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1.
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
2.
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
3.
S. Prakash Y. Veeranagouda L. Kyoung K. Sreeramulu 《World journal of microbiology & biotechnology》2009,25(2):197-204
A halophilic and alkali-tolerant Chromohalobacter sp. TPSV 101 with an ability to produce extracellular halophilic, alkali-tolerant and moderately thermostable xylanase was
isolated from solar salterns. Identification of the bacterium was done based upon biochemical tests and 16S rRNA sequence.
The culture conditions for higher xylanase production were optimized with respect to NaCl, pH, temperature, substrates and
metal ions and additives. Maximum xylanase production was achieved in the medium with 20% NaCl, pH-9.0 at 40°C supplemented
with 1% (w/v) sugarcane bagasse and 0.5% feather hydrolysate as carbon and nitrogen sources. Sugarcane bagasse (250 U/ml)
and wheat bran (190 U/ml) were the best inducer of xylanase when used as carbon source as compared to xylan (61 U/ml). The
xylanase that was partially purified by protein concentrator had a molecular mass of 15 kDa approximately. The xylanase from
Chromohalobacter sp. TPSV 101 was active at pH 9.0 and required 20% NaCl for optimal xylanolytic activity and was active over a broad range
of temperature 40–80°C with 65°C as optimum. The early stage hydrolysis products of sugarcane bagasse were xylose and xylobiose,
after longer periods of incubation only xylose was detected. 相似文献
4.
A. Mandal S. Kar P. K. Das Mohapatra C. Maity B. R. Pati K. C. Mondal 《Applied Biochemistry and Microbiology》2011,47(3):250-255
An extracellular xylanase from the fermented broth of Bacillus cereus BSA1 was purified and characterized. The enzyme was purified to 3.43 fold through ammonium sulphate precipitation, DEAE cellulose
chromatography and followed by gel filtration through Sephadex-G-100 column. The molecular mass of the purified xylanse was
about 33 kDa. The enzyme was an endoxylanase as it initially degraded xylan to xylooligomers. The purified enzyme showed optimum
activity at 55°C and at pH 7.0 and remained reasonably stable in a wide range of pH (5.0–8.0) and temperature (40–65°C). The
K
m
and V
max
values were found to be 8.2 mg/ml and 181.8 μmol/(min mg), respectively. The enzyme had no apparent requirement of cofactors,
and its activity was strongly inhibited by Cu2+, Hg2+. It was also a salt tolerant enzyme and stable upto 2.5 M of NaCl and retained its 85% activity at 3.0 M. For stability and
substrate binding, the enzyme needed hydrophobic interaction that revealed when most surfactants inhibited xylanase activity.
Since the enzyme was active over wide range of pH, temperature and remained active in higher salt concentration, it could
find potential uses in biobleaching process in paper industries. 相似文献
5.
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
6.
G. López A. Bañares-Hidalgo P. Estrada 《Journal of industrial microbiology & biotechnology》2011,38(1):113-125
Xylanase II, a key enzyme in the hydrolysis of xylan, was purified from cultures of Trichoderma reesei QM 9414 (anamorph of Hypocrea jecorina) grown on wheat straw as a carbon source. Xylanase treated with increasing guanidinium hydrochloride concentrations was denatured
in a cooperative way regarding secondary and tertiary structures with midpoint transitions 5.6 ± 0.1 and 3.7 ± 0.1 M, respectively,
whereas the enzymatic activity showed an intermediate state at 2–4 M denaturant. Treatment with urea showed that xylanase
secondary structure was stabilized up to 4 M urea to be destabilized thereafter in a cooperative way with a transition midpoint
Dm = 5.7 ± 0.2 M, but the ellipticity at 220 nm was greater than control in the presence of urea up to 6 M. Tertiary structure
in the presence of urea showed also intermediate states with partial cooperative transitions with a midpoint: Dm = 2.7 ± 0.04
and 6.7 ± 0.3 M, respectively, whereas the enzymatic activity was enhanced about 40% at 2 M and inhibited above 4 M urea.
