Publications (13)22.42 Total impact
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Dataset: science
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Article: Alkali Pretreatment of Wheat Straw (Triticum aestivum) at Boiling Temperature for Producing a Bioethanol Precursor.
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ABSTRACT: We evaluated the effect of dilute sodium hydroxide (NaOH) on wheat straw at boiling temperature for removing lignin and increasing the yield of reducing sugar. Various concentrations of NaOH (0.5% to 2%) were used for pretreating wheat straw at 105 °C for 10 min. Scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy studies revealed that the 2% NaOH-pretreated sample exposed more cellulose fiber. The maximum respective removal of lignin and hemicellulose was 70.3% and 68.2% from the 2% NaOH-pretreated liquor. The reducing sugar yield was 84.6% using an enzyme dose containing 20 FPU of cellulase, 40 IU of β-glucosidase and 4 FXU of xylanase/g of substrate. However, 2% NaOH-treated wheat straw had the lowest crystalline index of 52.5%, due to destructured cellulose fibers. The results indicate the effectiveness of producing the bioethanol precursor from wheat straw by using 2% NaOH at boiling temperature.Bioscience Biotechnology and Biochemistry 12/2012; · 1.28 Impact Factor -
Article: Effect of dilute alkali on structural features and enzymatic hydrolysis of barley straw (Hordeum vulgare) at boiling temperature with low residence time.
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ABSTRACT: This work was conducted to evaluate the effect of dilute sodium hydroxide (NaOH) on barley straw at boiling temperature and fractionation of its biomass components into lignin, hemicellulose, and reducing sugars. To this end, various concentrations of NaOH (0.5% to 2%) were applied for pretreatment of barley straw at 105 degrees C for 10 min. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy studies revealed that 2% NaOHpretreated barley straw exposed cellulose fibers on which surface granules were abolished due to comprehensive removal of lignin and hemicellulose. The X-ray diffractometer (XRD) result showed that the crystalline index was increased with increased concentration of NaOH and found a maximum 71.5% for 2% NaOH-pretreated sample. The maximum removal of lignin and hemicellulose was 84.8% and 79.5% from 2% NaOH-pretreated liquor, respectively. Reducing sugar yield was 86.5% from 2% NaOH-pretreated sample using an enzyme dose containing 20 FPU of cellulase, 40 IU of beta-glucosidase, and 4 FXU of xylanase/g substrate. The results of this study suggest that it is possible to produce the bioethanol precursor from barley straw using 2% NaOH at boiling temperature.Journal of Microbiology and Biotechnology 12/2012; 22(12):1681-1691. · 1.38 Impact Factor -
Article: Chitinibacter suncheonensis sp. nov., a chitinolytic bacterium from a mud flat in Suncheon Bay.
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ABSTRACT: A chitinolytic bacterium, designated strain SK16(T), was isolated from a mud flat in Suncheon Bay, Republic of Korea. Strain SK16(T) is Gram-negative, strictly aerobic, motile by a polar flagellum, and short rod-shaped. Phylogenetic analyses based on 16S rRNA gene sequences showed that the strain belonged to the genus Chitinibacter and was most closely related to Chitinibacter tainanensis S1(T) (98.2% similarity). DNA-DNA hybridization analyses showed a low association value of 20.45±4.08% between them. The major cellular fatty acids, the G+C content of the genomic DNA, and the predominant quinone of the strain were summed feature 3 (iso-C(15:0) 2-OH and/or C(16:1) ω7c; 50.5%) and C(12:0) (12.5%), 52.26 mol%, and Q-8, respectively. Based on the phylogenetic, chemotaxonomic, and phenotypic properties, strain SK16(T) represents a novel species of the genus Chitinibacter, for which the name Chitinibacter suncheonensis sp. nov. is proposed. The type strain is SK16(T) (=KCTC 23839(T) =DSM 25421(T)).The Journal of Microbiology 12/2012; 50(6):1058-62. · 1.10 Impact Factor -
Article: Activation of a casB gene encoding β-glucosidase of Pectobacterium carotovorum subsp. carotovorum LY34.
