Publications by authors named "Kyung-Hwan Jung"

50 Publications

Fundamental Understanding of the Formation Mechanism for Graphene Quantum Dots Fabricated by Pulsed Laser Fragmentation in Liquid: Experimental and Theoretical Insight.

Small 2020 Sep 23;16(38):e2003538. Epub 2020 Aug 23.

Korea Institute of Industrial Technology (KITECH), 137-41 Gwahakdanji-ro, Gangneung, Gangwon, 25440, Republic of Korea.

The pulsed laser fragmentation in liquid (PLFL) process is a promising technique for the synthesis of carbon-based functional materials. In particular, there has been considerable attention on graphene quantum dots (GQDs) derived from multiwalled carbon nanotubes (MWCNTs) by the PLFL process, owing to the low cost and rapid processing time involved. However, a fundamental deep understanding of the formation of GQDs from MWCNTs by PLFL has still not been achieved despite the high demand. In this work, a mechanism for the formation of GQDs from MWCNTs by the PLFL process is reported, through the combination of experimental and theoretical studies. Both the experimental and computational results demonstrate that the formation of GQDs strongly depends on the pulse laser energy. Both methods demonstrate that the critical energy point, where a plasma plume is generated on the surface of the MWCNTs, should be precisely maintained to produce GQDs; otherwise, an amorphous carbon structure is favorably formed from the scattered carbons.
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http://dx.doi.org/10.1002/smll.202003538DOI Listing
September 2020

One-step synthesis of sulfur-incorporated graphene quantum dots using pulsed laser ablation for enhancing optical properties.

Opt Express 2020 Jul;28(15):21659-21667

To tune the electronic and optoelectronic properties of graphene quantum dots (GQDs), heteroatom doping (e.g., nitrogen (N), boron (B), and sulfur (S)) is an effective method. However, it is difficult to incorporate S into the carbon framework of GQDs because the atomic size of S is much larger than that of C atoms, compared to N and B. In this study, we report a simple and one-step method for the synthesis of sulfur-doped GQDs (S-GQDs) via the pulsed laser ablation in liquid (PLAL) process. The as-prepared S-GQDs exhibited enhanced fluorescence quantum yields (0.8% → 3.89%) with a huge improved absorption band in ultraviolet (UV) region (200 ∼ 400 nm) and excellent photo stability under the UV radiation at 360 nm. In addition, XPS results revealed that the PLAL process can effectively facilitate the incorporation of S into the carbon framework compared to those produced by the chemical exfoliation method (e.g., hydrothermal method). And also, the mechanisms related with the optical properties of S-GQDs was investigated by time-resolved photoluminescence (TRPL) spectroscopy. We believe that the PLAL process proposed in this study will serve as a simple and one-step route for designing S-GQDs and opens up to opportunities for their potential applications.
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http://dx.doi.org/10.1364/OE.398124DOI Listing
July 2020

A facile and efficient method for the synthesis of crystalline tetrahydro-β-carbolines via the Pictet-Spengler reaction in water.

Sci Rep 2020 01 23;10(1):1057. Epub 2020 Jan 23.

Department of Biotechnology, Korea National University of Transportation, 61 Daehak-ro, Jeungpyeong-gun, Chungbuk, 27909, Republic of Korea.

A facile and efficient synthesis of tetrahydro-β-carbolines (tryptolines) in one step from tryptamine and aldehydes, in an environmentally friendly water solvent, has been investigated. This convenient and clean synthesis of various tryptolines was facilitated by L-tartaric acid, a natural compound, to obtain the desired products as clear crystals. Among the four crystalline products, the most substituted tryptoline 2 showed the best inhibitory activity against EJ cells and the least cytotoxicity, with an LC value of 1.49 mg/mL, against brine shrimp larvae.
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http://dx.doi.org/10.1038/s41598-020-57911-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6978303PMC
January 2020

Optimal Design of Patient-Specific Total Knee Arthroplasty for Improvement in Wear Performance.

J Clin Med 2019 Nov 19;8(11). Epub 2019 Nov 19.

Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.

Life expectancy is on the rise and, concurrently, the demand for total knee arthroplasty (TKA), which lasts a lifetime, is increasing. To meet this demand, improved TKA designs have been introduced. Recent advances in radiography and manufacturing techniques have enabled the production of patient-specific TKA. Nevertheless, concerns regarding the wear performance, which limit the lifespan of TKA, remain to be addressed. This study aims at reducing the wear in patient-specific TKA using design optimization and parametric three-dimensional (3D) finite-element (FE) modelling. The femoral component design was implemented in a patient-specific manner, whereas the tibial insert conformity remained to be determined by design variables. The gait cycle loading condition was applied, and the optimized model was validated by the results obtained from the experimental wear tests. The wear predictions were iterated for five million gait cycles using the computational model with force-controlled input. Similar patterns for internal/external rotation and anterior/posterior translation were observed in both initial and optimal models. The wear rates for initial and optimal models were recorded as 23.2 mm/million cycles and 16.7 mm/million cycles, respectively. Moreover, the experimental wear rate in the optimal design was 17.8 mm/million cycles, which validated our optimization procedure. This study suggests that tibial insert conformity is an important factor in influencing the wear performance of patient-specific TKA, and it is capable of providing improved clinical results through enhanced design selections. This finding can boost the future development of patient-specific TKA, and it can be extended to other joint-replacement designs. However, further research is required to explore the potential clinical benefits of the improved wear performance demonstrated in this study.
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http://dx.doi.org/10.3390/jcm8112023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6912647PMC
November 2019

MgF2-coated porous magnesium/alumina scaffolds with improved strength, corrosion resistance, and biological performance for biomedical applications.

