共查询到20条相似文献,搜索用时 15 毫秒
1.
Khwanchai Khucharoenphaisan Shinji Tokuyama Vichien Kitpreechavanich 《Mycoscience》2010,51(6):405-410
Highly thermostable β-xylanase produced by newly isolated Thermomyces lanuginosus THKU-49 strain was purified in a four-step procedure involving ammonium sulfate precipitation and subsequent separation on
a DEAE-Sepharose fast flow column, hydroxylapatite column, and Sephadex G-100 column, respectively. The enzyme purified to
homogeneity had a specific activity of 552 U/mg protein and a molecular weight of 24.9 kDa. The optimal temperature of the
purified xylanase was 70°C, and it was stable at temperatures up to 60°C at pH 6.0; the optimal pH was 5.0–7.0, and it was
stable in the pH range 3.5–8.0 at 4°C. Xylanase activity was inhibited by Mn2+, Sn2+, and ethylenediaminetetraacetic acid. The xylanase showed a high activity towards soluble oat spelt xylan, but it exhibited
low activity towards insoluble oat spelt xylan; no activity was found to carboxymethylcellulose, avicel, filter paper, locust
bean gum, cassava starch, and p-nitrophenyl β-d-xylopyranoside. The apparent K
m value of the xylanase on soluble oat spelt xylan and insoluble oat spelt xylan was 7.3 ± 0.236 and 60.2 ± 6.788 mg/ml, respectively.
Thin-layer chromatography analysis showed that the xylanase hydrolyzed oat spelt xylan to yield mainly xylobiose and xylose
as end products, but that it could not release xylose from the substrate xylobiose, suggesting that it is an endo-xylanase. 相似文献
2.
Santiago-Hernández A Vega-Estrada J del Carmen Montes-Horcasitas M Hidalgo-Lara ME 《Journal of industrial microbiology & biotechnology》2007,34(4):331-338
We report the purification and characterization of two thermophilic xylanases from the mesophilic bacteria Cellulomonas flavigena grown on sugarcane bagasse (SCB) as the only carbon source. Extracellular xylanase activity produced by C. flavigena was found both free in the culture supernatant and associated with residual SCB. To identify some of the molecules responsible
for the xylanase activity in the substrate-bound fraction, residual SCB was treated with 3 M guanidine hydrochloride and then
with 6 M urea. Further analysis of the eluted material led to the identification of two xylanases Xyl36 (36 kDa) and Xyl53
(53 kDa). The pI for Xyl36 was 5.0, while the pI for Xyl53 was 4.5. Xyl36 had a K
m value of 1.95 mg/ml, while Xyl53 had a K
m value of 0.78 mg/ml. In addition to SCB, Xyl36 and Xyl53 were also able to bind to insoluble oat spelt xylan and Avicel,
as shown by substrate-binding assays. Xyl36 and Xyl53 showed optimal activity at pH 6.5, and at optimal temperature 65 and
55°C, respectively. Xyl36 and Xyl53 retained 24 and 35%, respectively, of their original activity after 8 h of incubation
at their optimal temperature. As far as we know, this is the first study on the thermostability properties of purified xylanases
from microorganisms belonging to the genus Cellulomonas. 相似文献
3.
Jeyaraman Vikramathithan Gali Nirmal kumar Pandurangan Muthuraman Kotteazeth Srikumar 《The protein journal》2010,29(7):481-486
A thermo stable xylanase was purified and characterized from the cladodes of Cereus pterogonus plant species. The enzyme was purified to homogeneity by ammonium sulfate (80%) fractionation, ion exchange and size exclusion
chromatography. The enzyme showed a final specific activity of 216.2 U/mg and the molecular mass of the protein was 80 KDa.
The optimum pH and temperature for xylanase activity were 5.0 and 80 °C, respectively,. With oat spelt xylan as a substrate
the enzyme yielded a Km value of 2.24 mg/mL and a Vmax of 5.8 μmol min−1 mg−1. In the presence of metal ions (1 mM) such as Co2+,Mn2+, Ni2+, Ca2+ and Fe3+ the activity of the enzyme increased, where as strong inhibition of the enzyme activity was observed with the use of Hg2+, Cd2+, Cu2+, while partial inhibition was noted with Zn2+ and Mg2+. The substrate specificity of the xylanase yielded maximum activity with oat spelt xylan. 相似文献
4.
