• 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.

• Journal of Marine Bioscience and Biotechnology
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• v.6 no.2
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• pp.110-117
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• 2014

Recently microalgae have been proposed as a promising biodiesel feedstock, owing to their higher lipid productivity and non-arable land based cultivation system. Biomass and lipid productivities of microalgae are largely affected by various environmental and nutritional factors. In this study, the effects of nitrogen (nitrate and ammonium) and organic carbon (glucose and glycerol) sources on the cell growth and lipid production of Chlorella sp. KR-1 were examined in flask cultures. Under autotrophic culture conditions for 15 days, overall cell growth and lipid (fatty acid methyl ester, FAME) production with nitrate were better than those of ammonium, resulting in 1.06 g cell/L and 333 mg FAME/L, respectively. Maximal intracellular lipid contents (348 - 352 mg FAME/g cell) were observed at low concentrations of 1 mM for both nitrate and ammonium. In the supply of light, addition of glucose in the range of 1 - 20 g/L showed higher cell densities than the autotrophic cell growth condition. Higher lipid accumulation of 375 mg FAME/g cell could achieved at 5 g glucose/L albeit of relatively short incubation of 7 days. With glycerol, intracellular lipid contents were ~1.9 times lower than glucose cases although similar cell growths were observed for both carbon sources.

• Journal of Marine Bioscience and Biotechnology
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• v.16 no.1
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• pp.36-44
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• 2024

This study attempted to improve the growth of the freshwater microalgae, Parachlorella kessleri, through the sequential optimization of culture conditions. This attempt aimed to enhance the microalgae's ability to fixate atmospheric CO₂. Culture temperature and light intensity appropriate for microalgal growth were scanned using a high-throughput photobioreactor system. The supplied air flow rate varied from 0.05 to 0.3 vvm, and its effect on the growth rate of P. kessleri was determined. Next, sodium phosphate buffer was added to the culture medium (BG11) to enhance CO₂ fixation by increasing the availability of CO₂(HCO₃^-) in the culture medium. The results indicated that optimal culture temperature and light intensity were 20℃-25℃ and 300 μE/m²/s, respectively. Growth rates of P. kessleri under various air flow rates highly depended on the increase of the culture's flow rate and pH which determines CO₂ availability. Adding sodium phosphate buffer to BG11 to maintain a constant neutral pH (7.0) improved microalgal growth compared to control conditions (BG11 without sodium phosphate). These results indicate that the CO₂ fixation rate in the air could be enhanced via the sequential optimization of microalgal culture conditions.

• Fisheries and Aquatic Sciences
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• v.25 no.10
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• pp.499-516
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• 2022

Endobiotic microalgae inhabit various groups of organisms, including bivalves. In this group, the association between the giant molluscs Tridacna and Symbiodinium is one of the most recognizable. This consortium allows hydrobionts to survive in oligotrophic waters by regulating their metabolism. The available research has provided an understanding of the interaction and adaptation of these symbionts, but the problem of the beginning of the formation of these relationships remains unresolved. In the case of Tridacninae, symbiosis is essential for the survival of bivalves, in contrast to representatives of the Mytilidae and the Coccomyxa found in them. A few works devoted mainly to the morphological aspects of invasion have shown that endobiont causes inflammation and pathology. Having data to clarify the exact "diagnosis" of the interaction of these organisms is not enough. It is possible that the relationship between bivalves and Coccomyxa is in the early stages of being established, which may lead to mutualism or parasitism in the future. We assume that the analysis of works on the symbiosis of Symbiodinium and bivalves will facilitate the course of research for the less studied Coccomyxa and their hosts. By postulating the Coccomyxa represent a unique evolutionary model for the formation of a symbiotic system, it is possible to use this system to study the interaction of organisms during their initial contact. The identified signalling pathways and mechanisms that allow the photobionts to evade host immunity can be useful for constructing new forms of symbiosystems.

• Journal of Microbiology and Biotechnology
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• v.33 no.2
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• pp.251-259
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• 2023

Immobilizing microalgae cells in a hyphal matrix can simplify harvest while producing novel mycoalgae products with potential food, feed, biomaterial, and renewable energy applications; however, limited quantitative information to describe the process and its applicability under various conditions leads to difficulties in comparing across studies and scaling-up. Here, we demonstrate the immobilization of both active and heat-deactivated marine diatom Phaeodactylum tricornutum (UTEX 466) using different loadings of fungal pellets (Aspergillus sp.) and model the process through kinetics and equilibrium models. Active P. tricornutum cells were not required for the fungal-assisted immobilization process and the fungal isolate was able to immobilize more than its original mass of microalgae. The Freundlich isotherm model adequately described the equilibrium immobilization characteristics and indicated increased normalized algae immobilization (g algae removed/g fungi loaded) under low fungal pellet loadings. The kinetics of algae immobilization by the fungal pellets were found to be adequately modeled using both a pseudo-second order model and a model previously developed for fungal-assisted algae immobilization. These results provide new insights into the behavior and potential applications of fungal-assisted algae immobilization.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.611-614
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• 2003

