共查询到20条相似文献,搜索用时 15 毫秒
1.
Aysegul Ersayin Yasinok Suzan Biran Aytac Kocabas Ufuk Bakir 《World journal of microbiology & biotechnology》2010,26(9):1641-1652
A xylanase producer, Bacillus pumilus SB-M13, was isolated from soil and identified using various tests based on carbohydrate fermentation preferences and fatty
acid analysis. Xylanase gene, isolated using PCR amplification, was partially sequenced and it showed 89–94% sequence similarity
to the xylanase genes of other B. pumilus strains. Xylanase with very low level of cellulase was produced on agricultural byproducts. The enzyme has been purified
186-fold by hydrophobic interaction chromatography and biochemically characterized. It has a molecular weight of 24.8 kDa
and pI of 9.2. Xylanolytic activity is stable at alkaline pH and highest activity is observed at 60 °C and pH 7.5. Enzyme
K
m and k
cat values were determined as 1.9 mg/mL and 42,600 U/mg, respectively. In aqueous-two-phase system, xylanase always partitioned
to the top phase. Basic pH, low PEG concentration, salt addition, and presence of microbial cells enhanced xylanase partitioning.
A maximum sevenfold purification, 10-fold concentration and 100% xylanase recovery were obtained, separately, by adjusting
system parameters. A fourfold concentrated xylanase was obtained with 70% enzyme recovery only in one step ATPS process without
cell harvesting. 相似文献
2.
P Prakash SK Jayalakshmi B Prakash M Rubul K Sreeramulu 《World journal of microbiology & biotechnology》2012,28(1):183-192
The alkaliphilic Bacillus halodurans strain PPKS-2 was shown to produce extracellular alkaliphilic, thermostable and halotolerent xylanase. The culture conditions
for xylanase production were optimized with respect to pH, temperature, NaCl and inexpensive agro waste as substrates. Xylanase
yield was enhanced more than four fold in the presence of 1% corn husk and 0.5% peptone or feather hydrolysate at pH 11 and
37°C. Xylanase was purified to 11.8-fold with 8.7% yield by using traditional chromatographic methods whereas the same enzyme
purified to 20-fold with 72% yield by using corn husk as ligand. Its molecular mass was estimated to be 24 kDa by SDS–PAGE.
The xylanase had maximal activity at pH 11 and 70°C. The enzyme was active over broad range, 0–20% sodium chloride. The enzyme
was thermostable retaining 100% of the original activity at 70°C for 3 h. The apparent K
m values for oat spelt xylan and brichwood xylan were 4.1 and 4.4 mg/ml respectively. The deduced internal amino acid sequence
of PPKS-2 xylanase resembled the sequence of β-1,4-endoxylanase, which is member of glycoside hydrolase family 11. 相似文献
3.
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
4.
A cellulase-free xylanase production by Thermomyces lanuginosus SSBP using bagasse pulp was examined under submerged (SmC) and solid-state cultivation (SSC). Higher level of xylanase activity
(19,320 ± 37 U g−1 dried carbon source) was obtained in SSC cultures than in SmC (1,772 ± 15 U g−1 dried carbon source) after 120 h with 10% inoculum. The biobleaching efficacy of crude xylanase was tested on bagasse pulp,
and the maximum brightness of 46.1 ± 0.06% was observed with 50 U of crude xylanase per gram of pulp, which was 3.8 points
higher than the brightness of untreated samples. Reducing sugars (26 ± 0.1 mg g−1) and UV-absorbing lignin-derived compounds in the pulp filtrates were observed as maximum in 50 U of crude xylanase-treated
samples. T. lanuginosus SSBP has potential applications due to its high productivity of xylanase and its efficiency in pulp bleaching. 相似文献
5.
