共查询到20条相似文献,搜索用时 15 毫秒
1.
Liab K Azadi P Collins R Tolan J Kim JS Eriksson KL 《Enzyme and microbial technology》2000,27(1-2):89-94
Structures of five water-soluble xylans have been determined. Four purified xylanase enzymes have been studied for the hydrolysis of the xylans. Different xylanases have different activities against various xylan structures. The key factors that influence the rate of xylan hydrolysis are chain length and degree of substitution. Two family 11 xylanases, Orpinomyces pc2 xylanase and Trichoderma longibrachiatum xylanase, can rapidly hydrolyze xylans that have a chain length greater than 8 xylose residues, and their hydrolytic rates are not sensitive to substituents on the xylan backbone. A family 11 xylanase from Aureobasidium pullulans is most effective on xylans that have a long chain (greater than 19 xylose residues), and also is effective against substituent groups. Although Thermatoga maritima xylanase is also more active on a long xylan chain (greater than 19 xylose residues), its hydrolytic rate is greatly reduced by substituents on xylan backbones. 相似文献
2.
The hydrolysis of five xylan substrates was examined using combinations of two pairs of xylanases from two species of Trichoderma. Antisynergy was observed in acetylated xylan isolated from aspen when the maximum hydrolysis achieved by certain xylanase combinations was significantly lower than that achieved by the most effective enzyme in the combination. Cooperative interactions among xylanases were observed in pine holocellulose where xylanase combinations were more effective than single xylanases. 相似文献
3.
A strain of Aspergillus giganteus cultivated in a medium with xylan produced two xylanases (xylanase I and II) which were purified to homogeneity. Their molar mass, estimated by SDS-PAGE, were 21 and 24 kDa, respectively. Both enzymes are glycoproteins with 50 degrees C temperature optimum; optimum pH was 6.0-6.5 for xylanase I and 6.0 for xylanase II. At 50 degrees C xylanase I exhibited higher thermostability than xylanase II. Hg2+, Cu2+ and SDS were strong inhibitors, 1,4-dithiothreitol stimulated the reaction of both enzymes. Both xylanases are xylan-specific; kinetic parameters indicated higher efficiency in the hydrolysis of oat spelts xylan. In hydrolysis of this substrate, xylotriose, xylotetraose and larger xylooligosaccharides were released and hence the enzymes were classified as endoxylanases. 相似文献
4.
Dieter Kluepfel Nicole Daigneault Rolf Morosoli François Shareck 《Applied microbiology and biotechnology》1992,36(5):626-631
Summary A third extracellular xylanase produced by Streptomyces lividans 66 was isolated from a clone obtained by shotgun cloning through functional complementation of a xylanase- and cellulase-negative mutant using the multicopy vector pIJ702. This enzyme, designated xylanase C, has a relative molecular mass of 22000 and acts on xylan similarly to xylanase B as an endo-type xylanase producing short-chain oligoxylosides. Its specific activity determined at 1100 IU·mg–1 of protein corresponds on a molecular basis to that of xylanase B and is about three times that of xylanase A. The enzyme shows optimal activity at pH 6.0 and 57°C, values that correspond closely to those observed previously for xylanase A and B. Xylanase C appears not to be glycosylated and has a pI > 10.25. Its K
m and V
max on birchwood xylan are 4.1 mg·ml–1 and 3.0 mol·min–1·mg–1 of enzyme respectively. Whereas specific antibodies raised against xylanase A show no cross-reaction with either xylanase B or with xylanase C, the anti-(xylanase C) antibodies react slightly with xylanase B but not with xylanase A. A comparison of hydrolysis products obtained by reacting individually the three enzymes with birchwood xylan showed characteristic endo-activity patterns for xylanases B and C, whereas xylanase A hydrolysed the substrate preferentially into xylobiose and xylotriose. Sequential xylanase action on the same substrates showed synergistic hydrolysis only when endo-xylanase activity was followed by that of xylanase A. 相似文献
5.
