• Microbiology and Biotechnology Letters
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• v.44 no.4
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• pp.512-521
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• 2016

A bacterial strain was isolated from a soil sample collected on Jeju Island, Korea. The strain, designated WJ-2, exhibited a high xylanase activity, whereas cellulase activity was not detected. The 16S rRNA gene sequence of WJ-2 was highly similar to type strains of the genus Streptomyces. A neighbor-joining phylogenetic tree based on 16S rRNA gene sequences showed that strain WJ-2 is phylogenetically related to Streptomyces atrovirens. Furthermore, DNA-DNA hybridization analysis confirmed that strain WJ-2 is a novel subspecies of Streptomyces atrovirens. The genomic DNA G+C content was 73.98 mol% and the major fatty acid present was anteiso-C15:0 (36.19%). The growth and xylanase production of strain WJ-2 were significantly enhanced by using soytone and xylan as nitrogen and carbon sources, respectively. Crude enzyme preparations from the culture broth of strain WJ-2 exhibited maximal total xylanase activities at pH 7.0 and $55^{\circ}C$. Thin-layer chromatography analysis revealed that the crude enzyme degrades beechwood xylan to yield xylobiose and xylotriose as the principal hydrolyzed end products.

• Microbiology and Biotechnology Letters
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• v.46 no.3
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• pp.234-243
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• 2018

The Antarctic Ocean contains numerous microorganisms that produce novel biocatalysts that can have applications in various industries. We screened various psychrophilic bacterial strains isolated from the Ross Sea and found that a Croceibacter atlanticus strain (Stock No. 40-F12) showed high lipolytic activity on a tributyrin plate. We isolated the corresponding lipase gene (lipCA) by shotgun cloning and expressed the LipCA enzyme in Escherichia coli cells. Homology modeling of LipCA was carried out using the Spain Arreo lake metagenome alpha/beta hydrolase as a template. According to the model, LipCA has an ${\alpha}/{\beta}$ hydrolase fold, Gly-X-Ser-X-Glymotif, and lid sequence, indicating that LipCA is a typical lipase enzyme. Active LipCA enzyme was purified fromthe cell-free extract by ammonium sulfate precipitation and gel filtration chromatography. We determined its enzymatic properties including optimum temperature and pH, stability, substrate specificity, and organic solvent stability. LipCA was immobilized by the cross-linked enzyme aggregate (CLEA) method and its enzymatic properties were compared to those of free LipCA. After cross-linking, temperature, pH, and organic solvent stability increased considerably, whereas substrate specificities did not changed. The LipCA CLEA was recovered by centrifugation and showed approximately 40% activity after 4th recovery. This is the first report of the expression, characterization, and immobilization of a C. atlanticus lipase, and this lipase could have potential industrial application.

• Microbiology and Biotechnology Letters
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• v.46 no.2
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• pp.127-134
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• 2018

In this study, 79 bacterial isolates were collected from the surface of marine algae Umbraulva japonica. As a result of analysis of 16s rRNA gene sequence, the 79 isolated bacteria were divided into 4 major groups: [Proteobacteria (74.69%), Actinobacteria (2.53%), Fimicutes (2.53%), and Bacteroidetes (20.25%)] - 7 classes (Actinobacteria, Flavobacteria, Sphingobacteria, Baciili, Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria), 12 orders, 17 families and 31 genera. The newly isolated 3 strains could be novel species because of less than 97% similarity in 16s rRNA sequence. Therefore, it is considered that additional experiments should be conducted together with the standard strain. Analysis of 79 bacterial antibacterial activity against human and fish pathogens, such as Edwardsiella tarda, Vibrio harveyi, Streptococcus iniae, Steptococcus parauberis, Escherichia coli, Steptococcus mutans, Listeria monocytogenes and Vibrio vulnificus, was performed by using the supernatant liquid and pellet. As a result, pellet of UJT9, UJT20 and UJR17 showed antibacterial activity against V. vulnificus, UJR17 also showed antibacterial activity against S. parauberis. UJT7 and UJT20, UJR17 have been identified as Bacillus sp. and Pseudomonas sp. and it may be safely assented that it's beneficial to carry out additional experiments for various applications.

• Microbiology and Biotechnology Letters
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• v.45 no.3
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• pp.185-199
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• 2017

Methane, which is emitted from natural and anthropogenic sources, is a representative greenhouse gas for global warming. Methanotrophs are widespread in the environment and play an important role in the biological oxidation of methane via methane monooxygenases (MMOs), key enzymes for methane oxidation with broad substrate specificity. Methanotrophs have attracted attention as multifunctional bacteria with promising applications in biological methane mitigation technology and environmental bioremediation. In this review, we have summarized current knowledge regarding the biodiversity of methanotrophs, catalytic properties of MMOs, and high-cell density cultivation technology. In addition, we have reviewed the recent advances in biological methane mitigation technologies using methanotrophs in field-scale systems as well as in lab-scale bioreactors. We have also surveyed information on the dynamics of the methanotrophic community in biological systems and discussed the various challenges pertaining to methanotroph-related biotechnological innovation, such as identification of suitable methanotrophic strains with better and/or novel metabolic activity, development of high-cell density mass cultivation technology, and the microbial consortium (methanotrophs and non-methanotrophs consortium) design and control technology.

