• Polymer(Korea)
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• v.32 no.4
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• pp.385-389
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• 2008

Chain propagation and chain transfer in anionic polymerization of hexafluoropropylene oxide were investigated under various reaction conditions such as the stabilization of reaction temperature, the amount of hexafluoropropylene solvent, and the feeding rate of hexafluoropropylene oxide monomer. Anionic initiator for the polymerization was synthesized from cesium fluoride and hexafluoropropylene oxide in tetraethyleneglycol dimethylether. It was possible to obtain a high molecular weight poly(HFPO) ($M_w$ 14800) using the anionic initiator in conditions of stabilized reaction temperature, and optimized addition of solvent and monomer feeding (HFP/initiator mole ratio=31.5 and HFPO feeding rate=11.67 g/hr). Otherwise, chain transfer reaction in anionic polymerization was increased. From the results of molecular weight in various reaction conditions, it was found that chain propagation and chain transfer in anionic polymerization of HFPO were very sensitive to reaction conditions.

• Journal of Microbiology and Biotechnology
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• v.32 no.4
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• pp.464-472
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• 2022

An endo-polygalacturonase (endo-PGase) exhibiting excellent performance during acidic fruit juice production would be highly attractive to the fruit juice industry. However, candidate endo-PGases for this purpose have rarely been reported. In this study, we expressed a gene from Penicillium oxalicum in Pichia pastoris. The recombinant enzyme PoxaEnPG28C had an optimal enzyme activity at pH 4.5 and 45℃ and was stable at pH 3.0-6.5 and < 45℃. The enzyme had a specific activity of 4,377.65 ± 55.37 U/mg towards polygalacturonic acid, and the K_m and V_max values of PoxaEnPG28C were calculated as 1.64 g/l and 6127.45 U/mg, respectively. PoxaEnPG28C increased the light transmittance of orange, lemon, strawberry and hawthorn juice by 13.9 ± 0.3%, 29.4 ± 3.8%, 95.7 ± 10.2% and 79.8 ± 1.7%, respectively; it reduced the viscosity of the same juices by 25.7 ± 1.6%, 52.0 ± 4.5%, 48.2 ± 0.7% and 80.5 ± 2.3%, respectively, and it increased the yield of the juices by 24.5 ± 0.7%, 12.7 ± 2.2%, 48.5 ± 4.2% and 104.5 ± 6.4%, respectively. Thus, PoxaEnPG28C could be considered an excellent candidate enzyme for acidic fruit juice production. Remarkably, fruit juice production using hawthorn as an material was reported for the first time.

• Mass Spectrometry Letters
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• v.4 no.1
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• pp.1-9
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• 2013

Fungal biotechnology has been well established in food and healthcare sector, and now being explored for lignocellulosic biorefinery due to their great potential to produce a wide array of extracellular enzymes for nutrient recycling. Due to global warming, environmental pollution, green house gases emission and depleting fossil fuel, fungal enzymes for lignocellulosic biomass refinery become a major focus for utilizing renewal bioresources. Proteomic technologies tender better biological understanding and exposition of cellular mechanism of cell or microbes under particular physiological condition and are very useful in characterizing fungal secretome. Hence, in addition to traditional colorimetric enzyme assay, mass-spectrometry-based quantification methods for profiling lignocellulolytic enzymes have gained increasing popularity over the past five years. Majority of these methods include two dimensional gel electrophoresis coupled to mass spectrometry, differential stable isotope labeling and label free quantitation. Therefore, in this review, we reviewed more commonly used different proteomic techniques for profiling fungal secretome with a major focus on two dimensional gel electrophoresis, liquid chromatography-based quantitative mass spectrometry for global protein identification and quantification. We also discussed weaknesses and strengths of these methodologies for comprehensive identification and quantification of extracellular proteome.

• Journal of Microbiology and Biotechnology
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• v.26 no.7
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• pp.1242-1251
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• 2016

The ethanol production of Trichoderma reesei was improved by genome shuffling in our previous work. Using RNA-Seq, the transcriptomes of T. reesei wild-type CICC40360 and recombinant strain HJ48 were compared under fermentation conditions. Based on this analysis, we defined a set of T. reesei genes involved in ethanol production. Further expression analysis identified a series of glycolysis enzymes, which are upregulated in the recombinant strain HJ48 under fermentation conditions. The differentially expressed genes were further validated by qPCR. The present study will be helpful for future studies on ethanol fermentation as well as the roles of the involved genes. This research reveals several major differences in metabolic pathways between recombinant strain HJ48 and wild-type CICC40360, which relates to the higher ethanol production on the former, and their further research could promote the development of techniques for increasing ethanol production.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.189-194
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• 2013

A sulfonated activated carbon (AC-$SO_3H$) was used as a solid acid catalyst for dehydration of sorbitol to isosorbide and its catalytic performance was compared with the commercial solid acid such as acidic ion exchange resin, Amberlyst-36, and sulfated copper oxide. The catalytic performance with 100% sorbitol conversion and 52% isosorbide selectivity was obtained over AC-$SO_3H$ at 423.15 K. Although AC-$SO_3H$ possessed only 0.5 mmol/g of sulfur content, it showed the similar dehydration activity of sorbitol to isosorbide with Amberlyst-36 (5.4 mmol/g) at 423.15 K. Based on the high thermal and chemical stability of AC-$SO_3H$, one-step reactive distillation, where isosorbide separation can be carried out simultaneously with sorbitol dehydration, was tried to increase the recovery yield of isosobide from sorbitol. The reactive distillation process using AC-$SO_3H$, the turnover number of AC-$SO_3H$ was 4 times higher than the conventional two-step process using sulfuric acid.