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ABSTRACT: Two cas genes were isolated from Pectobacterium carotovorum subsp. carotovorum LY34 (Pcc LY34). Sequence analysis of the 4873bp cloned DNA fragment (accession number AY866383) revealed two open reading frames (casF and casB) that are predicted to encode 658 and 467 amino acid proteins, respectively. The CasF protein is similar to other PTS enzyme II components. casB encodes β-glucosidase, a member of the glycosyl hydrolase family 1. An inverted repeat sequence was identified in the casB promoter region, and was hypothesized to have a negative effect on casB transcription. Replacement of the casB promoter of Pcc LY34 with the bglB promoter activated the casB gene, consistent with the repeats inhibiting expression of casB. Purified CasB enzyme was estimated to be 53,000Da by SDS-PAGE, and hydrolyzed salicin, arbutin, pNPG, and MUG. CasB exhibited maximal activity toward pNPG at pH 7.0 and 40°C, and Mg(2+) is essential for its activity. Two conserved glutamate residues (Glu(177) and Glu(366)) were shown to be important for CasB activity.Microbiological Research 11/2012; · 2.31 Impact Factor -
Article: Cloning and identification of a new group esterase (Est5S) from noncultured rumen bacterium.
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ABSTRACT: The gene encoding an esterase enzyme was cloned from a metagenomic library of cow rumen bacteria. The esterase gene (est5S) was 1,026 bp in length, encoding a protein of 366 amino acid residues with a calculated molecular mass of 40,168 Da. The molecular mass of the enzyme was estimated to be 40,000 Da. The Est5S protein contains the Gly-X-Ser-X-Gly motif found in most bacterial and eukaryotic serine hydrolases. However, the Asp or Glu necessary for the catalytic triad [Ser-Asp-(Glu)-His] was not present, indicating Est5S represents a novel member of the GHSQG family of esterolytic enzymes. BlastP in the NCBI database analysis of Est5S revealed homology to hypothetical proteins and it had no homology to previous known lipases and esterases. Est5S was optimally active at pH 7.0 and 40 degrees C. Among the p-nitrophenyl acylesters tested, high enzymatic activities were observed on the short-chain p-nitrophenyl acylesters, such as p-nitrophenyl acetate, etc. The conserved serine residue (Ser190) was shown to be important for Est5S activity. The primers that amplified the est5S gene did not show any relative band with 49 species of culturable rumen bacteria. This implies that a new group esterase gene, est5S, may have come from a noncultured cow rumen bacterium.Journal of Microbiology and Biotechnology 08/2012; 22(8):1044-53. · 1.38 Impact Factor -
Article: Production of XynX, a Large Multimodular Protein of Clostridium thermocellum, by Protease-Deficient Bacillus subtilis Strains.
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ABSTRACT: XynX of Clostridium thermocellum is a large, multimodular xylanase of 116 kDa. An Escherichia coli transformant carrying the entire xynX produced three active truncated xylanase species of 105, 85, and 64 kDa intracellularly. The Bacillus subtilis WB700 transformant with the xynX, a strain deficient in seven proteases including Vpr, secreted two active truncated xylanase species of 65 and 44 kDa. The B. subtilis WB800 transformant with xynX, a strain deficient in eight proteases including Vpr and WprA, secreted more active enzymes, 8.46 U ml(-1), mostly in the form of 105 and 85 kDa, than the WB700 transformant, 6.93 U ml(-1). This indicates that the additional deletion of wprA enabled the WB800 to secrete XynX in its intact form. B. subtilis WB800 produced more total enzyme activity than E. coli (1,692 ± 274 U vs. 141.9 ± 27.1 U), and, more importantly, secreted almost all the enzyme activity. The results suggest the potential use of B. subtilis WB800 as a host system for the production of large multimodular proteins.Applied biochemistry and biotechnology 06/2012; 168(2):375-82. · 1.94 Impact Factor -
Article: Cloning and biochemical analysis of β-glucoside utilization (bgl) operon without phosphotransferase system in Pectobacterium carotovorum subsp. carotovorum LY34.