Assays with the fluorescent probe 4,4′-bis-1-phenylamine-8-naphftalene sulfonate (bis-ANS) proved that the intermediate states
had the characteristics of molten globule structures. The change of free energy for xylanase in absence of denaturants obtained
from the spectral centre of mass (SCM) data at 298 K is
\Updelta GH2 O0 \Updelta G_{{{\rm H}_{2} {\rm O}}}^{0} = ~17 kJ mol−1. In the presence of increasing trifluoroethanol (TFE), the enzyme gained α-helix content and lose tertiary structure and
catalytic activity. Changes in pH (2–9) had practically no effect on the secondary structure of the enzyme, whereas the SCM
values indicated that tertiary structure is maintained above pH 4. Bis-ANS binds to xylanase at pH 2 and 2.5 and in the presence
of 30–40% TFE (v/v) characterizing molten globule states in those environmental conditions. 相似文献
7.
Biodegradation of crude oil and pure hydrocarbons by extreme halophilic archaea from hypersaline coasts of the Arabian Gulf 总被引:3,自引:0,他引:3
D. M. Al-Mailem N. A. Sorkhoh H. Al-Awadhi M. Eliyas S. S. Radwan 《Extremophiles : life under extreme conditions》2010,14(3):321-328
Two extreme halophilic Haloferax strains and one strain each of Halobacterium and Halococcus were isolated from a hypersaline coastal area of the Arabian Gulf on a mineral salt medium with crude oil vapor as a sole
source of carbon and energy. These archaea needed at least 1 M NaCl for growth in culture, and grew best in the presence of
4 M NaCl or more. Optimum growth temperatures lied between 40 and 45oC. The four archaea were resistant to the antibiotics
chloramphenicol, cycloheximide, nalidixic acid, penicillin, streptomycin and tetracycline. The strains could grow on a wide
scope of aliphatic and aromatic (both mono-and polynuclear) hydrocarbons, as sole sources of carbon and energy. Quantitative
measurements revealed that these extreme halophilic prokaryotes could biodegrade crude oil (13–47%, depending on the strain
and medium salinity), n-octadecane (28–67%) and phenanthrene (13–30%) in culture after 3 weeks of incubation. The rates of biodegradation by all
strains were enhanced with increasing NaCl concentration in the medium. Optimal concentration was 3 M NaCl, but even with
4 M NaCl the hydrocarbon-biodegradation rates were higher than with 1 and 2 M NaCl. It was concluded that these archaea could
contribute to self-cleaning and bioremediation of oil-polluted hypersaline environments. 相似文献
8.
A new xylanase from thermoacidophilic Alicyclobacillus sp. A4 with broad-range pH activity and pH stability 总被引:1,自引:0,他引:1
Yingguo Bai Jianshe Wang Zhifang Zhang Peilong Yang Pengjun Shi Huiying Luo Kun Meng Huoqing Huang Bin Yao 《Journal of industrial microbiology & biotechnology》2010,37(2):187-194
We have identified a highly pH-adaptable and stable xylanase (XynA4) from the thermoacidophilic Alicyclobacillus sp. A4, a strain that was isolated from a hot spring in Yunnan Province, China. The gene (xynA4) that encodes this xylanase was cloned, sequenced, and expressed in Escherichia coli. It encodes a 338-residue polypeptide with a calculated molecular mass of 42.5 kDa. The deduced amino acid sequence is most
similar to (53% identity) an endo-1,4-β-xylanase from Geobacillus stearothermophilus that belongs to family 10 of the glycoside hydrolases. Purified recombinant XynA4 exhibited maximum activity at 55°C and
pH 7.0, had broad pH adaptability (>40% activity at pH 3.8–9.4) and stability (retaining >80% activity after incubation at
pH 2.6–12.0 for 1 h at 37°C), and was highly thermostable (retaining >90% activity after incubation at 60°C for 1 h at pH
7.0). These properties make XynA4 promising for application in the paper industry. This is the first report that describes
cloning and expression of a xylanase gene from the genus Alicyclobacillus. 相似文献
9.