Johanna Buchert Marjatta Ranua Anne Kantelinen Liisa Viikari 《Applied microbiology and biotechnology》1992,37(6):825-829
Summary The two major xylanases of Trichoderma reesei with different pI values and pH optima were compared for increasing the bleachability of pine kraft pulp. The efficiencies of the two enzymes acting on pulp substrate were very similar in hydrolysis yield, extraction kappa number or final brightness value. Only slight synergism between the two enzymes was observed in both hydrolysis and bleaching tests. The pH optimum of the pI 5.5 xylanase was similar in pulp treatment and in the hydrolysis of isolated substrates, and the bleaching result also correlated well with the hydrolysis of pulp xylan. By contrast, the pI 9.0 xylanase acted differently on pulp than on isolated xylans at different pH values and the pH optimum on pulp was increased. The bleachability of pulp by the pI 9.0 xylanase was improved more than expected at pH 7.0, although the hydrolysis of pulp xylan was substantially decreased. A similar phenomenon was also observed when the hydrolysis was performed in water instead of buffer. It thus appears that the degree of hydrolysis needed to obtain improved bleachability with pI 9.0 xylanase can be minimized by proper adjustment of the hydrolysis conditions.
Correspondence to: J. Buchert 相似文献
6.
Of 20 strains of Clostridium spp. screened, 17 hydrolyzed larch wood xylan. Two strains of Clostridium acetobutylicum, NRRL B527 and ATCC 824, hydrolyzed xylan but failed to grow on solid media with larch xylan as the sole carbon source; however, strain ATCC 824 was subsequently found to grow on xylan under specified conditions in a chemostat. These two strains possessed cellulolytic activity and were therefore selected for further studies. In cellobiose-limited continuous cultures, strain NRRL B527 produced maximum xylanase activity at pH 5.2. Strain ATCC 824 produced higher xylanase, xylopyranosidase, and arabinofuranosidase activities in chemostat culture with xylose than with any other soluble carbon source as the limiting nutrient. The activities of these enzymes were markedly reduced when the cells were grown in the presence of excess glucose. The xylanase showed maximum activity at pH 5.8 to 6.0 and 65°C. The enzyme was stable on the alkaline side of pH 5.2 but was unstable below this pH value. The extracellular xylanolytic activity from strain ATCC 824 hydrolyzed 12% of the larch wood xylan during a 24-h incubation period, yielding xylose, xylobiose, and xylotriose as the major hydrolysis products. Strain ATCC 824, after being induced to grow in batch culture in xylan medium supplemented with a low concentration of xylose, failed to grow reproducibly in unsupplemented xylan medium. A mutant obtained by mutagenesis with ethyl methanesulfonate was able to grow reproducibly in batch culture on xylan. Both the parent strain and the mutant were able to grow with xylan as the sole source of carbohydrate in continuous culture with the pH maintained at either 5.2 or 6.0. Under these conditions, the cells utilized approximately 50% of the xylan. 相似文献
7.
Hajime Yoshioka Nobuo Nagato Surina Chavanich Naline Nilubol Shinsaku Hayashida 《Bioscience, biotechnology, and biochemistry》2013,77(11):2425-2432
Thermostable xylanase from Talaromyces byssochlamydoides YH-50 was fractionated into three components, tentatively named X-a, X-b-I and X-b-II during the purification steps. X-a, X-b-I and X-b-II were further purified by consecutive column chromatographies until found to be in homogeneous states on disc electrophoresis. X-a, X-b-I and X-b-II contained 36.6%, 31.5% and 14.2% carbohydrate residues, respectively. The carbohydrate residues were glucose, mannose and fucose. X-a, X-b-I and X-b-II were optimally active at 70 ~ 75°C and pH 4.5 ~ 5.5. X-a, X-b-I and X-b-II retained 65, 54 and 30%, respectively, of the original activity after heating at 95°C for 5 min. The activities of X-a, X-b-I and X-b-II were considerably inhibited by HgCl2 and KMnO4. The hydrolysis products from xylan with X-a were xylose, arabinose, glucose, xylobiose and other xylooligosaccharides, whereas the hydrolysis products from xylan with X-b-I and X-b-II were xylose and xylobiose. 相似文献
8.
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
forβ-1,4 xylose-rich polymer, optimally active, respectively, at pH 6.6 and 5.6, and at 65°C. The xylanases were stable between
pH 5 to 10 at 50°C for 24 h. Xylanases released xylobiose, xylotriose and higher oligomers from xylans from different sources.
