• Journal of Microbiology and Biotechnology
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• v.24 no.9
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• pp.1216-1225
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• 2014

Biofilm-related infections of Candida albicans are a frequent cause of morbidity and mortality in hospitalized patients, especially those with immunocompromised status. Options of the antifungal drugs available for successful treatment of drug-resistant biofilms are very few, and as such, new strategies need to be explored against them. The aim of this study was to evaluate the efficacy of phenylpropanoids of plant origin against planktonic cells, important virulence factors, and biofilm forms of C. albicans. Standard susceptibility testing protocol was used to evaluate the activities of 13 phenylpropanoids against planktonic growth. Their effects on adhesion and yeast-to-hyphae morphogenesis were studied in microplate-based methodologies. An in vitro biofilm model analyzed the phenylpropanoid-mediated prevention of biofilm development and mature biofilms using XTT-metabolic assay, crystal violet assay, and light microscopy. Six molecules exhibited fungistatic activity at ${\leq}0.5mg/ml$, of which four were fungicidal at low concentrations. Seven phenylpropanoids inhibited yeast-to-hyphae transition at low concentrations (0.031-0.5 mg/ml), whereas adhesion to the solid substrate was prevented in the range of 0.5-2 mg/ml. Treatment with ${\leq}0.5mg/ml$ concentrations of at least six small molecules resulted in significant (p < 0.05) inhibition of biofilm formation by C. albicans. Mature biofilms that are highly resistant to antifungal drugs were susceptible to low concentrations of 4 of the 13 molecules. This study revealed phenylpropanoids of plant origin as promising candidates to devise preventive strategies against drug-resistant biofilms of C. albicans.

• Journal of Microbiology and Biotechnology
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• v.28 no.2
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• pp.255-261
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• 2018

Aglycon protopanaxatriol (APPT) has valuable pharmacological effects such as memory enhancement and tumor inhibition. ${\beta}$-Glycosidase from the hyperthermophilic bacterium Dictyoglomus turgidum (DT-bgl) hydrolyzes the glucose residues linked to APPT, but not other glycoside residues. ${\beta}$-Glycosidase from the hyperthermophilic bacterium Pyrococcus furiosus (PF-bgl) hydrolyzes the outer sugar at C-6 but not the inner glucose at C-6 or the glucose at C-20. Thus, the combined use of DT-bgl and PF-bgl is expected to increase the biotransformation of PPT-type ginsenosides to APPT. We optimized the ratio of PF-bgl to DT-bgl, the concentrations of substrate and enzyme, and the reaction time to increase the biotransformation of ginsenoside Re and PPT-type ginsenosides in Panax ginseng leaf extract to APPT. DT-bgl combined with PF-bgl converted 1.0 mg/ml PPT-type ginsenosides in ginseng leaf extract to 0.58 mg/ml APPT without other ginsenosides, with a molar conversion of 100%. We achieved the complete biotransformation of ginsenoside Re and PPT-type ginsenosides in ginseng leaf extract to APPT by the combined use of two ${\beta}$-glycosidases, suggesting that discarded ginseng leaves can be used as a source of the valuable ginsenoside APPT. To the best of our knowledge, this is the first quantitative production of APPT using ginsenoside Re, and we report the highest concentration and productivity of APPT from ginseng extract to date.

• Journal of Microbiology and Biotechnology
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• v.28 no.9
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• pp.1482-1492
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• 2018

Fusarium oxysporum trypsin (FOT) is a fungal serine protease similar to mammal trypsin. The FOT could be successfully expressed in Pichiapastoris by engineering the natural propeptide APQEIPN. In this study, we constructed two recombinant enzymes with engineered amino acid sequences added to the N-terminus of FOT and expressed in P. pastoris. The N-terminal residues had various effects on the structural and functional properties of trypsin. The FOT, and the recombinants TE (with peptide YVEF) and TS (with peptide YV) displayed the same optimum temperature ($40^{\circ}C$) and pH (8.0). However, the combinants TE and TS showed significantly increased thermal stability at $40^{\circ}C$ and $50^{\circ}C$. Moreover, the combinants TE and TS also showed enhanced tolerance of alkaline pH conditions. Compared with those of wild-type FOT, the intramolecular hydrogen bonds and the cation ${\pi}$-interactions of the recombinants TE and TS were significantly increased. The recombinants TE and TS also had significantly increased catalytic efficiencies (referring to the specificity constant, $k_{cat}/K_m$), 1.75-fold and 1.23-fold than wild-type FOT. In silico modeling analysis uncovered that the introduction of the peptides YVEF and YV resulted in shorter distances between the substrate binding pocket (D174, G198, and G208) and catalytic triad (His42, Asp102, and Ser180), which would improve the electron transfer rate and catalytic efficiency. In addition, N-terminal residues modification described here may be a useful approach for improving the catalytic efficiencies and characteristics of other target enzymes.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1227-1234
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• 2020

