Showing papers on "Xylanase published in 1999"
TL;DR: A wide range of applications in the pulp and paper industry have now been identified, and the most important application of enzymes is in the prebleaching of kraft pulp, where Xylanase enzymes have been found to be most effective.
Abstract: The pulp and paper industry processes huge quantities of lignocellulosic biomass every year. The technology for pulp manufacture is highly diverse, and numerous opportunities exist for the application of microbial enzymes. Historically, enzymes have found some uses in the paper industry, but these have been mainly confined to areas such as modifications of raw starch. However, a wide range of applications in the pulp and paper industry have now been identified. The use of enzymes in the pulp and paper industry has grown rapidly since the mid 1980s. While many applications of enzymes in the pulp and paper industry are still in the research and development stage, several applications have found their way into the mills in an unprecedented short period of time. Currently the most important application of enzymes is in the prebleaching of kraft pulp. Xylanase enzymes have been found to be most effective for that purpose. Xylanase prebleaching technology is now in use at several mills worldwide. This technology has been successfully transferred to full industrial scale in just a few years. The enzymatic pitch control method using lipase was put into practice in a large-scale paper-making process as a routine operation in the early 1990s and was the first case in the world in which an enzyme was successfully applied in the actual paper-making process. Improvement of pulp drainage with enzymes is practiced routinely at mill scale. Enzymatic deinking has also been successfully applied during mill trials and can be expected to expand in application as increasing amounts of newsprint must be deinked and recycled. The University of Georgia has recently opened a pilot plant for deinking of recycled paper. Pulp bleaching with a laccase mediator system has reached pilot plant stage and is expected to be commercialized soon. Enzymatic debarking, enzymatic beating, and reduction of vessel picking with enzymes are still in the R&D stage but hold great promise for reducing energy. Other enzymatic applications, i.e., removal of shives and slime, retting of flax fibers, and selective removal of xylan, are also expected to have a profound impact on the future technology of the pulp and paper-making process.
527 citations
TL;DR: The first isolation of a xylanase inhibitor from any organism is described, with a Ki value of 0.35 microM, showing that the inhibitor binds at or close to the active site of free xylan enzyme.
Abstract: We have purified a novel class of protein that can inhibit the activity of endo-beta-1,4-xylanases. The inhibitor from wheat (Triticum aestivum, var. Soisson) is a glycosylated, monomeric, basic protein with a pI of 8.7-8.9, a molecular mass of 29 kDa and a unique N-terminal sequence of AGGKTGQVTVFWGRN. We have shown that the protein can inhibit the activity of two family-11 endo-beta-1, 4-xylanases, a recombinant enzyme from Aspergillus niger and an enzyme from Trichoderma viride. The inhibitory activity is heat and protease sensitive. The kinetics of the inhibition have been characterized with the A. niger enzyme using soluble wheat arabinoxylan as a substrate. The Km for soluble arabinoxylan in the absence of inhibitor is 20+/-2 mg/ml with a kcat of 103+/-6 s-1. The kinetics of the inhibition of this reaction are competitive, with a Ki value of 0.35 microM, showing that the inhibitor binds at or close to the active site of free xylanase. This report describes the first isolation of a xylanase inhibitor from any organism.
191 citations
TL;DR: Four experiments were conducted to examine the effects of a microbial phytase, individually and in combination with glycanase preparations with predominantly xylanase (Natugrain Blend) and glucanase ( Natugrain) activities, on the nutritive value of wheat and barley.
180 citations
TL;DR: One of the extracellular xylanases that is stable in an alkaline state was purified to homogeneity by affinity adsorption-desorption on insoluble xylan, and it was demonstrated that the enzyme could hydrolyze the raw lignocellulosic substances effectively.
Abstract: An alkaliphilic bacterium, Bacillus sp. strain K-1, produces extracellular xylanolytic enzymes such as xylanases, β-xylosidase, arabinofuranosidase, and acetyl esterase when grown in xylan medium. One of the extracellular xylanases that is stable in an alkaline state was purified to homogeneity by affinity adsorption-desorption on insoluble xylan. The enzyme bound to insoluble xylan but not to crystalline cellulose. The molecular mass of the purified xylan-binding xylanase was estimated to be approximately 23 kDa. The enzyme was stable at alkaline pHs up to 12. The optimum temperature and optimum pH of the enzyme activity were 60°C and 5.5, respectively. Metal ions such as Fe2+, Ca2+, and Mg2+ greatly increased the xylanase activity, whereas Mn2+ strongly inhibited it. We also demonstrated that the enzyme could hydrolyze the raw lignocellulosic substances effectively. The enzymatic products of xylan hydrolysis were a series of short-chain xylooligosaccharides, indicating that the enzyme was an endoxylanase.