Xylanase IA had a Mr of 38 kDa and contained 7% carbohydrate whereas xylanase IIIA had a Mr of 24 kDa and no detectable carbohydrate. The Km for larchwood xylan (mg ml−1) and Vmax (μmol xylose min−1 mg−1 protein) of xylanase IA were 0.33 and 311, and of xylanase IIIA 1.69 and 500, respectively. Xylanases IA, II and 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 elongation, 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. 相似文献
9.
Junhua Zhang Päivi TuomainenMatti Siika-aho Liisa Viikari 《Bioresource technology》2011,102(19):9090-9095
Recombinant xylanase preparations from Nonomuraea flexuosa (Nf Xyn, GH11) and Thermoascus aurantiacus (Ta Xyn, GH10) were evaluated for their abilities to hydrolyze hydrothermally pretreated wheat straw. The GH family 10 enzyme Ta Xyn was clearly more efficient in solubilizing xylan from pretreated wheat straw. Improvement of the hydrolysis of hydrothermally pretreated wheat straw by addition of the thermostable xylanase preparations to thermostable cellulases was evaluated. Clear synergistic enhancement of hydrolysis of cellulose was observed when cellulases were supplemented even with a low amount of pure xylanases. Xylobiose was the main hydrolysis product from xylan. It was found that the hydrolysis of cellulose increased nearly linearly with xylan removal during the enzymatic hydrolysis. The results also showed that the xylanase preparation from T. aurantiacus, belonging to GH family 10 always showed better hydrolytic capacity of solubilizing xylan and acting synergistically with thermostable cellulases in the hydrolysis of hydrothermally pretreated wheat straw. 相似文献
10.
It was found that crude preparation obtained from the culture medium of Fusarium avenaceum degraded cellulose and xylan. After chromatography on CM-Sepharose CL-6B of this preparation six fraction were obtained. The eluted fractions II and V showed xylanase activity, fraction IV — cellulase activity and fraction III — xylanase and cellulase activity. The end products of xylan hydrolysis by all xylanase fractions (II, III, V) were xylobiose, xylose, xylotriose and xylotetrose. The end products of cellulose hydrolysis by fractions III and IV was cellobiose, glucose and cellotriose. The data from gel filtration on Sephacryl S-200 indicated a molecular weight of more than 250,000 for both cellulase IV and xylanase V. After gel filtration in the presence of urea disaggregation of those high molecular xylanase and cellulase particles was observed. Xylanase II in difference from the other fractions contained higher amount of sugar. Digestion of fraction II with cellulase-hemicellulase preparation from Phoma hibernica decreased the content of sugar from 17% to 8%, but did not change its enzymatic properties. Cellulase IV as well as xylanase V were inactivated by N-bromosuccinimide, 2-hydroxy-5-nitrobenzyl bromide and tetranitromethane, hence it is suggested that tryptophan and tyrosine are the essential for the activity of these enzymes. 相似文献
11.
The influence of lignin, lignin model compounds, and black liquor from the kraft pulping process on the hydrolysis of xylan by xylanase was investigated. Addition of vanillic acid, acetovanillone, and protocatechuic acid increased the rate of hydrolysis of xylan by as much as 18–50% at low concentrations, but reached maxima at about 0.05% concentration. Addition of vanillin caused a 15% improvement in xylan hydrolysis, while addition of guaiacol more than doubled the hydrolysis rate. Increasing concentrations of either lignin or black liquor also increased the hydrolysis rate of xylan. Circular dichroism spectroscopy indicated a change in the structure of xylanase in the presence of black liquor. 相似文献
12.
Lee CC Smith M Kibblewhite-Accinelli RE Williams TG Wagschal K Robertson GH Wong DW 《Current microbiology》2006,52(2):112-116
Xylan is the major component of hemicellulose, and xylan should be fully utilized to improve the efficiencies of a biobased
economy. There are a variety of industrial reaction conditions in which an active xylanase enzyme would be desired. As a result,
xylanase enzymes with different activity profiles are of great interest. We isolated a xylanase gene (xyn10) from a Flavobacterium sp. whose sequence suggests that it is a glycosyl hydrolase family 10 member. The enzyme has a temperature optimum of 30°C,
is active at cold temperatures, and is thermolabile. The enzyme has an apparent Km of 1.8 mg/ml and kcat of 100 sec−1 for beechwood xylan, attacks highly branched native xylan substrates, and does not have activity against glucans. 相似文献
13.