In this study, yeast cell immobilization was carried out in a packed bed reactor (PBR) to investigate the effects of the volumetric capacity of carriers as well as the different fermentation modes on fuel ethanol production. An optimal volumetric capacity of 10 g/l was found to obtain a high cell concentration. The productivity of immobilized cell fermentation was 16% higher than that of suspended-cell fermentation in batch and it reached a higher value of 4.28 g/l/h in repeated batches. Additionally, using this method, the ethanol yield (95.88%) was found to be higher than that of other tested methods due to low concentrations of residual sugars and free cells. Continuous ethanol production using four bioreactors showed a higher productivity (9.57 g/l/h) and yield (96.96%) with an ethanol concentration of 104.65 g/l obtained from 219.42 g/l of initial total sugar at a dilution rate of 0.092 h^-1. Furthermore, we reversed the substrate-feed flow directions in the in-series bioreactors to keep the cells at their highest activity and to extend the length of continuous fermentation. Our study demonstrates an effective method of ethanol production with a new immobilized approach, and that by switching the flow directions, traditional continuous fermentation can be greatly improved, which could have practical and broad implications in industrial applications.

• Journal of Conservation Science
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• v.23
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• pp.39-51
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• 2008

Adding chemical additives in bamboo paper making procedure in China became common in last decades to increase productivity. Supply of repair paper for paper based artefacts became more and more difficult due to this tendency. Furthermore, stains and spots on paper which happen to appear during dying procedure make it difficult to use modern bamboo paper for repair treatment. In this research, lime fermentation and sun bleaching were main elements which affect texture and color of paper. Impurities, however, add some effects on paper quality. Less thouroughly washed raw materials after fermentation also affects texture of paper substrate. One most significant impurity is lime. Minimum residue of lime can make stains and spots after dying. Reproduction of white bamboo paper would become useful resource in various conservation treatments as a repair paper, and also, for reproduction of paper woven painting. However, further research to improve quality at early stage of paper making procedure in China required.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.596-602
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• 2018

Nanoimprint lithography (NIL) is an emerging technology that enables cost-effective and high-throughput nanofabrication. In ultraviolet (UV) NIL, low-cost and high-speed production can be achieved using a non-vacuum environment at room temperature and low pressure. However, there are problems with the formation of bubble defects in such an environment. This paper investigates the shape of the mold cavity and the bubble defect formation in UV NIL in a non-vacuum environment. The bubble defect formation was simulated using two-dimensional flow analysis and the VOF method for commonly used cavity mold shapes (rectangular, elliptical, and triangular). The characteristics of the resist flow front and various contact angles were also analyzed. The shape of the mold cavity had a very significant effect on the bubble defect formation. For all cavity shapes, a smaller contact angle with the mold and larger contact angle with the substrate decreased the possibility of bubble defect formation. The elliptical shape was the most effective for preventing bubble defect formation.

• Nutrition Research and Practice
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• v.3 no.2
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• pp.128-133
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• 2009

Few studies have examined short tenn responses to the different contents of carbohydrate or fat in the meal, although long tenn effects of the high fat meal have been considered as compound risk factor for metabolic disorders. The aim of this study was to investigate the postprandial changes of plasma glucose, insulin and lipids upon intakes of high carbohydrate or high fat meal in young healthy women. Subjects were randomly assigned to either the high carbohydrate meal (HCM, 75% carbohydrate, n=13) or the high fat meal (HFM, 60% fat, n=12) groups. The meals were prepared as isocaloric typical Korean menu. Blood samples were obtained prior to and 30, 60, 90, 120, 180 and 240 minute after the meal. There were no significant differences on fasting blood parameters including glucose, insulin, lipids concentrations between the groups prior to the test. The HCM had higher blood glucose and insulin concentrations, reached the peak at 30 min and maintained for 240 min compared to the HFM (P<0.05). The HFM had higher plasma triglyceride (TG) and free fatty acid (FFA) concentrations, reached the peak at 120 min and maintained for 240 min compared to the HCM (P<0.05). It is concluded that macronutrients content in the meal may be an important determinant of postprandial substrate utilization in healthy women.