176 citations
TL;DR: Strains of Aspergillus terreus and A. niger, known to produce xylanase with undetectable amounts of cellulase, were studied for xylan enzyme production on various lignocellulosic substrates using solid state fermentation.
Abstract: Strains of Aspergillus terreus and A. niger, known to produce xylanase with undetectable amounts of cellulase, were studied for xylanase (EC 3.2.1.8) production on various lignocellulosic substrates using solid state fermentation. Of the lignocellulosic substrates used, wheat bran was the best for xylanase production. The effects of various parameters, such as moistening agent, level of initial moisture content, temperature of incubation, inoculum size and incubation time, on xylanase production were studied. The best medium for A. terreus was wheat bran moistened with 1:5 Mandels and Strenberg mineral solution containing 0·1% tryptone, at 35 °C, and at inoculum concentration 2×107−2×108 spores 5 g−1 substrate; forA. niger, the best medium was wheat bran moistened with 1:5 Mandels and Strenberg mineral solution containing 0·1% yeast extract, at 35 °C, and at an inoculum concentration of 2×107−2×108 spores 5 g−1 substrate. Under these conditions, A. terreus produced 68·9 IU ml−1 of xylanase, and A. niger, 74·5 IU ml−1, after 4 d of incubation. A crude culture filtrate of the two Aspergillus strains was used for the hydrolysis of various lignocellulosic materials. Xylanase preparations from the two strains selectively removed the hemicellulose fraction from all lignocellulosic materials tested.
167 citations
TL;DR: The use of solid-state fermentation for the production of xylanase by Bacillus sp.
153 citations
TL;DR: Results provide direct evidence that enzyme activity is not necessary for elicitor activity of fungal xylanase, and indicate that xylanases from Trichoderma spp.
Abstract: Fungal xylanases from Trichoderma spp. are potent elicitors of defense responses in various plants. To determine whether enzymatic activity is necessary for elicitor activity, we used site-directed mutagenesis to reduce the catalytic activity of xylanase II from Trichoderma reesei. For this, the glutamic acid residue at position 210, which is part of the active center in this family of enzymes, was changed to either aspartic acid (E210D) or serine (E210S). Wild-type and mutated forms of xylanase II were expressed in yeast cells and purified to homogeneity. Compared with the wild-type form of xylanase II, E210D had >100-fold and E210S 1,000-fold lower enzymatic activity. In contrast, these mutated forms showed no comparable drop in elicitor activity. They fully stimulated medium alkalinization and ethylene biosynthesis in suspension-cultured tomato (Lycopersicon esculentum) cells, as well as hypersensitive necrosis in leaves of tomato and tobacco (Nicotiana tabacum) plants. These results provide direct evidence that enzyme activity is not necessary for elicitor activity of fungal xylanase.
143 citations
TL;DR: In this article, xylanase, peroxidase, or glucose oxidase (GOX) were used to extract arabinoxylans from wheat and formed covalent bonds between proteins and gluten proteins.
Abstract:
Baking trials were performed with six wheat doughs prepared with xylanase, peroxidase, or glucose oxidase (GOX), and their combinations. Judging dough properties, baking performance, bread volume, and crumb structure, the dough containing xylanase plus peroxidase performed best. Flow relaxation measurements with doughs indicated that peroxidases introduced new transient linkages, whereas glucose oxidase also introduced cross-links permanent on long time scales. Rheological tests and chemical analysis revealed small differences between control and xylanase and/ or peroxidase containing gluten and more pronounced differences for GOX containing gluten. No evidence was found that xylanase specifically removed arabinoxylans from gluten or that peroxidase catalyzed the formation of covalent bonds between arabinoxylans and gluten proteins.