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ABSTRACT: β-Glucosidases are widespread in bacteria and involved in the metabolism of various carbohydrate substrates. Studying of β-glucoside utilization (bgl) operons on operon of Pectobacterium carotovorum subsp. carotovorum LY34 (Pcc LY34) will help us understanding how β-glucoside utilization (bgl) operon can cooperate with other systems in bacterium caused soft-rot disease. Pcc LY34 causes soft-rot disease in plants and expresses multiple enzymatic forms of β-glucosidases. To fully explore the β-glucoside utilization system in Pcc LY34, we have isolated a bgl operon from a genomic library for screening of β-glucosidase activities. Sequence analysis of a 3050bp cloned DNA fragment (accession number AY870655) shows two open reading frames (bglY and bglK) that are predicted to encode proteins of 474 and 278 amino acid residues, respectively. Pair wise similarity analysis suggests BglY is a beta-glucosidase (a member of glycosyl hydrolase family 1) and BglK is a transcriptional antiterminator protein. bglY promoter region contains an inverted repeat sequence similar to transcriptional terminator. Different from other four β-glucoside utilization operons of Pcc LY34 strain, BglY contains signal peptide sequences as extracellular β-glucosidase. Comparisons of five β-glucoside utilization operons of Pcc LY34 strain showed that bglYK operon does not have phosphotransferase system domain which are responsible for sugar transportation. BglY shares 33-44% identity with other four β-glucosidases of Pcc LY34 strain. Enzyme assay showed that purified BglY enzyme hydrolyzed salicin, arbutin, pNPG, and MUG, and exhibited maximal activity at pH 7.0 and 40°C. This activity was enhanced Mg(2+). Site-directed mutagenesis revealed E166 and E371 are critical of BglY's β-glucosidase activity.Microbiological Research 04/2012; 167(8):461-9. · 2.31 Impact Factor -
Article: Characterization of xyn10J, a novel family 10 xylanase from a compost metagenomic library.
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ABSTRACT: A gene encoding an extracellular xylanase was cloned from a compost metagenomic library. The xylanase gene, xyn10J, was 1,137 bp in length and was predicted to encode a protein of 378 amino acid residues with a putative signal peptide of 27 amino acid residues. The molecular mass of the mature Xyn10J was calculated to be 39,882 Da with a pI of 6.09. Xyn10J had a motif GVKVHFTEMDI characteristic of most members of glycosyl hydrolase family 10. The amino acid sequence of Xyn10J showed 60.0% identity to that of XynH, a xylanase from an uncultured soil bacterium and 55% identity to XylC of Cellvibrio mixtus. Site-directed mutagenesis of the expected active site based on the sequence analysis indicated that an aspartic acid residue (Asp207), in addition to the identified catalytic residues Glu165 and Glu270, plays a crucial role for the catalytic activity. The purified Xyn10J had a mass of about 40 kDa and was optimally active at pH 7.0 and 40 °C. Xyn10J hydrolyzed beechwood xylan > birchwood xylan > oat spelt xylan > arabinoxylan. Xyn10J hydrolyzed xylotetraose and xylohexaose exclusively to xylobiose, xylopentaose, and xylotriose mainly to xylobiose with transglycosylation activity. The saccharification of reed (Phragmites communis) powder by commercial enzymes was significantly increased by the addition of a small amount of Xyn10J to the commercial preparation. Xyn10J is the first xylanase screened directly from a compost metagenomic library, and the enzyme has the potential to be used in the conversion of biomass to fermentable sugars for biofuel production.Applied biochemistry and biotechnology 01/2012; 166(5):1328-39. · 1.94 Impact Factor -
Article: The role of carbohydrate-binding module (CBM) repeat of a multimodular xylanase (XynX) from Clostridium thermocellum in cellulose and xylan binding.
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ABSTRACT: A non-cellulosomal xylanase from Clostridium thermocellum, XynX, consists of a family-22 carbohydratebinding module (CBM22), a family-10 glycoside hydrolase (GH10) catalytic module, two family-9 carbohydrate-binding modules (CBM9-I and CBM9-II), and an S-layer homology (SLH) module. E. coli BL21(DE3) (pKM29), a transformant carrying xynX', produced several truncated forms of the enzyme. Among them, three major active species were purified by SDS-PAGE, activity staining, gel-slicing, and diffusion from the gel. The truncated xylanases were different from each other only in their C-terminal regions. In addition to the CBM22 and GH10 catalytic modules, XynX(1) had the CBM9-I and most of the CBM9-II, XynX(2) had the CBM9-I and about 40% of the CBM9-II, and XynX(3) had about 75% of the CBM9-I. The truncated xylanases showed higher binding capacities toward Avicel than those toward insoluble xylan. XynX(1) showed a higher affinity toward Avicel (70.5%) than XynX(2) (46.0%) and XynX(3) (42.1%); however, there were no significant differences in the affinities toward insoluble xylan. It is suggested that the CBM9 repeat, especially CBM9-II, of XynX plays a role in xylan degradation in nature by strengthening cellulose binding rather than by enhancing xylan binding.The Journal of Microbiology 12/2010; 48(6):856-61. · 1.10 Impact Factor -
Article: Molecular cloning and characterization of a novel family VIII alkaline esterase from a compost metagenomic library.
