• Proceedings of the Korean Society of Life Science Conference
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• 2008.10a
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• pp.55.1-55.1
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• 2008

• Microbiology and Biotechnology Letters
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• v.41 no.1
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• pp.8-16
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• 2013

An agar-hydrolyzing marine bacterium, strain GNUM08120, was isolated from Sargassum fulvellum collected from Yeongil bay of East Sea of Korea. The isolate was Gram-negative, aerobic, motile with single polar flagellum, and grew at 1-10% NaCl, pH 5.0-8.0, and $15-37^{\circ}C$. G+C content and the predominant respiratory quinone were 46.13 mol% and Q-8, respectively. The major cellular fatty acids were Summed feature 3 (24.5%), $C_{16:0}$ (21.7%), and $C_{18:1}{\omega}7c$ (12.5%). Based on 16S rRNA gene sequence similarity and DNA-DNA hybridization analyses, strain GNUM08120 was identified as a novel subspecies of Alteromonas macleodii, designated Alteromonas macleodii subsp. GNUM08120. Production of agarase by strain GNUM08120 was likely repressed by the effect of carbon catabolite repression caused by glucose. The crude agarase prepared from 12-h culture broth of strain GNUM08120 exhibited an optimum pH and temperature for agarase activity at 7.0 and $40^{\circ}C$, respectively. The crude enzyme produced (neo)agarobiose, (neo)agarotetraose, and (neo)agarohexaose as the hydrolyzed product of agarose.

• Journal of Food Hygiene and Safety
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• v.15 no.4
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• pp.282-286
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• 2000

Agarooligosaccharides were produced by $\beta$-agarase from Bacillus cereus ASK 202. LD$_{50}$ of Agarooligosaccharides was determined to be 1359 mg/kg which corresponded to GRAS material. Agarooligosaccharides at 5% level exhibited 88.3% inhibition on TA98 and 54% on TA100, indicating agarooligosaccharides to be potent antimutagenic substance. Immunologic activity of agarooligosaccharides was also confirmed by mouse spleen cell culture. Agrooligosaccharides addition of 200 $\mu$l/ml stabilized spleen cells (2.5$\times$10$^{6}$ cells/ml) as compared to control (6.4$\times$10$^4$ cells/ml).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.630-634
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• 2011

Enzymatic hydrolysate of porphyran from Porphyra yezoensis was prepared by treatment with ${\beta}$-agarase. The hydrolysate was fractioned into molecular sizes of <3, 3-30, and 30-300 kDa using an ultrafiltration membrane. The membrane fractions were further separated into neutral and anionic fractions using Dowex $1{\times}8$ ion exchange chromatography. After hydrolysis of porphyran with ${\beta}$-agarase, 23.2% of the starting porphyran was recovered as a neutral fraction of low-molecular weight (<3 kDa), and 28.9% remained as an enzyme-resistant anionic fraction of high molecular weight (>300 kDa). Desulfation of porphyran and $^{13}C$-NMR analysis of the anionic fraction of low molecular weight (<3 kDa) showed that the anionic fraction has a backbone consisting of 3-linked ${\beta}$-D-galactose units alternating with either 4-linked a-L-galactose 6-sulfate or 3, 6-anhydro-a-L-galactose units. These results indicate that porphryan is a copolymer of two moieties, about 25% of which are composed of neoagarose moieties and 75% as anionic moieties.

• Fisheries and Aquatic Sciences
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• v.13 no.1
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• pp.36-48
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• 2010

An agar-degrading Agarivorans sp. AG17 strain was isolated from the red seaweed Grateloupia filicina collected from Jeju Island. A beta-agarase gene from Agarivorans sp. AG17 was cloned and designated as agrA. agrA has a 2,985 bp coding region encoding 995 amino acids and was classified into the glycoside hydrolase family (GHF)-50. Predicted molecular mass of the mature protein was 105 kDa. His-tagged agrA was overexpressed in Escherichia coli and purified as a fusion protein. The enzyme showed 158.8 unit/mg specific activity (optimum temperature at $65^{\circ}C$ and pH 5.5 in acetate buffer) with unique biochemical properties (high thermal and pH stabilities). Enzyme produced neoagarohexaose, neoagarotetraose and neoagarobiose by degrading agar, and hydrolyzed neoagaro-oligosaccharides were biologically active. Hence the purified enzyme has potential for use in industrial applications such as the development of cosmetics and pharmaceuticals.