Mater Sci Eng C Mater Biol Appl 2016 May 30;62:634-42. Epub 2016 Jan 30.

Liquid Processing & Casting Technology R&D Group, Korea Institute of Industrial Technology, Incheon 406-840, Republic of Korea. Electronic address:

Porous magnesium (Mg) has recently emerged as a promising biodegradable alternative to biometal for bone ingrowth; however, its low mechanical properties and high corrosion rate in biological environments remain problematic. In this study, porous magnesium was implemented in a scaffold that closely mimics the mechanical properties of human bones with a controlled degradation rate and shows good biocompatibility to match the regeneration rate of bone tissue at the affected site. The alumina-reinforced Mg scaffold was produced by spark plasma sintering and coated with magnesium fluoride (MgF2) using a hydrofluoric acid solution to regulate the corrosion rate under physiological conditions. Sodium chloride granules (NaCl), acting as space holders, were leached out to achieve porous samples (60%) presenting an average pore size of 240 μm with complete pore interconnectivity. When the alumina content increased from 0 to 5 vol%, compressive strength and stiffness rose considerably from 9.5 to 13.8 MPa and from 0.24 to 0.40 GPa, respectively. Moreover, the biological response evaluated by in vitro cell test and blood test of the MgF2-coated porous Mg composite was enhanced with better corrosion resistance compared with that of uncoated counterparts. Consequently, MgF2-coated porous Mg/alumina composites may be applied in load-bearing biodegradable implants.
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http://dx.doi.org/10.1016/j.msec.2016.01.085DOI Listing
May 2016

Ethanol Production from Glycerol by the Yeast Pachysolen tannophilus Immobilized on Celite during Repeated-Batch Flask Culture.

Mycobiology 2014 Sep 30;42(3):305-9. Epub 2014 Sep 30.

Department of Biotechnology, Korea National University of Transportation, Jeungpyung 368-701, Korea.

We investigated a novel process for production of ethanol from glycerol using the yeast Pachysolen tannophilus. After optimization of the fermentation medium, repeated-batch flask culture was performed over a period of 378 hr using yeast cells immobilized on Celite. Our results indicated that the use of Celite for immobilization of P. tannophilus was a practical approach for ethanol production from glycerol, and should be suitable for industrial ethanol production.
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http://dx.doi.org/10.5941/MYCO.2014.42.3.305DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4206801PMC
September 2014

Evaluating Carriers for Immobilizing Saccharomyces cerevisiae for Ethanol Production in a Continuous Column Reactor.

Mycobiology 2014 Sep 30;42(3):249-55. Epub 2014 Sep 30.

Department of Biotechnology, Korea National University of Transportation, Jeungpyung 368-701, Korea.

We evaluated a more practical and cost-effective immobilization carriers for ethanol production using the yeast Saccharomyces cerevisiae. Three candidate materials-rice hull, rice straw, and sawdust-were tested for their cell-adsorption capacity and operational durability. Derivatizations of rice hull, rice straw, and sawdust with the optimal concentration of 0.5 M of 2-(diethylamino)ethyl chloride hydrochloride (DEAE · HCl) resulted in > 95% adsorption of the initial yeast cells at 2 hr for DEAE-rice hull and DEAE-sawdust and in only approximately 80% adsorption for DEAE-rice straw. In addition, DEAE-sawdust was found to be a more practical carrier for immobilizing yeast cells in terms of operational durability in shaking flask cultures with two different speeds of 60 and 150 rpm. Furthermore, the biosorption isotherms of DEAE-rice hull, -rice straw, and -sawdust for yeast cells revealed that the Qmax of DEAE-sawdust (82.6 mg/g) was greater than that of DEAE-rice hull and DEAE-rice straw. During the 404-hr of continuous column reactor operation using yeast cells immobilized on DEAE-sawdust, no serious detachment of the yeast cells from the DEAE-sawdust was recorded. Ethanol yield of approximately 3.04 g/L was produced steadily, and glucose was completely converted to ethanol at a yield of 0.375 g-ethanol/g-glucose (73.4% of the theoretical value). Thus, sawdust is a promising practical immobilization carrier for ethanol production, with significance in the production of bioethanol as a biofuel.
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http://dx.doi.org/10.5941/MYCO.2014.42.3.249DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4206790PMC
September 2014

Ethanol production from glycerol using immobilized Pachysolen tannophilus during microaerated repeated-batch fermentor culture.

J Microbiol Biotechnol 2015 Mar;25(3):366-74

Department of Biotechnology, Korea National University of Transportation, Jeungpyung 368-701, Republic of Korea.

Herein, we established a repeated-batch process for ethanol production from glycerol by immobilized Pachysolen tannophilus. The aim of this study was to develop a more practical and applicable ethanol production process for biofuel. In particular, using industrial-grade medium ingredients, the microaeration rate was optimized for maximization of the ethanol production, and the relevant metabolic parameters were then analyzed. The microaeration rate of 0.11 vvm, which is far lower than those occurring in a shaking flask culture, was found to be the optimal value for ethanol production from glycerol. In addition, it was found that, among those tested, Celite was a more appropriate carrier for the immobilization of P. tannophilus to induce production of ethanol from glycerol. Finally, through a repeated-batch culture, the ethanol yield (Ye/g) of 0.126 ± 0.017 g-ethanol/g-glycerol (n = 4) was obtained, and this value was remarkably comparable with a previous report. In the future, it is expected that the results of this study will be applied for the development of a more practical and profitable long-term ethanol production process, thanks to the industrial-grade medium preparation, simple immobilization method, and easy repeated-batch operation.
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http://dx.doi.org/10.4014/jmb.1409.09030DOI Listing
March 2015

Escherichia coli β-galactosidase-catalyzed synthesis of 2-phenoxyethanol galactoside and its characterization.