Chenyan Zhou Dongfeng Li Minchen Wu Wu Wang 《World journal of microbiology & biotechnology》2008,24(8):1393-1401
The xylanase gene xyn II from Aspergillus usamii E001 was placed under the control of an alcohol oxidase promoter (AOX1) in the plasmid pPIC9K and integrated into the genome of a methylotrophic yeast, P. pastoris GS115, by electroporation. His+ transformants were screened for on the basis of their resistance to G418 and activity assay. A transformant, P. pastoris GSC12, which showed resistance to over 6 mg G418/ml and highest xylanase activity was selected. Recombinant xylanase was
secreted by P. pastoris GSC12 24 h after methanol induction of shake-flask cultures, and reached a final yield of 3139. About 68 U/mg 120 h after
the induction. The molecular mass of this xylanase was estimated to be 21 kDa by SDS-PAGE. The optimum pH and temperature
were 4.2 and 50 °C, respectively. Xylanase was stable below 50 °C and within pH 3.0–7.0. Its activity was increased by EDTA
and Co2+ ion and strongly inhibited by Mn2+, Li+ and Ag+ ions. The K
m and V
max values with birchwood xylan as the substrate were found to be 5.56 mg/ml and 216 μmol/mg/min, respectively. This is the first
report on expression and characterization of xylanase from A. usamii in P. pastoris. The hydrolysis products consisted of xylooligosaccharides together with a small amount of xylose. This property made the
enzyme attractive for industrial purposes, as relatively pure xylooligosaccharides could be obtained. 相似文献
6.
Kumar GR Sharma A Kumari M Jagannadham MV Debnath M 《European biophysics journal : EBJ》2011,40(8):923-935
Equilibrium unfolding of A. niger RNase with chemical denaturants, for example GuHCl and urea, and thermal unfolding have been studied as a function of pH
using fluorescence, far-UV, near-UV, and absorbance spectroscopy. Because of their ability to affect electrostatic interactions,
pH and chemical denaturants have a marked effect on the stability, structure, and function of many globular proteins. ANS
binding studies have been conducted to enable understanding of the folding mechanism of the protein in the presence of the
denaturants. Spectroscopic studies by absorbance, fluorescence, and circular dichroism and use of K2D software revealed that
the enzyme has α + β type secondary structure with approximately 29% α-helix, 24% β-sheet, and 47% random coil. Under neutral
conditions the enzyme is stable in urea whereas GuHCl-induced equilibrium unfolding was cooperative. A. niger RNase has little ANS binding even under neutral conditions. Multiple intermediates were populated during the pH-induced unfolding
of A. niger RNase. Urea and temperature-induced unfolding of A. niger RNase into the molten globule-like state is non-cooperative, in contrast to the cooperativity seen with the native protein,
suggesting the presence of two parts/domains, in the molecular structure of A. niger RNase, with different stability that unfolds in steps. Interestingly, the GuHCl-induced unfolding of the A state (molten globule state) of A. niger RNase is unique, because a low concentration of denaturant not only induces structural change but also facilitates transition
from one molten globule like state (AMG1) into another (IMG2). 相似文献
7.
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
8.
Chaoning Liang Yanfen Xue Marco Fioroni Francisco Rodríguez-Ropero Cheng Zhou Ulrich Schwaneberg Yanhe Ma 《Applied microbiology and biotechnology》2011,89(2):315-326
A β-1,4-endoglucanase (Cel5A) was cloned from the genomic DNA of saccharolytic thermophilic eubacterium Thermoanaerobacter tengcongensis MB4 and functionally expressed in Escherichia coli. Substrate specificity analysis revealed that Cel5A cleaves specifically the β-1,4-glycosidic linkage in cellulose with high
activity (294 U mg−1; carboxymethyl cellulose sodium (CMC)). On CMC, kinetics of Cel5A was determined (K
m 1.39 ± 0.12 g l−1; k
cat/K
m 1.41 ± 0.13 g−1 s−1). Cel5A displays an activity optimum between 75 and 80 °C. Residues Glu187 and Glu289 were identified as key catalytic amino
acids by sequence alignment. Interestingly, derived from a non-halophilic bacterium, Cel5A exhibits high residual activities
in molar concentration of NaCl (3 M, 49.3%) and KCl (4 M, 48.6%). In 1 M NaCl, 82% of Cel5A activity is retained after 24
h incubation. Molecular Dynamics studies performed at 0 and 3 M NaCl, correlate the Cel5A stability to the formation of R-COO−···Na+ ···−OOC-R salt bridges within the Cel5A tertiary structure, while activity possibly relates to the number of Na+ ions trapped into the negatively charged active site, involving a competition mechanism between substrate and Na+. Additionally, Cel5A is remarkably resistant in ionic liquids 1-butyl-3-methyllimidazolium chloride (1 M, 54.4%) and 1-allyl-3-methylimidazolium
chloride (1 M, 65.1%) which are promising solvents for cellulose degradation and making Cel5A an attractive candidate for
industrial applications. 相似文献
9.
