- Hydrolysis behaviors of sugarcane bagasse pith in subcritical carbon dioxide-water
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The aim of this study was to describe the hydrolysis behavior of sugarcane bagasse pith (SCBP) in subcritical CO2-water. The hydrolysis was carried out in a batch reactor using different temperatures (160 to 260 °C), liquid to solid ratios (20:1 to 100:1), CO2 pressures (0 to 7.3 MPa), stirring speeds (0 to 500 rpm) and reaction times (0 to 40 min). The highest total reducing sugar yield (43.6%) was obtained at 200 °C, liquid to solid ratio 30:1, 2 MPa CO2, 500 rpm and 50 min. Two-dimensional heteronuclear single quantum coherence (2D HSQC) nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FT-IR) were used to help elucidate the physical and chemical characteristics of the raw material and residual solid particles, with results consistent with the removal of hemicellulose during hydrolysis. The changes in the concentration of products with time were analyzed to understand product distribution through high-performance liquid chromatography (HPLC) and to infer the reaction mechanism.
- Liang, Jiezhen,Chen, Xiaopeng,Wang, Linlin,Wei, Xiaojie,Qiu, Feifei,Lu, Chaochao
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p. 99322 - 99330
(2016/11/02)
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- Xylanase XYN IV from Trichoderma reesei showing exo- and endo-xylanase activity
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A minor xylanase, named XYN IV, was purified from the cellulolytic system of the fungus Trichoderma reesei Rut C30. The enzyme was discovered on the basis of its ability to attack aldotetraohexenuronic acid (HexA-2Xyl-4Xyl-4Xyl, HexA3Xyl3), releasing the reducing-end xylose residue. XYN IV exhibited catalytic properties incompatible with previously described endo-β-1,4-xylanases of this fungus, XYN I, XYN II and XYN III, and the xylan-hydrolyzing endo-β-1,4-glucanase EG I. XYN IV was able to degrade several different β-1,4-xylans, but was inactive on β-1,4-mannans and β-1,4-glucans. It showed both exo-and endo-xylanase activity. Rhodymenan, a linear soluble β-1,3-β-1,4-xylan, was as the best substrate. Linear xylooligosaccharides were attacked exclusively at the first glycosidic linkage from the reducing end. The gene xyn4, encoding XYN IV, was also isolated. It showed clear homology with xylanases classified in glycoside hydrolase family 30, which also includes glucanases and mannanases. The xyn4 gene was expressed slightly when grown on xylose and xylitol, clearly on arabinose, arabitol, sophorose, xylobiose, xylan and cellulose, but not on glucose or sorbitol, resembling induction of other xylanolytic enzymes from T. reesei. A recombinant enzyme prepared in a Pichia pastoris expression system exhibited identical catalytic properties to the enzyme isolated from the T. reesei culture medium. The physiological role of this unique enzyme remains unknown, but it may involve liberation of xylose from the reducing end of branched oligosaccharides that are resistant toward β-xylosidase and other types of endoxylanases. In terms of its catalytic properties, XYN IV differs from bacterial GH family 30 glucuronoxylanases that recognize 4-O-methyl-d-glucuronic acid (MeGlcA) substituents as substrate specificity determinants. 2012 The Authors Journal compilation
- Tenkanen, Maija,Vrsanska, Maria,Siika-Aho, Matti,Wong, Dominic W.,Puchart, Vladimir,Penttilae, Merja,Saloheimo, Markku,Biely, Peter
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p. 285 - 301
(2013/03/28)
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- The enhancement of xylose monomer and xylotriose degradation by inorganic salts in aqueous solutions at 180 °C
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The inorganic salts KCl, NaCl, CaCl2, MgCl2, and FeCl3, and especially the latter, significantly increased xylose monomer and xylotriose degradation in water heated to 180 °C with unaccountable losses of xylose amounting to as high as 65% and 78% for xylose and xylotriose, respectively, after 20 min incubation with 0.8% FeCl3. Furthermore, losses of both xylose and xylotriose were well described by first order homogeneous kinetics, and the rate constants for xylose and xylotriose disappearance increased 6- and 49-fold, respectively, when treated with 0.8% FeCl3 solution compared to treatment with just pressurized hot water at the same temperature. Although the addition of these inorganic salts produced a significant drop in pH, the degradation rates with salts were much faster than could be accounted for by a pH change. For example, the rate constants for the disappearance of xylose and xylotriose with 0.8% FeCl3 were 3-fold and 7-fold greater, respectively, than for treatment with very dilute sulfuric acid at the same pH. In addition, xylose losses were greater than could be accounted for by just furfural production, suggesting that other degradation products were also formed, and xylose losses to unidentified compounds increased significantly with the addition of FeCl3. The unidentified compounds could be formed through aqueous furfural resinification and condensation reactions that are accelerated by FeCl3, but the actual mechanisms are still not clear.
