• Korean Journal of Food Science and Technology
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• v.24 no.4
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• pp.353-360
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• 1992

This study was carried out to investigate the changes of quality in yogurt during delivery and storage. To do this, microbiological, physico-chemical and sensory properties in stirred yogurt were studied at different temperatures $(10^{\circ}C$ & $20^{\circ}C)$ and shakings (100 rpm & 200 rpm for 30 min). Titratable acidity and TCA soluble nitrogen in yogurt were increased in accordance with increase of temperature and time, while pH, lactose and lactic acid bacteria tended to be decreased. Interestingly enough, shaking conditions almost did not influence these studies. In sensory evaluation it showed that acidity was strong and sweetness was weak as increasing the storage temperature and time, but there were no significant differences until 10 days at $10^{\circ}C$ and 3 days at $20^{\circ}C$. Off-flavor was developed after 12 days at $10^{\circ}C$ with only 200 rpm shaking and after 6 days at $20^{\circ}C$ in both shaking conditions. These yogurts were not suitable for consumer. Viscosity in the yogurt became high as the temperature and time were increased. Viscosity was lower in yogurt shaked at 200 rpm than in non-shaked yogurt. Finally, this study indicates that temperature and shaking during delivery of yogurt may be critical in keeping quality of yogurt.

• Korean Journal of Veterinary Research
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• v.34 no.3
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• pp.517-527
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• 1994

An attempt was made to isolate a causative viral agents from the fecal specimens of the diseased dogs with the gastroenteritis symptoms. Two coronavirus-like agents were isolated by serial dilution end point method and plaque assay. The isolates were characterized in terms of cytopathology, antigenicity, replication, physicochemical and morphological properties. The results obtained through the experiment were as follows; 1. Among 7 fecal specimens collected from the dogs with enteric disease, 2(28.6%)coronavirus-like agents showing typical cytopathic effects of canine coronavirus were isolated, and designated as CCV D1 and CCV D2, respectively. 2. By the cross-neutralization test and indirect immunofluoresence antibody test, the isolates were antigenically indentified as the standard CCV. The viruses were replicated only in the cytoplasm of A-72 cells. 3. The isolates showed no haemagglutinating activity against the erythrocytes from 11 kinds of animals. 4. The electron microscopic observation for the isolates showed spherical and pleomorphic features, covered with club-shaped projections on the surface. The size of particles was ranged from 70 to 150nm. 5. In one-step growth curve for the isolates in A-72 cells, maximum titers of intracellular vius was $10^{4.6}$ $TCID_{50}/0.1ml$ at 46 hrs postinoculation(pi) of CCV Dl and $10^{4.4}$ $TCID_{50}/0.1ml$ at 34 hrs pi of CCV D2. The maximum titers of extracellular virus was $10^{5.5}$ $TCID_{50}/0.1ml$ at 58 hrs pi of CCV D1 and $10^{5.8}$ $TCID_{50}/0.1ml$ at 46 hrs pi of CCV D2. 6. In physicochemical property test, the isolates were very sensitive to choroform and were found to be RNA virus. The viruses was stable at pH 3.0 for 1 hr and at $22{^{\circ}C}$ for 5 hrs. However, infectivity titers reduced remarkably by treatment with $56{^{\circ}C}$ for 10min.

• Korean Journal of Microbiology
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• v.50 no.3
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• pp.254-260
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• 2014

Sulfur compound includes major electron acceptors for anaerobic respiration. In this study, cultivation-based study on sulfate- and sulfur-reducing bacteria of various wetlands of Korea was attempted. To isolate sulfate- and sulfur-reducing bacteria, anaerobic roll tube method was used to obtain typical black colonies of sulfate- and sulfur-reducing bacteria. Total 11 strains obtained were tentatively identified based on comparative 16S rDNA similarity and physiological property analysis. All sulfate-reducing bacteria (8 strains) belonged to genus Desulfovibrio with >99% 16S rDNA similarities. Three sulfur reducing bacteria were also isolated: two and one isolates were affiliated with Sulfurospirillum and Desulfitobacterium, respectively. These sulfate- and sulfur-reducing bacteria were able to utilize lactate and pyruvate and sulfite and thiosulfate as common electron donors and electron acceptors, respectively. This case study will provide fundamental information for obtaining useful indigenous sulfate- and sulfur-reducing bacteria from Korean wetlands employing various combinations of cultivation conditions.

• Korean Journal of Microbiology
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• v.50 no.1
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• pp.8-14
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• 2014

The objective of this work is to investigate and compare several functional properties of lactic acid bacteria (LAB), Lactobacillus casei SK-7 isolated from home-made yogurt and Lactobacillus bulgaricus YK-11 from commercial yogurt. Initially, physiological and biochemical properties of SK-7 and YK-11 were characterized. Phylogenetic analysis using 16S rRNA sequencing were performed to identify the strains, and the strain could be assigned to Lactobacillus casei and Lactobacillus bulgaricus, designated as L. casei SK-7 and L. bulgaricus YK-11. Phylogenetic tree of SK-7 and YK-11 was plotted based on 16S rRNA sequence comparisons. Production of lactic acid and organic acid, and pH changes in the cultures of SK-7 and YK-11 were monitored during 72 h. During the incubation period, several functional properties of L. casei SK-7 and L. bulgaricus YK-11 were examined. L. casei SK-7 and L. bulgaricus YK-11 cultures eliminated 93.9% and 88.2% of nitrite, respectively. Antioxidant activity of cultural supernatants of SK-7 and YK-11 were 62.6%, 54.9%, and activity of ${\beta}$-galactosidase were 14.9 units/mg and 13.1 units/mg, respectively. The antimicrobial activities were examined with 20-fold concentrated culture supernatants from the cultures of SK-7 and YK-11. The activities of SK-7 supernatants were clearly observed against all microorganisms in this work, whereas no activities were observed in YK-11 supernatants. Although it might be conducted additional functional research, functional properties of LAB isolated from home-made yogurt have been shown to be better than those of commercial yogurt in this work.

