• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1501-1502
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• 2011

• Ocean and Polar Research
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• v.34 no.4
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• pp.365-384
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• 2012

Microalgae are photosynthetic microorganisms that are highly productive in the presence of basic renewable natural sources (light, $CO_2$, water and nutrients). They can synthesize lipids, carbohydrates and proteins in a small number of days. Subsequently, these carbon-captured products can be processed into both biofuels and valuable co-products. Additionally, microalgae would be an ideal feedstock for replacing land-based food crops with cellular products as high energy density transportation fuels. These microscopic organisms could contribute a significant amount of renewable energy on a global scale. In Korea, microalgae biofuel research was common in the early 1990s. The research activities were unfortunately stopped due to limited governmental funds and low petroleum prices. Interest in algal biofuels in Korea has been growing recently due to an increased concern over oil prices, energy security, greenhouse gas emissions, and the potential for other biofuel feedstock to compete for limited agricultural resources. The high productivity of microalgae suggests that much of the Korean transportation fuel requirements can be met by biofuels at a production cost competitive with the increasing cost of petroleum seen in early 2008. At this time, the development of microlalgal biomass production technology remains in its infancy. This study reviewed microalgae culture systems and biomass production, harvesting, oil extraction, conversion, and technoeconomical bottlenecks. Many technical and economic barriers to using microalgal biofuels need to be overcome before mass production of microalgal-derived fuel substitutes is possible. However, serious efforts to overcome these barriers could become a large-scale commercial reality. Overall, this study provides a brief overview of the past few decades of global microalgal research.

• Journal of Aquaculture
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• v.19 no.4
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• pp.310-314
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• 2006

This study was carried out to investigate grazing of brackish water cyclopoid copepod Paracyclopina nana on four microalgae species (Tetraselmis suecica, Isochrysis galbana, Phaeodactylum tricornutum and Dunaliella tertiolecta) and different food concentrations raging from 5 to 55 ng chl a/ml. The grazing of P. nana was examined by the analysis of decreased number of microalgae and chlorophyll a content in rearing water and pigment content in the gut of P. nana. The maximum content of decreased chlorophyll a and gut pigment in P. nana varied with microalgae species and concentrations. It appeared at the food concentration 30 ng chl a/ml in T. suecica, 40 ng chl a/ml in I. galnaba and D. tertiolecta, and 45 ng chl a/ml in P. tricornutum, respectively. The grazing rate of a P. nana per hour also varied with different microalgae species and concentrations. The maximum grazing rate per hour of P. nana fed T. suecica with 39.3 ng chl a/ml was the highest with 0.63 ng chl a/h, but lowest with 0.52 ng chl a/h. From these results, it can be concluded that T. suecica is the best species among four microalgae species for the mass culture of P. nana and daily optimum food concentration of P. nana is $25{\sim}39$ ng chl a (approximately $10{\sim}15{\times}10^4$ cells).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.70-77
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• 2020

Microalgae are independent organisms that perform photosynthesis and can alter the culture environment to increase accumulation of useful substances derived from microalgae. In this study, cell growth was measured by incubation for 39 days using MBBM, Neo medium, and seven light sources, which is the main factor affecting cell growth of microalgae S. obliquus. In the case of S. oliquus, which grew in MBBM and Neo medium, cell growth was highest under fluorescent light sources and Red2 LED (R660) light sources, and cell growth was lowest under Infra Red LED (R741) light sources. The average cell growth rate was 17.7% for MBBM and 15.4% for Neo. Comparing the effects of dry cell weight of Neo medium containing nutrients on the production of aquatic plants, MBBM and dry cell weight of Neo resulted in higher cell growth than Neo medium under all LED light sources except for Blue LED (B450). This proves that MBBM is more suitable for increasing the cell growth of microalgae than Neo medium and confirms that light source selection is important in the production of useful materials through mass cultivation of microalgae in the future.

