Showing papers on "Xylanase published in 2002"
TL;DR: Under the optimized conditions, the activity and productivity of xylanase obtained after 5 days of fermentation were 5,071 IU/g of rice straw and 14,790 IU l–1 h–1, respectively.
Abstract: The initial moisture content, cultivation time, inoculum size and concentration of basal medium were optimized in solid state fermentation (SSF) for the production of xylanase by an Aspergillus niger mutant using statistical experimental designs. The cultivation time and concentration of basal medium were the most important factors affecting xylanase activity. An inoculum size of 5 x 10(5) spores/g, initial moisture content of 65%, cultivation time of 5 days and 10 times concentration of basal medium containing 50 times concentration of corn steep liquor were optimum for xylanase production in SSF. Under the optimized conditions, the activity and productivity of xylanase obtained after 5 days of fermentation were 5,071 IU/g of rice straw and 14,790 IU l(-1) h(-1), respectively. The xylanase activity predicted by a polynomial model was 5,484 IU/g of rice straw.
222 citations
TL;DR: This novel xylanase, isolated from the Antarctic bacterium Pseudoalteromonas haloplanktis, is not homologous to family 10 or 11 enzymes but has 20–30% identity with family 8 members and NMR analysis shows that this enzyme hydrolyzes with inversion of anomeric configuration, in contrast to other known xylanases which are retaining.
208 citations
TL;DR: It was concluded that dietary cereals producing high intestinal viscosities lead to increased overall bacterial activity in the small intestine, especially in the first week of life.
Abstract: Several studies were carried out to investigate the influence of dietary cereals differing in soluble non starch polysaccharides (NSP) content and a xylanase preparation on selected bacterial parameters in the small intestine of broiler chicken. Compared to a maize diet colony forming units (CFU) of mucosa associated bacteria were higher in a wheat/rye diet, most notably for enterobacteria and enterococci. Xylanase supplementation to the wheat/rye diet generally led to lower CFU, especially in the first week of life. However, xylanase supplementation also displayed higher in vitro growth potentials for enterobacteria and enterococci. Bacterial growth of luminal samples in minimal media supplemented with selected NSP showed that the wheat/rye diet enhanced bacterial capacities to utilize NSP only in ileal samples. The xylanase application generally shifted respective maximum growth to the proximal part of the small intestine. The presence of soluble NSP from wheat or rye in the diet per se did not enhance ...
145 citations
TL;DR: The addition of xylanase and β-glucanase to the wheat and bar- ley-based diet significantly reduced the viscosity of the small intestine contents and improved the weight gain, feed intake and feed conversion ratio.
Abstract: Corn- or wheat and barley-based diets were supplemented or not with xylanase and β-glucanase (Quatrazyme HP, Nutri-Tomen, France) and fed to broiler chickens (n = 12 per group) from 3 to 25 days of age. The unsupplemented wheat and barley-based diet reduced (P ≤ 0.05) weight gain and feed intake, and increased the feed conversion ratio as compared to the corn-based diet. Vis- cosity in the supernatant of the small intestine contents was increased (P ≤ 0.05), whereas pH and osmolality values decreased (P ≤ 0.05). Crude fat and protein digestibility were reduced as well as the apparent metabolizable energy (P ≤ 0.05). Moreover, wheat and barley consumption, when com- pared with the corn-based diet, produced an increase in the microflora of the caeca, with 10.0 vs. 8.9 log CFU·g -1 for facultative anaerobic bacteria, 6.5 vs. 5.6 log CFU·g -1 for E. coli and 9.7 vs. 8.3 log CFU·g -1 for Lactobacillus. The addition of xylanase and β-glucanase to the wheat and bar- ley-based diet significantly reduced the viscosity of the small intestine contents and improved (P ≤ 0.05) weight gain, feed intake and feed conversion ratio. The digestibility of the nutrients, the apparent metabolizable energy and the osmolality of the small intestine contents were also increased without alteration in pH values. At the same time, the number of total facultative anaerobic bacteria and E. coli decreased significantly (P ≤ 0.05). In conclusion, the addition of xylanase and β-glucanase improves the digestibility of a wheat and barley-based diet, probably by reducing the viscosity of the intestine content and by impeding the growth of bacteria (total facultative anaerobic bacteria, E. coli). xylanase / -glucanase / wheat / barley / broiler / microflora
141 citations
TL;DR: The results indicated that the selected microorganisms, and the cultivation process, have great biotechnological potential.
128 citations
TL;DR: It is shown that XIP-I inhibits family-10 and -11 fungal xylanases and binds to the slow-binding inhibitor of Aspergillus niger xylanase.