120 citations
TL;DR: A group of 17 strains of the thermophilic fungus Thermomyces lanuginosus was examined for the production of xylanases, β-mannanases, arabinanase, and pectinases, and several were proven to be outstanding producers of microbial xylanase on glucuronoxylan and corn cobs.
118 citations
TL;DR: Two similar xylanase genes, xynU and xynV, were cloned from C. thermocellum strain YS and sequenced and the xylanases were shown to be remarkably thermostable and resistant to proteolytic inactivation.
Abstract: Clostridium thermocellum produces a consortium of plant-cell-wall hydrolases that form a cell-bound multi-enzyme complex called the cellulosome. In the present study two similar xylanase genes, xynU and xynV, were cloned from C. thermocellum strain YS and sequenced. The deduced primary structures of both xylanases, xylanase U (XylU) and xylanase V (XylV), were homologous with the previously characterized xylanases from C. thermocellum strain F1. Truncated derivatives of XylV were produced and their biochemical properties were characterized. The xylanases were shown to be remarkably thermostable and resistant to proteolytic inactivation. The catalytic domains hydrolysed xylan by a typical endo-mode of action. The type VI cellulose-binding domain (CBD) homologue of XylV bound xylan and, to a smaller extent, Avicel and acid-swollen cellulose. Deletion of the CBD from XylV abolished the capacity of the enzymes to bind polysaccharides. The polysaccharide-binding domain was shown to have a key role in the hydrolysis of insoluble substrates by XylV. The C-terminal domain of XylV, which is absent from XylU, removed acetyl groups from acetylated xylan and acted in synergy with the glycosyl hydrolase catalytic domain of the enzyme to elicit the hydrolysis of acetylated xylan.
107 citations
TL;DR: Although the two xylanases differed in their abilities to remove reducing sugars from pulp, their biobleaching abilities, when assessed in hydrogen peroxide delignification of pulp, were very similar: both of them increased brightness by 1.4 points and removed 7% of hemicellulose from pulp.
TL;DR: In this paper, the authors investigated xylanase production by Thermoascus aurantiacus using semisolid fermentation and multivariant statistical approaches were employed to evaluate the effects of several variables (initial moisture in the medium, cultivation time, inoculum level, and bagasse mass) on xylanases production.
Abstract: We investigated xylanase production by Thermoascus aurantiacus using semisolid fermentation. Multivariant statistical approaches were employed to evaluate the effects of several variables (initial moisture in the medium, cultivation time, inoculum level, and bagasse mass) on xylanase production. The initial moisture content and bagasse mass were the most important factors affecting xylanase activity. The xylanase activity produced by the fungus under the optimized conditions (81% moisture content and 17 g bagasse) was found to be 2700 U per gram of initial dry matter, whereas its value predicted by a polynomial model was 2400 U per gram of initial dry matter.
TL;DR: The data show that the xylanase activity of EIX elicitor can be separated from the elicitation process, as some of the mutants lack the former but retain the latter.
Abstract: Ethylene-inducing xylanase (EIX) elicits plant defense responses in certain tobacco (Nicotiana tabacum) and tomato cultivars in addition to its xylan degradation activity. It is not clear, however, whether elicitation occurs by cell wall fragments released by the enzymatic activity or by the xylanase protein interacting directly with the plant cells. We cloned the gene encoding EIX protein and overexpressed it in insect cells. To determine the relationship between the two activities, substitution of amino acids in the xylanase active site was performed. Substitution at glutamic acid-86 or -177 with glutamine (Gln), aspartic acid (Asp), or glycine (Gly) inhibited the β-1-4-endoxylanase activity. Mutants having Asp-86 or Gln-177 also lost the ability to induce the hypersensitive response and ethylene biosynthesis. However, mutants having Gln-86, Gly-86, Asp-177, or Gly-177 retained ability to induce ethylene biosynthesis and the hypersensitive response. Our data show that the xylanase activity of EIX elicitor can be separated from the elicitation process, as some of the mutants lack the former but retain the latter.
TL;DR: A comparison of the deduced amino acid sequence of xylanase C with known beta-glycanase sequences showed that the encoded enzyme is a modular protein containing three different domains, indicating that the cloned enzyme is an endoxylanase.
