• 한국물환경학회지
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• 제32권2호
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• pp.197-204
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• 2016

본 연구는 당화된 도토리의 전분이 미세조류(Chlorella vulgaris) 바이오매스 증식과 바이오오일 함량에 미치는 영향을 알아보고자 하였다. 실험결과 도토리의 전분은 당화 후에 81.3%가 글루코스로 전환되었다. 도토리-글루코스를 이용한 복합영양 상태에서 미세조류는 독립영양 상태보다 높은 바이오매스 증식률과 TAGs (Triacyglycerols)의 함유량을 나타내었는데, 최대 바이오매스 생산량과 TAGs의 함유량은 3 g/L의 도토리-글루코스의 농도에서 각각 12.44 g/L와 32.9%를 나타내었다. 이는 3 g/L의 도토리-글루코스 농도에서 독립영양 상태의 바이오매스 생산량과 비교하면 16.4배의 많은 양의 바이오매스를 생산하였음을 알 수 있었다. 따라서 경제성과 바이오매스의 생산량/생산률 그리고 TAGs의 함유량을 고려한다면 3 g/L의 도토리-글루코스 농도가 미세조류의 증식에 가장 효과적이였다. 본 연구의 결과는 미세조류 유래 바이오에너지의 생산 비용을 절감하는 데 도움이 될 수 있을 것으로 생각된다.

• ALGAE
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• 제39권2호
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• pp.109-127
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• 2024

High production and efficient harvesting of microalgae containing high omega-3 levels are critical concerns for industrial use. Aeration can elevate production of some microalgae by providing CO₂ and O₂. However, it may lower the production of others by generating shear stress, causing severe cell damage. The mixotrophic dinoflagellate Gymnodinium smaydae is a new, promising microalga for omega-3 fatty acid production owing to its high docosahexaenoic acid content, and determining optimal conditions and methods for high omega-3 fatty acid production and efficient harvest using G. smaydae is crucial for its commercial utilization. Therefore, to determine whether continuous aeration is required, we measured densities of G. smaydae and the dinoflagellate prey Heterocapsa rotundata in a 100-L semi-continuous cultivation system under no aeration and continuous aeration conditions daily for 9 days. Furthermore, to determine the optimal conditions for harvesting through centrifugation, different rotational speeds of the continuous centrifuge and different flow rates of the pump injecting G. smaydae + H. rotundata cells into the centrifuge were tested. Under continuous aeration, G. smaydae production gradually decreased; however, without aeration, the production remained stable. Harvesting efficiency and the dry weights of omega-3 fatty acids of G. smaydae + H. rotundata cells at a rotational speed of 16,000 rpm were significantly higher than those at 2,000-8,000 rpm. However, these parameters did not significantly differ at injection pump flow rates of 1.0-4.0 L min^-1. The results of the present study provide a basis for optimized production and harvest conditions for G. smaydae and other microalgae.

• ALGAE
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• 제31권3호
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• pp.189-204
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• 2016

Microalgal bioremediation of CO₂, nutrients, endocrine disruptors, hydrocarbons, pesticides, and cyanide compounds have evaluated comprehensively. Microalgal mitigation of nutrients originated from municipal wastewaters, surface waters, and livestock wastewaters has shown great applicability. Algal utilization on secondary and tertiary treatment processes might provide unique and elegant solution on the removing of substances originated from various sources. Microalgae have displayed 3 growth regimes (autotrophic, heterotrophic, and mixotrophic) through which different organic and inorganic substances are being utilized for growth and production of different metabolites. There are still some technology challenges requiring innovative solutions. Strain selection investigation should be directed towards identification of algal that are extremophiles. Understanding and manipulation of metabolic pathways of algae will possible unfold solution to utilization of algae for mitigation of dissolve organic nitrogen in wastewaters.