Periplasmic metal binding protein characterized by high histidine content was cloned from moderate halophile, Chromohalobacter salexigens. The protein, termed histidine-rich metal binding protein (HP), was expressed in and purified from E. coli as a native form. HP bound to Ni- and Cu-loaded chelate columns with high affinity, and Co- and Zn-columns with moderate
affinity. Although the secondary structure was not grossly altered by the addition of 0.2–2.0 M NaCl, the thermal transition
pattern was considerably shifted to higher temperature with increasing salt concentration: melting temperature was raised
by ~20 °C at 2.0 M NaCl over the melting temperature at 0.2 M NaCl. HP showed reversible refolding from thermal melting in
0.2–1.15 M NaCl, while it formed irreversible aggregates upon thermal melting at 2 M NaCl. Addition of 0.01–0.1 mM NiSO4 stabilized HP against thermal melting with high reversibility, while addition above 0.5 mM resulted in irreversible melting
due to aggregation. 相似文献
10.
Jianshe Wang Yingguo Bai Peilong Yang Pengjun Shi Huiying Luo Kun Meng Huoqing Huang Jun Yin Bin Yao 《World journal of microbiology & biotechnology》2010,26(5):917-924
A xylanase gene, xynE2, was cloned from thermoalkaline Anoxybacillus sp. E2 and was expressed in Escherichia coli BL21 (DE3). The gene consisted of 987 bp and encoded a 328-residue xylanase with a calculated molecular weight of 38.8 kDa.
On the basis of amino acid sequence similarities, this enzyme was assigned as a member of glycoside hydrolase family 10. Purified
recombinant XynE2 showed maximal activity at pH 7.8 and 65°C, and was thermostable at 60°C. The enzyme was highly active and
stable over a broad pH range, showing more than 90% of maximal activity at pH 6.6–pH 8.6 and retaining more than 80% of activity
at pH 4.6–pH 12.0, 37°C for 1 h, respectively. These favorable properties make XynE2 a good candidate in the pulp and paper
industries. This is the first report on gene cloning, expression and characterization of a xylanase from the genus Anoxybacillus. 相似文献
11.
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
12.
Nitraria retusa and Atriplex halimus (xero-halophytes) plants were grown in the range 0–800 mM NaCl while Medicago arborea (glycophyte) in 0–300 mM NaCl. Plants were harvested after 120 days of salt-treatment. The present study was designed to
study the effect of salinity on root, stem and leaf anatomy, water relationship, and plant growth in greenhouse conditions.
Salinity induced anatomical changes in the roots, stems and leaves. The cuticle and epidermis of N. retusa and A. halimus stems were unaffected by salinity. However, root anatomical parameters (root cross section area, cortex thickness and stele
to root area ratio), and stem anatomical parameters (stem cross section area and cortex area) were promoted at 100–200 mM
NaCl. Indicating that low to moderate salinity had a stimulating effect on root and stem growth of these xero-halophytic species.
At higher salinities, root and stem structures were altered significantly, and their percentages of reduction were higher
in A. halimus than in N. retusa whereas, in M. arborea, they were strongly altered as salinity rose. NaCl (100–300 mM) reduced leaf water content by 21.2–56.2% and specific leaf
area by 51–88.1%, while increased leaf anatomical parameters in M. arborea (e.g. increased thickness of upper and lower epidermis, palisade and spongy mesophyll, entire lamina, and increased palisade
to spongy mesophyll ratio). Similar results were evidenced in A. halimus leaves with salinity exceeding 100 mM NaCl. Leaves of N. retusa were thinner in salt-stressed plants while epidermis thickness and water content was unaffected by salinity. The size of
xylem vessel was unchanged under salinity in the leaf’s main vein of the three species while we have increased number in M. arborea leaf main vein in the range of 200–300 mM NaCl. A longer distance between leaf vascular bundle, a reduced size and increased
number of xylem vessel especially in stem than in root vascular system was evidenced in M. arborea treated plants and only at (400–800 mM) in the xero-halophytic species. The effects of NaCl toxicity on leaf, stem and root
ultrastructure are discussed in relation to the degree of salt resistance of these three species. Our results suggest that
both N. retusa and A. halimus show high tolerance to salinity while M. arborea was considered as a salt tolerant species. 相似文献
13.
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
14.
