• ALGAE
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• v.28 no.2
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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.

• Korean Journal of Microbiology
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• v.50 no.4
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• pp.313-318
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• 2014

The world is in need of sustainable and eco-friendly energy sources such as microalgal biodiesel due to global warming and fossil fuel shortages. In this study, we compared the effectiveness of liquid fertilizer produced from swine manure and agriculture grade solid fertilizers as nutrient sources for microalgal biomass production. Mixed culture (Chlorella spp., Scenedesmus spp., Stigeoclonium spp.; CSS) was cultivated for 28 days in Small Scale Raceway Pond (SSRP) using various nutrient sources (swine manure liquid fertilizer, agricultural solid fertilizer, and mixture of these two fertilizers). Biomass and lipid productivity of fertilizer mixture were the highest at 0.8 g/L and 5.8 mg/L/day, respectively. These results indicate that the fertilizer mixture can provide microalgae necessary nutrient sources for stable biodiesel production and biomass growth. In addition, overall cost of microalgal cultivation and subsequently biodiesel production would be significantly reduced.

• Journal of Microbiology and Biotechnology
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• v.33 no.9
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• pp.1250-1256
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• 2023

Herein, different extracts of Scenedesmus deserticola JD052, a green microalga, were evaluated in vitro as a potential anti-aging bioagent. Although post-treatment of microalgal culture with either UV irradiation or high light illumination did not lead to a substantial difference in the effectiveness of microalgal extracts as a potential anti-UV agent, the results indicated the presence of a highly potent compound in ethyl acetate extract with more than 20% increase in the cellular viability of normal human dermal fibroblasts (nHDFs) compared with the negative control amended with DMSO. The subsequent fractionation of the ethyl acetate extract led to two bioactive fractions with high anti-UV property; one of the fractions was further separated down to a single compound. While electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy analysis identified this single compound as loliolide, its identification has been rarely reported in microalgae previously, prompting thorough systematic investigations into this novel compound for the nascent microalgal industry.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.3
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• pp.255-263
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• 2013

Carbon dioxide reduction technologies using photosynthetic microorganism were suggested to overcome environmental destruction caused by $CO_2$ in flue gases from power plant and other industries. However, there are many toxic constituents in flue gas including CO, NOx, SOx. Continuous and Excessive supply of these noxious gases to cells will leads to inhibition of microalgal growth along with partial cell death. In this study, we tested the noxious effect of SOx and NOx on the pH and microalgal growth under photoautotrophic culture in three microalgae of Neochloris oleoabundans, Chlorella vulgaris and Haematococcus pluvialis. As a result, SOx concentration more than 50 ppm led to the rapid reduction of pH, thereby inhibiting of the growth in Neochloris oleoabundans and Chlorella vulgaris. NOx concentration more the 100 ppm reduced the exponential growth of N. oleoabundans and C. vulgaris. And H. pluvialis exhibited low sensitivity to SOx and NOx. Consequently, the three microalgae of N. oleabundas, C. vulagaris and H. pluvialis showed the normal vegetative growth in 25 ppm of NOx and SOx. Above all, H. pluvialis was useful for the $CO_2$ sequestration of the flue gas including high concentrations of NOx and SOx.

• 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 Microbiology and Biotechnology
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• v.31 no.3
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• pp.387-397
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• 2021

There is growing interest in the production of microalgae-based, high-value by-products as an emerging green biotechnology. However, a cultivation platform for Oocystis sp. has yet to be established. We therefore examined the effects of bacterial culture additions on the growth and production of valuable compounds of the microalgal strain Oocystis sp. KNUA044, isolated from a locally adapted region in Korea. The strain grew only in the presence of a clear supernatant of Sphingomonas sp. KNU100 culture solution and generated 28.57 mg/l/d of biomass productivity. Protein content (43.9 wt%) was approximately two-fold higher than carbohydrate content (29.4 wt%) and lipid content (13.9 wt%). Oocystis sp. KNUA044 produced the monosaccharide fucose (33 ㎍/mg and 0.94 mg/l/d), reported here for the first time. Fatty acid profiling showed high accumulation (over 60%) of polyunsaturated fatty acids (PUFAs) compared to saturated (29.4%) and monounsaturated fatty acids (9.9%) under the same culture conditions. Of these PUFAs, the algal strain produced the highest concentration of linolenic acid (C18:3 ω3; 40.2%) in the omega-3 family and generated eicosapentaenoic acid (C20:5 ω3; 6.0%), also known as EPA. Based on these results, we suggest that the application of Sphingomonas sp. KNU100 for strain-dependent cultivation of Oocystis sp. KNUA044 holds future promise as a bioprocess capable of increasing algal biomass and high-value bioactive by-products, including fucose and PUFAs such as linolenic acid and EPA.

• Journal of Microbiology
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• v.42 no.4
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• pp.305-314
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• 2004

An exopolysaccharide-producing microalgal dinoflagellate was isolated from a red-tide bloom and des­ignated strain KG03. A bacteria-free culture of strain KG03 was achieved using a modified wash with phototaxis and antibiotic treatment. Combined treatment with neomycin and cephalosporin was the most effective for eliminating the bacteria associated with the microalgae. Strain KG03 was identified as Gyrodinium impudicum by analyzing the ITS regions of the 5.8S rDNA, 18S rDNA, morphological phenotype and fatty acid composition. The exopolysaccharide production and cell growth in a 300-ml photobioreactor were increased 2.7- and 2.4-fold, respectively, compared with that in a flask culture at the first isolation step.

• Journal of Marine Bioscience and Biotechnology
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• v.12 no.1
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• pp.40-49
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• 2020

This article emphasized the physiological characteristics of the selected marine microalgal strains obtained from the culture collection of the National Marine Biodiversity Institute of Korea (MABIK). Therefore, in this study, 13 different marine microalgal strains belonging to the phylum Chlorophyta were analyzed for the composition of fatty acids, elements, photosynthetic pigments, and monosaccharides, as well as the lipid and protein contents. The results presented that the primary fatty acids were palmitic (C_16:0), palmitoleic (C_16:1 n-7), stearic (C_18:0), oleic (C_18:1 n-9), linoleic (C_18:2 n-6), and α-linolenic (ALA, C_18:3 n-3) acid in the evaluated microalgae. The lipid contents of heterotrophically grown strains ranged from 15.1% to 20.4%. The calorific values of the strains were between 17.4 MJ kg^-1 and 21.3 MJ kg^-1. The major monosaccharides were galactose, glucose, and mannose, while the primary photosynthetic pigments were chlorophyll-a (Chla), chlorophyll-b (Chlb), and lutein, respectively. Based on the results, the microalgal strains showed high potentials in the use of microalgae-based technologies to produce biochemicals, food, and renewable fuels as they are rich in sustainable sources of high-value bio-compounds, such as antioxidants, carbohydrates, and fatty acids.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.501-502
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• 2001

Characteristics of $CO_2$ fixation by Chlorella sp. HA -1 were studied in a high cell culture using semi-continuous mode. As a result, it may be possible to obtain not only high cell concentration but also effective $CO_2$ removal at a moderate dilution ratio, which is' the most significant factor to control the microalgal growth in the semi-continuous mode.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.151-152
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• 2000

During in door or outdoor mass culture, Porphyra have been easily contaminated with bacteria, protozoa and microalgal species. Several axenic treatments for Porphyra thalli have been published (Polne-Fuller and Gibo 1984; Chen and McCracken 1993), but axenic techniques for neutral spores and conchocelis we not developed. In this work we describe the procedure for axenic isolation of neutral spores and conchocelis of Porphyra yezoensis (omitted)