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ABSTRACT: A metagenomic library was constructed from completely fermented compost using a fosmid vector. From a total of 23,400 clones, 19 esterase-positive clones were selected on LB plates containing 1% glyceryl tributyrate as the substrate. The esterase gene of an esterase-positive clone, est2K, was on an ORF of 1299 bp and encoded a protein of 432 amino acids. Est2K had a SMTK motif and was a family VIII esterase. Unlike most family VIII esterases, Est2K had a signal peptide of 27 amino acids. The molecular mass and pI of the mature Est2K was calculated to be 44,668 Da and 4.48, respectively. The amino acid sequence of Est2K showed 72% identity with that of EstC, an esterase of an uncultured bacterium from leachate. The purified Est2K was optimally active at pH 10.0 and 50 degrees C. Est2K was stable in the presence of 30% methanol and exhibited a 2.4-fold higher activity in the presence of 5% methanol than in the presence of 1% isopropanol. Est2K preferred short to medium length p-nitrophenyl esters, especially p-nitrophenyl butyrate, as the substrate. Est2K did not hydrolyze beta-lactam antibiotics ampicillin and nitrocefin, even though Est2K showed the highest similarity to EstC.Biochemical and Biophysical Research Communications 02/2010; 393(1):45-9. · 2.48 Impact Factor -
Article: Fungal diversity in composting process of pig manure and mushroom cultural waste based on partial sequence of large subunit rRNA.
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ABSTRACT: Fungal diversity during composting was investigated by culture-independent rDNA sequence analysis. Composting was carried out with pig manure and mushroom cultural waste using a field-scale composter (Hazaka system), and samples were collected at various stages. Based on partial sequence analysis of large subunit (LSU) ribosomal RNA (rRNA) and sequence identity values, a total of 12 different fungal species were found at six sampling sites; Geotrichum sp., Debaryomyces hansenii, Monographella nivalis, Acremonium strictum, Acremonium alternatum, Cladosporium sphaerospermum, Myriangium durosai, Pleurotus eryngii, Malassezia globosa, Malassezia restricta, Rhodotorula glutinis, and Fusarium sporotrichioides. Geotrichum sp. of the class Saccharomycetes was the most predominant fungal species throughout the composting process (185 out of a total of 236 identified clones, or 78.4%), followed by Acremonium strictum (7.6%), Monographella nivalis (5.1%), and Pleurotus eryngii (3.8%). The prevalence of Geotrichum sp. was the lowest (61.1%) at the beginning of composting, and then gradually increased to 92.5% after 10 days of composting.Journal of Microbiology and Biotechnology 09/2009; 19(8):743-8. · 1.38 Impact Factor -
Article: Influence of the transposition of the thermostabilizing domain of Clostridium thermocellum xylanase (XynX) on xylan binding and thermostabilization.
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ABSTRACT: A xylanase gene, xynX, of Clostridium thermocellum had one thermostabilizing domain (TSD) between the signal peptide sequence and the catalytic domain (CD). The TSD of a truncated xylanase gene, xynX'(TSD-CD), was transpositioned from the N terminus to the C terminus of the CD by overlapping PCRs, and a modified product, xynX'(CD-TSD), was constructed. XynX'(TSD-CD) had a higher optimum temperature (70 degrees C versus 65 degrees C) and was more thermostable (residual activity of 68% versus 46% after a 20-min preincubation at 70 degrees C) than the one without the TSD, XynX'(CD). However, the domain-transpositioned enzyme, XynX'(CD-TSD), showed a lower optimum temperature (30 degrees C) and thermostability (20%) than XynX'(CD). Both XynX'(TSD-CD) and XynX'(CD-TSD) showed significantly higher binding capacity toward xylan than XynX'(CD), and the domain transposition did not cause any change in the binding ability. XynX'(TSD-CD) and XynX'(CD-TSD) also showed considerable binding to lichenan but not to carboxymethyl cellulose and laminarin. XynX'(TSD-CD) and XynX'(CD-TSD) had higher activities for insoluble xylan than XynX'(CD), while XynX'(CD) was more active against soluble xylan than XynX'(TSD-CD) and XynX'(CD-TSD). These results indicate that the TSD of XynX has dual functions, xylan binding and thermostabilization, and the domain should also be classified as a xylan-binding domain (XBD). The binding capacity of the XBD was not affected by domain transpositioning within the gene.Applied and Environmental Microbiology 08/2002; 68(7):3496-501. · 3.83 Impact Factor
Top co-authors
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Institutions
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2012
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Gyeongsang National University
Chinju, South Gyeongsang, South Korea -
University of Nevada School of Medicine
Reno, NV, USA
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2002–2012
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Sunchon National University
- Department of Agricultural Chemistry
Sunchun, South Jeolla, South Korea
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