Abdul Ghaffar Sher Afzal Khan Zahid Mukhtar Muhammad Ibrahim Rajoka Farooq Latif 《Molecular biology reports》2011,38(5):3227-3233
We studied heterologous expression of xylanase 11A gene of Chaetomium thermophilum in Pichia pastoris and characterized the thermostable nature of the purified gene product. For this purpose, the xylanase 11A gene of C. thermophilum was cloned in P. pastoris GS115 under the control of AOX1 promoter. The maximum extracellular activity of recombinant xylanase (xyn698: gene with intron) was 15.6 U ml−1 while that of recombinant without intron (xyn669) was 1.26 U ml−1 after 96 h growth. The gene product was purified apparently to homogeneity level. The optimum temperature of pure recombinant
xylanase activity was 70°C and the enzyme retained its 40.57% activity after incubation at 80°C for 10 min. It exhibited quite
lower demand of activation energy, enthalpy, Gibbs free energy, entropy, and xylan binding energy during substrate hydrolysis
than that required by that of the donor, thus indicating its thermostable nature. pH-dependent catalysis showed that it was
quite stable in a pH range of 5.5–8.5. This revealed that gene was successfully processed in P. pastoris and remained heat stable and may qualify for its potential use in paper and pulp and animal feed applications. 相似文献
15.
M. Michelin S. C. Peixoto-Nogueira J. H. A. Betini T. M. da Silva J. A. Jorge H. F. Terenzi M. L. T. M. Polizeli 《Bioprocess and biosystems engineering》2010,33(7):813-821
Aspergillus terricola and Aspergillus ochraceus, isolated from Brazilian soil, were cultivated in Vogel and Adams media supplemented with 20 different carbon sources, at
30 °C, under static conditions, for 120 and 144 h, respectively. High levels of cellulase-free xylanase were produced in birchwood
or oat spelt xylan-media. Wheat bran was the most favorable agricultural residue for xylanase production. Maximum activity
was obtained at 60 °C and pH 6.5 for A. terricola, and 65 °C and pH 5.0 for A. ochraceus. A. terricola xylanase was stable for 1 h at 60 °C and retained 50% activity after 80 min, while A. ochraceus xylanase presented a t
50 of 10 min. The xylanases were stable in an alkali pH range. Biobleaching of 10 U/g dry cellulose pulp resulted in 14.3% delignification
(A. terricola) and 36.4% (A. ochraceus). The brightness was 2.4–3.4% ISO higher than the control. Analysis in SEM showed defibrillation of the microfibrils. Arabinase
traces and β-xylosidase were detected which might act synergistically with xylanase. 相似文献
16.
Muthu Manikandan Lejla Pašić Vijayaraghavan Kannan 《World journal of microbiology & biotechnology》2009,25(12):2247-2256
An extremely halophilic archaeon Haloferax lucentensis VKMM 007, isolated from a solar saltern, was found to produce a protease. This extracellular enzyme consisted of a single
polypeptide chain of 57.8 kDa as determined by SDS–PAGE and was purified by a combination of ultrafiltration, bacitracin–Sepharose
affinity chromatography and Sephadex G-100 gel filtration. The purified protein was stable in a wide range of temperatures
(20–70°C), NaCl concentrations (0.85–5.13 M) and pH (5.0–9.0) with maximal activity observed at 60°C, 4.3 M NaCl and pH 8.0.
Proteolytic activity was enhanced by Ca2+, K+, Mg2+, Na+, and Fe2+ ions and the protein was classified as a trypsin-like serine protease. Further assays indicated highest degree of specificity
when hemoglobin was used as an enzyme substrate. Most importantly, the proteolytic activity remained stable or only marginally
inhibited in the presence of various polar and non-polar solvents, surfactants and reducing agents thus emphasizing the biotechnological
potential of this novel halophilic protease. 相似文献
17.