The rheological properties of exopolysaccharide, p-KG03, produced by marine microalgae Gyrodinium impudicum strain KG03 had been studied. The intrinsic viscosity of this p-KG03 was calculated to 65.22 and 50.75 $d{\ell}/g$ using Huggins and Kramer equations (xanthan gum 24.41 and 24.03). Aqueous dispersions at p-KG03 concentrations ranging from 0.1 to 1.0 % (w/w) showed marked shear-thinning properties as Power-Law behavior. In aqueous dispersions of p-KG03 1.0 %, consistency index (K) and flow behavior index (n) were 2,172 and 0.52. The apparent viscosity and the influence of shear rate on different conditions as p-KG03 concentrations, pH, NaCl, $CaCl_2$ and temperature in aqueous solutions were measured. And p-KG03 had mixed with aqueous solutions of xanthan gum and gellan gum, and invested the change of mixed aqueous solution behavior.

• KSBB Journal
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• v.25 no.2
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• pp.109-115
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• 2010

The demand of biodiesel that is a renewable, alternative fuel for fossil-based petrodiesel seems to keep increasing. Exploiting lipids of microalgae as a raw material for biodiesel is already technically feasible. To realize economical production of microalgal biodiesel, several factors or strategies should be addressed and improved. Especially, researches on improvement of lipid synthesis by genetic or metabolic engineering are now in early stage, and prospects of this field are bright, requiring concerns and interests of many researchers to put practical use of microalgal biodiesel forward.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.339-345
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• 2011

Although culture techniques for the abalone Haliotis discus hannai are well known, mass culture of the benthic microalgae that are essential live food for the abalone larvae is still not practiced. This study was conducted to identify the microalgal species suitable for the growth of early larvae of H. discus hannai. The growth and attachment rates of 31 microalgal species were examined. Acrylic plates were used as the substrate. Among the 31 microalgal species, nine showing high growth and attachment rates were selected and tested for their dietary values via factors including settlement, metamorphosis, and survival rates of abalone larvae. Tetraselmis hazeni and Rhaphoneis sp. induced the highest settlement rate (65-69%) in abalone larvae. The metamorphosis rate was highest (57%) in larvae fed Rhaphoneis sp. and was also significantly higher in larvae fed Oscillatoria splendida (29%) and T. hazeni (22%) than in those fed other species. The highest survival rate of the larvae during the 15 days after metamorphosis was 67% in those fed Rhaphoneis sp., followed by T. hazeni (42%) and O. splendida (35%). In conclusion, Rhaphoneis sp. is the most suitable diatom for use as a live food for the culture of early larvae of H. discus hannai. In addition, T. hazeni and O. splendida are also potential species to be further developed and utilized in larval culture.

• Fisheries and Aquatic Sciences
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• v.11 no.3
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• pp.149-158
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• 2008

Labyrinthulids are unicellular heterotrophic marine microalgae. Two labyrinthulid strains, L4 and L75, which produce generous amounts of polyunsaturated fatty acids(PUFAs), were isolated from leaves floating in the coastal areas of Quang Ninh province, Vietnam, and Fukuoka Prefecture, Japan, respectively. Both strains had spindle-shaped cells surrounded by ectoplasmic networks. Numerous oil bodies were observed in each cell, mostly in the vicinity of cell membranes. When soybean oil or soybean lecithin was used as a carbon source with peptone as a nitrogen source, the proportion of PUFAs reached 25-30% and 50-56% for L4 and L75, respectively. After 14 days of growth at $25^{\circ}C$, L4 produced 0.3 mg PUFAs/g-agar in PYA-SBO medium and 0.6 mg PUFAs/g-agar in PYA-SBL medium. In comparison, L75 produced 0.2 mg PUFAs/g-agar in both types of media. The differences between the two strains included changes in cellular morphology and the capacity for attaching tightly to fibers when cultured in liquid PYA medium containing 2% SBL. In addition, when the strains were grown under the same conditions, L4 had a higher growth rate and produced more PUFAs than L75.

• Journal of Marine Bioscience and Biotechnology
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• v.5 no.4
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• pp.46-50
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• 2011

Phytoplankton forms the base of sea ecosystems. Various environmental factors and anthropogenic pollution, primarily, affect the concentration and photosynthetic activity algal cells, and the changes in the phytoplankton photosynthesis influence other elements of aquatic ecosystems. The increase in anthropogenic pollution markedly damages natural aquatic ecosystems, particularly, in the coastal zones, where an intense blooming of microalgae occurs, including the release of highly dangerous ecotoxic substances of various chemical natures (red tides). In this study, we tried to apply as a parameter for the algal blooming prediction in the ocean from fluorescence values in the taken samples around Busan coastal area. F0 value was almost constant but Fv/Fm value showed the irregular pattern. We presume that these results are due to the changes of the ocean environment and climate. To predict or give early warning the algal blooming, we need to investigate the specific area or fixed area through real-time monitoring. Especially, algal blooming prediction or warning can be achieved via continuously monitoring and interpretation of fluorescence changes.