• 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.

• Polymer(Korea)
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• v.30 no.2
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• pp.146-151
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• 2006

Linear and branched copolymers consisting of poly(ethylene glycol) (PEG) and $Poly({\varepsilon}-caprolactone)$ (PCL) were prepared to compare the characterization of star-shaped copolymers with various molecular architecture. Linear and branched PEG-PCL (1-arm, 2-arm, 4-arm, and 8-arm) copolymers were synthesized by the ring-opening polymerization of ${\varepsilon}-caprolactone$ in the presence of HCl $Et_2O$ as a monomer activator at room temperature. The synthesized copolymers were characterized with $^1H-NMR$, GPC, DSC, and XRD. As a result of the DSC and XRD, each copolymers showed different thermal properties and crystallinity according to the number of ms. The micellar characterization of linear and branched copolymers in an aqueous phase was carried out by using NMR, dynamic light scattering, AM, and fluorescence techniques. The critical micelle concentration (CMC) and diameters of micelles depended on the number of arms. Most micelles exhibited a spherical shape in AFM. In this study, we characterized star-shaped PEG-PCL copolymers and investigated their molecular architecture effect on the various properties. Furthermore, we confirmed that the micelles termed with linear and branched PEG-PCL copolymers have possibility as a potential hydrophobic drug delivery vehicle.

• Polymer(Korea)
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• v.35 no.2
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• pp.161-165
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• 2011

This study is related to the preparation of biocompatible gold nanoparticles (AuNPs) which are stable in aqueous solutions for a long time. Ultrasmall polyethyleneimine (PEI)-capped AuNPs (PEI-AuNPs) with limited agglomeration were prepared in aqueous solutions at room temperature, which were based on the roles of PEI as a reductant and a stabilizer. PEI-AuNPs with an average size of 8~12 nm formed highly stable nanocolloids with an average hydrodynamic cluster size of around 50 nm in aqueous media. At a low concentration of metal precursor hydrogen tetrachloroaurate (III), the particle size was reduced noticeably. The typical peaks of gold were observed in the X-ray diffraction pattern of AuNPs. The cell viability of 98% was obtained in the case of PEI-AuNPs, while PEI was cytotoxic. The PEI-AuNP is considered to be a potential candidate as a contrast agent for computed tomography.

• Food Science and Preservation
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• v.19 no.5
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• pp.757-766
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• 2012

The SSH100-10 bacterial strain, which exhibits strong antifungal (anti-mold and anti-yeast) activity, was isolated from traditional korean soysauce aged 100 years. The strain was identified as Bacillus velezensis based on Gram-staining, the biochemical properties and 16S rRNA gene sequence determination. B. velezensis SSH100-10 showed strong proteinase activity and NaCl tolerance, but did not produce enterotoxin. Two-antifungal compounds from B. velezensis SSH100-10 were purified using SPE, preparative HPLC, and reverse phase-HPLC. The purified antifungal compounds were identified as $C_{14}$ and $C_{15}$ iturin through MALDI-TOF-MS and amino acid composition analysis. The stability characteristics of the antifungal compounds after temperature, pH, and enzyme treatments suggested that B. velezensis SSH100-10 produced more than two antifungal compounds; pH-stable $C_{14}$ iturin A and $C_{15}$ iturin A, and unidentified pH-unstable compounds. The results suggested that B. velezensis SSH100-10 can be used in soybean fermentation as a starter. Moreover it has potential as a biopreservative in the food and feed industry and as a biocontrol agent in the field of agriculture.

• Restorative Dentistry and Endodontics
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• v.26 no.5
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• pp.372-378
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• 2001

