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1.
Purification and Biochemical Characterization of Two Xylanases from <Emphasis Type="Italic">Aspergillus sydowii</Emphasis> SBS 45 总被引:1,自引:0,他引:1
Two xylanases were isolated and purified from crude culture filtrate of Aspergillus sydowii SBS 45 after 9 days of growth on wheat bran containing 0.5% (w/v) birch wood xylan as the carbon source under solid-state fermentation. After a three-step purification scheme involving ammonium sulfate precipitation, gel filtration chromatography (Sephadex G-200), and anion exchange chromatography (DEAE-Sephadex A-50), xylanase I was purified 93.41 times, and xylanase II was purified 77.40 times with yields of 4.49 and 10.46, respectively. Molecular weights of xylanase I and II were 20.1 and 43 kDa, respectively, in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Optimum temperature was 50 degrees C, and optimum pH was 10.0 for both xylanase I and II. The Km value of xylanase I for birch wood xylan was 3.18 mg ml(-1) and for oat spelt xylan 6.45 mg ml(-1), while the Km value of xylanase II for birch wood xylan was 6.51 mg ml(-1) and for oat spelt xylan 7.69 mg ml(-1). Metal ions like Al3+, Ba2+, Ca2+, Na+, and Zn2+ enhanced the activity of xylanase I and II at 10 mM concentration. Among the additives, L-tryptophan enhanced the activity of xylanase I and II at 10-, 20-, and 30-mM concentrations. Both xylanases appeared to be glycoproteins. 相似文献
2.
When grown on a purified cellulose such as CF11 cellulose,Aspergillus fumigatus produces mainly exoglucanase (Avicelase) and endoglucanase (CMCase) with small amounts of Β-glucosidase and xylanase. In
such cultures, the pH drops to 3–3.5 after 2 d incubation, which may account for the low levels of Β-glucosidase.
The amounts of extracellular enzymes produced are larger when the organism is grown on hay or straw than when grown on CF11
cellulose. In particular, CMCase levels increase approximately seven times and xylanase levels increase 40–50 times. In such
cultures the pH remains fairly constant at 6–7 over the 10-d incubation period used and so Β-glucosidase levels are also increased.
Extraction of the hay or straw substrate with ethanol had little effect on enzyme production and so there appears to be no
soluble material present that influences enzyme production.
The organism produced elevated levels of CMCase and xylanase on barley straw, oat straw, and wheat straw, there being little
difference between the varieties of each tested. However, grasses dried at elevated temperatures (260–500‡C) gave enzyme levels
similar to CF11 cellulose. Similarly, chemical delignification of hay or straw gave enzyme levels similar to CF11 cellulose.
Thus, both these treatments must lead to degradation of the hemicellulose present in the substrate.
A. fumigatus was able to grow on a number of laboratory prepared and commercially available xylans (hay, barley straw, oat straw, and
larch) as a pelletted mycelium. In all cases xylanase levels were increased 10–30 times over CF11 cellulose as substrate,
but CMCase levels were similar to those with CF11 cellulose as substrate. Β-Glucosidase in most cases was not detectable,
probably because the pH fell to 3–3.5 during incubation. Thus it appears that cellulase and xylanase can be independently
induced in this organism.
The optimum incubation time at 37‡C for xylanase production was 4–7 d and the optimum concentration of hay as substrate was
4–5%, even though this produces a very thick slurry that does not shake well. 相似文献
3.
Dengeti Shrinivas Gunashekaran Savitha Kumar Raviranjan Gajanan Ramchandra Naik 《Applied biochemistry and biotechnology》2010,162(7):2049-2057
A highly thermostable alkaline xylanase was purified to homogeneity from culture supernatant of Bacillus sp. JB 99 using DEAE-Sepharose and Sephadex G-100 gel filtration with 25.7-fold increase in activity and 43.5% recovery.