Bioprocess Biosyst Eng 2015 Feb 13;38(2):365-72. Epub 2014 Sep 13.

Department of Biotechnology, Korea National University of Transportation, Jeungpyung, Chungbuk, 368-701, Republic of Korea,

We synthesized 2-phenoxyethanol galactoside (PE-Gal) from 2-phenoxyethanol (PE), in which Escherichia coli β-gal (as E. coli cells) and lactose were added in the reaction mixture for galactosylation. About 40 mM PE-Gal was maximally synthesized from about 80 mM PE at 24 h as about 50% conversion yield. After purifying PE-Gal, the structure of PE-Gal was identified using LC-MS, (1)H NMR, and (13)C NMR analyses. In addition, it was observed that the water solubility of PE-Gal was increased by galactosylation of PE. The MICs of PE and PE-Gal against Gram-negative and Gram-positive bacteria were fairly similar with each other (23.3-61.3 mM as the average value). PE-Gal was noticeably less cytotoxic against HACAT cells, in particular a remarkable difference in cell viability was observed at concentrations of 20-60 mM PE or PE-Gal. Finally, we accomplished the synthesis of less toxic PE-Gal, compared with PE, using β-gal-containing E. coli cells without changing in the MICs against microorganisms. In the future, PE-Gal will be applicable as a substitute for PE as a less toxic preservative for the cosmetic, pharmaceutical, and food industries.
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http://dx.doi.org/10.1007/s00449-014-1276-4DOI Listing
February 2015

Enzymatic synthesis of 2-phenoxyethanol galactoside by whole cells of β-galactosidase-containing Escherichia coli.

J Microbiol Biotechnol 2014 Sep;24(9):1254-9

Department of Biotechnology, Korea National University of Transportation, Chungbuk 368-701, Republic of Korea.

We investigated whether β-galactosidase (β-gal)-containing Escherichia coli cells could transfer a galactose to 2-phenoxyethanol, resulting in 2-phenoxyethanol galactoside (PE-Gal). PE-Gal was confirmed by liquid chromatography-mass spectrometry. In addition, we also confirmed that a galactose molecule was covalently bonded with PE during thin-layer chromatography analysis of the β-gal hydrolysate of PE-Gal. The yield for PE-Gal synthesis was about 37.5% (weight basis), which was about 7-8 times greater than that of a previous report. In addition, the concentration of β-gal (0.96 U/ml) used in this PE-Gal synthesis was about 20 times less than that in a previous report.
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http://dx.doi.org/10.4014/jmb.1404.04004DOI Listing
September 2014

Febuxostat contributes to improvement of endothelial dysfunction in an experimental model of streptozocin-induced diabetic rats.

Int J Cardiol 2014 Feb 22;171(3):e110-2. Epub 2013 Dec 22.

Department of Cardiology, Kyung Hee University Hospital, Kyung Hee University, Seoul, Republic of Korea. Electronic address:

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http://dx.doi.org/10.1016/j.ijcard.2013.12.023DOI Listing
February 2014

Two-step process using immobilized Saccharomyces cerevisiae and Pichia stipitis for ethanol production from Ulva pertusa Kjellman hydrolysate.

J Microbiol Biotechnol 2013 Oct;23(10):1434-44

Department of Biotechnology, Korea National University of Transportation, Jeungpyung, 368-701, Republic of Korea.

We established a two-step production process using immobilized S. cerevisiae and P. stipitis yeast to produce ethanol from seaweed (U. pertusa Kjellman) hydrolysate. The process was designed to completely consume both glucose and xylose. In particular, the yeasts were immobilized using DEAE-corncob and DEAE-cotton, respectively. The first step of the process included a continuous column reactor using immobilized S. cerevisiae, and the second step included a repeated-batch reactor using immobilized P. stipitis. It was verified that the glucose and xylose in 20 L of medium containing the U. pertusa Kjellman hydrolysate was converted completely to about 5.0 g/l ethanol through the two-step process, in which the overall ethanol yield from total reducing sugar was 0.37 and the volumetric ethanol productivity was 0.126 g/ l/h. The volumetric ethanol productivity of the two-step process was about 2.7 times greater than that when P. stipitis was used alone for ethanol production from U. pertusa Kjellman hydrolysate. In addition, the overall ethanol yield from glucose and xylose was superior to that when P. stipitis was used alone for ethanol production. This two-step process will not only contribute to the development of an integrated process for ethanol production from glucose and xylose-containing biomass hydrolysates, but could also be used as an alternative method for ethanol production.
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http://dx.doi.org/10.4014/jmb.1304.04014DOI Listing
October 2013

Production of chlorphenesin galactoside by whole cells of β-galactosidase-containing Escherichia coli.

J Microbiol Biotechnol 2013 Jun;23(6):826-32

Department of Biotechnology, Korea National University of Transportation, Jeungpyung, Chungbuk 368-701, Korea.