- Liu, Chaogang,Wyman, Charles E.
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p. 2550 - 2556
(2007/10/03)
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- Process for manufacturing high purity xylose
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A process for manufacturing xylose by extracting hemicellulose from a cellulosic material, such as by a cold caustic extraction method, concentrating the extract, such as by nanofiltration, into a hemicaustic stream containing hemicellulose with greater than about 85 wt % xylan content, and subsequently hydrolysing the xylan from the hemicaustic stream to xylose. The high concentration of xylan within the concentrated hemicaustic stream enables hydrolyzation of the xylan to food-grade xylose and, optionally, hydrogenation of the xylose to xylitol without the need of a chromatographic separation step as previously required.
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Page/Page column 10
(2008/06/13)
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- Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Sporotrichum thermophile
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An endo-β-1,4-xylanase (1,4-β-D-xylan xylanoxydrolase, EC 3.2.1.8) present in culture filtrates of Sporotrichum thermophile ATCC 34628 was purified to homogeneity by Q-Sepharose and Sephacryl S-200 column chromatographies. The enzyme has a molecular mass of 25,000 Da, an isoelectric point of 6.7, and is optimally active at pH 5 and at 70°C. Thin-layer chromatography (TLC) analysis showed that endo-xylanase liberates mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-D-glucuronoxylan, O-acetyl-4-O-methylglucuronoxylan and rhodymenan (a β-(1→4)-β(1→3)-xylan). Also, the enzyme releases an acidic xylo-oligosaccharide from 4-O-methyl-D-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. Analysis of reaction mixtures by high performance liquid chromatography (HPLC) revealed that the enzyme cleaves preferentially the internal glycosidic bonds of xylooligosaccharides, [1-3H]-xylooligosaccharides and xylan. The enzyme also hydrolyses the 4-methylumbelliferyl glycosides of β-xylobiose and β-xylotriose at the second glycosidic bond adjacent to the aglycon. The endoxylanase is not active on pNPX and pNPC. The enzyme mediates a decrease in the viscosity of xylan associated with a release of only small amounts of reducing sugar. The enzyme is irreversibly inhibited by series of ω-epoxyalkyl glycosides of D-xylopyranose. The results suggest that the endoxylanase from S. thermophile has catalytic properties similar to the enzymes belonging to family 11.
- Katapodis, Petros,Vrsanska, Maria,Kekos, Dimitris,Nerinckx, Wim,Biely, Peter,Claeyssens, Marc,Macris, Basil J.,Christakopoulos, Paul
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p. 1881 - 1890
(2007/10/03)
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- Mode of action of (1→4)-β-D-arabinoxylan arabinofuranohydrolase (AXH) and α-L-arabinofuranosidases on alkali-extractable wheat-flour arabinoxylan
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Arabinoxylan-derived oligosaccharides were treated with (1→4)-β-D-arabinoxylan arabinofuranohydrolase (AXH) and two types of α-L-arabinofuranosidase, A and B. Analysis of reaction products by high performance anion-exchange chromatography indicated the removal of arabinofuranosyl groups from singly substituted xylopyranosyl residues. In addition, differences in the specificity of these enzymes towards the various differently substituted oligosaccharides were observed. 1H NMR spectroscopy and methylation analysis of alkali-extractable wheat-flour arabinoxylan treated with AXH confirmed the specificity of AXH towards (1→3)-linked arabinofuranosyl groups on singly substituted xylopyranosyl residues. With these techniques, α-L-arabinofuranosidase B was found to cause minor changes in (1→2)- and (1→3)-linked arabinofuranosyl groups on doubly substituted xylopyranosyl residues. Arabinoxylan-derived oligosaccharides were treated with (1 → 4)-B-D-arabinoxylan arabinofuranohydrolase (AXH) and two types of A-L-arabinofuranosidase, A and B. Analysis of reaction products by high performance anion-exchange chromatography indicated the removal of arabinofuranosyl groups from singly substituted xylopyranosyl residues. In addition, differences in the specificity of these enzymes towards the various differently substituted oligosaccharides were observed. 1H NMR spectroscopy and methylation analysis of alkali-extractable wheat-flour arabinoxylan treated with AXH confirmed the specificity of AXH towards (1 → 3)-linked arabinofuranosyl groups on singly substituted xylopyranosyl residues. With these techniques, A-L-arabinofuranosidase B was found to cause minor changes in (1 → 2) and (1 → 3) linked arabinofuranosyl groups on doubly substituted xylopyranosyl residues.