Abstract: The gene xynC encoding xylanase C from Bacillus sp. BP-23 was cloned and expressed in Escherichia coli. The nucleotide sequence of a 3538 bp DNA fragment containing xynC gene was determined, revealing an open reading frame of 3258 bp that encodes a protein of 120567 Da. A comparison of the deduced amino acid sequence of xylanase C with known β-glycanase sequences showed that the encoded enzyme is a modular protein containing three different domains. The central region of the enzyme is the catalytic domain, which shows high homology to family 10 xylanases. A domain homologous to family IX cellulose-binding domains is located in the C-terminal region of xylanase C, whilst the N-terminal region of the enzyme shows homology to thermostabilizing domains found in several thermophilic enzymes. Xylanase C showed an activity profile similar to that of enzymes from mesophilic microorganisms. Maximum activity was found at 45°C, and the enzyme was only stable at 55°C or lower temperatures. Xylotetraose, xylotriose, xylobiose and xylose were the main products from birchwood xylan hydrolysis, whilst the enzyme showed increasing activity on xylo-oligosaccharides of increasing length, indicating that the cloned enzyme is an endoxylanase. A deletion derivative of xylanase C, lacking the region homologous to thermostabilizing domains, was constructed. The truncated enzyme showed a lower optimum temperature for activity than the full-length enzyme, 35°C instead of 45°C, and a reduced thermal stability that resulted in a complete inactivation of the enzyme after 2 h incubation at 55°C.
TL;DR: The three‐dimensional X‐ray structure of Xylanase I is determined to near atomic resolution by molecular replacement, and thereby corrected the chemically determined sequence previously published, and may provide a useful guide for site‐directed mutagenesis aimed to improve the thermostability of βα‐barrel proteins.
Abstract: Xylanase I is a thermostable xylanase from the fungus Thermoascus aurantiacus, which belongs to family 10 in the current classification of glycosyl hydrolases. We have determined the three-dimensional X-ray structure of this enzyme to near atomic resolution (1.14 A) by molecular replacement, and thereby corrected the chemically determined sequence previously published. Among the five members of family 10 enzymes for which the structure has been determined, Xylanase I from T. aurantiacus and Xylanase Z from C. thermocellum are from thermophilic organisms. A comparison with the three other available structures of the family 10 xylanases from mesophilic organisms suggests that thermostability is effected mainly by improvement of the hydrophobic packing, favorable interactions of charged side chains with the helix dipoles and introduction of prolines at the N-terminus of helices. In contrast to other classes of proteins, there is very little evidence for a contribution of salt bridges to thermostability in the family 10 xylanases from thermophiles. Further analysis of the structures of other proteins from thermophiles with eight-fold βα-barrel architecture suggests that favorable interactions of charged side chains with the helix dipoles may be a common way in which thermophilic proteins with this fold are stabilized. As this is the most common type of protein architecture, this finding may provide a useful guide for site-directed mutagenesis aimed to improve the thermostability of βα-barrel proteins. Proteins 1999;36:295–306. © 1999 Wiley-Liss, Inc.
TL;DR: Using monomeric xylose as well as a variety of linear and branched xylooligomers at high concentrations (typically 20% w/v) as cryoprotectant for low-temperature crystallographic experiments suggests itself as a simple and widely applicable alternative to the use of crystallographic flow-cells for substrate-saturation experiments.
Abstract: Following a recent low-temperature crystal structure analysis of the native xylanase from Penicillium simplicissimum [Schmidt et al. (1998) Protein Sci. 7, 2081−2088], where an array of glycerol mo...
TL;DR: Three agricultural wastes were evaluated for xylanolytic enzymes production by Aspergillus tamarii in solid state fermentation and the addition of xylan or β-methyl-xyloside in the cultures increased considerably the production of both xylanase and β- xylosidase without increasing theProduction of protease.
Abstract: Three agricultural wastes were evaluated for xylanolytic enzymes production by Aspergillus tamarii in solid state fermentation. A high production of xylanase and β-xylosidase was obtained in all waste materials. A high proteolytic activity was co-produced in wheat bran cultures, while a low proteolytic activity was detected in corn cob and sugar cane bagasse cultures. Optimal initial moisture contents for xylanolytic enzyme production were 86%, 80% and 75%, respectively to wheat bran, corn cob and sugar cane bagasse cultures. The addition of xylan or β-methyl-xyloside in the cultures increased considerably the production of both xylanase and β-xylosidase without increasing the production of protease. Neither heating, alkali nor hydrogen peroxide treatment of the milled substrate caused further improvement in enzyme production.