We investigated the transgalactosylation reaction of chlorphenesin (CPN) using β-galactosidase (β-gal)-containing Escherichia coli (E. coli) cells, in which galactose from lactose was transferred to CPN. The optimal CPN concentration for CPN galactoside (CPN-G) synthesis was observed at 40 mM under the conditions that lactose and β-gal (as E. coli cells) were 400 g/l and 4.8 U/ml, respectively, and the pH and temperature were 7.0 and 40oC, respectively. The time-course profile of CPN-G synthesis under these optimal conditions showed that CPN-G synthesis from 40 mM CPN reached a maximum of about 27 mM at 12 h. This value corresponded to an about 67% conversion of CPN to CPN-G, which was 4.47-5.36-fold higher than values in previous reports. In addition, we demonstrated by thin-layer chromatography to detect the sugar moiety that galactose was mainly transferred from lactose to CPN. Liquid chromatography-mass spectrometry revealed that CPN-G and CPN-GG (CPN galactoside, which accepted two galactose molecules) were definitively identified as the synthesized products using β-gal-containing E. coli cells. In particular, because we did not use purified β-gal, our β-gal-containing E. coli cells might be practical and cost-effective for enzymatically synthesizing CPN-G. It is expected that the use of β-gal-containing E. coli will be extended to galactose derivatization of other drugs to improve their functionality.
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http://dx.doi.org/10.4014/jmb.1211.11009DOI Listing
June 2013

β-galactosidase-catalyzed synthesis of galactosyl chlorphenesin and its characterization.

Appl Biochem Biotechnol 2013 Nov 7;171(6):1299-312. Epub 2013 Apr 7.

Department of Biotechnology, Korea National University of Transportation, Jeungpyung, Chungbuk, 368-701, Republic of Korea.

We synthesized galactosyl chlorphenesin (CPN-G) using β-gal-containing Escherichia coli (E. coli) cells in which the conversion yield of chlorphenesin (CPN) to CPN-G reached about 64 % during 12 h. CPN-G was identified and characterized using high-performance liquid chromatography, liquid chromatography-mass spectrometry, Fourier transform-infrared spectrometry, and nuclear magnetic resonance analysis ((1)H and (13)C). We verified that a galactose was covalently bound to a CPN alcohol group during CPN-G synthesis throughout these analyses. In particular, by the hydrolysis of CPN-G using β-gal, it was confirmed that a galactose was bound to CPN. The minimal inhibitory concentration (MIC) results showed that the CPN-G MICs were fairly similar to those of CPN. HACAT cell viability was significantly higher in CPN-G-treated cells than in CPN-treated cells at concentrations of 0.0-20.0 mM. Finally, we accomplished the synthesis of less toxic CPN-G, compared with CPN, using β-gal-containing E. coli cells as whole cells without changes in the MICs against microorganisms.
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http://dx.doi.org/10.1007/s12010-013-0213-3DOI Listing
November 2013

Stable isolation of phycocyanin from Spirulina platensis associated with high-pressure extraction process.

Int J Mol Sci 2013 Jan 16;14(1):1778-87. Epub 2013 Jan 16.

Department of Medical Biomaterials Engineering, Kangwon National University, Chuncheon 200-701, Korea.

A method for stably purifying a functional dye, phycocyanin from Spirulina platensis was developed by a hexane extraction process combined with high pressure. This was necessary because this dye is known to be very unstable during normal extraction processes. The purification yield of this method was estimated as 10.2%, whose value is 3%-5% higher than is the case from another conventional separation method using phosphate buffer. The isolated phycocyanin from this process also showed the highest purity of 0.909 based on absorbance of 2.104 at 280 nm and 1.912 at 620 nm. Two subunits of phycocyanin namely α-phycocyanin (18.4 kDa) and β-phycocyanin (21.3 kDa) were found to remain from the original mixtures after being extracted, based on SDS-PAGE analysis, clearly demonstrating that this process can stably extract phycocyanin and is not affected by extraction solvent, temperature, etc. The stability of the extracted phycocyanin was also confirmed by comparing its DPPH (α,α-diphenyl-β-picrylhydrazyl) scavenging activity, showing 83% removal of oxygen free radicals. This activity was about 15% higher than that of commercially available standard phycocyanin, which implies that the combined extraction method can yield relatively intact chromoprotein through absence of degradation. The results were achieved because the low temperature and high pressure extraction effectively disrupted the cell membrane of Spirulina platensis and degraded less the polypeptide subunits of phycocyanin (which is a temperature/pH-sensitive chromoprotein) as well as increasing the extraction yield.
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http://dx.doi.org/10.3390/ijms14011778DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565347PMC
January 2013

Preparation of corncob grits as a carrier for immobilizing yeast cells for ethanol production.

J Microbiol Biotechnol 2012 Dec;22(12):1673-80

Department of Biotechnology, Chungju National University, Jeungpyung, Chungbuk, Korea.

In this study, DEAE-corncobs [delignified corncob grits derivatized with 2-(diethylamino)ethyl chloride hydrochloride (DEAE·HCl)] were prepared as a carrier to immobilize yeast (Saccharomyces cerevisiae) for ethanol production. The immobilized yeast cell reactor produced ethanol under optimized DEAE·HCl derivatization and adsorption conditions between yeast cells and the DEAE-corncobs. When delignified corncob grit (3.0 g) was derivatized with 0.5M DEAE·HCl, the yeast cell suspension (OD600 = 3.0) was adsorbed at >90% of the initial cell OD600. This amount of adsorbed yeast cells was estimated to be 5.36 mg-dry cells/g-DEAE corncobs. The Qmax (the maximum cell adsorption by the carrier) of the DEAE-corncobs was estimated to be 25.1 (mg/g), based on a Languir model biosorption isotherm experiment. When we conducted a batch culture with medium recycling using the immobilized yeast cells, the yeast cells on DEAE-corncobs produced ethanol gradually, according to glucose consumption, without cells detaching from the DEAE-corncobs. We observed under electron microscopy that the yeast cells grew on the surface and in the holes of the DEAEcorncobs. In a future study, DEAE-corncobs and the immobilized yeast cell reactor system will contribute to bioethanol production from biomass hydrolysates.
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http://dx.doi.org/10.4014/jmb.1202.02049DOI Listing
December 2012

Long-term repeated-batch operation of immobilized Escherichia coli cells to synthesize galactooligosaccharide.

