• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.87-94
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• 2012

To compare monthly variations of phytoplankton biomass and community composition between in seawater and sediment of the Gomso Bay (tidal flat: approximately 75%), the photosynthetic pigments were analyzed by HPLC every month in 1999 and every two months in 2000. Ambient physical and chemical parameters (temperature, salinity, nutrients, dissolved oxygen, and chemical oxygen demand) were also examined to find the environmental factors controlling structure of phytoplankton community. The temporal and spatial variations of chlorophyll a concentration in seawater were correlated well with the magnitude of freshwater discharge from land. The biomass of microphytobenthos at the surface sediments was lower than that in other regions of the world and 2-3 times lower than phytoplankton biomass integrated in the seawater column. Based on the results of HPLC pigment analysis, fucoxanthin, a marker pigment of diatoms, was the most prominent pigment and highly correlated with chlorophyll a in seawater and sediment of the Gomso Bay. These results suggest that diatoms are the predominant phytoplankton in seawater and sediment of the Gomso Bay. However, the monthly variation of chlorophyll a concentration in seawater at the subtidal zone was not a good correlation with that in sediment of the Gomso Bay. Although pelagic plankton was identified in seawater by microscopic examination, benthic algal species were not found in the seawater. These results suggest that contribution from the suspended microphytobenthos in the tidal flat to the subtidal zone of the Gomso Bay may be low as a food source to the primary consumer in the upper water column of the subtidal zone. Further study needs to elucidate the vertical and horizontal transport magnitude of the suspended microphytobenthos in the tidal flat to the subtidal zone.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.363-369
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• 2018

One of the recent environmental problems is climate change due to the increase of atmospheric $CO_2$, which causes ecological changes and various environmental problems. Therefore, various studies are being carried out to reduce $CO_2$ in the world in order to solve various environmental problems caused by increase of $CO_2$. The $CO_2$ reduction using microalgae is an environmentally friendly method by using photosynthesis reaction of microalgae. However, most studies using single species. There is no study on the $CO_2$ fixing efficiency of microalgae in natural rivers. Therefore, this study was to identify the microalgae in the Sum river and to analyze the growth characteristics of microalgae in the river to obtain optimal culture conditions. And the changes of biomass and chlorophyll-a of microalgae were analyzed according to $CO_2$ concentration and injection rate. The purpose of this study was to investigate the fixing efficiency of carbon dioxide in microalgae in natural rivers. Six kinds of dominant species were observed as a result of the identification of microalgae in Sum river(Ankistrodesmus falcatus, Scenedesmus intermedius, Selenodictyum sp., Xanthidium apiculatum var. laeve, Cosmarium pseudoquinarium, Dictyosphaerium pulchellum). All of these species were green algae. Biomass and chlorophyll-a increased with the increase of $CO_2$ concentration and biomass and chlorophyll-a increased faster flow rate at the same $CO_2$ concentration. Also, the quantity of $CO_2$ fixation on the microalgae tended to be higher when the flow rate of injected gas was faster. This study can be referred as being significant in the micro-algae in river. In addition, the optimal conditions for $CO_2$ fixation of microalgae in rivers and the quantification of the quantity of $CO_2$ fixation from microalgae in rivers can be used as basic data for future policy of $CO_2$ reduction.

• Korean Journal of Environmental Biology
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• v.32 no.1
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• pp.26-34
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• 2014

Due to the rapid energy consumption and fossil fuel abundance reduction, the world is progressively in need of alternative and renewable energy sources such as biodiesel. Biodiesel from microalgae offers high hopes to the scientific world for its potential as well as its non-competition with arable lands. Taking consideration to reduce the cost of production as well as to attain twin environmental goals of treatment and use of animal waste material the microalgal cultivation using piggery manure has been tested in this study. Unialgal strains such as Chlorella sp. JK2, Scenedesmus sp. JK10, and an indigenous mixed microalgal culture CSS were cultured for 20 days in diluted piggery manure using Small Scale Raceway Pond (SSRP). Biomass production and lipid productivity of CSS were $1.19{\pm}0.09gL^{-1}$, $12.44{\pm}0.38mgL^{-1}day^{-1}$, respectively and almost twice that of unialgal strains. Also, total nitrogen and total phosphorus removal efficiencies of CSS was 93.6% and 98.5% respectively and 30% higher removal efficiency compared to the use of unialgal strains. These results indicate that the piggery manure can provide microalgae necessary nitrogen and phosphorus for growth thereby effectively treating the manure. In addition, overall cost of microalgal cultivation and subsequently biodiesel production would be significantly reduced.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.80-85
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• 2017