Abstract: We previously reported on the xylanase-inhibiting protein I (XIP-I) from wheat [McLauchlan, Garcia-Conesa, Williamson, Roza, Ravestein and Maat (1999), Biochem. J. 338, 441-446]. In the present study, we show that XIP-I inhibits family-10 and -11 fungal xylanases. The K(i) values for fungal xylanases ranged from 3.4 to 610 nM, but bacterial family-10 and -11 xylanases were not inhibited. Unlike many glycosidase inhibitors, XIP-I was not a slow-binding inhibitor of the Aspergillus niger xylanase. Isothermal titration calorimetry of the XIP-I-A. niger xylanase complex showed the formation of a stoichiometric (1:1) complex with a heat capacity change of -1.38 kJ x mol(-1) x K(-1), leading to a predicted buried surface area of approx. 2200+/-500 A(2) at the complex interface. For this complex with A. niger xylanase (K(i)=320 nM at pH 5.5), titration curves indicated that an observable interaction occurred at pH 4-7, and this was consistent with the pH profile of inhibition of activity. In contrast, the stronger complex between A. nidulans xylanase and XIP-I (K(i)=9 nM) led to an observable interaction across the entire pH range tested (3-9). Using surface plasmon resonance, we show that the differences in the binding affinity of XIP-I for A. niger and A. nidulans xylanase are due to a 200-fold lower dissociation rate k(off) for the latter, with only a small difference in association rate k(on).
115 citations
TL;DR: A simple, robust and highly reproducible method for the determination of xylanase, β-glucanase, and cellulase in commercial feed enzyme preparations is described and is independent of enzyme standards.
Abstract: A simple, robust and highly reproducible method for the determination of xylanase, β-glucanase, and cellulase in commercial feed enzyme preparations is described. The method is based on measurement of reducing moieties released by the enzymes from arabinoxylan, β-glucan, or carboxymethylcellulose (CMC) and is independent of enzyme standards.
109 citations
TL;DR: A purified thermostable (1→4)-β-endo-xylanase, solubilised 50% of the arabinoxylan in cell walls of wheat bran, and showed that the aleurone layer had been completely disorganised and was resistant to endoxylanase treatment.
108 citations
TL;DR: This bacterial strain was able to produce a medium–high range of extracellular xylanolytic activity levels for liquid cultures containing commercial xylans and agro-industrial by-products and wastes and could be considered as a thermotolerant biocatalyst being interesting for biotechnological applications.
107 citations
TL;DR: Results indicate that Aspergillus ferulic acid esterase is able to break the ester linkage between FA and the attached sugar, releasing FA from oat hulls, likely to improve rumen biodegradability, thus improving the nutritional value of oat Hulls.
Abstract: Oat hulls, an agricultural byproduct, contain a relatively high amount of ferulic acid (FA; 4-hydroxy-3-methoxycinnamic acid), which is believed to be inhibitory to oat hull biodegradability by rumen microorganisms. In this paper, Aspergillus ferulic acid esterase (FAE) was investigated for its ability to release FA from oat hulls. The objectives were to determine the effects of particle size of oat hulls (ground to pass through 1 mm and 250 microm screens and a 100 microm sieve) on release of FA by FAE both in the presence and in the absence of Trichoderma xylanase. The results show that the release of FA by FAE was dependent upon the particle size of oat hulls (< or = 250 microm). In the absence of Trichoderma xylanase, little FA was released by FAE. In the presence of Trichoderma xylanase, there was a significant release of FA by FAE, indicating a synergistic interaction between FAE and Trichoderma xylanase on release of FA from oat hulls. These results indicate that FAE is able to break the ester linkage between FA and the attached sugar, releasing FA from oat hulls. This may leave the remainder of the polysaccharides open for further hydrolytic attack by rumen microorganisms. It is likely that removing FA from oat hulls could improve rumen biodegradability, thus improving the nutritional value of oat hulls.
101 citations
TL;DR: A second-order model was proposed to represent the enzymic activity as a function of xylan concentration and cultivation time, which predicted a xylanase activity of 19.1 U/ml.
TL;DR: The purified xylanase was fully stable at pH 5.0–7.5 and temperature up to 55 °C and hydrolyzed a variety of xylan substrates mainly to xylobiose and higher short-chain xylooligosaccharides and no xylose was formed.
TL;DR: The xylanase activity was stimulated (+25%) by Na+ and Fe2+ and was strongly inhibited (maximum by 70%) by Tween-20, 40, 60, SDS, acetic anhydride, phenylmethane sulphonyl fluoride, Triton-X-100.
