value experiment, survival rate and growth were not significantly different.

• Journal of Microbiology and Biotechnology
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• v.16 no.5
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• pp.689-694
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• 2006

We investigated the potential use of various carbon sources (fructose, glucose, mannose, lactose, and glycerol) for culturing Phaeodactylum tricornutum UTEX-640 in mixotrophic and heterotrophic batch cultures. Concentrations of carbon substrates tested ranged from 0.005 M to 0.2 M. P. tricornutum did not grow heterotrophically on any of the C-sources used, but successive additions of organic carbon in mixotrophic growth mode substantially increased the biomass concentration and productivity relative to photoautotrophic controls. The maximum biomass productivities in mixotrophic cultures for glycerol, fructose, and glucose were 21.30 mg/l h, 15.80 mg/l h, and 10.20 mg/l h, respectively. These values were respectively 10-, 8-, and 5-fold higher than those obtained in the corresponding photoautotrophic control cultures. Mannose and lactose did not significantly affect microalgal growth. The biomass lipids, eicosapentaenoic acid (EPA) and pigments contents were considerably enhanced with glycerol and fructose in relation to photoautotrophic controls. The EPA content was barely affected by the sugars, but were more than 2-fold higher in glycerol-fed cultures than in photoautotrophic controls.

• Journal of Microbiology and Biotechnology
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• v.23 no.10
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• pp.1413-1421
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• 2013

The marine microalga Isochrysis sphaerica is rich in the very-long-chain polyunsaturated fatty acids, including eicosapentaenoic acid (EPA, $C20:5{\omega}-3$) and docosahexaenoic acid (DHA, $C22:6{\omega}-3$) that are important to human health. Here, we report a functional characterization of a ${\Delta}4$-fatty acid desaturase gene (FAD4) from I. sphaerica. IsFAD4 contains a 1,284 bp open reading frame encoding a 427 amino acid polypeptide. The deduced amino sequence comprises three conserved histidine motifs and a cytochrome b5 domain at its N-terminus. Phylogenetic analysis indicated that IsFad4 formed a unique Isochrysis clade distinct from the counterparts of other eukaryotes. Heterologous expression of IsFAD4 in Pichia pastoris showed that IsFad4 was able to desaturate docosapentaenoic acid (DPA) to form DHA, and the rate of converting DPA to DHA was 79.8%. These results throw light on the potential industrial production of specific polyunsaturated fatty acids through IsFAD4 transgenic yeast or oil crops.

• Fisheries and Aquatic Sciences
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• v.19 no.7
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• pp.31.1-31.6
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• 2016

Background: The objective of this study was to develop an efficient selectable marker for transgenic Dunaliella salina. Results: Tests of the sensitivity of D. salina to the antibiotic chloramphenicol and the herbicide Basta$^{(R)}$ showed that cells ($1.0{\times}10^6cells/ml$) treated with 1000 or $1500{\mu}g/ml$ chloramphenicol died in 8 or 6 days, respectively, whereas D. salina cells ($1.0{\times}10^6cells/ml$) treated with 5, 10, 20, or $40{\mu}g/ml$ Basta$^{(R)}$ died in 2 days. Therefore, D. salina is more sensitive to Basta$^{(R)}$ than to chloramphenicol. To examine the possibility of using the phosphinothricin N-acetyltransferase (pat) gene as a selectable marker gene, we introduced the pat genes into D. salina with particle bombardment system under the condition of helium pressure of 900 psi from a distance of 3 cm. PCR analysis confirmed that the gene was stably inserted into the cells and that the cells survived in $5{\mu}g/ml$ Basta$^{(R)}$, the medium used to select the transformed cells. Conclusions: The findings of this study suggest that the pat gene can be used as an efficient selectable marker when producing transgenic D. salina.