J Microbiol Biotechnol 2012 Nov;22(11):1486-93

Department of Biotechnology, Korea National University of Transportation, Jeungpyung, Chungbuk 368-701, Korea.

In this study, we investigated whether galactooligosaccharide (GOS) can be stably and steadily synthesized using immobilized beta-galactosidase (β-gal) inclusion body (IB)- containing E. coli cells during long-term repeated-batch operation. To improve the operational stability of this enzyme reactor system, immobilized E. coli cells were crosslinked with glutaraldehyde (GA) after immobilization of the E. coli. When we treated with 2% GA for E. coli crosslinking, GOS production continued to an elapsed time of 576 h, in which seven batch runs were operated consecutively. GOS production ranged from 51.6 to 78.5 g/l (71.2 ± 10.5 g/l, n = 7) during those batch operations. In contrast, when we crosslinked E. coli with 4% GA, GOS production ranged from 31.5 to 64.0 g/l (52.3 ± 10.8, n = 4), and only four consecutive batch runs were operated. Although we did not use an industrial β-gal for GOS production, in which a thermophile is used routinely, this represents the longest operation time for GOS production using E. coli β-gal. Improved stability and durability of the cell immobilization system were achieved using the crosslinking protocol. This strategy could be directly applied to other microbial enzyme reactor systems using cell immobilization to extend the operation time and/or improve the reactor system stability.
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http://dx.doi.org/10.4014/jmb.1204.04020DOI Listing
November 2012

Development of a practical and cost-effective medium for bioethanol production from the seaweed hydrolysate in surface-aerated fermentor by repeated-batch operation.

J Microbiol Biotechnol 2012 Jan;22(1):107-13

Department of Biotechnology, Chungju National University, Jeungpyung, Chungbuk 368-701, Korea.

To develop a practical and cost-effective medium for bioethanol production from the hydrolysate of seaweed Sargassum sagamianum, we investigated the feasibility and performance of bioethanol production in CSL (cornsteep liquor)-containing medium, where yeast Pichia stipitis was used and the repeated batch was carried out in a surface-aerated fermentor. The optimal medium replacement time during the repeated operation was determined to be 36 h, and the surface aeration rates were 30 and 100 ml/min. Under these conditions, the repeatedbatch operation was successfully carried out for 6 runs (216 h), in which the maximum bioethanol concentrations reached about 11-12 g/l at each batch operation. These results demonstrated that bioethanol production could be carried out repeatedly and steadily for 216 h. In these experiments, the total cumulative bioethanol production was 57.9 g and 58.0 g when the surface aeration rates were 30 ml/min and 100 ml/min, respectively. In addition, the bioethanol yields were 0.43 (about 84% of theoretical value) and 0.44 (about 86% of theoretical value) when the surface aeration rates were 30 ml/min and 100 ml/min, respectively. CSL was successfully used as a medium ingredient for the bioethanol production from the hydrolysate of seaweed Sargassum sagamianum, indicating that this medium may be practical and cost-effective for bioethanol production.
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http://dx.doi.org/10.4014/jmb.1106.06019DOI Listing
January 2012

Platelet reactivity in patients with chronic kidney disease receiving adjunctive cilostazol compared with a high-maintenance dose of clopidogrel: results of the effect of platelet inhibition according to clopidogrel dose in patients with chronic kidney disease (PIANO-2 CKD) randomized study.

Am Heart J 2011 Dec 8;162(6):1018-25. Epub 2011 Nov 8.

Department of Internal Medicine, Division of Cardiology, School of Medicine, Kyung Hee University, Seoul, Republic of Korea.

Background: Chronic kidney disease (CKD) is a factor of low response to clopidogrel. We sought to assess the functional impact of cilostazol in CKD patients with undergoing hemodialysis.

Methods: Seventy-four patients with CKD undergoing hemodialysis and percutaneous coronary intervention were enrolled. Patients were randomly assigned to receive clopidogrel (75 mg/d [group 1, n = 24]), high-maintenance dose of clopidogrel (150 mg/d [group 2, n = 25]), or clopidogrel (75 mg/d) with cilostazol (200 mg/d [group 3, n = 25]) for 14 days. Another 50 patients with normal renal function undergoing percutaneous coronary intervention were treated with 75 mg of clopidogrel and served as the control group. Platelet function was evaluated before and after antiplatelet therapy with light transmittance aggregometry and with VerifyNow P2Y12 assay (Accumetrics, San Diego, CA). Platelet activation markers (soluble CD40 ligand and soluble P-selectin) were also assessed.

Results: The baseline platelet function measurements were similar in the 3 groups of patients; however, the CKD groups had significantly higher platelet aggregation activity compared with the control groups. The rate of high on-treatment platelet reactivity was significantly lower in group 3 than in groups 1 and 2 (10% vs 43% vs 32%, respectively; P < .05). After 14 days of antiplatelet therapy, the changes in plasma soluble CD40 ligand and soluble P-selectin levels were significantly higher in group 3 compared with groups 1 and 2 (P < .01); however, there were no significant differences in platelet function and activation markers between groups 1 and 2.

