• Journal of Microbiology and Biotechnology
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• v.27 no.10
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• pp.1736-1743
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• 2017

Sourdough is made by fermentation of dough by lactic acid bacteria (LAB) and yeast to improve bread properties like volume, flavor, and texture. A Korean traditional sourdough was made by fermenting rice flour with rice wine (makgeolli) and used to make sponge-like bread (jeung-pyun). The aim of this study was to investigate the microbial diversity of makgeolli products and their influence on the organoleptic quality of jeung-pyun. Three commercial makgeolli were tested for jeung-pyun production, with each product exhibiting varied dough swelling rates and organoleptic qualities, and among them, J-product was ranked highest in texture and taste. Microbial analysis of the three makgeolli also showed a big difference in their population and diversity. J-product had the highest LAB and yeast counts, and the predominant species were Lactobacillus casei, Lactobacillus brevis, Leuconostoc pseudomenteroides, and Saccharomyces cerevisiae. Using J-product, sourdough was fermented at $25^{\circ}C$, $30^{\circ}C$, and $35^{\circ}C$, and the microbial growth in and textural properties of jeung-pyun were examined by instrumental and sensory tests. At high temperature ($35^{\circ}C$), the rates of dough swelling and acidification were fast due to rapid microbial growth mainly caused by LAB, resulting in a short leavening time and soft and sour jeung-pyun. Sensory tests showed consumer preference for the soft and mild-sour jeung-pyun. This study shows that LAB in makgeolli play key roles in production of jeung-pyun, influencing the textural and sensory properties. For the production of high-quality jeung-pyun, development of LAB starters with high gas productivity and low acidity and establishment of an optimal fermentation procedure for rice dough are necessary.

• The Korean Journal of Mycology
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• v.43 no.3
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• pp.137-141
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• 2015

This study focused on isolation of wild yeasts from natural flowers and elucidation of yeast diversity. Wild yeasts were isolated from various flowers collected from mountains on the islands including Jejudo, Ulleungdo, Yokjido, and Seonyudo as well as inlands including Gyejoksan, Oseosan, Beakamsan, and Deogyusan in Korea. Isolated yeasts were identified by comparison of nucleotide sequences for polymerrase chain reaction-amplified D1/D2 region of 26S rDNA or internal transcribed spacer 1 and 2 including 5.8S rDNA using BLAST. 289 strains belonging to 134 yeast species were isolated. Cryptococcus genus strains were the most frequently isolated species among the identified yeasts. Metschnikowia reukaufii was also frequently isolated. Twenty three species including Cryptococcus aureus were overlapped between those of mountains on islands and inland. Physiological functionalities such as antioxidant activity, xanthine oxidase inhibitory activity, and tyrosinase inhibitory activity for the 289 identified yeast strains were investigated using their supernatant and cell-free extracts. The supernatants of Candida sp. 78-J-2 and Metschnikowia reukaufii SY44-6 showed antioxidant activity of 22.5%, and anti-gout xanthine oxidase inhibitory activity of 49.6%, respectively.

• Proceedings of the Microbiological Society of Korea Conference
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• 2002.10a
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• pp.90-93
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• 2002

The revolution in molecular biology has given us greatly increased ability to obtain and to modify biological resources and to use them for the benefit of all humankind. The sequencing and the associated analysis of gene functions for a growing number of genomes will have an unprecedented effect on the uses of biological resources and the need for access to them. To investigate the diversity of microbial community in swamp, molecular systematic methods were applied. By amplified rDNA restriction analysis (ARDRA) and rDNA partial sequence analysis, $75\%$ of the isolates were known species. In case of uncultured analysis, almost all the selected clones were new species candidate. Especially archea and uncultured bacterial analyses, all clones were new taxon candidates. As for the eukaryotic diversity, several yeast form cultures were isolated from various samples of swamp. Among them, about $60\%$ of the isolates were easily identified. In case of a new species candidate, most strain were included in hymenomycetal yeasts.

