• Journal of Microbiology and Biotechnology
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• v.30 no.5
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• pp.708-716
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• 2020

The purpose of this study was to identify strawberry wilt pathogens and evaluate the efficacy of Chlorella fusca CHK0059 for improving plant growth and suppressing Fusarium wilt. We identified 10 isolates of wilt pathogens of non-pesticide Seolhyang strawberry plant, including Fusarium oxysporum f. sp. fragariae, using morphological and molecular analysis. On the 15^th day after 0.4% CHK0059 treatment, the plant height of the untreated control strawberry plants was significantly greater than that of the CHK0059-treated strawberry plants. After 85 days, both treatments showed a similar tendency regarding the height of the strawberry plants. However, the thickness of strawberry leaves treated with the CHK0059 was found to be 1 mm thicker than that of the untreated control. The flowering percentage of the CHK0059 plants was also 40.2% higher on average than that of the untreated control. The chlorophyll content of strawberry leaves treated with the CHK0059 was also, on average, 6.63% higher than that of the untreated control. After 90 days of the CHK0059 treatment, the incidence of Fusarium wilt in the CHK0059-treated plants had reduced by 9.8% on average compared to the untreated control. The population density of F. oxysporum f. sp. fragariae was also reduced by approximately 86.8% in the CHK0059-treated plants by comparison to the untreated control at 70 days after treatment. The results indicate that the microalga C. fusca CHK0059 is an efficient biological agent for improving strawberry plant growth and suppressing Fusarium wilt disease in organic strawberries.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.526-534
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• 2019

Chlorella gloriosa (Chlorellaceae, Trebouxiophyceae) was isolated from seawater off the coast of the Dokdo Islands in Korea. An axenic culture was established using the streak-plate method on f/2 agar media supplemented with antibiotics, allowing identification of the isolate by morphological, molecular, and physiological analyses. The morphological characteristics observed by light and electron microscopy revealed typical morphologies of C. gloriosa species. The molecular phylogenetic inference drawn from the small-subunit 18S rRNA sequence verified that the microalgal strain belongs to C. gloriosa. Additionally, gas chromatography-mass spectrometry analysis showed that the isolate was rich in nutritionally important omega-3 and -6 polyunsaturated fatty acids and high-performance liquid chromatography analysis revealed that the high-value antioxidants lutein and violaxanthin were biosynthesized as accessory pigments by this microalga, with arabinose, galactose, and glucose as the major monosaccharides. Therefore, in this study, a Korean marine C. gloriosa species was discovered, characterized, and described, and subsequently added to the national culture collection.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.770-775
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• 2014

The green microalga of the genus Nannochloropsis (class Eustigmatophyceae) is a leading candidate for biofuel production due to its ability to accumulate high oil content (28.7% of cellular ash-free dry weight). We investigated the anti-inflammatory and anticancer activities of sterol-rich fraction from nannochloropsis oculata n-hexane (NOH) extract after saponification of the microalga. Among the fractions with n-hexane, chloroform and ethyl acetate, the n-hexane fraction showed the highest anti-inflammatory activity in LPS-stimulated RAW 264.7 macrophage as well as anticancer activity against human leukemia HL-60 cells without the cytotoxity. And the sterol-rich fraction was obtained from the n-hexane fraction by open silica column under the gradient solvent condition with 100% hexane (1L), hexane : ethyl acetate (20 : 1, 10 : 1, 5 : 1, 1 : 1, v/v). Among the four fractions (NOH-1~4), especially NOH-1 contained the highest content of sterols. NOH1 showed the highest HL-60 (about 85%) and NO inhibitory activities at the concentration of $100{\mu}g/mL$. These results demonstrated that the sterol-rich fraction from N. oculata might be a useful candidate as anti-inflammatory and anticancer agents for anti-inflammatory and anticancer activity.

