• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1640-1645
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• 2006

We studied the diversity of the halophilic archaea and bacteria in crystallizer ponds of a Korean solar saltern by analyzing 16S rRNA gene libraries. Although diverse halophilic archaeal lineages were detected, the majority (56%) were affiliated with the uncultured and cultured Halorubrum group. Halophilic archaea that have been frequently observed in solar saltern environments previously, such as Halogeometricum, Halococcus, Haloarcula, and Haloferax, were not detected in our samples. The majority of clones (53%) belonged to the Cytophaga-Flavobacterium-Bacteroides and ${\alpha}-,\;{\gamma}-,\;and\;{\delta}-Proteobacteria$ groups, with 47% of the clones being affiliated with ${\gamma}-Proteobacteria$. We also identified new ${\delta}-Proteobacteria$-related bacteria that have not been observed in hypersaline environments previously. Our data show that the diversity of the halophilic archaea and bacteria in our Korean saltern differs from that of solar salterns found in other geographic locations. We also showed by quantitative real-time PCR analysis that bacteria can form a significant component of the microbial community in solar salterns.

• Journal of Microbiology and Biotechnology
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• v.29 no.3
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• pp.401-409
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• 2019

Heat-resistant microbial hosts are required for bioprocess development using high cell density cultivations at the industrial scale. We report that the thermotolerance of Escherichia coli can be enhanced by overexpressing ybeD, which was known to encode a hypothetical protein of unknown function. In the wild-type E. coli BL21(DE3), ybeD transcription level increased over five-fold when temperature was increased from $37^{\circ}C$ to either $42^{\circ}C$ or $46^{\circ}C$. To study the function of ybeD, a deletion strain and an overexpression strain were constructed. At $46^{\circ}C$, in comparison to the wild type, the ybeD-deletion reduced cell growth half-fold, and the ybeD-overexpression promoted cell growth over two-fold. The growth enhancement by ybeD-overexpression was much more pronounced at $46^{\circ}C$ than $37^{\circ}C$. The ybeD-overexpression was also effective in other E. coli strains of MG1655, W3110, DH10B, and BW25113. These findings reveal that ybeD gene plays an important role in enduring high-temperature stress, and that ybeD-overexpression can be a prospective strategy to develop thermotolerant microbial hosts.

• Journal of Microbiology and Biotechnology
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• v.32 no.5
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• pp.672-679
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• 2022

Microbial lipases are used widely in the synthesis of various compounds due to their substrate specificity and position specificity. 4-Ethyl malate (4-EM) made from diethyl malate (DEM) is an important starting material used to make argon fluoride (ArF) photoresist. We tested several microbial lipases and found that Photobacterium lipolyticum M37 lipase position-specifically hydrolyzed DEM to produce 4-EM. We purified the reaction product through silica gel chromatography and confirmed that it was 4-EM through nuclear magnetic resonance analysis. To mass-produce 4-EM, DEM hydrolysis reaction was performed using an enzyme reactor system that could automatically control the temperature and pH. Effects of temperature and pH on the reaction process were investigated. As a result, 50℃ and pH 4.0 were confirmed as optimal reaction conditions, meaning that M37 was specifically an acid lipase. When the substrate concentration was increased to 6% corresponding to 0.32 M, the reaction yield reached almost 100%. When the substrate concentration was further increased to 12%, the reaction yield was 81%. This enzyme reactor system and position-specific M37 lipase can be used to mass-produce 4-EM, which is required to synthesize ArF photoresist.

• Journal of Marine Life Science
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• v.8 no.1
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• pp.43-49
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• 2023

This study applied a metagenomic analysis of the penguins' gut microbiome from fecal samples of Adélie Penguin (Pygoscelis adeliae) and Emperor Penguin (Aptenodytes forsteri) living along the Ross Sea, Antarctica. As a result of taxonomic analysis, 7 phyla and 18 families were mainly present in the gut microbiome of Adélie and Emperor penguins. To assess microbial diversity, we performed alpha diversity and OTU abundance analyses. It was confirmed that the Adélie Penguin's gut microbial species had a higher diversity than Emperor Penguin's. Based on the Beta diversity analysis using PCoA, differences were observed in the clustering between Adélie and Emperor penguins, respectively. Through the KEGG pathway analysis using PICRUSt, the nucleoside and nucleotide biosynthesis pathway was the most prevalent in Adélie and Emperor penguins. This study enabled a comparison and analysis of the composition and diversity of the gut microbiome in Adélie and Emperor Penguins. It could be utilized for future research related to penguin feeding habits and could serve as a foundation for analyzing the gut microbiomes of various other Antarctic organisms.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.18 no.1_2
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• pp.33-38
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• 2012

Modified atmosphere packaging (MAP) was applied to steamed bread added with black rice in 10%. In terms of storage stability, the steamed bread was found to be susceptible to microbial spoilage and could be helped in its preservation and shelf life extension by MAP. According to microbial and sensory quality criteria, the product shelf life was determined as < 5 days for air package, 5 days for 100% $N_2$ package, 8 days for package of 60% $CO_2$/40% $N_2$, and 15 days for 100% $CO_2$ package. Even though MAP condition with $CO_2$ inclusion was effective in extending the shelf life based on microbial quality, it did not affect the staling of the bread.