Conclusions: Adjunctive cilostazol improves platelet inhibition compared with 75 or 150 mg of clopidogrel in CKD patients undergoing hemodialysis.
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http://dx.doi.org/10.1016/j.ahj.2011.09.003DOI Listing
December 2011

Galactooligosaccharide synthesis by active β-galactosidase inclusion bodies-containing Escherichia coli cells.

J Microbiol Biotechnol 2011 Nov;21(11):1151-8

Department of Biotechnology, Chungju National University, Jeungpyung, Chungbuk 368-701, Republic of Korea.

In this study, galactooligosaccharide (GOS) was synthesized using active β-galactosidase (beta-gal) inclusion bodies (IBs)- containing Escherichia coli (E. coli) cells. Analysis by MALDI-TOF (matrix-assisted laser desorption/ionizationtime of flight) mass spectrometry revealed that a trisaccharide was the major constituent of the synthesized GOS mixture. Additionally, the optimal pH, lactose concentration, amounts of E. coli β-gal IBs, and temperature for GOS synthesis were 7.5, 500 g/l, 3.2 U/ml, and 37 °C, respectively. The total GOS yield from 500 g/l of lactose under these optimal conditions was about 32%, which corresponded to 160.4 g/l of GOS. Western blot analyses revealed that β-gal IBs were gradually destroyed during the reaction. In addition, when both the reaction mixture and E. coli β-gal hydrolysate were analyzed by high-performance thin-layer chromatography (HP-TLC), the trisaccharide was determined to be galactosyl lactose, indicating that a galactose moiety was most likely transferred to a lactose molecule during GOS synthesis. This GOS synthesis system might be useful for the synthesis of galactosylated drugs, which have recently received significant attention owing to the ability of the galactose molecules to improve the drugs solubility while decreasing their toxicity. β-Gal IB utilization is potentially a more convenient and economic approach to enzymatic GOS synthesis, since no enzyme purification steps after the transgalactosylation reaction would be required.
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http://dx.doi.org/10.4014/jmb.1105.05021DOI Listing
November 2011

Complete genome sequence of strain s85, a novel member of the family Flavobacteriaceae.

J Bacteriol 2011 Nov;193(21):6107

Korea Ocean Research & Development Institute, Ansan 426-744, Republic of Korea.

An agar-degrading marine bacterium identified as a novel member of the family Flavobacteriaceae (strain S85) was isolated from seawater in Micronesia. The sequenced strain S85 genome is composed of 3,384,629 bp in a circular chromosome, which includes 2,883 complete open reading frames.
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http://dx.doi.org/10.1128/JB.05993-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3194900PMC
November 2011

Repeated-batch operation of immobilized β-galactosidase inclusion bodies-containing Escherichia coli cell reactor for lactose hydrolysis.

J Microbiol Biotechnol 2011 Sep;21(9):972-8

Department of Biotechnology, Chungju National University, Jeungpyung, Chungbuk 368-701, Korea.

In this study, we investigated the performance of an immobilized β-galactosidase inclusion bodies-containing Escherichia coli cell reactor, where the cells were immobilized in alginate beads, which were then used in repeated-batch operations for the hydrolysis of o-nitrophenyl-β-D-galactoside or lactose over the long-term. In particular, in the Tris buffer system, disintegration of the alginate beads was not observed during the operation, which was observed for the phosphate buffer system. The o-nitrophenyl-β-D-galactoside hydrolysis was operated successfully up to about 80 h, and the runs were successfully repeated at least eight times. In addition, hydrolysis of lactose was successfully carried out up to 240 h. Using Western blotting analyses, it was verified that the beta-galactosidase inclusion bodies were sustained in the alginate beads during the repeated-batch operations. Consequently, we experimentally verified that β-galactosidase inclusion bodies-containing Escherichia coli cells could be used in a repeated-batch reactor as a biocatalyst for the hydrolysis of o-nitrophenyl-β-D-galactoside or lactose. It is probable that this approach can be applied to enzymatic synthesis reactions for other biotechnology applications, particularly reactions that require long-term and stable operation.
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http://dx.doi.org/10.4014/jmb.1104.04029DOI Listing
September 2011

Repeated-batch operation of surface-aerated fermentor for bioethanol production from the hydrolysate of seaweed Sargassum sagamianum.

J Microbiol Biotechnol 2011 Mar;21(3):323-31

Department of Biotechnology, Chungju National University, Jeungpyung, Chungbuk, Korea.

In this study, we investigated the feasibility of sustainable long-term bioethanol production from the hydrolysate of a brown seaweed, Sargassum sagamianum. Because the hydrolysate was prepared as a liquid solution using a hightemperature liquefying system, a repeated-batch operation was utilized as the operational strategy for bioethanol production. Additionally, we used surface aeration to improve bioethanol production from the hydrolysate containing C5 monosaccharides such as xylose. In this study, the C5 monosaccharide-utilizable yeast strain Pichia stipitis was used for bioethanol production. Therefore, based on this repeated-batch flask culture, we designed a surface-aerated repeated-batch fermentor culture, in which the aeration was finely controlled at 100 ml/min and delivered into the headspace of a 2.5-l fermentor. When the medium was replaced every 48 h, bioethanol was continuously produced for 200 h under repeated-batch fermentor culture, where the level of bioethanol production was about 9~10 (g/l). Additionally, the bioethanol yield based on the reducing sugar was about 0.386, which was the average value throughout four consecutive cultures and was about 74.5% of the theoretical value. In addition, the bioethanol yield based on quantitative TLC analyses of glucose and xylose was about 0.431, which was the average value throughout four consecutive cultures and was about 84.3% of theoretical value. Consequently, throughout this repeated-batch operation, we demonstrated that it was actually feasible to produce bioethanol from the hydrolysate of seaweed S. sagamianum. In addition, the approach described here is a practical strategy for commercial bioethanol production from seaweed, particularly for finely controlling aeration through surface aeration.
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March 2011

Preparation of branched dextran microspheres of soluble interferon-alpha and its activity in vitro and in vivo.