M Saleem F Aslam MS Akhtar M Tariq MI Rajoka 《World journal of microbiology & biotechnology》2012,28(2):513-522
Delignification efficacy of xylanases to facilitate the consequent chemical bleaching of Kraft pulps has been studied widely.
In this work, an alkaline and thermally stable cellulase-less xylanase, derived from a xylanolytic Bacillus subtilis, has been purified by a combination of gel filtration and Q-Sepharose chromatography to its homogeneity. Molecular weight
of the purified xylanase was 61 kDa by SDS–PAGE. The purified enzyme revealed an optimum assay temperature and pH of 60°C
and 8.0, respectively. Xylanase was active in the pH range of 6.0–9.0 and stable up to 70°C. Divalent ions like Ca2+, Mg2+ and Zn2+ enhanced xylanase activity, whereas Hg2+, Fe2+, and Cu2+ were inhibitory to xylanase at 2 mM concentration. It showed K
m
and V
max
values of 9.5 mg/ml and 53.6 μmol/ml/min, respectively, using birchwood xylan as a substrate. Xylanase exhibited higher values
of turn over number (K
cat) and catalytic efficiency (K
cat/K
m) with birchwood xylan than oat spelt xylan. Bleach-boosting enzyme activity at 30 U/g dry pulp displayed the optimum bio-delignification
of Kraft pulp resulting in 26.5% reduction in kappa number and 18.5% ISO induction in brightness at 55°C after 3 h treatment.
The same treatment improved the pulp properties including tensile strength and burst index, demonstrating its potential application
in pre-bleaching of Kraft pulp. 相似文献
5.
Huiying Luo Yaru Wang Jiang Li Hui wang Jun Yang Yuhui Yang Huoqing Huang Yunliu Fan Bin Yao 《Enzyme and microbial technology》2009,45(2):126-133
A xylanase gene (xyl11B) was cloned from Bispora sp. MEY-1 and expressed in Pichia pastoris. xyl11B, with a 66-bp intron, encodes a mature protein of 219 residues with highest identity (57.1%) to the Trichoderma reesei xylanase of glycoside hydrolase family 11. The purified recombinant XYL11B was acidophilic, exhibiting maximum activity at pH 2.6 and 65 °C. The enzyme was also thermostable, pH stable, and was highly resistant to both pepsin and trypsin, suggesting good performance in the digestive tract as a feed supplement to improve animal nutrition. The activity of XYL11B was enhanced by most metal ions but was inhibited weakly by Hg2+, Pb2+and Cu2+, which strongly inhibit many other xylanases. The specific activity of XYL11B for oat spelt xylan substrate was 2049 U mg?1. The main hydrolysis products of xylan were xylose and xylobiose. 相似文献
6.
M. Irfan H. I. Guler A. O. Belduz A. A. Shah S. Canakci 《Applied Biochemistry and Microbiology》2016,52(3):277-286
Geobacillus thermodenitrificans AK53 xyl gene encoding xylanase was isolated, cloned and expressed in Escherichia coli. After purifying recombinant xylanase from G. thermodenitrificans AK53 (GthAK53Xyl) to homogeneity by ammonium sulfate precipitation and ion exchange chromatography, biochemical properties of the enzyme were determined. The kinetic studies for GthAK53Xyl showed KM value to be 4.34 mg/mL (for D-xylose) and Vmax value to be 2028.9 μmoles mg–1 min–1. The optimal temperature and pH for enzyme activity were found out to be 70°C and 5.0, respectively. The expressed protein showed the highest sequence similarity with the xylanases of G. thermodenitrificans JK1 (JN209933) and G. thermodenitrificans T-2 (EU599644). Metal cations Mg2+ and Mn2+ were found to be required for the enzyme activity, however, Co2+, Hg2+, Fe2+ and Cu2+ ions caused inhibitor effect on it. GthAK53Xyl had no cellulolytic activity and degraded xylan in an endo-fashion. The action of the enzyme on xylan from oat spelt produced xylobiose and xylopentose. The reported results are suggestive of a xylanase exhibiting desirable kinetics, stability parameters and metal resistance required for the efficient production of xylobiose at industrial scale. 相似文献
7.