• Journal of Integrative Natural Science
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• v.2 no.2
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• pp.73-77
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• 2009

Silyl-containing tetraphenylsilole, 1,1-bis(trisilyl)tetraphenylsilole, has been synthesized from the reaction of dichlorotetraphenylsilole and dichlorotrisilane and characterized by using NMR spectroscopy. Bis(trisilyl)tetraphenylsilole exhibits an unusual optical property and its optical property was characterized by UV-vis and fluorescence spectroscopy. Absorption wavelength maxima of bis(trisilyl)tetraphenylsilole was 380 nm. Bis(trisilyl)tetraphenylsilole displayed an emission band at 530 nm with an excitation wavelength of 380 nm.

• Korean Journal of Plant Resources
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• v.21 no.3
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• pp.222-225
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• 2008

Chemical composition and enzymatic saccharification characteristics of hemp woody core were investigated by their chemical composition analysis and enzymatic saccharification with commercially available cellulases (Celluclast 1.5L and Novozym 342). Hemp woody core have higher xylan and lower lignin contents than its bast fiber. Based on hemicelluloses and lignin composition, hemp woody core is similar with hardwood biomass. However, cellulose was more easily converted to glucose than xylan to xylose and this trend was confirmed both hemp woody core and yellow poplar. Hemp woody core biomass shows higher saccharification than yellow poplar (hardwood biomass) based on cellulose and xylan hydrolysis. With easier enzymatic saccharification in cellulose and xylan, and similar chemical composition, hemp woody core have better biorefinery feedstock characteristics than hardwood biomass.

• Journal of Microbiology and Biotechnology
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• v.24 no.6
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• pp.781-787
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• 2014

2-Ketogluconic acid production by Klebsiella pneumoniae is a pH-dependent process, strictly proceeding under acidic conditions. Unfortunately, cell growth is inhibited by acidic conditions, resulting in low productivity of 2-ketogluconic acid. To overcome this deficiency, a two-stage fermentation strategy was exploited in the current study. During the first stage, the culture was maintained at neutral pH, favoring cell growth. During the second stage, the culture pH was switched to acidic conditions favoring 2-ketogluconic acid accumulation. Culture parameters, including switching time, dissolved oxygen levels, pH, and temperature were optimized for the fed-batch fermentation. Characteristics of glucose dehydrogenase and gluconate dehydrogenase were revealed in vitro, and the optimal pHs of the two enzymes coincided with the optimum culture pH. Under optimum conditions, a total of 186 g/l 2-ketogluconic acid was produced at 26 h, and the conversion ratio was 0.98 mol/mol. This fermentation strategy has successfully overcome the mismatch between optimum parameters required for cell growth and 2-ketogluconic acid accumulation, and this result has the highest productivity and conversion ratio of 2-ketogluconic and produced by microorganism.

• Journal of Energy Engineering
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• v.22 no.3
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• pp.250-261
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• 2013

In order to overcome the 21st century's challenges such as national energy supply security, global warming, and resource depletion, we are struggling to accelerate the paradigm shift in our life style from fossil fuel-based economy to biomass-based economy. In the context of sustainable bioeconomy revitalization, we comprehensively review the development status of the biorefinery as a system for bioenergy/biochemicals co-products on the basis of the various categories according to six criteria.

• Journal of Microbiology and Biotechnology
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• v.31 no.10
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• pp.1455-1464
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• 2021

Trehalose is a non-reducing disaccharide in increasing demand for applications in food, nutraceutical, and pharmaceutical industries. Single-step trehalose production by trehalose synthase (TreS) using maltose as a starting material is a promising alternative process for industrial application due to its simplicity and cost advantage. Pseudomonas monteilii TBRC 1196 was identified using the developed screening method as a potent strain for TreS production. The TreS gene from P. monteilii TBRC 1196 was first cloned and expressed in Escherichia coli. Purified recombinant trehalose synthase (PmTreS) had a molecular weight of 76 kDa and showed optimal pH and temperature at 9.0 and 40℃, respectively. The enzyme exhibited >90% residual activity under mesophilic condition under a broad pH range of 7-10 for 6 h. Maximum trehalose yield by PmTreS was 68.1% with low yield of glucose (4%) as a byproduct under optimal conditions, equivalent to productivity of 4.5 g/l/h using enzyme loading of 2 mg/g substrate and high concentration maltose solution (100 g/l) in a lab-scale bioreactor. The enzyme represents a potent biocatalyst for energy-saving trehalose production with potential for inhibiting microbial contamination by alkaline condition.