• Journal of Microbiology and Biotechnology
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• v.24 no.4
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• pp.522-533
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• 2014

Bionanotechnology has revolutionized nanomaterial synthesis by providing a green synthetic platform using biological systems. Among such biological systems, microalgae have tremendous potential to take up metal ions and produce nanoparticles by a detoxification process. The present study explores the intracellular and extracellular biogenic syntheses of silver nanoparticles (SNPs) using the unicellular green microalga Scenedesmus sp. Biosynthesized SNPs were characterized by AAS, UV-Vis spectroscopy, TEM, XRD, FTIR, DLS, and TGA studies and finally checked for antibacterial activity. Intracellular nanoparticle biosynthesis was initiated by a high rate of $Ag^+$ ion accumulation in the microalgal biomass and subsequent formation of spherical crystalline SNPs (average size, 15-20 nm) due to the biochemical reduction of $Ag^+$ ions. The synthesized nanoparticles were intracellular, as confirmed by the UV-Vis spectra of the outside medium. Furthermore, extracellular synthesis using boiled extract showed the formation of well scattered, highly stable, spherical SNPs with an average size of 5-10 nm. The size and morphology of the nanoparticles were confirmed by TEM. The crystalline nature of the SNPs was evident from the diffraction peaks of XRD and bright circular ring pattern of SAED. FTIR and UV-Vis spectra showed that biomolecules, proteins and peptides, are mainly responsible for the formation and stabilization of SNPs. Furthermore, the synthesized nanoparticles exhibited high antimicrobial activity against pathogenic gram-negative and gram-positive bacteria. Use of such a microalgal system provides a simple, cost-effective alternative template for the biosynthesis of nanomaterials in a large-scale system that could be of great use in biomedical applications.

• Environmental Engineering Research
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• v.19 no.3
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• pp.283-287
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• 2014

Cultivation of microalgae using wastewater exhibits several advantages such as nutrient removal and the production of high valuable products such as lipid and pigments. With this study, two types of wastewater from instant noodle factory; mixed liquor suspended solids (MLSS) and effluents after sedimentation tank were investigated for green microalga Scenedesmus sp. cultivation under laboratory condition. Optimal wastewater dilution percentage was evaluated in 24 wells microplate. MLSS and effluent without dilution showed the highest specific growth rate (${\mu}$) of $1.63{\pm}0.11day^{-1}$ and $1.57{\pm}0.16day^{-1}$, respectively, in which they were significantly (p < 0.05) higher than Scenedesmus sp. grown in BG11 medium ($1.08{\pm}0.14day^{-1}$). Ten days experiment was also conducted using 2000 ml Duran bottle as culture vessel under continuous light at approximately 5000 lux intensity and continuous aeration. It was found that maximum biomass density of microalgae cultivated in MLSS and effluent were $344.16{\pm}105.60mg/L$ and $512.89{\pm}86.93mg/L$ respectively and there was no significant (p < 0.05) difference on growth to control (BG11 medium). Moreover, cultivation microalgae in wastewater could reduce COD in wastewater by 39.89%-73.37%. Therefore, cultivation of Scenedesmus sp. in wastewater from instant noodle factory can yield microalgae biomass production and wastewater reclamation using photobioreactor simultaneously.

• ALGAE
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• v.37 no.2
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• pp.175-183
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• 2022

Polar microorganisms produce physiologically active substances to adapt to harsh environments, and these substances can be used as biomedical compounds. The green microalga Micractinium variabile KSF0031, which was isolated from Antarctica, produced phytol, a natural antimicrobial agent. Furthermore, several polyunsaturated fatty acids (PUFAs), including omega-3, exhibit antioxidant properties. Here statistical methods (Plackett-Burman design and Box-Behnken design) were used to optimize the culture medium of KSF0031 to improve biomass production, and K₂HPO₄, MgSO₄·7H ₂O, and ammonium ferric citrate green (AFCg) were selected as significant components of the culture medium. Changes in the concentration of K₂HPO₄ and MgSO₄·7H ₂O as positive factors and AFCg as a negative factor affected cell growth to a remarkable degree. The biomass production in a 100 L culture using the optimized medium for 24 d at 18℃ was improved by 37.5% compared to that obtained using the original BG-11 medium. The quantities of PUFAs and phytol obtained were 13 mg g^-1 dry cell weight (DCW) and 10.98 mg g^-1 DCW, which represent improved yields of 11.70% and 48.78%, respectively. The results of this study could contribute to an improved production of phytol and fatty acids from Antarctic microalgae in the biomedical industry.