• ALGAE
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• 제35권3호
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• pp.277-292
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• 2020

Omega-3 fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are polyunsaturated fatty acids beneficial to human health. A limited number of microalgae have been used for commercial omega-3 production, which necessitates the identification of new microalgae with high omega-3 contents. We explored the fatty acid composition and EPA and DHA contents of the mixotrophic dinoflagellate Gymnodinium smaydae fed with the optimal algal prey species Heterocapsa rotundata. Cells of G. smaydae were found to be rich in omega-3 fatty acids. In particular, the DHA content of G. smaydae was 21 mg g^-1 dry weight, accounting for 43% of the total fatty acid content. The percentage of DHA in the total fatty acid content of G. smaydae was the highest among the reported microalgae except for Crypthecodinium cohnii. Moreover, to determine if the prey supply interval affected the growth rate of G. smaydae and its fatty acid content, three different prey supply intervals (daily, once every 2 d, and once for 4 d) were tested. Daily prey supply yielded the highest total fatty acid and DHA contents in G. smaydae. Furthermore, we successfully produced high-density G. smaydae cultures semi-continuously for 43 d with daily prey supply. During the semi-continuous cultivation period, the highest density of G. smaydae was 57,000 cells mL^-1, with an average growth rate of 0.7 d^-1. Taken together, the percentage of EPA and DHA in the total fatty acid content was maintained in the range of 54.2-56.9%. The results of this study support G. smaydae as a promising microalgal candidate for commercial DHA production and demonstrate that daily supply of prey can efficiently produce high-density G. smaydae cultures for more than a month.

• ALGAE
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• 제28권2호
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• pp.131-147
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• 2013

Major progress has been made in the past decade towards understanding of the biosynthesis of red carotenoid astaxanthin and its roles in stress response while exploiting microalgae-based astaxanthin as a potent antioxidant for human health and as a coloring agent for aquaculture applications. In this review, astaxanthin-producing green microalgae are briefly summarized with Haematococcus pluvialis and Chlorella zofingiensis recognized to be the most popular astaxanthin-producers. Two distinct pathways for astaxanthin synthesis along with associated cellular, physiological, and biochemical changes are elucidated using H. pluvialis and C. zofingiensis as the model systems. Interactions between astaxanthin biosynthesis and photosynthesis, fatty acid biosynthesis and enzymatic defense systems are described in the context of multiple lines of defense mechanisms working in concert against photooxidative stress. Major pros and cons of mass cultivation of H. pluvialis and C. zofingiensis in phototrophic, heterotrophic, and mixotrophic culture modes are analyzed. Recent progress in genetic engineering of plants and microalgae for astaxanthin production is presented. Future advancement in microalgal astaxanthin research will depend largely on genome sequencing of H. pluvialis and C. zofingiensis and genetic toolbox development. Continuous effort along the heterotrophic-phototrophic culture mode could lead to major expansion of the microalgal astaxanthin industry.

• Journal of Microbiology and Biotechnology
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• 제20권9호
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• pp.1276-1282
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• 2010

In traditional mixotrophic cultures of microalgae, all the inorganic nutrients and organic carbon sources are supplied in the medium before inoculation. In this study, however, an alternative approach was adopted in Haematococcus pluvialis Flotow, a microalga capable of growing mixotrophically on sodium acetate (Na-Ac). First, the cells were grown under 75 ${\mu}Mol$ photons $m^{-2}s^{-1}$ phototrophically without Na-Ac until the stationary phase and then exposed to five different light regimes by the addition of Na-Ac (e.g., dark, 20, 40, 75, and 150 ${\mu}Mol$ photons $m^{-2}s^{-1}$). Dry weight (DW), pigments, and especially cell number in alternative mixotrophy (AM) were higher than traditional mixotrophy (TM). Cell number in AM almost doubled up from 21.7 to $42.9{\times}10^4$ cells/ml during 5-day exposure to Na-Ac, whereas the increase was only 1.2-fold in TM. Maximum cell density was reached in 75 ${\mu}Mol$ photons $m^{-2}s^{-1}$ among the light intensities tested. We propose that Na-Ac in TM of H. pluvialis can not be utilized as efficiently as in AM. With this respect, AM has several advantages against TM such as a much higher cell density in a batch culture period and minimized risk of contamination owing to the shorter exposure of cells to organic carbon sources. In consequence, this method may be used for other strains of the species, and even for the other microalgal species able to grow mixotrophically.