• Microbiology and Biotechnology Letters
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• v.43 no.2
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• pp.134-141
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• 2015

An agarolytic marine bacterium (H9) was isolated from the coastal seawater of the West Sea, South Korea. The isolate, H9, was gram-negative and rod-shaped with a smooth surface and polar flagellum. Cells grew at 20-30℃, between pH 5.0 and 9.0, and in ASW-YP (Artificial Sea Water-Yeast extract, Peptone) media containing 1-5% (w/v) NaCl. The G+C content was 41.56 mol%. The predominant isoprenoid quinone in strain H9 was ubiquinone-8. The major fatty acids (>10%) were C_16:1ω7c (34.3%), C_16:0 (23.72%), and C_18:1ω7c (13.64%). Based on 16S rRNA gene sequencing, and biochemical and chemotaxonomic characterization, the strain was designated as Pseudoalteromonas sp. H9 (=KCTC23887). In liquid culture supplemented with 0.2% agar, the cell density and agarase activity reached a maximum level of OD = 4.32 (48 h) and OD = 3.87 (24 h), respectively. The optimum pH and temperature for the extracellular crude agarases of H9 were 7.0 and 40℃, respectively. Thin-layer chromatography analysis of the agarase hydrolysis products revealed that the crude agarases hydrolyze agarose into neoagarotetraose and neoagarohexaose. Therefore, the new agar-degrading strain, H9, can be applicable for the production of valuable neoagarooligosaccharides and for the complete degradation of agar in bio-industries.

• Journal of Life Science
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• v.15 no.6 s.73
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• pp.884-888
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• 2005

An agar-degrading bacterium was isolated from north-eastern sea of Jeju island and cultured in marine agar 2216 media. Biochemical and morphologicl characteristics and 165 rRNA gene revealed that isolated strain was member of Agarivorans genus, and named Agarivorans sp. JA-1. Agarase was produced as growth-related and expressed regardless of agar presence. Optimal pH was 8 at 50 mM Clycine-NaOH buffer, and activity was maximum at $40^{\circ}C$E Enzymatic activity was maintained over $80\%$ at $60^{\circ}C$t and $70\%$ at $80^{\circ}C$ which is thermotolerant. Hence isolated novel Agarivorans sp. JA-1 strain and its beta-agarase could be used for the production of functional oligosaccharide from agar in solution state.

• 한국수산학회:학술대회논문집
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• 2005.05a
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• pp.69-70
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• 2005

• Proceedings of the Korean Society of Life Science Conference
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• 2005.09a
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• pp.72-72
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• 2005

• Microbiology and Biotechnology Letters
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• v.45 no.3
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• pp.243-249
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• 2017

An agar-degrading bacterium, designated as the GNUM08123 strain, was isolated from samples of red algae collected from the Yongil Bay near East Sea, Korea. The isolated GNUM08123 strain was gram-negative, aerobic, motile, and beige-pigmented, with $C_{16:0}$ (25.9%) and summed feature 3 (comprising $C_{16:1}{\omega}7c/iso-C_{15:0}2-OH$, 34.4%) as its major cellular fatty acids. A similarity search based on the 16S rRNA gene sequence revealed that it belonged to class Gammaproteobacteria and shared 97.7% similarity with the type strain Vibrio chagasii $R-3712^T$. The DNA G+C content of strain $GNUM08123^T$ was 46.9 mol%. The major isoprenoid quinone was ubiquinone-8. The results of DNA-DNA relatedness and 16S rRNA sequence similarity analyses, in addition to its phenotypic and chemotaxonomic characteristics, suggest that strain GNUM08123 is a novel species within genus Vibrio, designated as Vibrio sp. GNUM08123. Agarase production by strain GNUM08123 was induced by agar and sucrose, but was repressed probably owing to carbon catabolite repression by glucose and maltose.