TL;DR: A proline residue in the middle of the alpha-helix alpha6 which may be contributing to better packing is observed for the first time in the F/10 family xylanases, and the refined protein model has allowed a detailed comparison with the other known structures in the P21 family of enzymes.
TL;DR: An in vitro procedure that simulated digestion in growing broilers was tested to predict phosphorus availability and arabinoxylan hydrolysis in samples of nine wheat varieties and in a wheat-based diet, and Effects observed by the in vitro procedures corresponded to in vivo phenomena described in the literature.
Abstract: An in vitro procedure that simulated digestion in growing broilers was tested to predict phosphorus availability and arabinoxylan hydrolysis in samples of nine wheat varieties and in a wheat-based diet. Amounts of dialysable phosphorus freed from wheat samples correlated with activities of endogenous phytase (R = 0.913; p < 0.0001), whereas amounts of pentoses released were correlated with viscosities of the digested samples (R = 0.899; p < 0.0001). Differences in phosphorus release resulting from graded levels of microbial phytase added to feeds that were either autoclaved or not autoclaved revealed a decreasing role of endogenous phytase in dephosphorylation as levels of microbial phytase supplementation grew. Amounts of pentoses released from feeds containing two different xylanase preparations reflected literature data on different in vivo efficacies of those preparations. Simultaneous addition of phytase and xylanase affected phosphorus release in a manner that depended upon the form of xylanase preparation used (liquid or powder). There was a positive influence of acid protease on both phytate and arabinoxylan hydrolysis in feeds supplemented with phytase. Effects observed by the in vitro procedures corresponded to in vivo phenomena described in the literature.
© 1999 Society of Chemical Industry
TL;DR: The cloning and characterisation of a protozoal enzyme involved in plant cell wall polysaccharide degradation are reported for the first time and phylogenetic analysis indicates a closer relationship with catalytic domains from Gram-positive bacteria than the other fibrolytic eukaryotes from the rumen, the anaerobic fungi.
Abstract: We report for the first time the cloning and characterisation of a protozoal enzyme involved in plant cell wall polysaccharide degradation. A cDNA library was constructed from the ruminal protozoan Polyplastron multivesiculatum and a stable clone expressing xylanase activity was isolated. The encoded enzyme belongs to the glycoside hydrolase family 11, and phylogenetic analysis indicates a closer relationship with catalytic domains from Gram-positive bacteria than the other fibrolytic eukaryotes from the rumen, the anaerobic fungi.
TL;DR: The in vitro dialysable phosphorus predicted 71% of the variability observed in body gains, whereas amounts of pentoses freed from feed samples in vitro were highly correlated with feed efficiencies when the data were subjected to Hanes transformation.
Abstract: In a 2 week study with broilers, graded levels of phytase added to feeds containing 6.70 g kg−1 of Ca, 4.80 g kg−1 of total phosphorus along with the recommended xylanase dosage (400 FXU kg−1) improved body weight gains quadratically (R2 = 0.55; p < 0.0001). Xylanase supplementation to feeds containing 0, 600 or 1000 units kg−1 of phytase significantly improved gains (p = 0.0072) and decreased viscosities of intestinal contents (p < 0.0001). High phytase concentrations in feeds (1000 FTU kg−1) increased intestinal viscosities, whereas, in the presence of xylanase, graded levels of phytase linearly reduced viscosities below the levels attained with xylanase fed as a sole supplemental enzyme (p = 0.033). Contents of ash in the toes were increased by phytase supplementation (p = 0.0011), the effect being more pronounced in birds consuming feeds that also contained xylanase. Improvements in performance and in bone mineralisation resulting from phytase and xylanase supplementation were lower than those observed in the control diets containing 4.50 g kg−1 of available phosphorus. The in vitro dialysable phosphorus predicted 71% of the variability observed in body gains, whereas amounts of pentoses freed from feed samples in vitro were highly correlated (R = 0.919) with feed efficiencies when the data were subjected to Hanes transformation.