The molecular weight of the purified xylanase was found to be 20 kDA by SDS-PAGE and zymogram analysis. The enzyme was optimally
active at 70 °C, pH 8.0 and stable over pH range of 6.0–10.0.The relative activity at 9.0 and 10.0 were 90% and 85% of that
of pH 8.0, respectively. The enzyme showed high thermal stability at 60 °C with 95% of its activity after 5 h. The K
m and V
max of enzyme for oat spelt xylan were 4.8 mg/ml and 218.6 μM min−1 mg−1, respectively. Analysis of N-terminal amino acid sequence revealed that the xylanase belongs to glycosyl hydrolase family
11 from thermoalkalophilic Bacillus sp. with basic pI. Substrate specificity showed a high activity on xylan-containing substrate and cellulase-free nature. The hydrolyzed product
pattern of oat spelt xylan on thin-layer chromatography suggested xylanase as an endoxylanase. Due to these properties, xylanase
from Bacillus sp. JB 99 was found to be highly compatible for paper and pulp industry. 相似文献
4.
A psychrotrophic fungus identified as Trichoderma sp. SC9 produced 36.7 U/ml of xylanase when grown on a medium containing corncob xylan at 20 °C for 6 days. The xylanase
was purified 37-fold with a recovery yield of 8.2%. The purified xylanase appeared as a single protein band on SDS-PAGE with
a molecular mass of approximately 20.5 kDa. The enzyme had an optimal pH of 6.0, and was stable over pH 3.5–9.0. The optimal
temperature of the xylanase was 42.5 °C and it was stable up to 35 °C at pH 6.0 for 30 min. The xylanase was thermolabile
with a half-life of 23.9 min at 45 °C. The apparent K
m
values of the xylanase for birchwood, beechwood, and oat-spelt xylans were found to be 3, 2.1, and 16 mg/ml respectively.
The xylanase hydrolyzed beechwood xylan and birchwood xylan to yield mainly xylobiose as end products. The enzyme-hydrolysed
xylotriose, xylotetraose, and xylopentose to produce xylobiose, but it hardly hydrolysed xylobiose. A xylanase gene (xynA) with an open reading frame of 669 nucleotide base pairs (bp), encoding 222 amino acids, from the strain was cloned and sequenced.
The deduced amino acid sequence of XynA showed 85% homology with Xyn2 from a mesophilic strain of Trichoderma viride. 相似文献
5.
Two xylanases from the crude culture filtrate of Penicillium sclerotiorum were purified to homogeneity by a rapid and efficient procedure, using ion-exchange and molecular exclusion chromatography.
Molecular masses estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 23.9 and 33.1 kDa for xylanase
I and II, respectively. The native enzymes’ molecular masses of 23.8 and 30.8 kDa were estimated for xylanase I and II, respectively,
by molecular exclusion chromatography. Both enzymes are glycoproteins with optimum temperature and pH of 50 °C and pH 2.5
for xylanase I and 55 °C and pH 4.5 for xylanase II. The reducing agents β-mercaptoethanol and dithio-treitol enhanced xylanase
activities, while the ions Hg2+ and Cu2+ as well the detergent SDS were strong inhibitors of both enzymes, but xylanase II was stimulated when incubated with Mn2+. The K
m value of xylanase I for birchwood xylan and for oat spelt xylan were 6.5 and 2.6 mg mL−1, respectively, whereas the K
m values of xylanase II for these substrates were 26.61 and 23.45 mg mL−1. The hydrolysis of oat spelt xylan by xylanase I released xylobiose and larger xylooligosaccharides while xylooligosaccharides
with a decreasing polymerization degree up to xylotriose were observed by the action of xylanase II. The present study is
among the first works to examine and describe an extracellular, highly acidophilic xylanase, with an unusual optimum pH at
2.5. Previously, only one work described a xylanase with optimum pH 2.0. This novel xylanase showed interesting characteristics
for biotechnological process such as feed and food industries. 相似文献
6.
Carvalho Andrade Carolina M. M. Aguiar Wilson Bucker Antranikian Garo 《Applied biochemistry and biotechnology》2001,91(1-9):655-669
Xylanases (EC3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could
greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals.