• Microbiology and Biotechnology Letters
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• v.41 no.2
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• pp.207-214
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• 2013

A concerted effort to develop alternative forms of energy is underway due to fossil fuel shortages and its deleterious effects. Recently, bioenergy from microalgae has gained prominence and the use of municipal wastewater as a low cost alternative for a nutrient source has significant advantages. In this study, we have employed municipal wastewater directly after primary treatment (primary settling basin) in a small scale raceway pond (SSRP) for microalgal growth. Indigenous microalgae in the wastewater were encouraged to grow in the SSRP under optimal conditions. The mean removal efficiencies of TN, TP, and $NH_3-N$ after 6 days were 77.77%, 63.55%, and 89.02%, respectively. The average lipid content of the microalgae was 19.51% of dry cell weight, and linolenate and linoleate (18:n) were the predominant fatty acids. The 18S rRNA gene analysis and microscopic observations of the indigenous microalgae community revealed the presence of Chlorella vulgaris and Scenedesmus obliquus as the dominant microalgae. These results indicate that untreated municipal wastewater, serving as an excellent nitrogen and phosphate source for microalgal growth, could be treated using microalgae in open raceway ponds. Moreover, microalgal biomass could be further profitable by the extraction of biodiesel.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.1
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• pp.32-40
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• 2017

The aim of this study was to evaluate a temperature-induced two-stage cultivation (TTC) strategy for the regulation of lipid and carbohydrate production by two microalgae, Chlorella vulgaris and Dunaliella salina, for biofuel production. The microalgae were grown under several temperature conditions (15, 25, 35, and $45^{\circ}C$) and optimal growth was observed at $25^{\circ}C$ for both microalgae. To test the TTC, aseptically cultured microalgae were incubated under optimal conditions ($25^{\circ}C$) for 20 days, and then divided into four aliquots that were incubated at 15, 25, 35, and $45^{\circ}C$ for 5 days. Similar but somewhat decreased growth rates were observed at the non-optimal temperatures (15, 35, and $45^{\circ}C$). In addition, while total lipid accumulation increased in a temperature-dependent manner in both microalgae, total carbohydrate increased with temperature in C. vulgaris but decreased in D. salina. However, for lipid and carbohydrate production, while the highest lipid productions of C. vulgaris and D. salina were observed at $25^{\circ}C$ and $35^{\circ}C$, respectively, the highest total carbohydrate productions of C. vulgaris and D. salina were obtained at $15^{\circ}C$ and $25^{\circ}C$, respectively. These results suggest that the TTC strategy may be easily and efficiently applied to bioprocessing for biofuel production.

• Korean Journal of Microbiology
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• v.48 no.3
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• pp.192-199
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• 2012

Microalgal biotechnology has gained prominence because of the ability of microalgae to produce value-added products including biodiesel through photosynthesis. However, carbon and nutrient source is often a limiting factor for microalgal growth leading to higher input costs for sufficient biomass production. Use of municipal wastewater as a low cost alternative to grow microalgae as well as to treat the same has been demonstrated in this study using mini raceway open ponds. Municipal wastewater was collected after primary treatment and microalgae indigenous in the wastewater were encouraged to grow in open raceways under optimum conditions. The mean removal efficiencies of TN, TP, COD-$_{Mn}$, $NH_3$-N after 6 days of retention time was 80.18%, 63.56%, 76.34%, and 96.74% respectively. The 18S rRNA gene analysis of the community revealed the presence of Chlorella vulgaris and Scenedesmus obliquus as the dominant microalgae. In addition, 16S rRNA gene analysis demonstrated that Rhodobacter, Luteimonas, Porphyrobacter, Agrobacterium, and Thauera were present along with the microalgae. From these results, it is concluded that microalgae could be used to effectively treat municipal wastewater without aerobic treatment, which incurs additional energy costs. In addition, municipal wastewater shall also serve as an excellent carbon and nitrogen source for microalgal growth. Moreover, the microalgal biomass shall be utilized for commercial purposes.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.2
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• pp.91-95
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• 2009