• Journal of Microbiology and Biotechnology
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• v.10 no.1
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• pp.1-7
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• 2000

Bioconversion of fumarate to succinate was anaerobically conduced in a synthetic medium containing glycerol as a hydrogen donor and fumarate as a hydrogen acceptor. We investigated the effects of pH, carbon and nitrogen sources, conversion substrate, and other culture conditions on the production of succinate using a nwely isoloated Enterococcus facalis PKY1. Addition of a variety of carbonates to the medium significantly increasd the rates of production of succinate. The production of succinate and cell growth were relatively satisfactory in the pH range of 7.0-7.6. By using glycerol as a hydrogen donor, high purity succinate was produced with few byproducts. Yeast extract as a sole nitrogen source was the most effective for producing succinalte. As a result, the optimum condition of biconversion was obtained at a medium containing 20g/I glycerol, 50 g/l fumarate, 15 g/l yeast extract, 10 g/l $K_2HPO_4$, 1 g/I NaCl, 50ppm $MgCl_2{\cdot}6H_2O$, 10ppm $FeSo_4{\cdot}7H_2O$, and 5 g/I $Na_2CO_3$ at pH 7.0-7.6. Under the optimum condition, a succinate concentration of 153 g/I was produced in 36 h. The total volumetric production rate and the molar yield of succinate were 4.3 g/l/h and 85%, respectively.

• Journal of Microbiology and Biotechnology
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• v.17 no.11
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• pp.1772-1781
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• 2007

Activated sludge was sequentially adapted to benzene, toluene, and o-xylene (BTX) to study the effects on the change of microbial community. Sludge adapted to BTX separately degraded each by various rates in the following order; toluene>o-xylene>benzene. Degradation rates were increased after exposure to repeated spikes of substrates. Eleven different kinds of sludge were prepared by the combination of BTX sequential adaptations. Clustering analyses (Jaccard, Dice, Pearson, and cosine product coefficient and dimensional analysis of MDS and PCA for DGGE patterns) revealed that acclimated sludge had different features from nonacclimated sludge and could be grouped together according to their prior treatment. Benzene- and xylene-adapted sludge communities showed similar profiles. The sludge profile was affected from the point of the final adaptation substrate regardless of the adaptation sequence followed. In the sludge adapted to 50 ppm toluene, Nitrosomonas sp. and bacterium were dominant, but these bands were not dominant in benzene and benzene after toluene adaptations. Instead, Flexibacter sp. was dominant in these cultures. Dechloromonas sp. was dominant in the culture adapted to 50 ppm benzene. Thauera sp. was the main band in the sludge adapted to 50 ppm xylene, but became vaguer as the xylene concentration was increased. Rather, Flexibacter sp. dominated in the sludge adapted to 100 ppm xylene, although not in the culture adapted to 250 ppm xylene. Two bacterial species dominated in the sludge adapted to 250 ppm xylene, and they also existed in the sludge adapted to 250 ppm xylene after toluene and benzene.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2199-2205
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• 2016

In this paper, a design method for a coplanar waveguide (CPW)-fed 2-element quasi-Yagi antenna (QYA) is studied. A balun between CPW and coplanar strip (CPS) which feeds a planar dipole is implemented by connecting the one end of ground strips in a CPW to a signal strip. The antenna size is reduced by bent strip dipole and reflector, and an integrated balun. The proposed antenna was designed for the operation in a UHF radio frequency identification (RFID) band of 902-928 MHz, and the effects of various parameters such as dipole length, reflector length, distance between dipole and reflector, feed position were examined. The antenna with a size of $90mm{\times}80mm$ was fabricated on an FR4 substrate, and the experiment results reveal a frequency band of 885-942 MHz for a voltage standing wave ratio < 2, a gain > 4.3 dBi, and a front-to-back ratio > 7 dB over the frequency band for the UHF RFID.