Facchini FD Vici AC Reis VR Jorge JA Terenzi HF Reis RA Polizeli Mde L 《Bioprocess and biosystems engineering》2011,34(3):347-355
Solid-state fermentation obtained from different and low-cost carbon sources was evaluated to endocellulases and endoxylanases
production by Aspergillus japonicus C03. Regarding the enzymatic production the highest levels were observed at 30 °C, using soy bran added to crushed corncob
or wheat bran added to sugarcane bagasse, humidified with salt solutions, and incubated for 3 days (xylanase) or 6 days (cellulase)
with 70% relative humidity. Peptone improved the xylanase and cellulase activities in 12 and 29%, respectively. The optimum
temperature corresponded to 60 °C and 50–55 °C for xylanase and cellulase, respectively, both having 4.0 as optimum pH. Xylanase
was fully stable up to 40 °C, which is close to the rumen temperature. The enzymes were stable in pH 4.0–7.0. Cu++ and Mn++ increased xylanase and cellulase activities by 10 and 64%, respectively. A. japonicus C03 xylanase was greatly stable in goat rumen fluid for 4 h during in vivo and in vitro experiments. 相似文献
10.
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
11.
The anaerobic fungus Anaeromyces mucronatus KF8 grown in batch culture on M10 medium with rumen fluid and microcrystalline cellulose as carbon source produced a broad
range of enzymes requisite for degradation of plant structural and storage saccharides including cellulase, endoglucanase,
xylanase, α-xylosidase, β-xylosidase, α-glucosidase, β-glucosidase, β-galactosidase, mannosidase, cellobiohydrolase, amylase,
laminarinase, pectinase and pectate lyase. These enzymes were detected in both the intra- and extracellular fractions, but
production into the medium was prevalent with the exception of intracellular β-xylosidase, chitinases, N-acetylglucosaminidase, and lipase. Xylanase activity was predominant among the polysaccharide hydrolases. Extracellular production
of xylanase was stimulated by the presence of cellobiose and oat spelt xylan. Zymogram of xylanases of strain KF8 grown on
different carbon sources revealed several isoforms of xylanases with approximate molar masses ranging from 26 to 130 kDa. 相似文献
12.
In recent years, the biotechnological use of xylanases has grown remarkably. To efficiently produce xylanase for food processing
and other industry, a codon-optimized recombinant xylanase gene from Streptomyces sp. S38 was synthesized and extracellularly expressed in Pichia pastoris under the control of AOX1 promoter. SDS-PAGE and activity assay demonstrated that the molecular mass of the recombinant xylanase was estimated to be
25 kDa, the optimum pH and optimum temperature were 5.5 and 50°C, respectively. In shake flask culture, the specific activity
of the xylanase activity was 5098.28 U/mg. The K
m
and V
max
values of recombinant xylanase were 11.0 mg/ml and 10000 μmol min−1 mg−1, respectively. In the presence of metal ions such as Ca2+, Cu2+, Cr3+ and K+, the activity of the enzyme increased. However, strong inhibition of the enzyme activity was observed in the presence of
Hg2+. This is the first report on the expression properties of a recombinant xylanase gene from the Streptomyces sp. S38 using Pichia pastoris. The attractive biochemical properties of the recombinant xylanase suggest that it may be a useful candidate for variety
of commercial applications. 相似文献
13.