• Korean Journal of Microbiology
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• v.46 no.2
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• pp.223-227
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• 2010

RNase E plays a major role in the degradation and processing of a large number of RNA transcripts in Escherichia coli and forms the core component of the degradosome, a large protein complex involved in RNA metabolism. RraA and RraB are recently discovered protein inhibitors of RNase E and are evolutionarily conserved. In this study, we observed that, unlike RraA, overexpression of RraB did not rescue growth arrest of E. coli cells overexpressing RNase E. To examine whether this phenomenon stems from differential inhibitory effects of RraA and RraB on RNase E substrates, we analyzed three in vivo RNase E substrates. The results showed that RraA inhibited RNase E activity more efficiently than RraB on the degradation of RNA I, which controls the copy number of ColE1-type plasmid, and rpsO mRNA encoding ribosomal protein S15, while RraB was unable to inhibit the processing of pM1 RNA, a precursor of the RNA component of RNase P, by RNase E. Our results imply that RraB inhibits RNase E activity in a more substrate-dependent manner than RraA and this property of RraB may explain why overexpression of RraB could not rescue cells overexpressing RNase E from growth arrest.

• Korean Journal of Microbiology
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• v.46 no.2
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• pp.122-126
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• 2010

RAD53 functions as an effector kinase of checkpoint pathways in Saccharomyces cerevisiae, which plays a central role to regulate many downstream cellular processes in response to DNA damage. It also involves in transcriptional activation of various genes including RNR genes which encode the key enzyme required for dNTP synthesis. In this study, we identified CYC8 as a suppressor for the hydroxyurea sensitivity of $rad53{\Delta}$ mutation. $Rad53{\Delta}$ mutant transformed with a multi-copy plasmid containing CYC8 showed increased hydroxyurea resistance. In contrast, TUP1 which forms a complex with CYC8 did not function as a suppressor. In the case of mutations, both $cyc8{\Delta}$ and $tup1{\Delta}$ suppressed hydroxyurea sensitivity of $rad53{\Delta}$. Since CYC8 can propagate as a prion in yeast, overexpression of CYC8 induced misfolding of the normal CYC8 proteins, resulting in dominant cyc8-phenotype. Therefore, it is suggested that CYC8 can act as a multi-copy suppressor due to its prion property. It was observed that the levels of RNR transcription were increased in the yeast strains containing either multi-copies of CYC8 gene or $cyc8{\Delta}$ mutation, suggesting that the increased level of RNR will elevate the intracellular pools of dNTPs, which, in turn, suppress the phenotype of $rad53{\Delta}$ mutation.

• Food Science and Preservation
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• v.15 no.1
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• pp.144-149
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• 2008

Physiological, sensory and microbiological evaluations were conducted during fermentation of Chungkookjang. with Choi-cha (non-fermented green tea) powder in efforts to improve the sensory quality of Chungkookjang. Growth of fermentative microorganisms in Chungkookjang was inhibited by Choi-cha; the pH and VBN value decreased as the concentration of Choi-cha increased. Brightness (L) and redness (a) of Chungkookjang fermented with Choi-cha were significantly decreased, resulting in the appearance of all samples fermented with Choi-cha being less attractive than was the control. The sensory quality of Chungkookjang was significantly increased when Choi-cha was added up to 3%, (w/v), and off-odor was reduced. The antioxidative property of Chungkookjang fermented with 3% (w/v) Choi-cha was significantly higher than that of the control. This result indicated that the sensory quality of Chungkookjang was improved by fermentation with 3% (w/v) of Choi-cha powder.

• Korean Journal of Microbiology
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• v.38 no.3
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• pp.153-161
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• 2002

Sox4, a transcription factor, consists of three functional domains: an HMG-box domain as a DNA binding domain, serine rich region as a transactivation domain and glycine rich region (GRR), an unknown functional domain. Although Sox4 is known to be functionally involved in heart, B-cell and reproductive system development, its physiological function remains to be elucidated. We used pGEX expression system to develop a simple and rapid method for purifying Sox4 protein in suitable forms for biochemical studies of their functions. Unexpectedly, we observed that full-length Sox4 appears to be protease-sensitive during expression and purification in E. coli. To map the protease-sensitive site in Sox4, we generated various constructs with each of functional domains of Sox4 and purified as the GST-Sox4 fusion proteins using glutathione beads. We found that the specific cleavage site for the proteolytic enzyme, which exists in E. coli, is localized within the novel GRR of Sox4. Our study suggest that the GRR of Sox4 may a target for the cellular protease action and this cleavage in the GRR may be involved in regulating physiological function of Sox4. Additionally, our study may provide a useful method for investigating the proteolytic cleavage of the target molecule in E. coli.