• Journal of Microbiology and Biotechnology
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• v.19 no.12
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• pp.1547-1556
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• 2009

A novel thermostable $\alpha$-glucosidase (TtGluA) from Thermoanaerobacter tengcongensis MB4 was successfully expressed in E. coli and characterized. The TtgluA gene contained 2,253 bp, which encodes 750 amino acids. The native TtGluA was a trimer with monomer molecular mass of 89 kDa shown by SDS-PAGE. The purified recombinant enzyme showed hydrolytic activity on maltooligosaccharides, p-nitrophenyl-$\alpha$-D-glucopyranide, and dextrin with an exotype cleavage manner. TtGluA showed preference for short-chain maltooligosaccharides and the highest specific activity for maltose of 3.26 units/mg. Maximal activity was observed at $60^{\circ}C$ and pH 5.5. The half-life was 2 h at $60^{\circ}C$. The enzyme showed good tolerance to urea and SDS but was inhibited by Tris. When maltose with the concentration over 50 mM was used as substrate, TtGluA was also capable of catalyzing transglycosylation to produce $\alpha$-1,4-linked maltotriose and $\alpha$-1,6-linked isomaltooligosaccharides. More importantly, TtGluA showed exclusive regiospecificity with high yield to produce $\alpha$-1,6-linked isomaltooligosaccharides when the reaction time extended to more than 10 h.

• Journal of Microbiology and Biotechnology
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• v.29 no.9
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• pp.1391-1400
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• 2019

Canine parvoviral enteritis (PVE) is an important intestinal disease of the puppies; however, the potential impact of the canine parvovirus (CPV) on the gut microbiota has not been investigated. Therefore, the aim of this study was to evaluate the gut microbial shifts in puppies naturally infected with CPV. Fecal samples were collected from healthy dogs and those diagnosed with PVE at 4, 6, 8, and 12 weeks of age. The distal gut microbiota of dogs was characterized using Illumina MiSeq sequencing of the bacterial 16S rRNA genes. The sequence data were analyzed using QIIME with an Operational Taxonomic Unit definition at a similarity cutoff of 97%. Our results showed that the CPV was associated with significant microbial dysbiosis of the intestinal microbiota. Alpha diversity and species richness and evenness in dogs with PVE decreased compared to those of healthy dogs. At the phylum level, the proportion of Proteobacteria was significantly enriched in dogs with PVE while Bacteroidetes was significantly more abundant in healthy dogs (p < 0.05). In dogs with PVE, Enterobacteriaceae was the most abundant bacterial family accounting for 36.44% of the total bacterial population compared to only 0.21% in healthy puppies. The two most abundant genera in healthy dogs were Prevotella and Lactobacillus and their abundance was significantly higher compared to that of dogs with PVE (p < 0.05). These observations suggest that disturbances of gut microbial communities were associated with PVE in young dogs. Evaluation of the roles of these bacterial groups in the pathophysiology of PVE warrants further studies.

• Food Science of Animal Resources
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• v.30 no.5
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• pp.780-786
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• 2010

This study compared the effects of autoclaving (AC; $121^{\circ}C$ for 15 min), gamma (GR), and electron beam irradiation (EB; 0-20 kGy) on the microbial, physicochemical, and sensory properties of ready-to-eat bulgogi during storage at $35^{\circ}C$ for 90 d. No viable cells were observed (p<0.05) upon AC, GR or EB at more than 15 kGy. However, adverse effects such as tenderization and deterioration of sensory properties were induced in bulgogi upon AC and high dose irradiation. Especially, the hardness and sensory qualities (texture and taste) of the AC-treated samples were extremely deteriorated (p<0.05). These results indicate that use of GR and EB (15 kGy) can ensure the microbial safety of bulgogi without compromising the hardness and sensory properties (texture, taste and flavor).

• KSBB Journal
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• v.19 no.5
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• pp.399-405
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• 2004

A reticulated PU-g-PAAc foam was modified through the surface treatment of PU foam by one atmospheric pressure plasma. The synthesized PU-g-PAAc foam was prepared for the purpose of immobilizing microbial organisms. We also attempted different plasma treatment methods including simple plasma treatment, plasma induced grafting and plasma induced grafting followed by plasma re-treatment. The effect of grafting on equilibrium water content (EWC) of PU forms was examined by swelling measurements. Adhesion test was performed to investigate the effect of different plasma treatment methods on the improvement of microbial immobilization. Two foams modified by plasma induced grafting and plasma re-treatment after grafting showed 2.7 and 3.0 fold higher microbial immobilization than unmodified one, respectively. Meanwhile, simple plasma treatment showed a little enhancement. FT-IR analysis of each sample verified the contribution of surface functional groups on the enhancement of microbial immobilization. SEM observation confirmed microbial adherence.

• Journal of Applied Biological Chemistry
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• v.65 no.1
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• pp.63-74
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• 2022

Microbial dysbiosis in the gut is associated with human diseases, and variations in mucus alter gut microbiota. Therefore, we explored the effects of mucin on the gut microbiota using a community of 19 synthetic gut microbial species. Cultivation of these species in modified Gifu anaerobic medium (GAM) supplemented with mucin before synthetic community assembly facilitated substantial growth of the Bacteroides, Akkermansia, and Clostridium genera. The results of 16S rRNA microbial relative abundance profiling revealed more of the beneficial microbes Collinsella, Bifidobacterium, Ruminococcus, and Lactobacillus. This increased acetate levels in the community cultivated with, rather than without (control), mucin. We identified differences in predicted cell function and metabolism between microbes cultivated in GAM with and without mucin. Mucin not only changed the composition of the gut microbial community, but also modulated metabolic functions, indicating that it could help to modulate microbial changes associated with human diseases.