The hyperthermophilic archaeon Pyrodictium abyssi, which was originally isolated from marine hot abyssal sites, grows optimally at 97°C and is a prospective source of highly
thermostable xylanase. Its endoxylanase was shown to be highly thermostable (over 100 m in at 105°C) and active even at 110°C.
The growth of the deep-sea archaeon P. abyssi was investigated using different culture techniques. Among the carbohydrates used, beech wood xylan, birch wood glucuronoxylan
and the arabinoxylan from oats pelt appeared to be good inducers for endoxylanase and β-xylosidase production. The highest
production of arabinofuranosidase, however, was detected in the cell extracts after growth on xylose and pyruvate, indicating
that the intermediate of the tricarboxylic acid cycle acted as a nonrepressing carbon source for the production of thi enzyme.
Electron microscopic studies did not show a significant difference in the cell surface (e.g., xylanosomes) when P. abyssi cells were grown on different carbohydrates. The main kinetic parameters of the organism have been determined. The cell yield
was shown to be very low owing to incomplete substrate utilization, but a very high maximal specific growth rate was determined
(μmax=0.0195) at 90°C and pH 6.0. We also give information on the problems that arise during the fermentation of this hyperthermophilic
archaeon at elevated temperatures. 相似文献
7.
Taibi Z Saoudi B Boudelaa M Trigui H Belghith H Gargouri A Ladjama A 《Applied biochemistry and biotechnology》2012,166(3):663-679
An extracellular thermostable xylanase from a newly isolated thermophilic Actinomadura sp. strain Cpt20 was purified and characterized. Based on matrix-assisted laser desorption–ionization time-of-flight mass
spectrometry analysis, the purified enzyme is a monomer with a molecular mass of 20,110.13 Da. The 19 residue N-terminal sequence
of the enzyme showed 84% homology with those of actinomycete endoxylanases. The optimum pH and temperature values for xylanase
activity were pH 10 and 80 °C, respectively. This xylanase was stable within a pH range of 5–10 and up to a temperature of
90 °C. It showed high thermostability at 60 °C for 5 days and half-life times at 90 °C and 100 °C were 2 and 1 h, respectively.
The xylanase was specific for xylans, showing higher specific activity on soluble oat-spelt xylan followed by beechwood xylan.
This enzyme obeyed the Michaelis–Menten kinetics, with the K
m and k
cat values being 1.55 mg soluble oat-spelt xylan/ml and 388 min−1, respectively. While the xylanase from Actinomadura sp. Cpt20 was activated by Mn2+, Ca2+, and Cu2+, it was, strongly inhibited by Hg2+, Zn2+, and Ba2+. These properties make this enzyme a potential candidate for future use in biotechnological applications particularly in
the pulp and paper industry. 相似文献
8.
An extracellular xylanase produced by a Mexican Aspergillus strain was purified and characterized. Aspergillus sp. FP-470 was able to grow and produce extracellular xylanases on birchwood xylan, oat spelt xylan, wheat straw, and corncob,
with higher production observed on corncob. The strain also produced enzymes with cellulase, amylase, and pectinase activities
on this substrate. A 22-kDa endoxylanase was purified 30-fold. Optimum temperature and pH were 60°C and 5.5, respectively,
and isoelectric point was 9.0. The enzyme has good stability from pH 5.0 to 10.0 retaining >80% of its original activity within
this range. Half-lives of 150 min at 50°C and 6.5 min at 60°C were found. K
m
and activation energy values were 3.8 mg/mL and 26 kJ/mol, respectively, using birch wood xylan as substrate. The enzyme
showed a higher affinity for 4-O-methyl-d-glucuronoxylan with a K
m
of 1.9 mg/mL. The enzyme displayed no activity toward other polysaccharides, including cellulose. Baking trials were conducted
using the crude filtrate and purified enzyme. Addition of both preparations improved bread volume. However, addition of purified
endoxylanase caused a 30% increase in volume over the crude extract. 相似文献
9.