• Journal of Microbiology and Biotechnology
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• v.29 no.9
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• pp.1453-1459
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• 2019

Zeaxanthin is an important pigment in the photo-protection mechanism of microalgae. However, zeaxanthin epoxidase, an enzyme involved in the accumulation and conversion of zeaxanthin, has not been extensively studied in microalgae. In this work, we report the expression pattern of zeaxanthin epoxidase in Dunaliella tertiolecta (DtZEP) at different light and diverse salinity conditions. To confirm the responsiveness to light conditions, the ZEP expression pattern was investigated in photoperiodic (16 h of light and 8 h of dark) and continuous (24 h of light and 0 h of dark) light conditions. mRNA expression levels in photoperiodic conditions fluctuated along with the light/dark cycle, whereas those in continuous light remained unchanged. In varying salinity conditions, the highest mRNA and protein levels were detected in cells cultured in 1.5 M NaCl, and ZEP expression levels in cells shifted from 0.6 M NaCl to 1.5 M NaCl increased gradually. These results show that mRNA expression of DtZEP responds rapidly to the light/dark cycle or increased salinity, whereas changes in protein synthesis do not occur within a short period. Taken together, we show that DtZEP gene expression responds rapidly to light irradiation and hyperosmotic stress. In addition, ZEP expression patterns in light or salinity conditions are similar to those of higher plants, even though the habitat of D. tertiolecta is different.

• Microbiology and Biotechnology Letters
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• v.49 no.4
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• pp.528-533
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• 2021

The microalga, Tetrathelmis tetrathele, is used in the development of products for the aquaculture, food, and nutraceutical industries. In the present study, we investigated whether the T. tetrathele ethanolic extract (TTE), which has anti-inflammatory properties, can confer protection against alopecia and improve scalp health, influence the proliferation of human keratinocytes, HaCaT cells, and human hair follicle dermal papilla cells (HFDPC), or inhibit 5α-reductase activity. We found that TTE inhibited the production of the inflammatory mediator, nitric oxide (NO), and prostaglandin E₂ (PGE₂) without cytotoxicity in LPS-stimulated RAW 264.7 cells. In addition, TTE encouraged the proliferation of HaCaT cells and HFDPC. Our results showed that TTE had anti-inflammatory activities, proliferated HaCaT cells and HFDPC, and inhibited 5α-reductase activity. Therefore, we suggest that T. tetrathele could be a potent therapeutic agent for alopecia prevention and scalp improvement.

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.659-663
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• 2010

Microalgae has been seen all over the seawater and several species are used for human food. Specially, Nannochloropsis oculata, a photosynthetic microalgae, has been focused for a vast array of valuable nutritious compounds. In order to find high mass Nannochloropsis oculata culture conditions, some of important growth factors of pH, temperature, culture media, and $CO_2$ effect were tested. The optimal growth condition was found to be as follows : 3% artificial seawater, initial pH 8.5, and temperature $25^{\circ}C$. The alga mass and chlorophyll content were dramatically increased by applying 5% flue $CO_2$ gas (1.50 g/L algae in a continuous $CO_2$ flue; 0.76 g/L alga without $CO_2$). It was shown that the chlorophyll biosynthesis was also closely associated with alga growth.

• 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.

• ALGAE
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• v.31 no.3
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• pp.257-266
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• 2016

Nitrogen is one of the most critical nutrients affecting cell growth and biochemical composition of microalgae, ultimately determining the lipid or carbohydrate productivity for biofuels. In order to investigate the effect of nitrogen sources on the cell growth and biochemical composition of the marine microalga Tetraselmis sp., nine different N sources, including NaNO₃, KNO₃, NH₄NO₃, NH₄HCO₃, NH₄Cl, CH₃COONH₄, urea, glycine, and yeast extract were compared at the given concentration of 8.82 mM. Higher biomass concentration was achieved under organic nitrogen sources, such as yeast extract (2.23 g L⁻¹) and glycine (1.62 g L⁻¹), compared to nitrate- (1.45 g L⁻¹) or ammonium-N (0.98 g L⁻¹). All ammonium sources showed an inhibition of cell growth, but accumulated higher lipids, showing a maximum content of 28.3% in ammonium bicarbonate. When Tetraselmis sp. was cultivated using yeast extract, the highest lipid productivity of 36.0 mg L⁻¹ d⁻¹ was achieved, followed by glycine 21.5 mg L⁻¹ d⁻¹ and nitrate 19.9 mg L⁻¹ d⁻¹. Ammonium bicarbonate resulted in the lowest lipid productivity of 14.4 mg L⁻¹ d⁻¹. The major fatty acids in Tetraselmis sp. were palmitic, oleic, linoleic and linolenic acids, regardless of the nutritional compositions, indicating the suitability of this species for biodiesel production.