Jia Ouyang Shen Wang Yan Wang Xin Li Mu Chen Qiang Yong Shiyuan Yu 《World journal of microbiology & biotechnology》2011,27(4):751-758
The purpose of this study was to produce a Trichoderma reesei xylanase (XYN2) in Pichia pastoris and to test its potential application for pulp bleaching. The recombinant xylanase was purified by a two-step process of
ultrafiltration and gel filtration chromatography. The molecular mass of the recombinant enzyme was 21 and 25 kDa by SDS–PAGE
analysis, due to different glycosylation of the native protein. The optimum pH and temperature of the recombinant XYN2 was
5.0 and 50 °C. Enzyme activity was stable at 50 °C and at pH 5.0–7.0. The bleaching ability of the recombinant xylanase was
also studied at 50 °C and pH 6.0, using wheat straw pulp. Biobleaching of the xylanase produced chlorine dioxide savings of
up to 60%, while retaining brightness at the control level and led to a lower kappa number and small enhancements in tensile,
burst and tear strength of pulp fibers. 相似文献
18.
P. Olguín-Lora S. Le Borgne G. Castorena-Cortés T. Roldán-Carrillo I. Zapata-Peñasco J. Reyes-Avila S. Alcántara-Pérez 《Biodegradation》2011,22(1):83-93
Haloalkaliphilic sulfur-oxidizing mixed cultures for the treatment of alkaline–saline effluents containing sulfide were characterized
and evaluated. The mixed cultures (IMP-PB, IMP-XO and IMP-TL) were obtained from Mexican alkaline soils collected in Puebla
(PB), Xochimilco (XO) and Tlahuac (TL), respectively. The Ribosomal Intergenic Spacer Analysis (RISA) revealed bacteria related
to Thioalkalibacterium and Thioalkalivibrio in IMP-XO and IMP-PB mixed cultures. Halomonas strains were detected in IMP-XO and IMP-TL. In addition, an uncultured Bacteroides bacterium was present in IMP-TL. Mixed cultures were evaluated at different pH and NaCl concentrations at 30°C. IMP-PB and
IMP-TL expressed thiosulfate-oxidizing activity in the 7.5–10.5 pH range, whereas IMP-XO presented its maximal activity with
19.0 mg O2 gprotein−1 min−1, at pH 10.6; it was not affected by NaCl concentrations up to 1.7 M. In continuous culture, IMP-XO showed a growth rate of
15 day−1, productivity of 433.4 mgprotein l−1 day−1 and haloalkaliphilic sulfur-oxidizing activity was also detected up to 170 mM by means of N-methyl-diethanolamine (MDEA). Saline–alkaline soil samples are potential sources of haloalkaliphilic sulfur-oxidizing bacteria
and the mixed cultures could be applied in the treatment of inorganic sulfur compounds in petroleum industry effluents under
alkaline–saline conditions. 相似文献
19.
Aspergillus flavus K49 secreted at least two xylanase activities when grown on a medium containing larch (wood) xylan as a sole carbon source.
Enzyme activity was assayed using an agar medium containing Remazol Brilliant Blue R conjugated oat spelt xylan as substrate.
Crude enzyme preparations were inhibited by Hg+2, with an ED50 of 17.5 mM and maximum inhibition of 83% at 50 mM. A concentrated sample of A. flavus K49 xylanase preparation was subjected to gel filtration chromatography on a P-30 column. A small protein peak coinciding
with the major peak of xylanase activity was separated from the other secreted fungal proteins. An additional peak of xylanase
activity was observed in fractions containing multiple fungal proteins. Analysis by denaturing sodium dodecyl sulfate–polyacrylamide
gel electrophoresis (SDS–PAGE) of fractions containing the smaller molecular weight xylanase revealed a major and minor protein
band in the vicinity of 14 kD. Analysis of these same fractions by acidic native PAGE revealed a single band. Confirmation
of identity for the isolated xylanase was provided by isolation of a protein band from a SDS–PAGE gel, followed by trypsin
digestion/analysis by tandem mass spectrometry. Comparison of the peptide library derived from this protein band with sequence
data from the A. oryzae genomic data base provided a solid match with an endo-1,4-β-xylanase, XlnA. This identification is consistent with a low
molecular weight protein associated with the major xylanolytic activity. XlnA may be a highly mobile (diffusible), plant wall
hemicellulose degrading factor with significant activity during plant infection. 相似文献
20.
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