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
8.
Caroline Mirande Pascale Mosoni Christel Béra-Maillet Annick Bernalier-Donadille Evelyne Forano 《Applied microbiology and biotechnology》2010,87(6):2097-2105
A xylanase gene xyn10A was isolated from the human gut bacterium Bacteroides xylanisolvens XB1A and the gene product was characterized. Xyn10A is a 40-kDa xylanase composed of a glycoside hydrolase family 10 catalytic
domain with a signal peptide. A recombinant His-tagged Xyn10A was produced in Escherichia coli and purified. It was active on oat spelt and birchwood xylans and on wheat arabinoxylans. It cleaved xylotetraose, xylopentaose,
and xylohexaose but not xylobiose, clearly indicating that Xyn10A is a xylanase. Surprisingly, it showed a low activity against
carboxymethylcellulose but no activity at all against aryl-cellobioside and cellooligosaccharides. The enzyme exhibited K
m and V
max of 1.6 mg ml−1 and 118 μmol min−1 mg−1 on oat spelt xylan, and its optimal temperature and pH for activity were 37°C and pH 6.0, respectively. Its catalytic properties
(k
cat/K
m = 3,300 ml mg−1 min−1) suggested that Xyn10A is one of the most active GH10 xylanase described to date. Phylogenetic analyses showed that Xyn10A
was closely related to other GH10 xylanases from human Bacteroides. The xyn10A gene was expressed in B. xylanisolvens XB1A cultured with glucose, xylose or xylans, and the protein was associated with the cells. Xyn10A is the first family 10
xylanase characterized from B. xylanisolvens XB1A. 相似文献
9.
Xin-chun Mo Chun-lan Chen Hao Pang Yi Feng Jia-xun Feng 《Applied microbiology and biotechnology》2010,87(6):2137-2146
A metagenomic library containing ca. 3.06 × 108 bp insert DNA was constructed from a rice straw degrading enrichment culture. A xylanase gene, umxyn10A, was cloned by screening the library for xylanase activity. The encoded enzyme Umxyn10A showed 58% identity and 73% similarity
with a xylanase from Thermobifida fusca YX. Sequence analyses showed that Umxyn10A contained a glycosyl hydrolase family 10 catalytic domain. The gene was expressed
in Escherichia coli, and the recombinant enzyme was purified and characterized biochemically. Recombinant Umxyn10A was highly active toward xylan.
However, the purified enzyme could slightly hydrolyze β-1,3/4-glucan and β-1,3/6-glucan. Umxyn10A displayed maximal activity
toward oat spelt xylan at a high temperature (75°C) and weak acidity (pH 6.5). The K
m
and V
max of Umxyn10A toward oat spelt xylan were 3.2 mg ml−1 and 0.22 mmol min−1 mg−1 and were 2.7 mg ml−1 and 1.0 mmol min−1 mg−1 against birchwood xylan, respectively. Metal ions did not appear to be required for the catalytic activity of this enzyme.
The enzyme Umxyn10A could efficiently hydrolyze birchwood xylan to release xylobiose as the major product and a negligible
amount of xylose. The xylanase identified in this work may have potential application in producing xylobiose from xylan. 相似文献
10.
Huiying Luo Jiang Li Jun Yang Hui Wang Yuhui Yang Huoqing Huang Pengjun Shi Tiezheng Yuan Yunliu Fan Bin Yao 《Extremophiles : life under extreme conditions》2009,13(5):849-857
A complete gene, xyl10C, encoding a thermophilic endo-1,4-β-xylanase (XYL10C), was cloned from the acidophilic fungus Bispora sp. MEY-1 and expressed in Pichia pastoris. XYL10C shares highest nucleotide and amino acid sequence identities of 57.3 and 49.7%, respectively, with a putative xylanase
from Aspergillus fumigatus Af293 of glycoside hydrolase family 10. A high expression level in P. pastoris (73,400 U ml−1) was achieved in a 3.7–l fermenter. The purified recombinant XYL10C was thermophilic, exhibiting maximum activity at 85°C,
which is higher than that reported from any fungal xylanase. The enzyme was also highly thermostable, exhibiting ~100% of
the initial activity after incubation at 80°C for 60 min and >87% of activity at 90°C for 10 min. The half lives of XYL10C
at 80 and 85°C were approximately 45 and 3 h, respectively. It had two activity peaks at pH 3.0 and 4.5–5.0 (maximum), respectively,
and was very acid stable, retaining more than 80% activity after incubation at pH 1.5−6.0 for 1 h. The enzyme was resistant
to Co2+, Mn2+, Cr3+ and Ag+. The specific activity of XYL10C for oat spelt xylan was 18,831 U mg−1. It also had wide substrate specificity and produced simple products (65.1% xylose, 25.0% xylobiose and 9.9% xylan polymer)
from oat spelt xylan. 相似文献
11.