- Kormelink,Gruppen,Voragen
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p. 345 - 353
(2007/10/02)
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- Hydrolysis of (1->3)- and (1->2)-β-D-xylosidic linkages by an endo-(1->4)-β-D-xylanase of Cryptococcus albidus
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The substrate specificity of an endo-(1->4)-β-D-xylanase of the yeast Cryptococcus albidus was investigated using a series of methyl β-D-xylotriosides.In addition to (1->4) linkages, the enzyme could cleave (1->3) and (1->2) linkages adjacent to a (1->4) linkage and further from the non-reducing end of the substrate.The enzyme could hydrolyse a (1->3) linkage that attached a terminal xylopyranosyl group to a (1->4)-linked xylobiosyl moiety.The enzyme did not attack α-D-xylosidic linkages.The rate of cleavage of (1->4) linkages was much higher than those of other linkages at 0.5 mM substrate, but the rates were comparable at 20 mM substrate when transglycosylation reactions also occurred that facilitated degradation of the substrates.
- Vrsanska, Maria,Hirsch, Jan,Kovac, Pavol,Biely, Peter
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p. 251 - 256
(2007/10/02)
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- The Modes of Action of Three Xylanases from Mesophilic Fungus Strain Y-94 on Xylooligosaccharides
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The modes of action of three thermostable endo-xylanases (Xn-A, Xn-B, and Xn-C) from the mesophilic fungus strain Y-94 on xylooligosaccharides and their alditols (DP 2 ca 8) were studied.Non of the enzymes could hydrolyse xylobiose.Oligosaccharides upwards from xylotetraose were immediately hydrolysed by the endo-xylanases, but xylotriose was slowly hydrolysed.Xn-A hydrolysed xylotriose more slowly than the other two.From the dependency of the molecular activity (ko) on the chain length of the substrates, it was suggested that the three xylanases had the same subsite size (5 xylose units).Analysis of the frequency distribution of bond cleavage of oligosaccharide-alditols showed that no enzymes could attack the first bond from the non-reducing end of oligosaccharides.The other bonds were hydrolysed by these enzymes ba endo-type action.The action pattern for xylopentaitol suggested that the catalytic site was located between the second and third subsite from the non-reducing end, since the substrate was mainly hydrolysed to xylobiose and xylotriitol.
- Mitsuishi, Yasushi,Yamanobe, Takashi,Yagisawa, Mitsuo
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p. 921 - 928
(2007/10/02)
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- ISOLATION AND IDENTIFICATION OF O-(5-O-FERULOYL-α-L-ARABINOFURANOSYL)-(1-3)-O-β-D-XYLOPYRANOSYL-(1-4)-D-XYLOPYRANOSE AS A COMPONENT OF Zea SHOOT CELL-WALLS
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Zea shoot cell-walls were hydrolyzed with 30 mM oxalic acid followed by treatment with "Driselase" (a Basidiomycetes enzyme preparation) to obtain carbohydrate fragments containing ferulic acid.The structure of the major feruloyl compound was identified as O-(5-O-feruloyl-α-L-arabinofuranosyl)-(1-3)-O-β-D-xylopyranosyl-(1-4)-D-xylopyranose on the basis of (13)C-n.m.r., methylation analysis, and partial acid-hydrolysis, alkali hydrolysis, or esterase hydrolysis followed by analyses of the hydrolyzate.
- Kato, Yoji,Nevins, Donald J.
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p. 139 - 150
(2007/10/02)
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