• Journal of Microbiology
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• v.42 no.4
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• pp.305-314
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• 2004

An exopolysaccharide-producing microalgal dinoflagellate was isolated from a red-tide bloom and des­ignated strain KG03. A bacteria-free culture of strain KG03 was achieved using a modified wash with phototaxis and antibiotic treatment. Combined treatment with neomycin and cephalosporin was the most effective for eliminating the bacteria associated with the microalgae. Strain KG03 was identified as Gyrodinium impudicum by analyzing the ITS regions of the 5.8S rDNA, 18S rDNA, morphological phenotype and fatty acid composition. The exopolysaccharide production and cell growth in a 300-ml photobioreactor were increased 2.7- and 2.4-fold, respectively, compared with that in a flask culture at the first isolation step.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.6
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• pp.331-337
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• 2003

Unicellular green algae of the genus Dunaliella thrive in extreme environmental conditions such as high salinity, low pH, high irradiance and subzero temperatures. Species of Dunaliella are well known in the alga biotechnological industry and are employed widely for the production of valuable biochemicals, such as carotenoids. Some strains of Dunaliella are cultivated commercially in large outdoor ponds and are harvested to produce dry algal meals, such as polyunsaturated fatty acids and oils for the health food industry, and coloring agents for the food and cosmetic industries. During the past decade, the advances in molecular biology and biochemistry of microalgae, along with the advances in biotechnology of microalgal mass cultivation, enabled this microalga to become a staple of commercial exploitation. In particular, the advent of molecular biology and mutagenesis in Dunaliella has permitted enhancements in the carotenoids content of this green alga, making it more attractive for biotechnological applications. Accordingly, the present review summarizes the recent developments and advances in biotechnology of carotenoid production in Dunaliella.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.181-184
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• 2001

The biological fixation of carbon dioxide using microalgae have many advantages over chemicals and remove carbon dioxide simultaneously. A ketocarotenoid astaxanthin is hyper-accumulated in the green freshwater microalga, Haematococcus pluvialis. In the present study, the combine effects of carbon dioxide concentration and light intensity on the growth of H. pluvilais were investigated. The carbon dioxide concentration above 10% caused a severe inhibition and around 5% is optimal for growth. Adaptation to high concentration of carbon dioxide enhanced the $CO_2$ tolerance. Specific growth rate calculated differently based upon cell number or dry weight because of the distinctive life cycle patterns of H. pluvialis : small-sized motile green cell and thick cell walled red cyst cell. Based on the light dependence of H. pluvialis, internally illuminated air-lift photobioreactor was designed and operated. Gradual increase of light supply gave more active growth and more effective productivity of astaxanthin than constant light supply.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1159-1163
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• 2005

The production of hydrogen by Chlamydomonas reinhardtii UTEX 90, a marine green alga, was performed under dark fermentation. The effects of initial nitrogen and phosphorus concentration on the cell growth and the production of hydrogen and organic substances were investigated. In the growth stage, the maximum dry cell weight (DCW) was 3 g/l when the initial ammonium concentration was 15 mM. In the dark fermentation, the maximum hydrogen production was $3.5\;{\mu}mol/\;mg$ DCW when the initial nitrogen concentration was 7.5 mM. The nitrogen concentration had a greater effect on organic compound and hydrogen production than the phosphorus concentration during the dark fermentation. An investigation of the duration of dark fermentation showed that, at least until three days, dark fermentation should be prolonged for maximum hydrogen production.