• Journal of Marine Bioscience and Biotechnology
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• v.8 no.1
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• pp.39-44
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• 2016

The microalgae have been studied for a source of biodiesel production. It is important to select the microalgae, which grows rapidly in local environmental conditions such as temperature range and ingredient of local seawater. The aim of this study was isolating microalga, which has rapid growth rate and high FAME contents in wide temperature ranges, for microalgal offshore cultivation in Korea, one of the country with four distinct seasons. Firstly, we had isolated a green microalga, Tetraselmis sp. KCTC12236BP, which has faster growth rate in low temperature (5 and $10^{\circ}C$) than Tetraselmis suecica and Dunaliella tertiolecta LB999 from Young Heung Island, Incheon, Korea. This microalga was cultivated in outdoor circulated tank photobioreactor (CT-PBR). As a result, this microalga could grow in wide temperature ranges (6 to $29^{\circ}C$), outdoors. After that, the biomass was recovered, and 13.2 g biodiesel could be acquired from 110 g dry biomass. These results indicate that the isolated microalga, Tetraselmis sp. KCTC12236BP is proper to biodiesel production using outdoor cultivation in Korea for all seasons.

• Environmental Engineering Research
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• v.21 no.3
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• pp.265-275
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• 2016

In this study, the microalga Neochloris oleoabundans was cultivated in a sustainable manner using diluted anaerobic digestate to produce biomass as a potential biofuel feedstock. Prior to microalgae cultivation, the anaerobic digestate was characterized and several pretreatment methods including hydrogen peroxide treatment, filtration, and supernatant extraction were investigated and their impact on the removal of suspended solids as well as other organic and inorganic matter was evaluated. It was found that the supernatant extraction was the most convenient pretreatment method and was used afterwards to prepare the nutrient media for microalgae cultivation. A bench-scale experiment was conducted using multiple dilutions of the supernatant and filtered anaerobic digestate in 16 mm round glass vials. The results indicated that the highest growth of the microalga N. oleoabundans was achieved with a total nitrogen concentration of 100 mg N/L in the 2.29% diluted supernatant in comparison to the filtered digestate and other dilutions.

• Journal of Life Science
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• v.25 no.5
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• pp.568-576
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• 2015

The marine microalga Pavlova viridis can grow fast and has the ability to accumulate essential nutrients for culturing marine animals, such as EPA and DHA, and it has been used as food for raring larval fish and prawn. The symbiotic relationship between the flagellate microalga Pavlova viridis and its associated bacteria was investigated. An axenic culture of P. viridis was obtained by repeated treatment of the microalga with an antibiotic cocktail. The axenic status was confirmed after sub-culturing three times in a sterile f/2 medium without an antibiotic. The axenic alga was then co-inoculated with five bacteria, arbitrarily designated as I1–I5, isolated from the alga to test the growth promotion of the algae. All bacterial strains promoted the growth of P. viridis, and bacterial isolate I3 was the most effective among the five bacteria tested. The cell number of P. viridis in the co-culture with I3 was significantly higher than that of the control culture. A sequence analysis of the 16S rRNA gene isolated from I3 revealed a 97% nucleotide sequence similarity to that of Citrobacter sp. The growth of strain I3 was also significantly enhanced by co-culturing with P. viridis, indicating a symbiotic relationship between the microalga and its associated bacterium. The association between the microalga and bacterium was confirmed by scanning electron microscopy.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.61-70
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• 2020

A eukaryotic microalga was isolated from seawater in Janghang Harbor, Korea and its morphological, molecular, and physiological characteristics were investigated. Due to its simple morphology, no distinctive characters were found by morphological observation, such as light microscope or scanning/transmission electron microscopy (S/TEM). However, molecular phylogenetic evidence inferred from the concatenated small subunit (SSU) 18S rRNA and internal transcribed spacer (ITS) sequence data indicated that the isolate belonged to the newly described Micractinium singularis. Furthermore, it was clustered with Antarctic Micractinium strains and it also showed a psychrotolerant property, surviving at temperatures as low as 5℃. However, its optimal growth temperatures range from 15℃ to 25℃, indicating that this microalga is a mesophile. Additionally, gas chromatography-mass spectrometry (GC/MS) analysis showed that the isolate was rich in nutritionally important omega-3 polyunsaturated fatty acid, and high-performance liquid chromatography analysis (HPLC) revealed that the high-value antioxidant lutein was biosynthesized as an accessory pigment by this microalga, with glucose as the major monosaccharide. Therefore, in this study, a Korean marine M. singularis species was discovered, characterized, and described. It was subsequently added to the national culture collections.

• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.11-19
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• 2019

The properties of microalgae as bioresources for biodiesel production can be improved by adding nitrogen sources into the culture medium. Thus, Nannochloropsis oceanica CCAP 849/10 was cultured in f/2 media supplemented with five different forms of nitrogen at $0.88mmol-N\;l^{-1}$ each: ammonium bicarbonate ($NH_4HCO_3$), ammonium sulfate ($(NH_4)_2SO_4$), sodium nitrate ($NaNO_3$), ammonium nitrate ($NH_4NO_3$), and urea. The cell density, lipid content, and fatty acid profile of the microalga were determined after 15 days of cultivation. The growth of N. oceanica based on cell number was lowest in the medium with $NH_4NO_3$, and increased significantly in the medium with $NH_4HCO_3$. Cells treated with $(NH_4)_2SO_4$, and $NH_4NO_3$ produced the highest total lipid contents (i.e., 65% and 62% by dry weight, respectively). The fatty acid profiles of the microalga were significantly different in the various nitrogen sources. The major fatty acids detected in cultures supplemented with $NH_4HCO_3$, $(NH_4)_2SO_4$, $NH_4NO_3$, or urea were C14:0, C16:0, C16:1, C18:0, C18:1, C18:2, C20:5, and C22:6. However, the C16:1 content in the $NaNO_3$-supplemented culture was very low. This study highlights that the nitrogen source can strongly influence lipid production in N. oceanica and its fatty acid composition.

• ALGAE
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• v.27 no.3
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• pp.197-203
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• 2012

A eukaryotic microalga, Asterarcys quadricellulare KNUA020, was isolated from garden soil at Kyungpook National University in Daegu, South Korea and its biotechnological potential was assessed. Optimal growth was obtained when the culture was incubated at $25^{\circ}C$ and around pH 7.0. The total lipid content of the isolate was 15.5% of dry weight and its most abundant fatty acid was nutritionally important C18:3 ${\omega}3$ (${\alpha}$-linolenic acid, ALA). In addition, a high-value fatty alcohol, hexadecenol ($C_{20}H_{40}O$), was also identified in this photosynthetic microorganism. Hence, A. quadricellulare KNUA020 appears to be promising for use in the production of microalgae-based biochemicals.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.16-28
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• 2017

In an aquatic environment, toxicity of metals to organisms depends on external factors (type of metal, exposure concentration and duration, environmental parameters, and water quality) and intracellular processes(metal-binding sites and detoxification). Toxicity of copper(Cu) on the marine microalga Tetraselmis suecica was investigated in this study. Dose-dependent (Cu concentration dependent) inhibition of growth and cell division, as well as, variation of intra- and extra-cellular Cu, Fe and Zn content was observed. T. suecica was sensitive to Cu; the 96 h $EC_{50}$ (concentration to inhibit growth-rate by 50%) of growth rate (${\mu}$) ($21.73{\mu}M\;L^{-1}$), cell division $day^{-1}$ ($18.39{\mu}M\;L^{-1}$), and cells $mL^{-1}$ ($13.25{\mu}M\;L^{-1}$) demonstrate the toxicity of Cu on this microalga. High intra-($19.86Pg\;cell^{-1}$) and extra-cellular($54.73Pg\;cell^{-1}$) Cu concentrations were recorded, on exposure to 24.3 and $72.9{\mu}M\;L^{-1}$ of Cu.

• Journal of Microbiology and Biotechnology
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• v.23 no.3
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• pp.375-381
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• 2013

A freshwater microalga, Chlamydomonas reinhardtii KNUA021, was characterized for its potential as a biochemical feedstock. Its optimal growth was observed when the culture was incubated at $25^{\circ}C$ and pH 9.4. However, the isolate was capable of survival and growth under a variety of temperatures (10-$30^{\circ}C$) and pH (pH 4.0-12.0) conditions. The total lipid content of the isolate was 21.7% of dry weight and it was found that a high-value fatty alcohol, hexadecenol ($C_{20}H_{40}O$), was autotrophically produced by strain KNUA021. In addition, a nutritionally important $C_{18:3}{\omega}3$ (${\alpha}$-linolenic acid, ALA) was also identified in this photosynthetic microorganism as one of the major fatty acids. Hence, C. reinhardtii KNUA021 appears to show promise for use in the production of microalgae-based biochemicals.

• Journal of Microbiology and Biotechnology
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• v.25 no.2
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• pp.238-246
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• 2015

A unicellular red microalga was isolated from environmental freshwater in Korea, and its morphological, molecular, and biochemical properties were characterized. Morphological analysis revealed that the isolate was a unicellular biflagellated green microalga that formed a non-motile, thick-walled palmelloid or red aplanospore. To determine the taxonomical position of the isolate, its 18S rRNA and rbcL genes were sequenced and phylogenetic analysis was performed. We found that the isolate was clustered together with other related Haematococcus strains showing differences in the rbcL gene. Therefore, the isolated microalga was classified into the genus Haematococcus, and finally designated Haematococcus sp. KORDI03. The microalga could be cultivated in various culture media under a broad range of pH and temperature conditions. Compositions of the microalgal cellular components were analyzed, and its protein, carbohydrate, and lipid compositions were estimated to be 21.1 ± 0.2%, 48.8 ± 1.8%, and 22.2 ± 0.9%, respectively. In addition, D-glucose and D-mannose were the dominant monosaccharides in the isolate, and its amino acids were composed mainly of aspartic acid, glutamic acid, alanine, and leucine. Moreover, several polyunsaturated fatty acids accounted for about 80% of the total fatty acids in Haematococcus sp. KORDI03, and the astaxanthin content in the red aplanospores was estimated to be 1.8% of the dry cell weight. To the best of our knowledge, this is the first report of an Haematococcus sp. isolated from Korea, which may be used for bioresource production in the microalgal industry.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.216-217
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• 2005