• 한국미생물·생명공학회지
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• 제48권3호
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• pp.337-343
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• 2020

Haematococcus sp.를 대상으로 mixotroph 형태에서 배양을 위한 배지 최적화 연구를 수행하였다. 기본 배지로는 modified MS 배지가 적절했으며, 탄소원으로는 glucose가, 그리고 농도는 10 g/l가 적합하였다. 질소원으로는 KNO₃를 선정하였으며, 농도는 1.9 g/l이 최적이었다. 최적의 배지조건에서 Haematococcus sp.를 초기 접종량(0.18 g/l)로 접종하여 14일 후에 5.58 ± 0.25 g/l로 성장하였으며, 이는 건조 세포중량 기준으로 약 31배의 성장한 것이다. 이때 생성된 클로로필은 172.16 ± 7.79 mg/l였으며, 카로티노이드는 42.33 ± 1.91 mg/l이었다. 본 연구의 결과는 추후 미세조류 대량 배양과 대사산물의 생산에 이용가능한 기초자료가 될 수 있을 것이라 판단된다.

• Korean Chemical Engineering Research
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• 제55권1호
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• pp.74-79
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• 2017

본 연구에서는 Chlorella saccharophila의 배양을 통하여 바이오에너지 자원을 대량으로 확보하고자 배지 최적화 실험을 진행하였다. 최적화 인자로는 배양 형태, 초기 접종량, 탄소원 종류 및 농도, 질소원 종류 및 농도, 배양시간이다. 실험 결과, 배양 형태는 광원과 외부탄소원을 모두 공급하는 mixotrophic 배양이 적절하였다. 초기 접종량은 3% (v/v), 탄소원은 glucose 30 g/L, 질소원은 $NaNO_3$ 0.95 g/L를 첨가하는 것이 우수하였다. 최적 배지 조건으로 배양한 결과, oil의 함량은 12일에서 가장 높았으나, 회수되는 C. saccharophila의 biomass양과 chlorophyll의 양은 10일에서 가장 높았다. 위의 결과는 미세조류의 배지 최적화를 통하여 대량배양을 위한 기초자료로 사용될 수 있으리라 판단된다.

• Fisheries and Aquatic Sciences
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• 제11권4호
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• pp.205-208
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• 2008

The mixotrophic dinoflagellate Cochlodinium polykrikoides was reported to be linked to major fish kills in Korea and Japan since the 1990s. Rapid and sensitive detection of microalgae has been problematic because morphological identification of dinoflagellates requires light microscopic and scanning electron microscopic observations that are time consuming and laborious compared to real-time PCR. To address this issue, a real-time PCR probe targeting the ITS2 rRNA gene was used for rapid detection and quantification of C. polykrikoides. PCR inhibitors in water column samples were removed by dilution of template DNA for elimination of false-negative reactions. A strong association between cell quantification using real-time PCR and microscopic counts suggests that the real-time PCR assay is an alternative method for cell estimation of C. polykrikoides in environment samples.

• ALGAE
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• 제31권4호
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• pp.391-401
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• 2016

To develop an easy and rapid method of quantifying lipid contents of marine dinoflagellates, we quantified lipid contents of common dinoflagellate species using a colorimetric method based on the sulpho-phospho-vanillin reaction. In this method, the optical density measured using a spectrophotometer was significantly positively correlated with the known lipid content of a standard oil (Canola oil). When using this method, the lipid content of each of the dinoflagellates Alexandrium minutum, Prorocentrum micans, P. minimum, and Lingulodinium polyedrum was also significantly positively correlated with the optical density and equivalent intensity of color. Thus, when comparing the color intensity or the optical density of a sample of a microalgal species with known color intensities or optical density, the lipid content of the target species could be rapidly quantified. Furthermore, the results of the sensitivity tests showed that only $1-3{\times}10^5cells$ of P. minimum and A. minutum, $10^4cells$ of P. micans, and $10^3cells$ of L. polyedrum (approximately 1-5 mL of dense cultures) were needed to determine the lipid content per cell. When the lipid content per cell of 9 dinoflagellates, a diatom, and a chlorophyte was analyzed using this method, the lipid content per cell of these microalgae, with the exception of the diatom, were significantly positively correlated with cell size, however, volume specific lipid content per cell was negatively correlated with cell size. Thus, this sulpho-phospho-vanillin method is an easy and rapid method of quantifying the lipid content of autotrophic, mixotrophic, and heterotrophic dinoflagellate species.