M. Costa-Ferreira A. Dias C. Maximo M. J. Morgado G. Sena-Martins J. Cardoso Duarte 《Applied biochemistry and biotechnology》1994,44(3):231-242
Production of xylanolytic enzymes by anAspergillus niger CCMI 850 isolate was investigated in batch cultures. The effect of the composition of a fermentation medium that did not
include chemical inducers, on β-xylanase, β-xylosidase, α-l-arabinofuranosidase, and total cellulase activity was studied. With 4% xylan as the carbon source, about 65 U/mL of β-xylanase
was obtained, whereas the total cellulase activity was undetectable, under the specified conditions. This β-xylanase activity
represents the highest reported for a wild-type strain ofA. niger. The effect of pH and temperature on the activity of β-xylanase was studied. Partial characterization of the β-xylanase showed
that with insoluble birchwood as substrate theK
m
andV
max were 0.3 mM and 19 μmol/min, respectively. Aspects of using the crude β-xylanase preparation for applications in the pulp and paper industry
were discussed. 相似文献
10.
Javier D. Breccia Nelson Torto Lo Gorton Faustino Siñeriz Rajni Hatti-Kaul 《Applied biochemistry and biotechnology》1998,69(1):31-40
A thermostable xylanase purified from a strain of Bacillus amyloliquefaciens MIR 32 was characterized with respect to its
substrate specificity and mode of hydrolytic action. The enzyme was highly specific for xylans as substrate and displayed
no activity toward other polysaccharides, including cellulose. The enzyme exhibited Km and Vmax of 4.5 mg/mL and 0.58 mmol/min/mg, respectively, with birchwood xylan as the substrate. Microdialysis sampling with anion
exchange chromatography and integrated pulsed electrochemical detection were used for rapid on-line monitoring of products
during hydrolysis of oat spelt and bagasse xylan, and xylooligosaccharides. Xylobiose and xylotriose were the main end products.
Xylotetraose was the smallest oligosaccharide to be acted on by the xylanase. The product pattern confirmed that the enzyme
was an endoxylanase. 相似文献
11.
de Almeida MN Guimarães VM Bischoff KM Falkoski DL Pereira OL Gonçalves DS de Rezende ST 《Applied biochemistry and biotechnology》2011,165(2):594-610
The aim of this work was to have cellulase activity and hemicellulase activity screenings of endophyte Acremonium species (Acremonium zeae EA0802 and Acremonium sp. EA0810). Both fungi were cultivated in submerged culture (SC) containing l-arabinose, d-xylose, oat spelt xylan, sugarcane bagasse, or corn straw as carbon source. In solid-state fermentation, it was tested as
carbon source sugarcane bagasse or corn straw. The highest FPase, endoglucanase, and xylanase activities were produced by
Acremonium sp. EA0810 cultivated in SC containing sugarcane bagasse as a carbon source. The highest β-glucosidase activity was produced
by Acremonium sp. EA0810 cultivated in SC using d-xylose as carbon source. A. zeae EA0802 has highest α-arabinofuranosidase and α-galactosidase activities in SC using xylan as a carbon source. FPase, endoglucanase,
β-glucosidase, and xylanase from Acremonium sp. EA0810 has optimum pH and temperatures of 6.0, 55 °C; 5.0, 70 °C; 4.5, 60 °C; and 6.5, 50 °C, respectively. α-Arabinofuranosidase
and α-galactosidase from A. zeae EA0802 has optimum pH and temperatures of 5.0, 60 °C and 4.5, 45 °C, respectively. It was analyzed the application of Acremonium sp. EA0810 to hydrolyze sugarcane bagasse, and it was achieved 63% of conversion into reducing sugar and 42% of conversion
into glucose. 相似文献
12.
