• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.222-228
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• 2022

As a possible feedstock for biodiesel, the marine green alga Tetraselmis sp. was cultivated under different conditions of phototrophic, mixotrophic and heterotrophic cultures. Glycerol, a byproduct from biodiesel production process, was used as the carbon source of mixotrophic and heterotrophic culture. The effects of glycerol supply and nitrate-repletion were compared for different trophic conditions. Mixotrophic cultivation exhibited higher biomass productivity than that of phototrophic and heterotrophic cultivation. Maximum lipid productivity of 55.5 mg L^-1 d^-1 was obtained in the mixotrophic culture with 5 g L^-1 of glycerol and 8.8 mM of nitrate due to the enhancement of both biomass and lipid accumulation. The major fatty acid methyl esters (FAME) in the produced biodiesel were palmitic acid (C16:0), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3). The degree of unsaturation was affected by different culture conditions. The biodiesel properties predicted by correlation equations based on the FAME profiles mostly complied with the specifications from the US, Europe and Korea, with the exception of the cold-filter plugging point (CFPP) criterion of Korea.

• KSBB Journal
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• v.24 no.4
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• pp.377-382
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• 2009

The culture condition of growing Chlorella minutissima was optimized to produce biodiesel for fed-batch cultivation. First, under heterotrophic cultivation, the optimum level of glucose was determined to be 10 g/L for 20 days. After, three cultivation conditions were operated: autotrophic, heterotrophic, and mixotrophic growth. The lipid level and the maximum cell concentration from the fed-batch heterotrophic process were 32.0 (%, v/v) and 15.0 (g-dry wt./L) in 20 L flask, respectively. In addition, since the relatively constant specific lipid production rate was observed as 0.040 (% lipid/g-dry wt./day) at the latter period of cultivation time, the fed-batch process could maintain continuous lipid production. Fed-batch process is higher than those values from the batch process. The lipids from the fed-batch process contained over 38% of $C_{18}$, known as the suitable composition for the biodiesel application. For mixotrophic and heterotrophic growth under fed-batch condition, glucose was proved to be an appropriate carbon source for a large scale outdoor cultivation. For fed-batch cultivation, the feeding rate of seawater medium containing glucose was decided to be 0.5 L/day. The mixotrophic cultivation maintained maximum cell concentration of 24 (g-dry wt./L) and the lipid level of 43 (%, w/w). The lipid composition from this process was also proved to be suitable for the biodiesel production. The fatty acids from the mixotrophic growth contains 18% of $C_{17}$ and 49% of $C_{18}$, implying It also tells that C. minutissima is a suitable resource of biodiesel. Especially, the mixotrophic cultivation with fed-batch process might be useful for the large scale cultivation for the biodiesel production.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.73-78
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• 2018

The main objective of this study was to evaluate the effects of acetate on the cultivation of anabena under mixotrophic condition. Four different types of acetates were used for the anebena cultivation. Among them, ethyl acetate was found to be the most effective and the growth rates linearly increased as the amount of ethyl acetate increased. When 40 mM of ethyl acetate was used, the highest values of specific growth rate of $0.979day^{-1}$ and maximum biomass productivity of $0.293g\;L^{-1}\;d^{-1}$ were obtained. On the contrary, input of acetic acid and butyl acetate inhibited the growth of anabena. For aeration tests, 0.54 vvm was optimum for anabena cultivation. For a semi-continuous cultivation test, ethyl acetate was used after 0.54 vvm test was finished. Then, test continued under 0.54 vvm and 40 mM of ethyl acetate. Lower specific growth rate and maximum biomass productivity were obtained compared to those from batch cultivation tests. However, the greatest maximum concentration of 5.91 g/L was obtained during the semi-continuous cultivation test.

• Environmental Engineering Research
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• v.24 no.2
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• pp.271-278
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• 2019

Mass cultivation of microalgae is necessary to achieve economically feasible production of microalgal biodiesel. However, the high cost of nutrients is a major limitation. In this study, corncob extract (CCE) was used as an inorganic and organic nutrient source for the mass cultivation of Chlorella vulgaris (C. vulgaris). Chemical composition analysis of CCE revealed that it contained sufficient nutrients for mixotrophic cultivation of C. vulgaris. The highest specific grow rate of C. vulgaris was obtained at pH of 7-8, temperature of $25-30^{\circ}C$, and CCE amount of 5 g/L. In the analysis using various growth models, Luong model was found to be the most suitable empirical formula for mass cultivation of C. vulgaris using CCE. Analysis of biomass and production of triacyglycerol showed that microalgae grown in CCE medium produced more than 17.23% and 3% more unsaturated fatty acids than cells cultured in Jaworski's Medium. These results suggest that growing microalgae in CCE-supplemented medium can increase lipid production. Therefore, CCE, agricultural byproduct, has potential use for mass cultivation of microalgae.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.337-343
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• 2020