TL;DR: A Bacillus subtilis strain isolated from a hot-spring was shown to produce xylanolytic enzymes and their associative/synergistic effect was studied using a culture medium with oat spelts xylan as xylanase inducer, showing full stability at 60°C during 3 h and under optimised fermentation conditions, no cellulolytic activity was detected.
TL;DR: Results indicate that XynA is a key enzymatic subunit for xylan degradation in C. cellulovorans.
Abstract: The Clostridium cellulovorans xynA gene encodes the cellulosomal endo-1,4-β-xylanase XynA, which consists of a family 11 glycoside hydrolase catalytic domain (CD), a dockerin domain, and a NodB domain. The recombinant acetyl xylan esterase (rNodB) encoded by the NodB domain exhibited broad substrate specificity and released acetate not only from acetylated xylan but also from other acetylated substrates. rNodB acted synergistically with the xylanase CD of XynA for hydrolysis of acetylated xylan. Immunological analyses revealed that XynA corresponds to a major xylanase in the cellulosomal fraction. These results indicate that XynA is a key enzymatic subunit for xylan degradation in C. cellulovorans.
TL;DR: There was a greater decrease in viscosity with the combination of xylanase and beta-glucanase than with addition ofxylanase or beta- glucanases alone and this synergistic action of x Dylanase and Beta-glue was observed only in Rialto wheat, Sidéral wheat, triticale, rye, barley, oats, and peas.
Abstract: This study was carried out to evaluate the effects of a pure xylanase, a pure beta-glucanase, a mix of the two pure enzymes, and a commercial enzyme preparation (Quatrazyme HP, Nutri-Tomen Les Ulis, France) on the viscosity exhibited by water-soluble nonstarch polysaccharides of several feedstuffs (Rialto wheat, Sideral wheat, Isengrain wheat, triticale, rye, barley, oats, corn, wheat bran, rice bran, wheat screenings, soybean meal, rapeseed meal, sunflower meal, and peas). The viscosity depended on the feedstuffs and varieties of the same feedstuff. There was a correlation (R (2) = 0.86) between viscosity of cereals and their arabinoxylan and beta-glucan contents. The correlation was greater (R (2) = 0.99) when the type of cereal was taken into account. The addition of pure xylanase significantly decreased the viscosity of all feedstuffs except sunflower meal (P < or = 0.05). However, pure beta-glucanase was unable significantly to decrease the viscosity of Isengrain wheat, corn, rice bran, wheat screenings, soybean meal, and sunflower meal. There was a greater decrease in viscosity with the combination of xylanase and beta-glucanase than with addition of xylanase or beta-glucanase alone. This synergistic action of xylanase and beta-glucanase was observed only in Rialto wheat, Sideral wheat, triticale, rye, barley, oats, and peas. Finally, the commercial enzyme preparation produced a greater reduction (P < or = 0.05) in viscosity for all feedstuffs compared to xylanase or beta-glucanase used alone or in combination. The greater effectiveness of the commercial enzyme preparation was due to the presence of side enzymatic activities (arabinofuranosidase, xylosidase, glucosidase, galactosidase, cellulase, and polygalacturonase).
TL;DR: Evidence is provided that fibrolytic enzymes can be used to improve milk production in lactating cows and in vitro production of gas from forages treated with enzymes was greater than from untreated forage.
TL;DR: A close inspection of the three-dimensional structure of A. niger xylanase suggests that the binding site of XIP-I is located at the conserved “thumb” hairpin loop of family 11 xylanases.
TL;DR: The inside part of plants is a novel and good source for isolating xylanase producers in comparison with soil.
TL;DR: The AT-rich xynB gene of Dictyoglomus thermophilum is reconstructed according to Trichoderma codon preferences and a dramatic increase in expression is demonstrated and a heterologous fungal gene, Humicola grisea xyn2, could be expressed without codon modification.
Abstract: Bulk production of xylanases from thermophilic microorganisms is a prerequisite for their use in industrial processes. As effective secretors of gene products, fungal expression systems provide a promising, industrially relevant alternative to bacteria for heterologous enzyme production. We are currently developing the yeast Kluyveromyces lactis and the filamentous fungus Trichoderma reesei for the extracellular production of thermophilic enzymes for the pulp and paper industry. The K. lactis system has been tested with two thermophilic xylanases and secretes gram amounts of largely pure xylanase A from Dictyoglomus thermophilum in chemostat culture. The T. reesei expression system involves the use of the cellobiohydrolase I (CBHI) promoter and gene fusions for the secretion of heterologous thermostable xylanases of both bacterial and fungal origin. We have reconstructed the AT-rich xynB gene of Dictyoglomus thermophilum according to Trichoderma codon preferences and demonstrated a dramatic increase in expression. A heterologous fungal gene, Humicola grisea xyn2, could be expressed without codon modification. Initial amounts of the XYN2 protein were of a gram per liter range in shake-flask cultivations, and the gene product was correctly processed by the heterologous host. Comparison of the expression of three thermophilic heterologous microbial xylanases in T. reesei demonstrates the need for addressing each case individually.