The aim of this in vitro study was to analyze the composition of human tooth enamel in terms of three components, Ca, P, and F after demineralization and remineralization in acid buffer solution. A total of 8 human premolars without any defects and cracks were selected and buccal and lingual sides of the teeth were cleaned with an ultrasonic device and pumice without fluoride 5$\times$5mm windows were opened, and other areas were completely covered with 3-coats of nail varnish to prevent from being in contact with demineralized and remineralized solutions. After demineralization process, each tooth was sectioned into two slices, highly polished one of them with$\gamma$-alumina, and then analyzed the composition of the demineralized tooth with EPMA(electron probe micro-analyzer). The other slices were put into the remineralized solution for 10 days, polished, and analyzed in the same manner. These data were statistically analyzed with one sample t-test(p<0.05). The results were as follows. 1. Normal tooth enamel consists of 49.76% Ca, 39.80% P, and 0.28% F. 2. After demineralization, percentage of Ca and P ratio were decreased by about 5.57 and 5.07% respectively. Percentage of F ratio was also decreased by about 0.01%, which was not statistically significant. 3. After remineralization, percentage of Ca, P increased about by 4.47 and 4.35% respectively Percentage of F decreased by about 0.01%, which was not statistically significant. In conclusion, remineralized solution used in our study has the potential to induce the uptake the Ca and P into the pore sites of the demineralized enamel. But, in the oral cavity. there were rapid temperature change, organic matrix that inhibits the movement of the ions, and limitation of continuous contact with this remineralized solution. Therefore, further in vivo study is necessary.

• Polymer(Korea)
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• v.30 no.6
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• pp.464-470
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• 2006

Diblock copolymers consisting of methoxy Poly (ethylene glycol) (MPEG) and poly (${\epsilon}-ca$ prolactone) (PCL), poly(${\delta}-valerolactone$) (PVL), poly(L-lactide) (PLLA), or poly(L-lactide-co-glycolide) (PLGA) were prepared to compare the characterization of diblock copolymers as a drug carrier. MPEG-PCL, MPEG-PVL, MPEG-PLLA, and MPEG-PLGA diblock copolymers were synthesized by the ring-opening polymerization of ${\epsilon}$-caprolactone or ${\delta}$-valerolactone in the presence of $HCl{\cdot}Et_2O$ as a monomer activator at room temperature and by the ring-opening polymerization of L-lactide or a mixture of L-lactide and glycolide in the presence of stannous octoate at $130^{\circ}C$, respectively. The synthesized diblock copolymers were characterized with $^1H-NMR$, GPC, DSC, and XRD. The micellar characterization of MPEG-polyester diblock copolymers in an aqueous phase was carried out by using NMR, dynamic light scattering, AFM, and fluorescence techniques. Most micelles exhibited a spherical shape in AFM. Thus, ore confirmed that the micelles formed with MPEG-polyester diblock copolymers have possibility as a potential hydrophobic drug delivery vehicle because a hydrophobic drug could be preferentially distributed in the micelle core.

• Journal of Life Science
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• v.25 no.3
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• pp.345-348
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• 2015

An organic solvent stable lipase from solvent-tolerant Pseudomonas sp. BCNU 171 had an optimal pH of 8 and an optimal temperature of 37℃. This crude extracellular lipase from BCNU 171 exhibited increased stability in the presence of various types of solvents at high concentrations (25%, v/v). The lipase stability was found to be highest in the presence of xylene (137%), followed by toluene (131%), octane (130%), and butanol (104%). Overall, BCNU 171 lipase tended to be more stable than immobilized commercial lipase (Novozyme435) in the presence of organic solvents. Furthermore, BCNU 171 lipase maintained about 90% of its enzyme original activity in the presence of NH₄⁺, Na⁺, Ba²⁺, Hg²⁺, Ni²⁺, Cu²⁺, and Ca²⁺ion and significantly increased its enzyme activity in the presence of various emulsifying agents. Thus, the organic solvent stable lipase from Pseudomonas sp. BCNU 171 could be usable as a potential whole cell biocatalyst and for synthetic applications of enzymes for industrial chemical processes in organic solvents without using immobilization.

• Journal of Life Science
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• v.19 no.11
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• pp.1672-1678
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• 2009

The purified antifungal substances produced by Bacillus amyloliquefaciens IUB158-03 was positive to ninhydrin but negative to aniline, suggesting that the antifungal substance could be a peptide. FAB-MS, UV adsorption spectrum, and amino acid composition analysis revealed that the molecular weight of the antifungal substance was 1042 and that maximal adsorption was at 220 nm and 277 nm. The antifungal substance was composed of $Asn_3$, $Gln_2$, $Ser_1$, $Gly_1$, and $Tyr_1$. The composition and structural characteristics of antifungal substance were analysed by $^1H$-NMR spectrum, $^1H$-COSY, HMQC, which revealed that the compound belongs to the iturin A family. Temperature and pH had little effect on the stability of the antifungal substance in the ranges of $-70{\sim}121^{\circ}C$ and pH 6.0~10.0, respectively. It showed strong antibiotic activity against fungi. An in vitro cytotoxicity test using NIH3T3 cell showed that the antifungal substance does not have cytotoxicity. The number of circulating leukocytes and the hematobiological analysis of the mice administered with the antifungal substances was similar to those of the control group, indicating no cytotoxicity in vivo. Therefore, the antifungal substances extracted from culture broth of Bacillus amyloliquefaciens IUB158-03 have future potential as biocontrol agents against plant diseases caused by fungi.