The cellulolytic myxobacterium Sorangium cellulosum is able to efficiently degrade many kinds of polysaccharides, but none of the enzymes involved have been characterized. In
this paper, a xylanase gene (xynA) was cloned from S. cellulosum So9733-1 using thermal asymmetric interlaced PCR. The gene is composed of 1,209 bp and has only 52.27% G + C content, which
is much lower than that of most myxobacterial DNA reported (67–72%). Gene xynA encodes a 402 amino acid protein that contains a single catalytic domain belonging to the glycoside hydrolase family 10.
The novel xylanase gene, xynA, was expressed in Escherichia coli BL21 (DE3) and the recombinant protein (r-XynA) was purified by Ni-affinity chromatography. The r-XynA had the optimum temperature
of 30–35°C and exhibited 33.3% activity at 5°C and 13.7% activity at 0°C. Approximately 80% activity was lost after 20-min
pre-incubation at 50°C. These results indicate that r-XynA is a cold-active xylanase with low thermostability. At 30°C, the
K
m values of r-XynA on beechwood xylan, birchwood xylan, and oat spelt xylan were 25.77 ± 4.16, 26.52 ± 4.78, and 38.13 ± 5.35 mg/mL,
respectively. The purified r-XynA displayed optimum activity at pH 7.0. The activity of r-XynA was enhanced by the presence
of Ca2+. The r-XynA hydrolyzed beechwood xylan, birchwood xylan, and xylooligosaccharides (xylotriose, xylotetraose, and xylopentose)
to produce primarily xylose and xylobiose. To our knowledge, this is the first report on the characterization of a xylanase
from S. cellulosum. 相似文献
12.
A new xylanase from a Trichoderma harzianum strain 总被引:1,自引:0,他引:1
F Q de Paula Silveira M V de Sousa C A O Ricart A M F Milagres C L de Medeiros E X F Filho 《Journal of industrial microbiology & biotechnology》1999,23(1):682-685
A new xylanase (XYL2) was purified from solid-state cultures of Trichoderma harzianum strain C by ultrafiltration and gel filtration. SDS-PAGE of the xylanase showed an apparent homogeneity and molecular weight
of 18 kDa. It had the highest activity at pH 5.0 and 45°C and was stable at 50°C and pH 5.0 up to 4 h xylanase. XYL2 had a
low K
m with insoluble oat spelt xylan as substrate. Compared to the amino acid composition of xylanases from Trichoderma spp, xylanase XYL2 presented a high content of glutamate/glutamine, phenylalanine and cysteine, and a low content of serine.
Xylanase XYL2 improved the delignification and selectivity of unbleached hardwood kraft pulp.
Received 02 February 1999/ Accepted in revised form 17 April 1999 相似文献
13.
S. Thiagarajan M. Jeya P. Gunasekaran 《World journal of microbiology & biotechnology》2006,22(5):487-492
Summary A high molecular weight endoxylanase (XylF2) from the solid state culture of Aspergillus fumigatus MKU1 was purified to homogeneity by a combination of tube gel electrophoresis and electroelution methods. The purity was
demonstrated by SDS-PAGE and the molecular mass of the XylF2 was found to be 66 kDa. The optimal pH and temperature for activity
were 5.0 and 90 °C, respectively. The apparent K
m and V
max values of XylF2 with oat spelt xylan as substrate were 1.6 mg/ml and 3.25 mmol/min/mg protein respectively. The enzyme showed
high activity towards oat spelt xylan while negligible activity was observed on carboxymethylcellulose. The activity of XylF2
was strongly inhibited by Hg2+, Ni2+, Zn2+, SDS and N-bromosuccinimide and stimulated by l-cysteine and iodoacetamide. The hydrolysis of oat spelt xylan by XylF2 released only xylo-oligosaccharides. 相似文献
14.