Patent•
05 Aug 2002
TL;DR: In this article, the authors provided nucleotide sequences of Aspergillus fumigatus that encode proteins which exhibit enzyme activities, including those of a tannase, cellulase, glucose oxidase, glucoamylase, phytase, β-glactosidases, invertase, lipase, α-amylases, laccase, polygalacturonase or xylanase.
Abstract: The present invention provides nucleotide sequences of Aspergillus fumigatus that encode proteins which exhibit enzyme activities. Vectors, expression constructs, and host cells comprising the nucleotide sequences of the enzyme genes are also provided. The invention further provides methods for producing the enzymes, and methods for modifying the enzymes in order to improve their desirable characteristics. The activities displayed by the enzymes of the invention include those of a tannase, cellulase, glucose oxidase, glucoamylase, phytase, β-glactosidases, invertase, lipase, α-amylase, laccase, polygalacturonase or xylanase. The enzymes of the invention can be used in a variety of industrial processes. Enzymatically active compositions in various forms as well as antibodies to the enzymes and fragments thereof, are also provided.
TL;DR: Arabinoxylan arabinosyltransferase (AX-AraT) activity was investigated using microsomes and Golgi vesicles isolated from wheat seedlings, indicating a high degree of UDP-arabinose (Ara) epimerization and the possible role of this protein in arabinox Dylan biosynthesis is discussed.
Abstract: Arabinoxylan arabinosyltransferase (AX-AraT) activity was investigated using microsomes and Golgi vesicles isolated from wheat (Triticum aestivum) seedlings. Incubation of microsomes with UDP-[14C]-β-l-arabinopyranose resulted in incorporation of radioactivity into two different products, although most of the radioactivity was present in xylose (Xyl), indicating a high degree of UDP-arabinose (Ara) epimerization. In isolated Golgi vesicles, the epimerization was negligible, and incubation with UDP-[14C]Ara resulted in formation of a product that could be solubilized with proteinase K. In contrast, when Golgi vesicles were incubated with UDP-[14C]Ara in the presence of unlabeled UDP-Xyl, the product obtained could be solubilized with xylanase, whereas proteinase K had no effect. Thus, the AX-AraT is dependent on the synthesis of unsubstituted xylan acting as acceptor. Further analysis of the radiolabeled product formed in the presence of unlabeled UDP-Xyl revealed that it had an apparent molecular mass of approximately 500 kD. Furthermore, the total incorporation of [14C]Ara was dependent on the time of incubation and the amount of Golgi protein used. AX-AraT activity had a pH optimum at 6, and required the presence of divalent cations, Mn2+ being the most efficient. In the absence of UDP-Xyl, a single arabinosylated protein with an apparent molecular mass of 40 kD was radiolabeled. The [14C]Ara labeling became reversible by adding unlabeled UDP-Xyl to the reaction medium. The possible role of this protein in arabinoxylan biosynthesis is discussed.
TL;DR: Aims: To express a gene encoding a heterologous fungal xylanase in Trichoderma reesei, and to demonstrate the ability of this gene to be switched on by the immune system.
Abstract: Aims: To express a gene encoding a heterologous fungal xylanase in Trichoderma reesei.
Methods and Results:Humicola grisea xylanase 2 (xyn2) cDNA was expressed in Trichoderma reesei under the main cellobiohydrolase I (cbh1) promoter (i) as a fusion to the cellobiohydrolase I (CBHI) secretion signal and (ii) the mature CBHI core-linker. The recombinant xylanase (HXYN2) was secreted into the cultivation medium and processed in a similar fashion to the endogenous T. reesei xylanases, resulting in an active enzyme.
Conclusions, Significance and Impact of the Study: HXYN2 was successfully processed in T. reesei. Composition of the culture medium affected the HXYN2 yields, favouring Avicel-lactose as a carbon source. Best yields (about 0·5 g l−1) in shake flask cultivations were obtained from a transformant where xyn2 was fused directly to the CBHI secretion signal.
TL;DR: Cellulase-free xylanase was produced by Streptomyces sp.