• Journal of the Korean Wood Science and Technology
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• v.37 no.3
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• pp.245-254
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• 2009

As a substitute for CCA, which is inhibited due to its environmental pollution and human harmfulness, and CuAz and ACQ with a high cost, okara-based wood preservatives were formulated with okara hydrolyzates using copper sulfate and/or borax as a metal salt. The efficacy of the preservatives and X-ray microanalysis of wood specimens treated with the preservatives were examined to confirm the potential of the okara-based wood preservatives. Most of the preservatives showed excellent decay resistance against brown-rot fungi, Postia placenta and Gloeophyllum trabeum. The efficacy was improved when the acid concentration and temperature used for the hydrolysis of okara increased. In addition, when borax was added into copper sulfate/okara hydrolyzates preservative formulations, any decay was not found in the specimens. From the microscopic observation of the specimens treated with okara-based wood preservatives, it seems that okara is contributed to the fixing of metal salts in wood blocks. Therefore, it is speculated that okara-based wood preservatives can effectively protect wood against fungal attack as CuAz, and that the preservatives are sufficient to use as an alternative wood preservative of CCA, ACQ and CuAz.

• Food Science of Animal Resources
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• v.26 no.3
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• pp.402-409
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• 2006

Although microorganisms are, in fact, the most diverse and abundant type of organism on Earth, the ecological functions of microbial populations remains poorly understood. A variety of bacteria including marine Vibrios encounter numerous ecological challenges, such as UV light, predation, competition, and seasonal variations in seawater including pH, salinity, nutrient levels, temperature and so forth. In order to survive and proliferate under variable conditions, they have to develop elaborate means of communication to meet the challenges to which they are exposed. In bacteria, a range of biological functions have recently been found to be regulated by a population density-dependent cell-cell signaling mechanism known as quorum-sensing (QS). In other words, bacterial cells sense population density by monitoring the presence of self-produced extracellular autoinducers (AI). N-acylhomoserine lactone (AHL)-dependent quorum-sensing was first discovered in two luminescent marine bacteria, Vibrio fischeri and Vibrio harveyi. The LuxI/R system of V. fischeriis the paradigm of Gram-negative quorum-sensing systems. At high population density, the accumulated signalstrigger the expression of target genes and thereby initiate a new set of biological activities. Several QS systems have been identified so far. Among them, an AHL-dependent QS system has been found to control biofilm formation in several bacterial species, including Pseudomonas aeruginosa, Aeromonas hydrophila, Burkholderia cepacia, and Serratia liquefaciens. Bacterial biofilm is a structured community of bacterial cells enclosed in a self-produced polymeric matrix that adheres to an inert or living surface. Extracellular signal molecules have been implicated in biofilm formation. Agrobacterium tumefaciens strain NT1(traR, tra::lacZ749) and Chromobacterium violaceum strain CV026 are used as biosensors to detect AHL signals. Quorum sensing in lactic acid bacteria involves peptides that are directly sensed by membrane-located histidine kinases, after which the signal is transmitted to an intracellular regulator. In the nisin autoregulation process in Lactococcus lactis, the NisK protein acts as the sensor for nisin, and NisR protein as the response regulator activatingthe transcription of target genes. For control over growth and survival in bacterial communities, various strategies need to be developed by which receptors of the signal molecules are interfered with or the synthesis and release of the molecules is controlled. However, much is still unknown about the metabolic processes involved in such signal transduction and whether or not various foods and food ingredients may affect communication between spoilage or pathogenic bacteria. In five to ten years, we will be able to discover new signal molecules, some of which may have applications in food preservation to inhibit the growth of pathogens on foods.