Maria Rodríguez Alfonso Gómez Fernando González Eduardo Barzana Agustin López-Munguía 《Applied biochemistry and biotechnology》1996,59(2):167-175
Enzyme synthesis of methyl fructoside was studied usingΒ-fructofuranosidase fromSacharomyces cerevisiae and sucrose and methanol as substrates. Taking into account the inhibition and deactivation effects of methanol on the enzyme,
a system with 4.9M (20%, v/v) methanol was selected. At this alcohol level, 35% of sucrose is converted to fructoside at low
or high substrate concentrations. The effect of enzyme concentration, pH, and temperature on both the synthesis and the hydrolysis
of the fructoside was investigated. It was found that if the reaction proceeds at pH 6.0, 4‡C and/or 0.014 mg/mL (3 U/mL)
of Β-fructofuranosidase at varying sucrose concentrations, methyl fructoside may be obtained with a minimum loss of the fructoside
at the end of the reaction. 相似文献
13.
Xylanase from Bacillus pumilus strain MK001 was immobilized on different matrices following varied immobilization methods. Entrapment using gelatin (GE)
(40.0%), physical adsorption on chitin (CH) (35.0%), ionic binding with Q-sepharose (Q-S) (45.0%), and covalent binding with
HP-20 beads (42.0%) showed the maximum xylanase immobilization efficiency. The optimum pH of immobilized xylanase shifted
up to 1.0 unit (pH 7.0) as compared to free enzyme (pH 6.0). The immobilized xylanase exhibited higher pH stability (up to
28.0%) in the alkaline pH range (7.0–10.0) as compared to free enzyme. Optimum temperature of immobilized xylanase was observed
to be 8 °C higher (68.0 °C) than free enzyme (60.0 °C). The free xylanase retained 50.0% activity, whereas xylanase immobilized
on HP-20, Q-S, CH, and GE retained 68.0, 64.0, 58.0, and 57.0% residual activity, respectively, after 3 h of incubation at
80.0 °C. The immobilized xylanase registered marginal increase and decrease in K
m and V
max values, respectively, as compared to free enzyme. The immobilized xylanase retained up to 70.0% of its initial hydrolysis
activity after seven enzyme reaction cycles. The immobilized xylanase was found to produce higher levels of high-quality xylo-oligosaccharides
from birchwood xylan, indicating its potential in the nutraceutical industry. 相似文献
14.
Dhananjay Soren Mohanlal Jana Subhabrata Sengupta Anil K. Ghosh 《Applied biochemistry and biotechnology》2010,162(2):373-389
A low molecular weight endo-xylanase (EC 3.2.1.8) was purified from an edible mushroom Termitomyces clypeatus grown in submerged medium with oat spelt xylan. Xylanase was purified to apparent homogeneity by ammonium sulfate fractionation
and gel filtration chromatography. Its molecular weight was determined by gel filtration chromatography and sodium dodecyl
sulfate-polyacrylamide gel electrophoresis to be 12 kDa. The enzyme was found to be most active at 50°C and pH 5.0, being
most stable at pH 6.5. The Km for oat spelt xylan was determined to be 10.4 mg/ml. The specificities of the enzyme was observed to be highly specific towards
oat spelt xylan and was inhibited by mercuric chloride (HgCl2), N-bromosuccinimide, and trans-1,2-diaminocyclohexane-N′,N′,N′,N′-tetraacetic acid strongly. The inhibitory action of N-bromosuccinimide on enzyme confirmed the presence of one tryptophan
residue in its substrate-binding site. Amino acid analysis for xylanase showed the presence of high amount of hydrophobic
serine, glycine, threonine, and alanine residues. The N-terminal sequencing study for the previously purified and characterized
56 kDa xylanolytic amyloglucosidase reveal the presence of 33.30% identity with glucoamylase chain A from Aspergillus awamori. The N-terminal sequence analysis of the present 12 kDa enzyme showed highest similarity (72.22% identity) towards xylanase
from Neurospora crassa. 相似文献
15.