Liu L Lei T Bankir L Zhao D Gai X Zhao X Yang B 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(1):65-72
Mammalian erythrocytes exhibit high urea permeability (P
urea) due to UT-B expression in their cytoplasmic membrane. This high P
urea allows fast equilibration of urea in erythrocytes during their transit in the hyperosmotic renal medulla. It also allows
more urea (in addition to that in plasma) to participate in counter-current exchange between ascending and descending vasa
recta, thus improving the trapping of urea in the medulla and improving urine concentrating ability. To determine if P
urea in erythrocytes is related to diet and urine concentrating ability, we measured P
urea in erythrocytes from 11 different mammals and 5 birds using stopped-flow light scattering. Carnivores (dog, fox, cat) exhibited
high P
urea (in ×10−5 cm/s, 5.3 ± 0.6, 3.8 ± 0.5 and 2.8 ± 0.7, respectively). In contrast, herbivores (cow, donkey, sheep) showed much lower P
urea (0.8 ± 0.2, 0.7 ± 0.2, 1.0 ± 0.1, respectively). Erythrocyte P
urea in human (1.1 ± 0.2), and pig (1.5 ± 0.1), the two omnivores, was intermediate. Rodents and lagomorphs (mouse, rat, rabbit)
had P
urea intermediate between carnivores and omnivores (3.3 ± 0.4, 2.5 ± 0.3 and 2.4 ± 0.3, respectively). Birds that do not excrete
urea and do not express UT-B in their erythrocytes had very low values (<0.1 × 10−5 cm/s). In contrast to P
urea, water permeability, measured simultaneously, was relatively similar in all mammals. The species differences in erythrocytes
P
urea most probably reflect adaptation to the different types of diet and resulting different needs for concentrating urea in the
urine. 相似文献
14.
Gopalakrishnan Menon Kalpana Mody Jitendra Keshri Bhavanath Jha 《Biotechnology and Bioprocess Engineering》2010,15(6):998-1005
A haloalkalitolerant xylanase-producing Bacillus pumilus strain, GESF1 was isolated from an experimental salt farm of CSMCRI. Birch wood xylan and xylose induced maximum xylanase
production with considerable activity seen in wheat straw and no activity at all with caboxymethyl cellulose (CMC). A three
step purification yielded 21.21-fold purification with a specific activity of 112.42 U/mg protein (unit expressed as μmole
of xylose released per min). Xylanase produced showed an optimum activity at pH 8.0, with approximately 50 and 30% relative
activity at a pH 6.0 and 10.0, respectively. The temperature optimum was 40°C and kinetic properties such as Km and Vmax were 5.3 mg/mL and 0.42 μmol/min/mL (6593.4 μmol/min/mg protein). Xylanase activity (160∼ 120%) was considerably enhanced
in 2.5 to 7.5% NaCl with 87 and 73% retention of activity in 10 and 15% of NaCl. Enzyme activity was enhanced by Ca2+, Mn2+, Mg2+, and Na+ but strongly inhibited by heavy metals such as Hg2+, Fe3+, Cu2+, Cd2+, and Zn2+. Organic reagents such as β-Mercaptoethanol enhanced xylanase activity whereas EDTA strongly inhibited its activity. Xylanase,
purified from the Bacillus pumilus strain, GESF1 could have potential biotechnological applications. 相似文献
15.
Krystyna Konopka Barbara Dorocka-Bobkowska Senait Gebremedhin Nejat Düzgüneş 《Antonie van Leeuwenhoek》2010,97(4):413-417
Candida-associated denture stomatitis has a high rate of recurrence. Candida biofilms formed on denture acrylic are more resistant to antifungals than planktonic yeasts. Histatins, a family of basic
peptides secreted by the major salivary glands in humans, especially histatin 5, possess significant antifungal properties.
We examined antifungal activities of histatin 5 against planktonic or biofilm Candida albicans and Candida glabrata. Candida biofilms were developed on poly(methyl methacrylate) discs and treated with histatin 5 (0.01–100 μM) or fluconazole (1–200 μM).