Recently, microalgae which can produce high-value products have attracted increasing attention for biological conversion of $CO_2$. However, low photosynthetic efficiency and productivity have limited the practical use of microalgae. Thus, we developed microdroplet photobioreactor for the analysis of photoautotrophic growth of model alga, Chlamydomonas reinhardtii. $CO_2$ transfer rate was increased by integrating micropillar arrays and adjusting height of microchamber. These results were identified by change of cell growth rate and fluorescence intensity. Lastly, the photoautotrophic growth kinetics of C. reinhardtii in microdroplet photobioreactor were investigated under different $CO_2$ concentrations and light intensities for 96 hours. As a result, microdroplet photobioreactor was efficient platform for isolation and rapid evaluation of microalgal strains which have enhanced productivity of high-value products and growth performance.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.1-9
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• 2016

The co-culture system of microalgae and bacteria enables simultaneous removal of BOD and nutrients in a single reactor if the pair of microorganisms is symbiotic. In this case, nutrients are converted to biomass constituents of microalgae. This review highlights the importance and recent researches using symbiotic co-culture system of microalgae and bacteria in wastewater treatment, focusing on the removal of nitrogen and phosphorus. During wastewater treatment, the microalgae produces molecular oxygen through photosynthesis, which can be used as an electron acceptor by aerobic bacteria to degrade organic pollutants. The released $CO_2$ during the bacterial mineralization can then be consumed by microalgae as a carbon source in photosynthesis. Microalgae and bacteria in the co-culture system could cooperate or compete each other for resources. In the context of wastewater treatment, positive relationships are prerequisite to accomplish the sustainable removal of nutrients. Therefore, the selection of compatible species is very important if the co-culture has to be utilized in wastewater treatment.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.87-92
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• 2013

Microalgae have been suggested as a promising feedstock for producing biofuel because of their potential of lipid production. In this study, a first principles ODE model for microalgae growth and neutral lipid synthesis proposed by Surisetty et al. (2010) is investigated for the purpose of maximizing the rate of microalgae growth and the amount of neutral lipid. The model has 6 states and 12 parameters and follows the assumption of Droop model which explains the growth as a two-step phenomenon; the uptake of nutrients is first occurred in the cell, and then use of intra-cellular nutrient to support cells growth. In this study, optimal input design using D-optimality criterion is performed to compute the system input profile and sensitivity analysis is also performed to determine which parameters have a negligible effect on the model predictions. Furthermore, model predictive control based on successive linearization is implemented to maximize the amount of neutral lipid contents.

• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.8-16
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• 2014

Microalgae have been considered as a promising microorganism in the field of bio-industry due to their abilities to fix carbon dioxide as well as biosynthesize valuable secondary metabolites. Of many lighting sources for microalgal cultivation, LED (Lighting Emitting Diode) has been emerged as the appropriate choice with multiple advantages over the conventional bulbs. However, it is only in recent years that we have witnessed the possibility of application of LED into microalgae cultivation system. LED will serve as an evolutionary lighting source for microalgae cultivation system and open the frontier for integrative bio-industries. In this paper, we present the comprehensive review on the recent trends of LED applications into microalgal biotechnology.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.175.2-175.2
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• 2011

바이오디젤의 국가별 의무 사용 정책 확대로 인해 원료유 가격이 상승하고 있으며 원료유가 부족한 상황으로 다양한 원료를 찾는 연구가 진행되고 있다. 육상 유지 작물보다 단위면적당 생산성이 매우 높은 미세조류는 제3세대 바이오매스로 주목받고 있으며 산업체 배출 이산화탄소를 이용해 작은 면적에서 배양할 수 있는 장점이 있다. 미세조류로부터 바이오디젤 생산은 먼저 오일 함량이 높은 미세조류 종의 선정과 배양 및 수확 후 효율적인 방법으로 바이오디젤 원료유를 추출하는 과정이 중요하다. 본 연구는 Microwave로 전처리된 미세조류로 부터 원료유를 추출하여, 인지질, 단백질, 엽록소 등의 반응저해 물질을 일부 감소시키고 추출수율을 높였지만, 산가가 80이상으로 높게 추출되고 추출된 오일이 높은 점성을 가지는 문제가 있다. 이로 인해 전이에스테르화 반응의 진행이 불가하였으며 이러한 문제를 해결하기 위해, 에스테르화 반응에 용매를 혼합하여 반응성을 개선하고자 하였다. 추가된 보조 용매는 오일과 쉽게 혼합되어 반응물의 점성을 낮추고, 반응 완료후, 물에 쉽게 용해되는 불순물, 미 반응물, 촉매 등의 분리 및 제거를 용이하게 하는 장점이 있다. 또한 오일과 비교하여 낮은 끓는점을 갖는 용매는 증류를 통해 쉽게 제거가 가능하다. 반응이 완료된 오일은 초기산가 80에서 10이하의 감소를 나타내 용매 혼합 에스테르화의 효율적인 부분을 확인하였다.

• 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.

• 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.