• Genomics & Informatics
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• v.7 no.4
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• pp.203-207
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• 2009

The target of rapamycin (TOR) signaling pathway conserved from yeast to human plays critical roles in regulation of eukaryotic cell growth. It has been shown that TOR pathway is involved in several cellular processes, including ribosome biogenesis, nutrient response, autophagy and aging. However, due to the functional diversity of TOR pathway, we do not know yet some key effectors of the pathway. To find unknown effectors of TOR signaling pathway, we took advantage of a green fluorescent protein (GFP)-tagged collection of budding yeast Saccharomyces cerevisiae. We analyzed protein abundance changes by measuring the GFP fluorescence intensity of 4156 GFP-tagged yeast strains under inhibition of TOR pathway. Our proteomic analysis argues that 83 proteins are decreased whereas 32 proteins are increased by treatment of rapamycin, a specific inhibitor of TOR complex 1 (TORC1). We found that, among the 115 proteins that show significant changes in protein abundance under rapamycin treatment, 37 proteins also show expression changes in the mRNA levels by more than 2-fold under the same condition. We suggest that the 115 proteins indentified in this study may be directly or indirectly involved in TOR signaling and can serve as candidates for further investigation of the effectors of TOR pathway.

• Mycobiology
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• v.49 no.6
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• pp.582-588
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• 2021

The interaction of mating pheromone and pheromone receptor from the B mating-type locus is the first step in the activation of the mushroom mating signal transduction pathway. The B mating-type locus of Lentinula edodes is composed of Bα and Bβ subloci, each of which contains genes for mating pheromone and pheromone receptor. Allelic variations in both subloci generate multiple B mating-types through which L. edodes maintains genetic diversity. In addition to the B mating-type locus, our genomic sequence analysis revealed the presence of a novel chromosomal locus 43.3 kb away from the B mating-type locus, containing genes for a pair of mating pheromones (PHBN1 and PHBN2) and a pheromone receptor (RCBN). The new locus (Bα-N) was homologous to the Bα sublocus, but unlike the multiallelic Bα sublocus, it was highly conserved across the wild and cultivated strains. The interactions of RcbN with various mating pheromones from the B and Bα-N mating-type loci were investigated using yeast model that replaced endogenous yeast mating pheromone receptor STE2 with RCBN. The yeast mating signal transduction pathway was only activated in the presence of PHBN1 or PHBN2 in the RcbN producing yeast, indicating that RcbN interacts with self-pheromones (PHBN1 and PHBN2), not with pheromones from the B mating-type locus. The biological function of the Bα-N locus was suggested to control the expression of A mating-type genes, as evidenced by the increased expression of two A-genes HD1 and HD2 upon the treatment of synthetic PHBN1 and PHBN2 peptides to the monokaryotic strain of L. edodes.

• Microbiology and Biotechnology Letters
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• v.47 no.3
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• pp.423-433
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• 2019

Midgut microbiota is known to play a fundamental role in the biology and physiology of the agricultural pest, Spodoptera litura. This study reports the difference in the larval midgut microbiota of field-caught and laboratory-reared populations of S. litura by performing 16S rDNA amplicon pyrosequencing. Field populations for the study were collected from castor crops, whereas laboratory-reared larvae were fed on a regular chickpea based diet. In total, 23 bacterial phylotypes were observed from both laboratory-reared and field-caught caterpillars. Fisher's exact test with Storey's FDR multiple test correction demonstrated that bacterial genus, Clostridium was significantly abundant (p < 0.05) in field-caught larvae of S. litura as compared to that in the laboratory-reared larvae. Similarly, bacterial genera, such as Bradyrhizobium, Burkholderia, and Fibrisoma were identified (p < 0.05) predominantly in the laboratory-reared population. The Bray-Curtis dissimilarity matrix depicted a value of 0.986, which exhibited the maximum deviation between the midgut microbiota of the laboratory-reared and field-caught populations. No significant yeast diversity was seen in the laboratory-reared caterpillars. However, two yeast strains, namely Candida rugosa and Cyberlindnera fabianii were identified by PCR amplification and molecular cloning of the internal transcribed space region in the field-caught caterpillars. These results emphasize the differential colonization of gut residents based on environmental factors and diet.

• The Korean Journal of Mycology
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• v.42 no.1
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• pp.21-27
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• 2014

Several kinds of yeasts from fruits and flowers of orchard in Yesan-gun of Chungcheongnam-do, Korea were isolated and identified by comparison of nucleotide sequences for PCR-amplified D1/D2 region of 26S rDNA using BLAST. Fourty eight yeast strains of twenty five species and one hundred eight yeast strains of fourty eight species were isolated from fruits and flowers of orchard in Sinam-myeon of Yesan-gun, Chungcheongnam-do, respectively. Among total one hundred fifty-six yeast strains, only sixteen species were overlapped from fruits and flowers.