The metabolic activity of the biofilms was measured by the XTT reduction assay. The fungicidal activity of histatin 5 against
planktonic Candida was tested by microdilution plate assay. Biofilm and planktonic C. albicans GDH18, UTR-14 and 6122/06 were highly susceptible to histatin 5, with 50% RMA (concentration of the agent causing 50% reduction
in the metabolic activity; biofilm) of 4.6 ± 2.2, 6.9 ± 3.7 and 1.7 ± 1.5 μM, and IC50 (planktonic cells) of 3.0 ± 0.5, 2.6 ± 0.1 and 4.8 ± 0.5, respectively. Biofilms of C. glabrata GDH1407 and 6115/06 were less susceptible to histatin 5, with 50% RMA of 31.2 ± 4.8 and 62.5 ± 0.7 μM, respectively. Planktonic
C. glabrata was insensitive to histatin 5 (IC50 > 100 μM). Biofilm-associated Candida was highly resistant to fluconazole in the range 1–200 μM; e.g. at 100 μM only ~20% inhibition was observed for C. albicans, and ~30% inhibition for C. glabrata. These results indicate that histatin 5 exhibits antifungal activity against biofilms of C. albicans and C. glabrata developed on denture acrylic. C. glabrata is significantly less sensitive to histatin 5 than C. albicans. 相似文献
16.
Giovanna Di Nardo Almerinda Di Venere Giampiero Mei Sheila J. Sadeghi Jon R. Wilson Gianfranco Gilardi 《Journal of biological inorganic chemistry》2009,14(4):497-505
Heme ligands were introduced in the hydrophobic core of an engineered monomeric ColE1 repressor of primer (rop-S55) in two
different layers of the heptad repeat. Mutants rop-L63M/F121H (layer 1) and rop-L56H/L113H (layer 3) were found to bind heme
with a K
D of 1.1 ± 0.2 and 0.47 ± 0.07 μM, respectively. The unfolding of heme-bound and heme-free mutants, in the presence of guanidinium
hydrochloride, was monitored by both circular dichroism and fluorescence spectroscopy. For the heme-bound rop mutants, the
total free energy change was 0.5 kcal/mol higher in the layer 3 mutant compared with that in the layer1 mutant. Heme binding
also stabilized these mutants by increasing the by 1.4 and 1.8 kcal/mol in rop-L63M/F121H and rop-L56H/L113H, respectively. The reduction potentials measured by spectroelectrochemical
titrations were calculated to be −154 ± 2 mV for rop-56H/113H and −87.5 ± 1.2 mV for rop-L63M/F121H. The mutant designed to
bind heme in a more buried environment (layer 3) showed tighter heme binding, a higher stability, and a different reduction
potential compared with the mutant designed to bind heme in layer 1. 相似文献
17.
Subhash Chandra Yadav Medicherla V. Jagannadham 《European biophysics journal : EBJ》2009,38(7):981-991
Spectroscopic, calorimetric, and proteolytic methods were utilized to evaluate the stability of the kinetically stable, differentially
glycosylated, dimeric serine protease milin as a function of pH (1.0–11.0), temperature, urea, and GuHCl denaturation in presence
of 8 M urea at pH 2.0. The stability of milin remains equivalent to that of native at pH 1.0–11.0. However, negligible and
reversible alteration in structure upon temperature transition has been observed at pH 2.0 and with 1.6 M GuHCl. Irreversible
and incomplete calorimetric transition with apparent T
m > 100°C was observed at basic pH (9.0 and 10.0). Urea-induced unfolding at pH 4.0, and at pH 2.0 with GuHCl, in presence
of 8 M urea also reveals incomplete unfolding. Milin has been found to exhibit proteolytic resistant in either native or denatured
state against various commercial proteases. These results imply that the high conformational stability of milin against various
denaturating conditions enable its potential use in protease-based industries. 相似文献
18.
