CO and CO2 Methanation Over Supported Cobalt Catalysts

Le, T. A.,Kim, M. S.,Lee, S. H.,Park, E. D. Baltzer Science Publishers 2017 Topics in catalysis Vol.60 No.9

<P>CO and CO2 methanation was investigated over cobalt catalysts supported on different supports such as gamma-Al2O3, SiO2, TiO2, CeO2, and ZrO2. Among them, the cobalt catalyst supported on the high-surface-area CeO2 was determined to be the most active for both CO and CO2 methanation. These catalytic activities increased with increasing surface area of CeO2. To increase the specific catalytic activity for CO and CO2 methanation, various Co-CeO2 catalysts with different cobalt contents were prepared with co-precipitation method. The optimum cobalt content was determined for both reactions. The prepared catalysts were characterized with N-2 physisorption, temperature-programmed reduction with H-2, pulsed-chemisorption of CO2, temperature-programmed desorption of CO2, and X-ray diffraction. The high cobalt dispersion and strong CO2 adsorption appeared to be responsible for the high catalytic activity for CO and CO2 methanation, respectively. This Co-CeO2 also showed the stable catalytic activity even after an exposure to high-temperature reaction conditions.</P>

Development of thermostable lipase B from Candida antarctica (CalB) through in silico design employing B-factor and RosettaDesign

Kim, H.S.,Le, Q.A.T.,Kim, Y.H. IPC Science and Technology Press ; Elsevier Scienc 2010 Enzyme and microbial technology Vol.47 No.1

Organic synthesis reactions demand improved characteristics of enzymes than wild type such as reactivity, thermostability, enantioselectivity and so on. Especially thermostability of enzyme is highly important since reaction at higher temperature has many advantages such as elevated reaction rate and increased solubility of substrates. Due to this requirement, a rational approach was employed to develop thermostable CalB. The first step of this approach was the selection of appropriate sites showing a high 'B-factor' value. These sites were chosen on the basis of atomic displacement parameters obtained from X-ray data. These selected sites were then substituted with other amino acids that were determined to be more rigid than the original amino acids by computational modeling using 'RosettaDesign'. As a result of this rational approach, several thermostable CalB mutants including R249L were produced. The residual activity of R249L CalB was two times higher than that of wild type CalB at 55<SUP>o</SUP>. Melting temperature (T<SUB>m</SUB> of R249L mutant increased to 56.8<SUP>o</SUP> compared with wild type CalB (T<SUB>m</SUB> 54.5<SUP>o</SUP>), which was determined by DSF (differential scanning fluorimetry). Additionally, packing analysis tool ''Voronoia'' pointed out that one cavity close to residue 249 of wild type CalB disappeared in CalB R249L, which could be the reason for the increase in thermal stability of CalB R249L mutant compared wild type CalB.

Comparative study on the hemocytes of subtropical oysters Saccostrea kegaki (Torigoe & Inaba, 1981), Ostrea circumpicta (Pilsbry, 1904), and Hyotissa hyotis (Linnaeus, 1758) in Jeju Island, Korea: Morphology and functional aspects

Hong, H.K.,Kang, H.S.,Le, T.C.,Choi, K.S. Academic Press 2013 Fish & shellfish immunology Vol.35 No.6

We first characterized the morphology and immune-related activities of hemocytes in the subtropical oysters Saccostrea kegaki, Ostrea circumpicta, and Hyotissa hyotis using light microscopy and flow cytometry. Hemocytes of these three oyster species were classified into three main types: 1) granulocytes containing numerous granules in the cytoplasm, 2) hyalinocytes with no or fewer granules, and 3) blast-like cells characterized by the smallest size and very thin cytoplasm. The percentage of each hemocyte population was similar in all species; hyalinocytes were the most abundant cell in the hemolymph accounting for more than 59%, followed by granulocytes (23-31%) and blast-like cells (3-5%). The size of granulocytes of S. kegaki was smaller (P < 0.05) than those of O. circumpicta and H. hyotis. Light microscopy also allowed the description of vacuolated cells characterized by large vacuoles in the cytoplasm. Flow cytometry analysis confirmed that the granulocytes of the three oyster species were the major hemocytes engaged in cellular defense with the largest lysosome content, and the most active phagocytosis activity and oxidative activity, as was previously reported in several marine bivalves. Phagocytic activity was the lowest in S. kegaki hemocytes, and PMA-stimulated oxidative activity was the lowest in H. hyotis hemocytes. Our results provide the basic information of hemocytes population of three subtropical oysters for further investigations associated with various environmental disease stresses.