In this study, the medium optimization for cell growth and metabolite formation of Haematococcus sp. under mixotrophic cultivation was investigated. As a result, modified MS medium was selected as the basal medium; glucose was selected as the carbon source, with an optimum concentration of 10 g/l, and potassium nitrate was chosen as the nitrogen source, with an optimum concentration of 1.9 g/l. Under optimum conditions, Haematococcus sp. demonstrated an increase in biomass concentration from 0.18 gDW/l to 5.58 gDW/l in 14 days, after which there was a 31-fold increase in its growth. At the same time, the concentrations of chlorophyll and carotenoids were 172.16 mg/l and 42.33 mg/l, respectively. This work will contribute to the basic data for mass cultivation of microalgae.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.945-946
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• 2012

• Journal of Marine Bioscience and Biotechnology
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• v.6 no.2
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• pp.68-75
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• 2014

This study investigated the potential use of various organic carbon sources (glucose, glycerol and acetate) and different concentrations of $CO_2$ for culturing marine microalga Dunaliella tertiolecta. Cell growth and lipid production were monitored under heterotrophic, mixotrophic and photoautotrophic modes of cultivation. D. tertiolecta showed the ability to grow under mixotrophic (acetate and glucose), heterotrophic (glucose) and photoautotrophic condition under high $CO_2$ concentration (15%). With all the organic carbon sources (glucose, glycerol and acetate) tested in this study, 1~5% acetate enhanced cell growth rate and lipid content, while higher concentrations of acetate (10% and 15%) were inhibitory and resulted in cell death.

• Journal of Microbiology and Biotechnology
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• v.32 no.10
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• pp.1325-1334
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• 2022

Global warming has accelerated in recent decades due to the continuous consumption of petroleum-based fuels. Cyanobacteria-derived biofuels are a promising carbon-neutral alternative to fossil fuels that may help achieve a cleaner environment. Here, we propose an effective strategy based on the large-scale cultivation of a newly isolated cyanobacterial strain to produce phycobiliprotein and biodiesel, thus demonstrating the potential commercial applicability of the isolated microalgal strain. A native cyanobacterium was isolated from Goryeong, Korea, and identified as Pseudanabaena mucicola GO0704 through 16s RNA analysis. The potential exploitation of P. mucicola GO0704 was explored by analyzing several parameters for mixotrophic culture, and optimal growth was achieved through the addition of sodium acetate (1 g/l) to the BG-11 medium. Next, the cultures were scaled up to a stirred-tank bioreactor in mixotrophic conditions to maximize the productivity of biomass and metabolites. The biomass, phycobiliprotein, and fatty acids concentrations in sodium acetate-treated cells were enhanced, and the highest biodiesel productivity (8.1 mg/l/d) was achieved at 96 h. Finally, the properties of the fuel derived from P. mucicola GO0704 were estimated with converted biodiesels according to the composition of fatty acids. Most of the characteristics of the final product, except for the cloud point, were compliant with international biodiesel standards [ASTM 6761 (US) and EN 14214 (Europe)].

• Journal of Microbiology and Biotechnology
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• v.18 no.3
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• pp.539-544
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• 2008

A mutant of Arthrospira platensis PCC 9108, strain M9108, obtained by mutagenesis with UV treatment, was able to mixotrophically grow in an SOT medium containing 40 g of glucose/l. The biomass and specific growth rate of strain M9108 (4.10 g/l and 0.70/d) were 1.9-fold and 1.4-fold higher, respectively, than those of the wild type (2.21 g/l and 0.58/d) under mixotrophic culture condition. In addition, when compared with the wild type, the content of ${\gamma}$-linolenic acid (GLA) in the mutant was increased when glucose concentration was increased. Compared with the wild type, the GLA content of the mutant was 2-fold higher in autotrophic culture and about 3-fold higher in mixotrophic culture. Thus, the mutant appears to possess more efficient facility to assimilate and metabolize glucose and to produce more GLA than its wild-type strain.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.1
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• pp.30-37
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• 2016

Microalgae are functional foods because they contain special anti-aging inhibitors and other functional components, such as ecosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and omega-3 polyunsaturated fatty acids. Many of these functional dietary components are absent in animals and terrestrial plants. Thus, microalgae are widely utilized in human functional foods and in the feed provided to farmed fish and terrestrial livestock. Many marine organisms consume microalgae, often because they are in an appropriate portion of the cell size spectrum, but also because of their nutritional content. The nutritional requirements of marine organisms differ from those of terrestrial animals. After hatching, marine animals need small live forage species that have high omega-3 polyunsaturated fatty acid contents, including EPA and DHA. Euglena cells have both plant and animal characteristics; they are motile, elliptical in shape, 15-500 μm in diameter, and have a valuable nutritional content. Mixotrophic cell cultivation provided the best growth rates and nutritional content. Diverse carbon (fructose, lactose, glucose, maltose and sucrose) and nitrogen (tryptone, peptone, yeast extract, urea and sodium glutamate) supported the growth of microalgae with high lipid contents. We found that the best carbon and nitrogen sources for the production of high quality Euglena cells were glucose (10 g L^–1) and sodium glutamate (1.0 g L^–1), respectively.