Maalej I Belhaj I Masmoudi NF Belghith H 《Applied biochemistry and biotechnology》2009,158(1):200-212
A thermostable xylanase from a newly isolated thermophilic fungus Talaromyces thermophilus was purified and characterized. The enzyme was purified to homogeneity by ammonium sulfate precipitation, diethylaminoethyl
cellulose anion exchange chromatography, P-100 gel filtration, and Mono Q chromatography with a 23-fold increase in specific
activity and 17.5% recovery. The molecular weight of the xylanase was estimated to be 25kDa by sodium dodecyl sulfate–polyacrylamide
gel electrophoresis and gel filtration. The enzyme was highly active over a wide range of pH from 4.0 to 10.0. The relative
activities at pH5.0, 9.0, and 10.0 were about 80%, 85.0%, and 60% of that at pH7.5, respectively. The optimum temperature
of the purified enzyme was 75°C. The enzyme showed high thermal stability at 50°C (7days) and the half-life of the xylanase
at 100°C was 60min. The enzyme was free from cellulase activity. K
m and V
max values at 50°C of the purified enzyme for birchwood xylan were 22.51mg/ml and 1.235μmol min−1 mg−1, respectively. The enzyme was activated by Ag+, Co2+, and Cu2+; on the other hand, Hg2+, Ba2+, and Mn2+ inhibited the enzyme. The present study is among the first works to examine and describe a secreted, cellulase-free, and
highly thermostable xylanase from the T. thermophilus fungus whose application as a pre-bleaching aid is of apparent importance for pulp and paper industries. 相似文献
16.
Bacillus circulans D1 is a good producer of extracellular thermostable xylanase. Xylanase production in different carbon sources was evaluated
and the enzyme synthesis was induced by various carbon sources. It was found that d-maltose is the best inducer of the enzyme synthesis (7.05 U/mg dry biomass at 48 h), while d-glucose and d-arabinose lead to the production of basal levels of xylanase. The crude enzyme solution is free of cellulases, even when
the microorganism was cultivated in a medium with d-cellobiose. When oat spelt xylan was supplemented with d-glucose, the repressive effect of this sugar on xylanase production was observed at 24 h, only when used at 5.0 g/L, leading
to a reduction of 60% on the enzyme production. On the other hand, when the xylan medium was supplemented with d-xylose (3.0 or 5.0 g/L), this effect was more evident (80 and 90% of reduction on the enzyme production, respectively). Unlike
that observed in the xylan medium, glucose repressed xylanase production in the maltose medium, leading to a reduction of
55% on the enzyme production at 24 h of cultivation. Xylose, at 1.0 g/L, induced xylanase production on the maltose medium.
On this medium, the repressive effect of xylose, at 3.0 or 5.0 g/L, was less expressive when compared to its effect on the
xylan medium. 相似文献
17.
The cellulase system ofBacillus circulans F-2 effectively hydrolyzed carboxymethyl cellulose (CMC), xylan, avicel, cellobiose, filter paper, cotton, andp-nitrophenyl-Β-D-cellobioside, and the crude enzyme produced mainly glucose from digestion of avicel. Two major and one minor
peaks of enzyme activities were eluted on DEAE ion-exchange chromatography, and designated cellulase complex I(C-I) and complex
II(C-II) for the two major peaks, and cellulase-III for a minor peak. C-I and C-II were further purified on gel filtration
column of a TSK-Gel SW G3000 ×L. The molecular masses of C-I and C-II were estimated to be about 669 and 443 kDa, respectively.
Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the C-I and C-II complexes showed that the C-I complex
was present as a multiple protein complex, consisting of at least five CMCases and two xylanases, and that the C-II complex
was consisted of at least three CMCase and four xylan ases. C-I showed high activities of cellohydrolase, CMCase, xylanase,
and Β-glucosidase, whereas C-II showed high activities of CMCase, xylanase, avicelase, and Β-glucosidase. The outstanding
property of the C-II was its high hydrolytic activity toward filter paper, a highly resistant substrate against enzymatic
degradation. However, cellulaseIII showed only strong avicelase activity. These results indicated that the cellulase system
of the strain exists as multiple complex forms. 相似文献
18.