• The Korean Journal of Mycology
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• v.42 no.1
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• pp.28-33
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• 2014

Various yeasts from wild flowers of Ulleungdo in Gyeongsangbuk-do and Yokjido in Gyeongsangnam-do, Korea were isolated and identified by comparison of nucleotide sequences for PCR-amplified D1/D2 region of 26S rDNA using BLAST. Forty eight yeast strains of twenty two species and sixty yeast strains of twenty five species were isolated from wild flowers of Ulleungdo and Yokjido, respectively. Only seven species were overlapped from the two different islands areas: Cryptococcus albidus, Cryptococcus laurentii, Metschnikowia reukafii, Pichia scolyti, Rhodotorula glutinis, Rhodotorula graminis and Rhodotorula mucilaginosa. Among forty species from two different islands, other thirty three species were restricted to specific collection site suggesting that each area has distinctive yeast flora.

• 한국균학회소식:학술대회논문집
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• 2015.11a
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• pp.11-11
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• 2015

A total of sixty-six samples of Nuruk, a fermention starter used to make the Korean traditional rice wine, Makgeolli, were collected from central and southern regions of Korea in 2013 and 2014. We classified two groups of the Nuruk samples, "commercial" and "home-made", according to the manufacturing procedure and purpose of use. Commercial Nuruks were made in a controlled environment where the temperature and humidity are fixed and the final product is supplied to Makgeolli manufacturers. Home-made Nuruks were made under uncontrolled conditions in the naturally opened environment and were intended for use in the production of small amounts of home-brewed Makgeolli. We obtained more than five hundred isolates including filamentous fungi and yeasts from the Nuruk samples followed by identification of fungal species. Also we stored glycerol stocks of each single isolate at $-70^{\circ}C$. We identified the species of each isolate based on the sequences of ITS regions amplified with two different universal primer pairs. We also performed morphological characterization of the filamentous fungi and yeast species through observations under the microscope. We investigated the major fungal species of commercial and home-made Nuruks by counting the colony forming units (CFU) and analyzing the occurrence tendency of fungal species. While commercial Nuruks contained mostly high CFU of yeasts, home-made Nuruks showed relatively high occurrence of filamentous fungi. One of the representative Nuruk manufacturers used both domestic wheat bran and imported ones, mainly from US, as raw material. Depending on the source of ingredient, the fungal diversity was somewhat different. Another commercial Nuruk sample was collected twice, once in 2013 and again in 2014, and showed different diversity of fungal species in each year. Nuruks obtained from the southern regions of Korea and Jeju island showed high frequency of yeast such as Saccharomycopsis fibuligera and Pichia species as well as unique filamentous fungus, Monascus species. S. fibuligera was easily found in many Nuruk samples with high CFU. The major filamentous fungi were Aspergillus, Lichtheimia, Mucor and Penicillium species. In order to further our understanding of the isolates and their potential industrial applications, we assayed three enzymes, alpha amylase, glucoamylase and acid protease from 140 isolates out of about five hundred isolates and selected about 10 excellent strains with high enzyme activities. With these fungal isolates, we will perform omics analyses including genomics, transcriptomics, metabolic pathway analyses, and metabolomics followed by whole genome sequencing of unique isolates associated with the basic research of Nuruk and that also has applications in the Makgeolli making process.

• Journal of Life Science
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• v.24 no.9
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• pp.995-1000
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• 2014

The studies of marine viruses in terms of viral isolation and detection have been limited due to the high mutation rate and genetic diversity of marine viruses. Of the modern methods currently used to detect marine viruses, serological methods based on enzyme-linked immunosorbent assay (ELISA) are the most common. They depend largely on the quality of the antibodies and on highly purified suitable antigens. Recently, a new experimental system for using viral capsid protein as an antigen has been developed using the yeast surface display (YSD) technique. In the present study, the capsid protein gene of the red-spotted grouper nervous necrosis virus (RGNNV) was expressed and purified via YSD and HA-tagging systems, respectively. Two regions of the RGNNV capsid protein gene, RGNNV1 and RGNNV2, were individually synthesized and subcloned into a yeast expression vector, pCTCON. The expressions of each RGNNV capsid protein in the Saccharomyces cerevisiae strain EBY100 were indirectly detected by flow cytometry with fluorescently labeled antibodies, while recognizing the C-terminal c-myc tags encoded by the display vector. The expressed RGNNV capsid proteins were isolated from the yeast surface through the cleavage of the disulfide bond between the Aga1 and Aga2 proteins after ${\beta}$-mercaptoethanol treatment, and they were directly detected by Western blot using anti-HA antibody. These results indicated that YSD and HA-tagging systems could be applicable to the expressions and purification of recombinant RGNNV capsid proteins.