• KSBB Journal
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• v.27 no.2
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• pp.75-85
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• 2012

Although, microbial arsenic mobilization by dissimilatory arsenate-reducing bacteria (DARB) and the practical use to the removal technology of arsenic from contaminated soil are expected, most previous research mainly has been focused on the geochemical circulation of arsenic. Therefore, in this review we summarized the previously reported DARB to grasp the characteristic for bioremediation of arsenic. Evidence of microbial growth on arsenate is presented based on isolate analyses, after which a summary of the physiology of the following arsenate-respiring bacteria is provided: Chrysiogenes arsenatis strain BAL-$1^T$, Sulfurospirillum barnesii, Desulfotomaculum strain Ben-RB, Desulfotomaculum auripigmentum strains OREX-4, GFAJ-1, Bacillus sp., Desulfitobacterium hafniense DCB-$2^T$, strain SES-3, Citrobacter sp. (TSA-1 and NC-1), Sulfurospirillum arsenophilum sp. nov., Shewanella sp., Chrysiogenes arsenatis BAL-$1^T$, Deferribacter desulfuricans. Among the DARB, Citrobacter sp. NC-1 is superior to other dissimilatory arsenate-reducing bacteria with respect to arsenate reduction, particularly at high concentrations as high as 60 mM. A gram-negative anaerobic bacterium, Citrobacter sp. NC-1, which was isolated from arsenic contaminated soil, can grow on glucose as an electron donor and arsenate as an electron acceptor. Strain NC-1 rapidly reduced arsenate at 5 mM to arsenite with concomitant cell growth, indicating that arsenate can act as the terminal electron acceptor for anaerobic respiration (dissimilatory arsenate reduction). To characterize the reductase systems in strain NC-1, arsenate and nitrate reduction activities were investigated with washed-cell suspensions and crude cell extracts from cells grown on arsenate or nitrate. These reductase activities were induced individually by the two electron acceptors. Tungstate, which is a typical inhibitory antagonist of molybdenum containing dissimilatory reductases, strongly inhibited the reduction of arsenate and nitrate in anaerobic growth cultures. These results suggest that strain NC-1 catalyzes the reduction of arsenate and nitrate by distinct terminal reductases containing a molybdenum cofactor. This may be advantageous during bioremediation processes where both contaminants are present. Moreover, a brief explanation of arsenic extraction from a model soil artificially contaminated with As (V) using a novel DARB (Citrobacter sp. NC-1) is given in this article. We conclude with a discussion of the importance of microbial arsenate reduction in the environment. The successful application and use of DARB should facilitate the effective bioremediation of arsenic contaminated sites.

• Pediatric Infection and Vaccine
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• v.27 no.2
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• pp.90-101
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• 2020

Purpose: The multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) test developed recently can help detect enteric pathogens of acute gastroenteritis (AGE). This study aimed to investigate the epidemiology of pathogens in children with AGE using the multiplex RT-PCR. Methods: From May 2015 to June 2018, multiplex RT-PCR tests were performed to identify pathogens in the feces of pediatric patients diagnosed with AGE at a secondary hospital in Seoul, Korea. Results: Of the 1,366 stool samples examined for viral pathogens, 483 (35.3%) tested positive for ≥1 pathogen. Group A rotavirus (RV) was detected in 106 cases (7.8%). The positivity rate increased annually from 3.0% (8/263) to 16.7% (48/288) and surged in 2018 (P<0.001). Norovirus (NoV) GII was the most common viral pathogen (263/1,366, 19.3%), and the positivity rate did not increase during the 3 years. Of the 304 stool samples tested for bacterial pathogens, Campylobacter spp. was the most common bacterial pathogen (32/304, 10.5%), followed by Clostridium difficile (22/304, 7.2%) and Salmonella spp. (17/304, 5.6%). The positivity rate of these bacterial pathogens did not change significantly during the study period. Conclusions: NoV GII is the main pathogen in childhood AGE since the introduction of RV vaccine, yet the number of rotavirus-infected patients increased during our study, especially in 2018. Therefore, further research is needed including the possibility of emergence of novel RV strains. Campylobacter spp. is the predominant cause of bacterial AGE in children. For proper treatment, the clinical characteristics of the bacteria should be taken into consideration, and continuous monitoring is necessary.