Ricardo Sposina Sobral Teixeira Félix Gonçalves Siqueira Marcelo Valle de Souza Edivaldo Ximenes Ferreira Filho Elba Pinto da Silva Bon 《Journal of industrial microbiology & biotechnology》2010,37(10):1041-1051
This study presents data on the production, purification, and properties of a thermostable β-xylanase produced by an Aspergillus awamori 2B.361 U2/1 submerged culture using wheat bran as carbon source. Fractionation of the culture filtrate by membrane ultrafiltration
followed by Sephacryl S-200 and Q-Sepharose chromatography allowed for the isolation of a homogeneous xylanase (PXII-1), which
was 32.87 kDa according to MS analysis. The enzyme-specific activity towards soluble oat spelt xylan, which was found to be
490 IU/mg under optimum reaction conditions (50°C and pH 5.0–5.5), was 17-fold higher than that measured in the culture supernatant.
Xylan reaction products were identified as xylobiose, xylotriose, and xylotetraose. K
m values (mg ml−1) for soluble oat spelt and birchwood xylan were 11.8 and 9.45, respectively. Although PXII-1 showed 85% activity retention
upon incubation at 50°C and pH 5.0 for 20 days, incubation at pH 7.0 resulted in 50% activity loss within 3 days. PXII-1 stability
at pH 7.0 was improved in the presence of 20 mM cysteine, which allowed for 85% activity retention for 25 days. This study
on the production in high yields of a remarkably thermostable xylanase is of significance due to the central role that this
class of biocatalyst shares, along with cellulases, for the much needed enzymatic hydrolysis of biomass. Furthermore, stable
xylanases are important for the manufacture of paper, animal feed, and xylooligosaccharides. 相似文献
15.
The model 3-D structure of xylanase KRICT PX3 (JF320814) identified by DNA sequence analysis revealed a catalytic domain and CBM4-9 which functions as a xylan binding domain (XBD). To identify its role in xylan hydrolysis, six expression plasmids were constructed encoding the N-terminal CBM plus the catalytic domain or different glycosyl hydrolases, and the biochemical properties of the recombinant enzymes were compared to the original structure of PX3 xylanase. All six of the recombinant xylanases with the addition of CBM in the pIVEX-GST expression vector showed no improved PX3 hydrolytic activity. However, the absence of the CBM domain resulted in a decrement of 40% in thermostability, movement of the optimal temperature from 55 °C to 45 °C, alteration of the optimal pH range from 510 to 68, and reduction of the enzymatic activity to one-second under the same condition, respectively. The putative XBD in PX3 comprises a new N-terminal domain homologous to the catalytic thermostabilizing domains from other xylanases. Analysis of the main products released from xylan indicate that the recombinant enzymes act as endo-1,4-β-xylanases but differ in their hydrolysis of xylan from beech wood, birch wood, and oat spelt. 相似文献
16.
The cellulolytic rumen bacteriumRuminococcus flavefaciens 17 was found to produce multiple xylanases ranging in apparent molecular weight from 55 to 200 kDa. A 55 kDa xylanase showed constitutive synthesis, but formation of the larger enzymes was increased in cultures grown with avicel, straw, or xylan, compared with cellobiose, as the energy source. At least six xylanases were detected in cultures grown with oat straw or oat xylan. Polyclonal antibodies were raised against the amino (A) or carboxy terminal (C) domains of the bifunctional XYNA product of the clonedR. flavefaciens xynA gene. Both antibody preparations recognized several xylanases larger than 80 kDa fromR. flavefaciens cells grown with avicel, straw, or xylan, indicating the production of multiple, antigenically related enzymes during growth on these substrates. Neither antibody preparation recognized the constitutive 55-kDa xylanase. 相似文献
17.
Fabiano de Aquino Ximenes Marcelo Valle de Sousa Jürgen Puls Francides Gomes da Silva Jr. Edivaldo Ximenes Ferreira Filho 《Current microbiology》1999,38(1):18-21
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 K
m
value for birchwood xylan was much lower than the K
m
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.