A combined hydrolysis factor (CHF) was developed to predict xylan hydrolysis during pretreatments of native aspen (Populus tremuloides) wood chips. A natural extension of previously developed kinetic models allowed us to account for the effect of catalysts by dilute acid and two sulfite pretreatments at different pH values. When xylan is modeled as two fractions with different hydrolysis rates, previously identified as fast and slow xylan, the model closely matches the experimental data. Extent of xylan hydrolysis is strongly correlated with pretreatment solids yield, energy consumption for size reduction, and substrate enzymatic digestibility (SED). Composition of the pretreatment hydrolysate was less correlated with extent of hydrolysis due to carbohydrate decomposition reactions. Substrate cellulose enzymatic conversion and enzymatic hydrolysis glucose yield can be predicted to approximately 10% accuracy using CHF alone. 相似文献
14.
A gene (arf) encoding an α-l-arabinofuranosidase (ARF) that hydrolyzes arabinose substituted on xylan was isolated from Penicillium sp. The gene was predicted to encode 339 amino acid residues showing 71–75% homology to GH family 54. E. coli expressed ARF showed optimal activity at 50°C and pH 5–6 on wheat arabinoxylan. The hydrolysis activities on oat spelt xylan
by ARF and xylanase were 1.67-fold higher than that of xylanase alone. The synergistic effects of ARF and commercial enzymes
(xylanase and cellulase) on popping-pretreated rice straw were 1.15–1.51-fold higher amounts of sugars released in the [ARF + xylanase + cellulase]
mixture than in the mixtures [ARF + xylanase], [ARF + cellulase], and [xylanase + cellulase]. Moreover, the liberation of
arabinose by ARF was enhanced 2.1–2.9-fold in a reaction with xylanase and cellulase as compared with [xylanase + cellulase]
and ARF alone. 相似文献
15.
An xylanase producing alkaliphilic Micrococcus sp was isolated from an alkaline soda lake. Xylose and xylan induced enzyme production but no activity was detected when
it was grown using other carbohydrate sources. The level of xylanase production was higher in the presence of xylose than
in the presence of xylan. The enzyme was purified to homogeneity and its molecular weight was estimated to be 56 kD on SDS-PAGE.
The optimum temperature and pH for xylanase activity were 55°C and 7.5–9.0, respectively. Sixty per cent of the maximum activity
was displayed at pH 11. The enzyme was very stable in the pH range of 6.5–10 and up to a temperature of 40°C. Xylanase activity
was inhibited by Cu2+ and Hg2+.
Received 03 October 1997/ Accepted in revised form 03 February 1998 相似文献
16.
A synthetic xylanase as a novel reporter in plants 总被引:2,自引:0,他引:2
Transient gene expression assays are often used to screen promoters before stable transformation. Current transient quantification methods have several problems, including a lack of reporter gene stability and expense. Here we report a synthetic, codon-optimised xylanase gene (sXynA) as a reporter gene for quantitative transient analyses in plants. Azurine-crosslinked xylan (AZCL-xylan) was used as a substrate for assaying xylanase activity. The enzymatic nature of the protein allows for sensitive assays at the low levels of transgene protein found in transiently transformed tissue extracts. The xylanase (XYN) protein is stable, activity slopes are linear over long time periods and assays are cost-effective. Coupled with the GUSPlus reporter gene, the XYN reporter allows sensitive and accurate quantification of gene control sequences in transient expression systems.Abbreviations Act1
Rice actin promoter
- AZCL-xylan
Azurine cross-linked xylan
- AU
absorbance units
- Blt4.9
Barley lipid transfer protein promoter
- GEB
GUS extraction buffer
- GFP
Green fluorescent protein
- GluB-1
Rice glutelin B-1 promoter
- GUS
-Glucuronidase
- LUC
Luciferase
- sXynA
Synthetic xylanase A gene
- Ubi-1
Maize ubiquitin promoter
- XAB
Xylanase assay buffer
- XYN
Xylanase
Communicated by P. Lakshmanan 相似文献
17.