The reproduction potentials of four entomopathogenic nematode strains related to cost-effective production for biological control

Chau Nguyen N.,Anh Le T.,Vu Nguyen H.,Phuc Hoang K. 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.2

Bioassays to evaluate the mortality, virulence and reproduction potentials of four indigenous EPN strains, SPQ16, S-BM12, H-KT3987 and H-CB3452 on insect larvae of mealworm (Tenebrio molitor) and greater wax moth (Galleria mellonella) revealed the highest mortality rates of two insect larvae at the highest inoculation dose of 100 IJs to range from 89 to 100 percent and 94.3–100 percent at 48 h after inoculation, respectively. Virulence was high for all nematode strains, with LC 50 values between 29.6 and 47.3 IJs/insect host. The highest IJ yields were different between nematode strains and insect host, from 66.8 × 10 3 IJs (S-PQ16) to 118.6 × 10 3 IJs (HKT3987) on T. molitor, and from 54.2 × 10 3 IJs (S-BM12) to 163.3 × 10 3 IJs (H-KT3987) on G. mellonella. The culturing cost in terms of food expenditure for rearing insect larvae varied between insect larvae and nematode strains, from 6.76 to 26.63 USD per billion IJs for nematode strains cultured on T. molitor larvae and from 3.54 to 7.81 USD per billion IJs for nematode strains cultured on G. mellonella larvae. The full cost for a nematode product of 2.5 × 10 9 IJs per hectare, produced through in vivo mass culturing, of the most efficient nematode strain, H-KT3987, was 191.3 USD, slightly cheaper than 199.4 USD for the same nematode product produced through in vitro mass culturing.

Highly regioselective hydroxylation of polydatin, a resveratrol glucoside, for one-step synthesis of astringin, a piceatannol glucoside, by P450 BM3

Le, T.K.,Jang, H.H.,Nguyen, H.T.H.,Doan, T.T.M.,Lee, G.Y.,Park, K.D.,Ahn, T.,Joung, Y.H.,Kang, H.S.,Yun, C.H. IPC Science and Technology Press ; Elsevier Scienc 2017 Enzyme and microbial technology Vol.97 No.-

<P>Enzymatic conversion of natural glycosides to their corresponding hydroxylated products using cytochromes P450 has significant advantages over synthetic chemistry and even enzyme-catalyzed glycosylation of chemicals. At present, the basic strategy for making glycosides of stilbenoid compounds is to use the glycosylation activity of enzymes, such as glycosyltransferases. Here, an efficient synthesis of a valuable (E)-astringin, a piceatannol glucoside, was developed using CYP102A1 via the highly regioselective C-3' hydroxylation of polydatin, a resveratrol glucoside. (E)-astringin is a high added value compound found in plants and wine. Benzylic hydroxylation of polydatin provides an attractive route to (E)-astringin, a catechol product. Thus far, chemical and enzymatic methods of producing (E)-astringin have not been developed. In the present study, a set of CYP102A1 mutants from Bacillus megaterium was found to catalyze regioselective hydroxylation of polydatin at the C-3' position to generate an (E)-astringin, a piceatannol glucoside. (C) 2016 Elsevier Inc. All rights reserved.</P>

Regioselective C-H hydroxylation of omeprazole sulfide by Bacillus megaterium CYP102A1 to produce a human metabolite

Jang, H. H.,Ryu, S. H.,Le, T. K.,Doan, T. T.,Nguyen, T. H.,Park, K. D.,Yim, D. E.,Kim, D. H.,Kang, C. K.,Ahn, T. Springer Science + Business Media 2017 Biotechnology letters Vol.39 No.1

<P>A highly efficient synthesis of 5'-OH omeprazole sulfide was developed using CYP102A1 from Bacillus megaterium as a biocatalyst.</P>