• Research in Plant Disease
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• v.17 no.2
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• pp.211-215
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• 2011

Cucumber mosaic virus (CMV)-like isolate was collected from Raphanus sativus (cv. Choon-hyang), which showed mosaic symptoms. The isolate was confirmed to a strain of CMV by host responses in Vigna unguiculata, Chenopodium amaranticolor and Gomphrena globosa, by viral genome composition with RT-PCR and PCR-RFLP, and by serological analysis. Symptom developed by the strain of CMV was severe in Nicotiana benthamiana, N. glutinosa, N. tabacum (cv. Samsun, cv. Xanthi), Cucumis melo (cv. Early hanover), Cucumis sativus (cv. White wonder), Capsicum annuum (cv. Chung-yang and cv. Geum-top), but mild symptom was developed in Raphanus sativus (cv. Choon-hyang), Brassica rapa ssp. pekinensis (cv. Bul-Am No. 3), and B. juncea (cv. Daenong Jukgot). Newly isolated strain of CMV could infect diverse crops including Solanaceae, Cucurbitaceae and Brassicaceae. We designated the new strain of CMV as Gn-CMV based on the novel infectivity of Brassicaceae. In double-stranded (ds) RNA analysis, Gn-CMV consisted of 3.3, 3.0, and 2.2 kb genomes likewise other strains of CMV. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) showed 28 kDa of the CMV coat protein. By restriction enzyme mapping using Cac8I, ClaI and MspI of RT-PCR products indicated that Gn-CMV belongs to CMV subgroup I.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.5
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• pp.362-368
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• 2008

In order to isolate novel oligotrophic bacteria exhibiting antifungal activities, soils were collected from pepper-cultivated fields of Yeongyang, Jecheon, Nonsan, Eumsong and Goesan area in Korea. From soils in pepper cultivated area, a total of 9,354 strains were isolated as oligotrophic bacteria by the R2A dilution method. Among 9,354 oligotrohic bacteria candidates, 1A strain was selected by screening against Phytophthora capsici causing phytophthora blight of hot pepper in the greenhouse and field. The strain was identified as Bacillus vallismortis based on its 16S rDNA sequence and key characteristics as compared with those of authentic cultures of B. vallismortis(KACC 12149) and B. mojavensis(KACC 12096). The strain showed broad spectrum of antibiotic activity in vitro test, as revealed in its strong inhibitory activity to the genera Phytophthora, Collectotrichum, Botrytis and Fusarium, but not to Rhizoctonia and Magnaporthe. In pot experiments, infection rate of hot pepper in the non-treated pots was about 89%, while it was only 29% in the pots treated with 1A strain. The result indicated B. vallismortis 1A is a potential biocontrol agent for phytophthora blight of hot pepper

• Journal of Mushroom
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• v.15 no.3
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• pp.111-117
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• 2017

The mushroom species Cordyceps militaris has been studied and cultivated as a medicinal mushroom due to its multiple valuable biological and pharmaceutical activities. For breeding new strains of C. militaris, multiplex PCR assays were performed using primers specific for its mating type genes, MAT1-1 and MAT1-2. Mating types and mating status were confirmed, as evidenced by DNA bands at 233-bp and 191-bp for MAT1-1 and MAT1-2 respectively. The novel 'Dowonhongcho 2ho' was developed through mating; they were found to possess high-quality fruiting bodies when grown in artificial media. The stromata of the new strain were club-shaped, with a bright orange-red color, and measured 7.1 cm in length. They had an average cordycepin content of 0.33%. Compared to 'Dowonhongcho,' the new strain had a 7% higher yield, as well as firm fruiting bodies. The optimum temperature for mycelial growth was $20{\sim}25^{\circ}C$, and the optimum temperature for stroma development was $18{\sim}22^{\circ}C$. The fruiting bodies developed after 49.1 days from inoculation. The use of mating type molecular markers improved the breeding efficiency of the new strain 'Dowonhongcho 2ho.' Thus, they may be valuable for artificial cultivation and industrial-scale production of C. militaris with excellent characteristics.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.443-450
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• 2016

In this study, we propose a novel fiber optic sensor to show the measurement feasibility of distributed temperature and strains in a single sensing fiber line. Distributed temperature can be measured using optical time domain reflectometry (OTDR) with a Raman anti-Stokes light in the sensing fiber line. Moreover, the strain can be measured by fiber Bragg gratings (FBGs) in the same sensing fiber line. The anti-Stokes Raman back-scattering lights from both ends of the sensing fiber, which consists of a 4 km single mode optical fiber, are acquired and inserted into a newly formulated equation to calculate the temperature. Furthermore, the center wavelengths from the FBGs in the sensing fiber are detected by an optical spectrum analyzer; these are converted to strain values. The initial wavelengths of the FBGs are selected to avoid a cross-talk with the wavelength of the Raman pulsed pump light. Wavelength shifts from a tension test were found to be 0.1 nm, 0.17 nm, 0.29 nm, and 0.00 nm, with corresponding strain values of $85.76{\mu}{\epsilon}$, $145.55{\mu}{\epsilon}$, $247.86{\mu}{\epsilon}$, and $0.00{\mu}{\epsilon}$, respectively. In addition, a 50 m portion of the sensing fiber from $30^{\circ}C$ to $70^{\circ}C$ at $10^{\circ}C$ intervals was used to measure the distributed temperature. In all tests, the temperature measurement accuracy of the proposed sensor was less than $0.50^{\circ}C$.