Lemos Judith L. S. Fontes Maria C. de A. Pereira Nei 《Applied biochemistry and biotechnology》2001,91(1-9):681-689
The use of purified xylan as a substrate for bioconversion into xylanases increases the cost of enzyme production. Consequently,
there have been attempts to develop a bioprocess to produce such enzymes using different lignocellulosic residues. Filamentous
fungi have been widely used to produce hydrolytic enzymes for industrial applications, including xylanases, whose levels in
fungi are generally much higher than those in yeast and bacteria. Considering the industrial importance of xylanases, the
present study evaluated the use of milled sugarcane bagasse, without any pretreatment, as a carbon source. Also, the effect
of different nitrogen sources and the C∶N ratio on xylanase production by Aspergillus awamori were investigated, in experiments carried out in solid-state fermentation. High extracellular xylanolytic activity was observed
on cultivation of A. awamori on milled sugarcane bagasse and organic nitrogen sources (45 IU/mL for endoxylanase and 3.5 IU/mL for β-xylosidase). Endoxylanase
and β-xylosidase activities were higher when sodium nitrate was used as the nitrogen source, when compared with peptone, urea,
and ammonium sulfate at the optimized C∶N ratio of 10∶1. The use of yeast extract as a supplement to the these nitrogen sources
resulted in considerable improvementin the production of xylanases, showing the importance of this organic nitrogen source
on A. awamori metabolism. 相似文献
19.
Extraction and characterization of native heteroxylans from delignified corn stover and aspen 总被引:1,自引:0,他引:1
Radnaa Naran Stuart Black Stephen R. Decker Parastoo Azadi 《Cellulose (London, England)》2009,16(4):661-675
Dimethylsulfoxide-solubilized polysaccharides from delignified corn stover and aspen were characterized. The biomass was delignified
by two different techniques; a standard acid chlorite and a pulp and paper QPD technique comprising chelation (Q), peroxide
(P), and acid-chlorite (D). Major polysaccharides in all fractions were diversely substituted xylan. Xylan acetylation was
intact after chlorite delignification and, as expected, xylan from QPD-delignified fraction was de-acetylated by the alkaline
peroxide step. The study of DMSO-extractable xylans from chlorite-delignified biomass revealed major differences in native
acetylation patterns between corn stover and aspen xylan. Xylan from cell walls of corn stover contains 2-O- and 3-O-mono-acetylated xylan and [MeGlcA-α-(1 → 2)][3-OAc]-xylp units. In addition, aspen xylan also contains 2,3-di-O-acetylated xylose. 1,4-β-d-xylp residues substituted with MeGlcA at O-2 position are absent in chlorite-delignified aspen xylan. Sugar composition in accord with NMR-spectroscopic data indicated
that corn stover xylan is arabinosylated while aspen xylan is not. We have shown that corn stover xylan has similar structure
with xylans from other plants of Poales order. No evidence was found to indicate the presence of 1,4-β-d-[MeGlcA-α-(1 → 2)][Ara-α-(1 → 3)]-xylp in corn stover xylan fractions. 相似文献
20.
Daniela A. Bocchini Valquiria B. Damiano Eleni Gomes Roberto Da Silva 《Applied biochemistry and biotechnology》2003,106(1-3):393-401
The alkalophilic Bacillus circulans D1 was isolated from decayed wood. It produced high levels of extracellular cellulase-free xylanase. The enzyme was thermally
stable up to 60°C, with an optimal hydrolysis temperature of 70°C. It was stable over a wide pH range (5.5—10.5), with an
optimum pH at 5.5 and 80% of its activity at pH 9.0. This cellulase-free xylanase preparation was used to biobleach kraft
pulp. Enzymatic treatment of kraft pulp decreased chlorine dioxide use by 23 and 37% to obtain the same kappa number (κ number)
and brightness, respectively. Separation on Sephadex G-50 isolated three fractions with xylanase activity with distinct molecular
weights. 相似文献