A new lignan and a new alkaloid, and α-glucosidase inhibitory compounds from the grains of Echinochloa utilis Ohwi & Yabuno

Nguyen, T.T.,Nguyen, D.H.,Zhao, B.T.,Le, D.D.,Choi, D.H.,Kim, Y.H.,Nguyen, T.H.,Woo, M.H. Academic Press 2017 Bioorganic chemistry Vol.74 No.-

A new lignan, utilisin (1), and a new alkaloid, echinoutilin (2), together with eleven known compounds 3-13 were isolated from the grains of Echinochloa utilis Ohwi & Yabuno. Their structures were identified through the analysis of spectroscopic data. The absolute configuration of 2 was determined by Mosher's method. These compounds were evaluated for α-glucosidase inhibitory activity. Among them, compounds 2, 3 and 6 exhibited considerable α-glucosidase inhibitory activity with IC<SUB>50</SUB> values of 42.1+/-1.3, 58.9+/-3.7, and 40.9+/-1.1μM, respectively. The results indicate that the grains of E. utilis will be useful in the treatment of diabetes control agents.

Devosia geojensis sp. nov., isolated from diesel-contaminated soil in Korea

Ryu, S. H.,Chung, B. S.,Le, N. T.,Jang, H. H.,Yun, P.-Y.,Park, W.,Jeon, C. O. Microbiology Society 2008 International journal of systematic and evolutiona Vol.58 No.3

<P>A Gram-negative, strictly aerobic, non-spore-forming bacterium, designated strain BD-c194(T), was isolated from diesel-contaminated soil in Geoje, Korea. The cells were short, motile rods with single polar flagella. Growth of strain BD-c194(T) was observed between 15 and 45 degrees C (optimally at 30-35 degrees C) and between pH 6.0 and 9.5 (optimally at pH 7.5-9.0). The predominant fatty acids were 11-methyl C(18 : 1)omega7c, C(16 : 0), C(18 : 1)omega7c, C(18 : 0) and an unknown fatty acid (equivalent chain-length 18.814); a large amount of phosphatidylglycerol and a small amount of diphosphatidylglycerol were present as polar lipids. The G+C content of the genomic DNA was 60.8 mol% and the major isoprenoid quinone was Q-10. A comparative 16S rRNA gene sequence analysis showed that strain BD-c194(T) formed a well-defined phyletic lineage within the genus Devosia (with 100 % bootstrap support). The levels of 16S rRNA gene sequence similarity with respect to the type strains of other Devosia species ranged from 95.0 to 96.1 %. On the basis of chemotaxonomic data and molecular properties, strain BD-c194(T) represents a novel species within the genus Devosia, for which the name Devosia geojensis sp. nov. is proposed. The type strain is BD-c194(T) (=KCTC 22082(T) =DSM 19414(T)).</P>

Image segmentation based on modified graph-cut algorithm

Le, T H,Jung, S.-W,Choi, K.-S,Ko, S.-J IET 2010 Electronics letters Vol.46 No.16

<P>The regularising parameter of the energy function in the graph-cut based image segmentation methods should be carefully determined since it strongly affects the image segmentation result. Presented is a modified graph-cut technique using a novel energy function without the regularising parameter for image segmentation. In addition, a mixture colour model is employed to apply the proposed technique to colour image segmentation effectively. Experimental results show that the proposed method outperforms the conventional graph-cut algorithm in terms of segmentation accuracy and ease of use.</P>

Very simple circularly polarised printed patch antenna with enhanced bandwidth

Le, T. T.,Park, H. C. IET 2014 Electronics letters Vol.50 No.25

<P>A very simple circularly polarised (CP) printed patch antenna with enhanced bandwidth has been designed, fabricated and tested. The antenna consists of two semi-circular patches and a rectangular ground plane, and is excited by a simple microstrip feedline. The total substrate size is 50 × 50 × 1.52 mm<SUP>3</SUP>. The measured -10 dB impedance bandwidth is 101% (2.84-8.7 GHz) and the measured 3 dB axial-ratio (AR) bandwidth is 49.8% (3.95-6.57 GHz). Good agreement is achieved between measured and simulated results.</P>