Received: 6 May 1998 / Accepted: 29 July 1998 相似文献
18.
S Canakcı Z Cevher K Inan M Tokgoz F Bahar M Kacagan FA Sal AO Belduz 《World journal of microbiology & biotechnology》2012,28(5):1981-1988
The gene encoding a xylanase from Geobacillus sp. 71 was isolated, cloned, and sequenced. Purification of the Geobacillus sp 7.1 xylanase, XyzGeo71, following overexpression in E. coli produced an enzyme of 47 kDa with an optimum temperature of 75°C. The optimum pH of the enzyme is 8.0, but it is active over
a broad pH range. This protein showed the highest sequence identity (93%) with the xylanase from Geobacillus thermodenitrificans NG80-2. XyzGeo71 contains a catalytic domain that belongs to the glycoside hydrolase family 10 (GH10). XyzGeo71 exhibited
good pH stability, remaining stable after treatment with buffers ranging from pH 7.0 to 11.0 for 6 h. Its activity was partially
inhibited by Al3+ and Cu2+ but strongly inhibited by Hg2+. The enzyme follows Michaelis–Menten kinetics, with Km and Vmax values of 0.425 mg xylan/ml and 500 μmol/min.mg, respectively. The enzyme was free from cellulase activity and degraded xylan
in an endo fashion. The action of the enzyme on oat spelt xylan produced xylobiose and xylotetrose. 相似文献
19.
Annick Pollet Tim Beliën Katleen Fierens Jan A. Delcour Christophe M. Courtin 《Enzyme and microbial technology》2009,44(4):189-195
When grown on arabinoxylan as the sole carbon source, the cereal phytopathogen Fusarium graminearum expresses four xylanases. Cloning and heterologous expression of the corresponding xylanase encoding genes and analysis of general biochemical properties, substrate specificities and inhibition sensitivities revealed some marked differences. XylA and XylB are glycoside hydrolase family (GH) 11 xylanases, while XylC and XylD belong to GH10. pH and temperature for optimal activity of the enzymes were between 6.0 and 7.0 and 40 °C, respectively. Interestingly, XylC displayed remarkable pH stability as it retained most of its activity even after pre-incubation at pH 1.0 and 13.0 for 120 min at room temperature. All xylanases hydrolysed xylotetraose, xylopentaose and xylohexaose, but to different extents, while only XylC and XylD hydrolysed xylotriose. The two GH10 xylanases released a higher percentage of smaller products from xylan and xylo-oligosaccharides than did their GH11 counterparts. Analysis of kinetic properties revealed that wheat arabinoxylan is the favoured XylC substrate while XylA and XylB prefer sparsely substituted oat spelt xylan. XylC and XylD were inhibited by xylanase inhibiting protein (XIP), while XylA and XylB were sensitive to Triticum aestivum xylanase inhibitor (TAXI). Because of its pH stability and preference for arabinoxylan, XylC is a valuable candidate for use in biotechnological applications. 相似文献
20.
Chang L Ding M Bao L Chen Y Zhou J Lu H 《Applied microbiology and biotechnology》2011,90(6):1933-1942
A new gene, RuCelA, encoding a bifunctional xylanase/endoglucanase, was cloned from a metagenomic library of yak rumen microorganisms. RuCelA
showed activity against xylan and carboxymethylcellulose (CMC), suggesting bifunctional xylanase/endoglucanase activity. The
optimal conditions for xylanase and endoglucanase activities were 65°C, pH 7.0 and 50°C, pH 5.0, respectively. In addition,
the presence of Co+ and Co2+ can greatly improve RuCelA's endoglucanase activity, while inhibits its xylanase activity. Further examination of substrate
preference showed a higher activity against barley glucan and lichenin than against xylan and CMC. Using xylan and barley
glucan as substrates, RuCelA displayed obvious synergistic effects with β-1,4-xylosidase and β-1,4-glucosidase. Generation
of soluble oligosaccharides from lignocellulose is the key step in bioethanol production, and it is greatly notable that RuCelA
can produce xylo-oligosaccharides and cello-oligosaccharides in the continuous saccharification of pretreated rice straw,
which can be further degraded into fermentable sugars. Therefore, the bifunctional RuCelA distinguishes itself as an ideal
candidate for industrial applications. 相似文献