J Microbiol Biotechnol 2011 Feb;21(2):176-82

Department of Medical Genetic Engineering, Keimyung University School of Medicine, Daegu 700-712, Korea.

The study objective was to prepare biodegradable branched dextran microspheres encapsulated with His-tagged interferon-alpha (BDM-hIFN-alpha) and evaluate its activity in vitro and in vivo. The glycidyl methacrylate derivatized dextrans (Dex-GMA) as precursor was primarily synthesized by substituting hydroxyl groups of either the branched or linear type of dextran with GMA. Dex-GMA microspheres loaded with hIFN-alpha was then prepared by the water-in-water emulsion technique. In vitro release and Western blotting experiments demonstrated the retained activity of hIFN-alpha released from branched dextran microspheres at 24 h by inducing phosphorylation of signal transducer and activator transcription-1 (STAT-1), a down-stream effector of IFN-alpha, in HepG2 cells. Animal data further revealed a peak of plasma levels of IFN-alpha in rats injected intravenously with BDM-hIFN-alpha at 10 min post-injection, but a sharp decline at 2 h. High plasma levels of neopterin, a plasma protein induced by IFN-alpha, were also detected in rats injected with BDM-hIFN-alpha at 10 min post-injection. Notably, plasma levels of neopterin remained high at 4 h, but largely declined thereafter.
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http://dx.doi.org/10.4014/jmb.1007.07060DOI Listing
February 2011

Bioethanol production from the hydrolysate of rape stem in a surface-aerated fermentor.

J Microbiol Biotechnol 2011 Jan;21(1):109-14

Department of Biotechnology, Chungju National University, Jeungpyung, Chungbuk 368-701, Korea.

In this study, we investigated the feasibility of producing bioethanol from the hydrolysate of rape stem. Specifically, the most ideal yeast strain was screened, and the microaeration was performed by surface aeration on a liquid medium surface. Among the yeast strains examined, Pichia stipitis CBS 7126 displayed the best performance in bioethanol production during the surface-aerated fermentor culture. Pichia stipitis CBS 7126 produced maximally 9.56 g/l of bioethanol from the initial total reducing sugars (about 28 g/l). The bioethanol yield was 0.397 (by the DNS method). Furthermore, this controlled surface aeration method holds promise for use in the bioethanol production from the xylose-containing lignocellulosic hydrolysate of biomass.
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http://dx.doi.org/10.4014/jmb.1008.08001DOI Listing
January 2011

Ultraviolet A regulates adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells via up-regulation of Kruppel-like factor 2.

J Biol Chem 2010 Oct 8;285(42):32647-56. Epub 2010 Aug 8.

Biospectrum Life Science Institute, Seongnam-Si, Gyunggi-Do 462-807, Republic of Korea.

Adipocyte dysfunction is strongly associated with the development of obesity, which is a major risk factor for many disorders, including diabetes, hypertension, and heart disease. This study shows that ultraviolet A (UVA) inhibits adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells and its action mechanisms. The mRNA levels of peroxidase proliferator-activated receptor (PPAR) γ and CCAAT/enhancer-binding protein α (C/EBPα), but not CCAAT/enhancer-binding protein ((C/EBP) β and δ, were reduced by UVA. Moreover, the mRNA levels of PPAR γ target genes (lipoprotein lipase (LPL), CD36, adipocyte protein (aP2), and liver X receptor α (LXR)) were down-regulated by UVA. Additionally, attempts to elucidate a possible mechanism underlying the UVA-mediated effects revealed that UVA induced migration inhibitory factor (MIF) gene expression, and this was mediated through activation of AP-1 (especially JNK and p42/44 MAPK) and nuclear factor-κB. In addition, reduced adipogenesis by UVA was recovered upon the treatment with anti-MIF antibodies. AMP-activated protein kinase phosphorylation and up-regulation of Kruppel-like factor 2 (KLF2) were induced by UVA. Taken together, these findings suggest that the inhibition of adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells by UVA occurs primarily through the reduced expression of PPAR γ, which is mediated by up-regulation of KLF2 via the activation of MIF-AMP-activated protein kinase signaling.
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http://dx.doi.org/10.1074/jbc.M110.135830DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2952267PMC
October 2010

c-Jun N-terminal kinase 1 is required for cordycepin-mediated induction of G2/M cell-cycle arrest via p21WAF1 expression in human colon cancer cells.

Food Chem Toxicol 2010 Jan 13;48(1):277-83. Epub 2009 Oct 13.

Department of Food and Biotechnology, Chungju National University, Chungju, Chungbuk 380-702, South Korea.