Peixoto-Nogueira Sde C Michelin M Betini JH Jorge JA Terenzi HF Polizeli Mde L 《Journal of industrial microbiology & biotechnology》2009,36(1):149-155
The ability of xylanolytic enzymes produced by Aspergillus fumigatus RP04 and Aspergillus niveus RP05 to promote the biobleaching of cellulose pulp was investigated. Both fungi grew for 4–5 days in liquid medium at 40°C,
under static conditions. Xylanase production was tested using different carbon sources, including some types of xylans. A. fumigatus produced high levels of xylanase on agricultural residues (corncob or wheat bran), whereas A. niveus produced more xylanase on birchwood xylan. The optimum temperature of the xylanases from A. fumigatus and A. niveus was around 60–70°C. The enzymes were stable for 30 min at 60°C, maintaining 95–98% of the initial activity. After 1 h at
this temperature, the xylanase from A. niveus still retained 85% of initial activity, while the xylanase from A. fumigatus was only 40% active. The pH optimum of the xylanases was acidic (4.5–5.5). The pH stability for the xylanase from A. fumigatus was higher at pH 6.0–8.0, while the enzyme from A. niveus was more stable at pH 4.5–6.5. Crude enzymatic extracts were used to clarify cellulose pulp and the best result was obtained
with the A. niveus preparation, showing kappa efficiency around 39.6% as compared to only 11.7% for that of A. fumigatus. 相似文献
19.
The genus Dierama comprises plants with a potential to be developed as ornamentals. D. erectum seeds were decontaminated and germinated on 1/10th strength Murashige and Skoog (Physiol Plant 15:473–497, 1962) (MS) media
without plant growth regulators or sucrose. In an experiment investigating the effects of 6-benzyladenine (BA), meta-Topolin (mT), kinetin (KIN) and zeatin (Z) with or without α-naphthaleneacetic acid (NAA), the highest shoot number per hypocotyl (4.20 ± 0.51)
was obtained from MS medium supplemented with 1.0 μM Z after 8 weeks. This was followed by a combination of 2.0 μM KIN and
2.0 μM NAA with 3.67 ± 0.81 shoots per explant. BA treatments produced 3.20 ± 0.22 shoots per hypocotyl explant when 2.0 μM
was combined with 1.0 μM NAA, while mT gave 3.09 ± 0.99 shoots per explant when 2.0 μM mT was combined with 2.0 μM NAA. Adventitious shoot regeneration was optimised when shoots were grown under a 16-h photoperiod
at 100 μmol m−2 s−1 on MS medium supplemented with 1.0 μM BA. This resulted in an average of 12.73 ± 1.03 shoots per hypocotyl explant. Various
concentrations of ancymidol, activated charcoal and sucrose did not promote in vitro corm formation of this species. Plants
rooted successfully after 8 weeks on MS medium supplemented with 1.0 μM indole-3-butyric acid (IBA) and had an average root
number of 2.73 ± 0.40. After 2 months of acclimatisation, plants had formed corms. The largest corms (of diameter 0.45 ± 0.03 cm)
were produced in plants pre-treated with 0.5 μM IBA. The highest plant survival percentage of 73% was also associated with
this treatment. 相似文献
20.
Jie Xie Lingling Song XinRan Li XiuLi Yi Hui Xu Jing Li Dairong Qiao Yi Cao 《Current microbiology》2011,62(1):242-248
Xylanase is one of the most important hemicellulases in industry. However, its low thermostability limits its applications.
In this study, one thermostable xylanase-producing strain 400264 was obtained from screening 11 Aspergillus niger strains (producing thermotolerant xylanase), and the optimum temperature of crude xylanase extracted from it was 55°C. Original
activity of the crude xylanase is 64% at 60°C and 55% at 85°C with an incubation time of 30 min, respectively. After the expression
of recombinant xylanase gene (xynA/xynB), the XYNB (xylanase B) showed higher thermostability than XYNA (xylanase A). Recombinant
enzyme XYNB retained 94% of its activity for 10 min at 85°C, while XYNA with no activity left. Site-directed mutagenesis was
performed to replace Ala33 of XYNB by Ser33 resulting 19% decrease in enzyme activity after incubating at 85°C for 30 min.
It suggested that the Ala33 residue may have a certain effect on the thermophilic adaptation of xylanase. 相似文献