TL;DR: The xylanase II (xyn2)- and endoglucanase I (egI)-encoding regions of Trichoderma reesei QM6a were successfully expressed in Aspergillus niger D15 under the transcriptional control of the glyceraldehyde-6-phosphate dehydrogenase (gpd) promoter from A. niger and the glaA terminator of As pergillus awamori.
Abstract: The xylanase II (xyn2)- and endoglucanase I (egI)-encoding regions of Trichoderma reesei QM6a were successfully expressed in Aspergillus niger D15 under the transcriptional control of the glyceraldehyde-6-phosphate dehydrogenase (gpd) promoter from A. niger and the glaA terminator of Aspergillus awamori. A stable xyn2 transformant produced β-xylanase activity of 8,000 nkat/ml and 5,000 nkat/ml in shake-flask cultures containing defined or 20% (v/v) molasses medium, respectively. The recombinant Xyn2 enzyme expressed highest activity at pH 5–6 and 50–60 °C and retained more than 75% of its activity after 3 h of incubation at 50 °C. A stable egI transformant produced endo-β-1,4-glucanase activity of 2,300 nkat/ml in shake-flask cultures containing defined media and about half the activity in 20% molasses medium. Maximum endoglucanase activity was obtained at pH 5 and 60 °C. Both Xyn2 and EgI retained >80% activity after incubation at 50 °C for 3 h. The heterologous Xyn2 and EgI represent a significant portion of the total extracellular proteins produced.
TL;DR: An aerobic, thermophilic, xylanolytic bacterium was isolated from local soil and the results of 16S rRNA sequence comparisons indicated that the isolate was closely related to Bacillus caldoxylolyticus and Bacillus sp strain AK1.
Abstract: An aerobic, thermophilic, xylanolytic bacterium was isolated from local soil. The results of 16S rRNA sequence comparisons indicated that the isolate was closely related to Bacillus caldoxylolyticus and Bacillus sp strain AK1. These organisms exhibited 94% levels of ribossomal DNA sequence homology. Studies on the xylanase characterisation from liquid cultures grown on beechwood xylan revealed that the enzyme retained 100% of activity for 2 hours at temperatures ranging from 30 to 50o C, while at 60, 70 and 100o C, 10%, 11% and 29% of the original activities were lost, respectively. The optimum pH of the enzyme was found to be between 6.5 and 7.0. After incubation of crude enzyme solution for 24 hours at 25o C and at pH 5.5 to 8.0, a decrease of about 12% of its original activity was observed.
TL;DR: Xylanase from Aspergillus tamarii was covalently immobilized on Duolite A147 pretreated with the bifunctional agent glutaraldehyde and retained about 73.0% of the initial catalytic activity even after being used 8 cycles.
TL;DR: Observation by fluorescence microscopy and analysis of the localization of beta-glucuronidase activity in transgenic A. thaliana plants containing a chimeric gene with the upstream sequence of the AtXyn1 gene and the GUS gene suggest that AtXn1 is involved in the secondary cell wall metabolism of vascular bundle cells.
Abstract: The cDNA clone RXF12, which encodes a xylanase (EC 3.2.1.8), was isolated from Arabidopsis thaliana. The C-terminal half of the amino acid sequence of the deduced protein, named AtXyn1, showed similarity with the catalytic domain of barley xylanase X-1. The N-terminal half of AtXyn1 also contained three regions with sequences similar to cellulose-binding domains (CBDs). A xylanase assay revealed that transgenic A. thaliana plants expressing exogenous AtXyn1 fused with enhanced green fluorescent protein (EGFP) possessed approximately twice as much xylanase activity as wild-type plants. Observation by fluorescence microscopy of transgenic A. thaliana plants expressing a fusion protein of AtXyn1 and EGFP suggested that AtXyn1 is a cell wall protein. Analysis of the localization of beta-glucuronidase (GUS) activity in transgenic A. thaliana plants containing a chimeric gene with the upstream sequence of the AtXyn1 gene and the GUS gene demonstrated that the AtXyn1 gene is predominantly expressed in vascular bundles, but not in vessel cells. These data suggest that AtXyn1 is involved in the secondary cell wall metabolism of vascular bundle cells. A database search revealed that four putative xylanase genes exist in the A. thaliana genome, besides the AtXyn1 gene. Of these, two also contain several regions with sequences similar to CBDs in their N-terminal regions. Comparison of the amino acid sequences of the five xylanases suggests a possible process for their molecular evolution.
TL;DR: Sugarcane bagasse was used as substrate for xylanase production by means of a strain of Trichoderma harzianum Rifai isolated from decaying Aspidosperma sp.
TL;DR: A Bacillus sp.