To understand the effect of attachment substrate on the growth of benthic microalgae, we experimentally investigated the growth of benthic microalgae Nitzschia sp. (Jinhae Bay strain) with additions of glass beads in different sizes. The glass beads used in this study are 0.09-0.15 mm (G1), 0.25-0.50 mm (G2), 0.75-1.00 mm (G3) and 1.25-1.65 mm (G4). No addition of glass beads used as controls. Highest specific growth rate (0.37/day) and maximum cell density ($9,232{\pm}840$ cells/mL) of Nitzschia sp. showed at the smallest glass beads (G1), and the specific growth rate and maximum cell density were decreasing with increasing size of glass beads (specific growth rate and maximum cell density of G4 was 0.24/day and $6,397{\pm}524$ cells/mL, respectively). Moreover, specific growth rate of the control experiment (0.23/day) was significantly lower than their of G1 to G3 experiment. The results indicated that the attachment substrate for benthic microalgae as Nitzschia sp. is important factor which affecting the growth rate as well as cell density. Therefore, the physiological experiment of benthic microalgae seems to be necessary to preliminary experiment, which is addition or not of the attachment suitable substrate and the grain size for the target species of benthic microalgae.

• Journal of Life Science
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• v.25 no.7
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• pp.733-739
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• 2015

Microalgae are a renewable natural resource that requires only sunlight, carbon dioxide, phosphorus, and nitrogen for rapid growth. They produce a broad variety of basic chemical substances―such as vitamins, fatty acids and carotenoids―that have high added value potential for the pharmaceutical and food industries. The aim of this study was to develop axenic culture and to establish a cell growth assay for microalgae. A further experiment was carried out to determine the yield of astaxanthin derived from microalgae. The axenic culture was developed using a mixture of antibiotics [ampicillin (100 ${\mu}g/ml$), streptomycin (10 ${\mu}g/ml$), chloramphenicol (10 ${\mu}g/ml$), penicillin (10 ${\mu}g/ml$), neomycin (50 ${\mu}g/ml$), gentamycin (50 ${\mu}g/ml$), kanamycin (10 ${\mu}g/ml$), and nystatin (1.5 ${\mu}g/ml$)] and then used to extract a variety of useful components from the microalgae. The optimal concentration for the antibiotic mixture was 1-3 percent. A spectrophotometric cell growth assay was also established. Astaxanthin was extracted from Haematococus lacustris with a yield of $1.9{\times}10^{-3}{\mu}g/l$ per 1 ml of culture medium. In conclusion, the axenic culture method developed here allows extraction of high-quality astaxanthin and other useful components from microalgae.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.379-386
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• 2021

This study was undertaken to develop a cascade-type continuous culture system (CCCS) that combines both ICT and biotechnology (BT), for the mass production of microalgae. This system is capable of maintaining the essential culture conditions of pH, temperature, carbon dioxide, and illuminance control, which are key parameters for the growth of microalgae, and is economical for producing microalgae regardless of the season or location. It has the added advantage of providing stable and high productivity. In the current study, this system was applied to culture microalgae for 71 days, with subsequent analysis of the experimental data. The initial O.D. of the culture measured from incubator 1 was 0.006. On the 71st day of culture, the O.D.s obtained were 0.399 (incubator 1), 0.961 (incubator 2), 0.795 (incubator 3), and 0.438 (incubator 4), thereby confirming the establishment of continuous culture. Thus, we present a smart-farm based on ISMC (in-situ monitoring and control) for a mass culture method. We believe that this developed technology is suitable for commercialization, and has the potential to be applied to hydroponics-based cultivation of microalgae and cultivation of high-value-added medicinal plants as well as other plants used in functional foods, cosmetics, and medical materials.