© 1999 Society of Chemical Industry
TL;DR: Three family 10 xylanase genes (xynA, xynB, and xynC) and a single family 11 xylan enzyme gene (xnD) were identified from the extreme thermophile Caldicellulosiruptor strain Rt69B.1 through the use of consensus PCR in conjunction with sequencing and polyacrylamide gel electrophoresis.
Abstract: Three family 10 xylanase genes (xynA, xynB, and xynC) and a single family 11 xylanase gene (xynD) were identified from the extreme thermophile Caldicellulosiruptor strain Rt69B.1 through the use of consensus PCR in conjunction with sequencing and polyacrylamide gel electrophoresis. These genes appear to comprise the complete endoxylanase system of Rt69B.1. The xynA gene was found to be homologous to the xynA gene of the closely related Caldicellulosiruptor strain Rt8B.4, and primers designed previously to amplify the Rt8B.4 xynA gene could amplify homologous full-length xynA gene fragments from Rt69B.1. The complete nucleotide sequences of the Rt69B.1 xynB, xynC, and xynD genes were obtained using genomic walking PCR. The full-length xynB and xynC genes are more than 5 kb in length and encode highly modular enzymes that are the largest xylanases reported to date. XynB has an architecture similar to the family 10 xylanases from Thermoanaerobacterium saccharolyticum (XynA) and Clostridium thermocellum (XynX) and may be cell wall associated, while XynC is a bifunctional enzyme with an architecture similar to the bifunctional beta-glycanases from Caldicellulosiroptor saccharolyticus. The xynD gene encodes a two-domain family 11 xylanase that is identical in architecture to the XynB family 11 xylanase from the unrelated extreme thermophile Dictyoglomus thermophilum strain Rt46B.1. The sequence similarities between the Rt69B.1 xylanases with respect to their evolution are discussed.
TL;DR: A xylanase has been found in the archaeon Thermococcus zilligii strain AN1 (DSM 2770), which grows optimally at 75°C, and is the first description of any archaeal hemicellulase.
Abstract: A xylanase has been found in the archaeon Thermococcus zilligii strain AN1 (DSM 2770), which grows optimally at 75°C. The enzyme had a molecular mass of 95 kDa and a unique N-terminal sequence. It had activity against all five xylans tested and against xylose oligomers, but not against other carbohydrate polymers. The Km values found for xylans were typical of those found for bacterial xylanases. The pH optimum for activity was pH 6, and the enzyme half-life at 100°C was 8 min. This is the first description of any archaeal hemicellulase.
TL;DR: Changes in molecular weight distributions of xylan were observed to be the same for xylanases from C. cellulolyticum confirming the endo-mode of action of these enzymes.
TL;DR: Application of the enzymes promoted the growth of methanogenic bacteria, with no effect on total bacterial or cellulolytic bacterial populations, and enhanced both β-endoglucanase and xylanase activities.
Abstract: The effects of exogenous fibrolytic enzymes, α-bromoethanesulfonate (BES) and monensin on fermentation and digestibility of grass hay were examined using two rumen simulation technique (RUSITEC) devices, each equipped with eight 820-mL fermenters with a liquid dilution rate of 0.73 d−1. Grass hay (10 g d−1) was fed either untreated or pre-treated with 0.2 g each of cellulase and xylanase, and in combination with no chemical or daily dosing of 20.5 µmol monensin, 20.5 µmol BES or 41 µmol BES. Pretreatment of hay with the fibrolytic enzymes increased (P < 0.05) organic matter (OM), cellulose and hemicellulose digestibilities by 9, 15, and 20%, respectively, and increased (P < 0.05) methane production per gram digestible OM by 43%. With the enzyme treatment, both β-endoglucanase and xylanase activities were enhanced (P < 0.05). Application of the enzymes promoted (P < 0.05) the growth of methanogenic bacteria, with no effect on total bacterial or cellulolytic bacterial populations. α-Bromoethanesulfonate did...
TL;DR: The formation of polysaccharide complexes during secondary thickening and the structure of the pectic-xylan–xyloglucan complexes in cauliflower stem tissues are discussed.
TL;DR: Extracellular endo-1,4-β-xylanase (EC 3.2.1.8) synthesis in the yeast Trichosporon cutaneum SL409 is inducible and can be induced in washed glucose-grown cells by xylan or xylose.