YaLi Brennan Walter N. Callen Leif Christoffersen Paul Dupree Florence Goubet Shaun Healey Myrian Hernndez Martin Keller Ke Li Nisha Palackal Ana Sittenfeld Giselle Tamayo Steve Wells Geoffrey P. Hazlewood Eric J. Mathur Jay M. Short Dan E. Robertson Brian A. Steer 《Applied microbiology》2004,70(6):3609-3617
Recombinant DNA technologies enable the direct isolation and expression of novel genes from biotopes containing complex consortia of uncultured microorganisms. In this study, genomic libraries were constructed from microbial DNA isolated from insect intestinal tracts from the orders Isoptera (termites) and Lepidoptera (moths). Using a targeted functional assay, these environmental DNA libraries were screened for genes that encode proteins with xylanase activity. Several novel xylanase enzymes with unusual primary sequences and novel domains of unknown function were discovered. Phylogenetic analysis demonstrated remarkable distance between the sequences of these enzymes and other known xylanases. Biochemical analysis confirmed that these enzymes are true xylanases, which catalyze the hydrolysis of a variety of substituted β-1,4-linked xylose oligomeric and polymeric substrates and produce unique hydrolysis products. From detailed polyacrylamide carbohydrate electrophoresis analysis of substrate cleavage patterns, the xylan polymer binding sites of these enzymes are proposed. 相似文献
18.
Johan Finell Jouni Jokela Matti Leisola Marja-Liisa Riekkola 《Biocatalysis and Biotransformation》2013,31(4):281-290
The ability of Trichoderma reesei xylanase II (EC 3.2.1.8) to hydrolyse the small xylo-oligomer substrates, xylotetraose and xylobiose, was studied. Xylanase was used in both soluble and cross-linked enzyme crystal (CLEC) form. Hydrolysis reactions with crystalline xylanase cross-linked with glutaraldehyde and lysine were performed in a column reactor. By using appropriate combination of column packing length and flow rate, xylotetraose and xylobiose (initial concentrations 10 mg ml m 1 ) were hydrolysed completely to xylose in less than 1 h. The observed reaction rate in the column depended substantially on the flow rate of the eluent, probably due to an enhanced mass-transfer with higher flow rates. With soluble xylanase, using extended reaction times of 24 h and extremely high enzyme/substrate ratios of 20 (w/w) or above, the hydrolysis reaction reached completion with both xylotetraose and xylobiose as substrates. Even with the lowest flow rate, the reaction in the column appeared to be faster than soluble enzyme hydrolysis with comparable enzyme/substrate ratios. 相似文献
19.
Summary Maximum xylanase production byChaetomium
cellulolyticum was obtained in the culture supernatant after 30 h of growth at 37°C in basal medium containing 1% xylan at pH maintained between 6.5 and 7.5. Addition of 0.05% Tween 80 to the medium increased the enzyme production considerably. Xylanase production was found to be growth associated. The optimal conditions for enzymatic hydrolysis of xylan were found to be pH 6.0 and 50°C. During enzymatic hydrolysis, xylose, xylobiose and other xylooligosaccharides were liberated from xylan. The pH values for xylanase production and for xylan hydrolysis were closely related to the utilization of hemicelluloses of aspen wood for fungal protein production by this organism as reported in our earlier work. 相似文献
20.
J. Jaskari P. Kontula A. Siitonen H. Jousimies-Somer T. Mattila-Sandholm K. Poutanen 《Applied microbiology and biotechnology》1998,49(2):175-181
Novel oligomers that resist digestion in the upper gut were prepared from oat mixed-linked β-glucan and xylan by enzymatic
hydrolysis with lichenase of Bacillus subtilis and xylanase of Trichoderma reesei respectively. The low-molecular-mass hydrolysis products of β-glucan and xylan were compared with fructooligomers and raffinose
in their ability to provide growth substrates for probiotic (Lactobacillus and Bifidobacterium) and intestinal (Bacteroides, Clostridium and Escherichia coli) strains in vitro. A degradation profile of each carbohydrate and total sugar consumption were analysed with HPLC, and bacterial growth rate
with an automatic turbidometer, the Bioscreen C system. β-Glucooligomers and xylooligomers both enhanced the growth of health-promoting
probiotic strains as compared with intestinal bacterial growth, but not to a significant level. Raffinose stimulated the probiotic
strains significantly, whereas fructooligomers induced high average growth for intestinal bacteria also.
Received: 16 May 1997 / Received revision: 12 September 1997 / Accepted: 19 September 1997 相似文献