Cordycepin (3'-deoxyadenosine) has many anti-cancer properties. However, neither its molecular mechanism nor its molecular targets are well understood. In the present study, we investigated novel molecular mechanisms for the anti-tumor effects of cordycepin in human colon cancer HCT116 cells. After treatment of cells with cordycepin, dose-dependent cell growth inhibition was observed at an IC(50) value of 200muM. Cordycepin treatment resulted in G2/M-phase cell-cycle arrest, which was associated with increased p21WAF1 levels and reduced amounts of cyclin B1, Cdc2, and Cdc25c in a p53-independent pathway. Moreover, cordycepin treatment induced activation of JNK (c-Jun N-terminal kinases). Pretreatment with SP600125, a JNK-specific inhibitor, abrogated cordycepin-mediated p21WAF1 expression, cell growth inhibition, and reduced cell-cycle proteins. Furthermore, JNK1 inhibition by small interfering RNA (siRNA) produced similar results: suppression of cordycepin-induced p21WAF1 expression, decreased cell growth, and reduced cell-cycle proteins. Together, these results suggest a critical role for JNK1 activation in cordycepin-induced inhibition of cell growth and G2/M-phase arrest in human colon cancer cells.
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http://dx.doi.org/10.1016/j.fct.2009.09.042DOI Listing
January 2010

Improved Bioethanol Production Using Activated Carbon-treated Acid Hydrolysate from Corn Hull in Pachysolen tannophilus.

Mycobiology 2009 Jun 30;37(2):133-40. Epub 2009 Jun 30.

Division of Food and Biotechnology, Chungju National University, Jeungpyung, Chungbuk 368-701, Korea.

To optimally convert corn hull, a byproduct from corn processing, into bioethanol using Pachysolen tannophlius, we investigated the optimal conditions for hydrolysis and removal of toxic substances in the hydrolysate via activated carbon treatment as well as the effects of this detoxification process on the kinetic parameters of bioethanol production. Maximum monosaccharide concentrations were obtained in hydrolysates in which 20 g of corn hull was hydrolyzed in 4% (v/v) H2SO4. Activated carbon treatment removed 92.3% of phenolic compounds from the hydrolysate. When untreated hydrolysate was used, the monosaccharides were not completely consumed, even at 480 h of culture. When activated carbon-treated hydrolysate was used, the monosaccharides were mostly consumed at 192 h of culture. In particular, when activated carbon-treated hydrolysate was used, bioethanol productivity (P) and specific bioethanol production rate (Qp) were 2.4 times and 3.4 times greater, respectively, compared to untreated hydrolysate. This was due to sustained bioethanol production during the period of xylose/arabinose utilization, which occurred only when activated carbon-treated hydrolysate was used.
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http://dx.doi.org/10.4489/MYCO.2009.37.2.133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3749403PMC
June 2009

Sanguinarine induces apoptosis in A549 human lung cancer cells primarily via cellular glutathione depletion.

Toxicol In Vitro 2009 Mar 24;23(2):281-7. Epub 2008 Dec 24.

Department of Medical Genetic Engineering, Keimyung University School of Medicine, 194 Dongsan-dong, Jung-gu, Daegu 700-712, Republic of Korea.

Sanguinarine is a plant-derived benzophenanthridine alkaloid and has been shown to possess anti-tumor activities against various cancer cells. In this study, we investigated whether sanguinarine induces apoptosis in A549 human lung cancer cells. Treatment of A549 cells with sanguinarine induced apoptosis in a dose- and time-dependent manner. Treatment with sanguinarine led to activation of caspases and MAPKs as well as increased MKP-1 expression. Importantly, pretreatment with z-VAD-fmk, a pan caspase inhibitor suppressed the sanguinarine-induced apoptosis in A549 cells. Moreover, pretreatment with NAC, a sulfhydryl group-containing reducing agent strongly suppressed the apoptotic response and caspase activation to sanguinarine. However, the sanguinarine-mediated cytotoxicity in A549 cells was not protected by pharmacological inhibition of MAPKs or MKP-1 siRNA-mediated knockdown of MKP-1. These results collectively suggest that sanguinarine induces apoptosis in A549 cells through cellular glutathione depletion and the subsequent caspase activation.
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http://dx.doi.org/10.1016/j.tiv.2008.12.013DOI Listing
March 2009

Inhibitory effects of the aqueous extract of Magnolia officinalis on the responses of human urinary bladder cancer 5637 cells in vitro and mouse urinary bladder tumors induced by N-Butyl-N-(4-hydroxybutyl) nitrosamine in vivo.

Phytother Res 2009 Jan;23(1):20-7

Department of Food and Biotechnology, Chungju National University, Chungju, Chungbuk 380-702, South Korea.

This study investigated the anticancer activity of Magnolia officinalis on urinary bladder cancer in vitro and in vivo, and elucidated the mechanism of its activity. An aqueous extract of M. officinalis inhibited cell viability and DNA synthesis in cultured human urinary bladder cancer 5637 cells. Inhibition of proliferation was the result of apoptotic induction, because FACS analyses of 5637 cells treated with M. officinalis showed a sub-G1 phase accumulation. M. officinalis extract also increased cytoplasmic DNA-histone complex dose-dependently. These inhibitory effects were associated with the upregulation of proapoptotic molecules Bax, cytochrome c and caspase 3. Treatment of 5637 cells with M. officinalis extract suppressed the expression of matrix metalloproteinase 2 (MMP-2) and MMP-9, as revealed by zymographic and immunoblot analyses. When M. officinalis extract was given to mice simultaneously with the carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine, which induces urinary bladder tumors, the size of the induced tumors was smaller. Finally, histological data indicated that the histological grade of carcinoma and the depth of invasion were dramatically decreased by treatment with M. officinalis extract in mice with N-butyl-N-(4-hydroxybutyl) nitrosamine-induced urinary bladder tumors. In conclusion, the findings showed that M. officinalis extract exhibited potential chemopreventive activity against urinary bladder tumor in vitro and in vivo.
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http://dx.doi.org/10.1002/ptr.2413DOI Listing
January 2009