TL;DR: The effects of xylanase and cellulase on plant cell Walls were consistent with the view that hemicellulose surrounds cellulose in plant cell walls.
Abstract: Melanocarpus albomyces, a thermophilic fungus isolated from compost by enrichment culture in a liquid medium containing sugarcane bagasse, produced cellulase-free xylanase in culture medium. The fungus was unusual in that xylanase activity was inducible not only by hemicellulosic material but also by the monomeric pentosan unit of xylan but not by glucose. Concentration of bagasse-grown culture filtrate protein followed by size-exclusion and anion-exchange chromatography separated four xylanase activities. Under identical conditions of protein purification, xylanase I was absent in the xylose-grown culture filtrate. Two xylanase activities, a minor xylanase IA and a major xylanase IIIA, were purified to apparent homogeneity from bagasse-grown cultures. Both xylanases were specific for beta-1,4 xylose-rich polymer, optimally active, respectively, at pH 6.6 an 5.6, and at 65 degree celcius.The xylanases were stable between pH 5 to 10 at 50 degree celcius for 24h. Xylanases released xylobiose, xylotriose and higher oligomers from xylans from different sources. Xylanase IA were 0.33 and 311, and of xylanase IIIa 1.69 and 500, respectively. Xylanases IA, II an IIIA showed no synergism in the hydrolysis of larchwood glucuronoxylan or oat spelt and sugarcane bagasse arabinoxylans. They had different reactivity on untreated and delignified bagasse. The xylanases were more reactive than cellulase on delignified bagasse. Simultaneous treatment of delignified bagasse by xylanase and cellulase released more sugar than individual enzyme treatments. By contrast, the primary cell walls of a plant, particularly from the region of elongaton, were more susceptible to the action of cellulase than xylanase. The effects of xylanase and cellulase on plant cell walls were consistent with the view that hemicellulose surrounds cellulose in plant cell walls.
TL;DR: The results obtained with enzymatic treatment of Kraft pulp indicated a reduction in the amount of chlorine compounds required for the process and enhanced brightness gain and XynI did not show significant sequence homology with other xylanases.
Abstract: A low-molecular-weight xylanase activity (XynI) was isolated from the fungus Acrophialophora nainiana after growth in a solid medium containing wheat bran. XynI was purified to apparent homogeneity by ultrafiltration and gel filtration chromatography. The purified enzyme had a molecular weight value of approx. 17 kDa, as determined by SDS-PAGE. This enzyme was most active at 50°C and pH 6.0. At 50°C the half-life was 150 min. The apparent Km value for birchwood xylan was much lower than the Km value for oat spelt xylan. XynI was activated by L-cysteine, DTE, β-mercaptoethanol, and L-tryptophan. XynI did not show significant sequence homology with other xylanases. The analysis of hydrolysis products of xylans and wood pulps showed that XynI was able to release xylooligomers ranging from X2 to X3 and X2 to X6, respectively. The enzyme was not active against acetylated xylan. A small amount of xylose was released from deacetylated, birchwood, and oat spelt xylans. The results obtained with enzymatic treatment of Kraft pulp indicated a reduction in the amount of chlorine compounds required for the process and enhanced brightness gain.
TL;DR: The proposed mechanism for production of octyl xylobioside and xyloside involved the reaction of xylan and octanol by xylanase to produce octyl £1,000,000-worth of xylotrioside and £1,500,000 ofxylobiose, the latter of which was simultaneously hydrolyzed byxylanase into octyl Xylosid and xyobiose.
Abstract: 1-Octyl β-d-xylobioside and xyloside were prepared by direct transglycosylation reaction of xylan and 1-octanol using purified xylanase from Aureobasidium pullulans. 2-Ethylhexyl β-d- xylobioside and xyloside were also prepared in the same way. The maximum yields of 2-ethylhexyl β-d-xylobioside and 2-ethylhexyl β-d-xyloside were 110 and 54 mg/g xylan, respectively. The proposed mechanism for production of octyl xylobioside and xyloside involved the reaction of xylan and octanol by xylanase to produce octyl xylobioside and xylotrioside, the latter of which was simultaneously hydrolyzed by xylanase into octyl xyloside and xylobiose.