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1.
Chaabouni SE Mechichi T Limam F Marzouki N 《Applied biochemistry and biotechnology》2005,125(2):99-112
Two endoglucanases (EGs), EG A and EG B, were purified to homogeneity from Penicillium occitanis mutant Pol 6 culture medium. The molecular weights of EG A and EG B were 31,000 and 28,000 kDa, respectively. The pI was about 3 for EG A and 7.5 for EG B. Optimal activity was obtained at pH 3.5 for both endoglucanases. Optimal temperature for enzyme activity was 60 degrees C for EG A and 50 degrees C for EG B. EG A was thermostable at 60 degrees C and remained active after 1 h at 70 degrees C. EGs hydrolyzed carboxymethylcellulose, phosphoric acid swollen cellulose, and beta-glucan efficiently, whereas microcrystalline cellulose (Avicel) and laminarin were poorly hydrolyzed. Only EG B showed xylanase activity. Furthermore, these EGs were insensitive to the action of glucose and cellobiose but were inhibited by the divalent cations Hg2+, Co2+, and Mn2+. 相似文献
2.
Dorra Driss Fatma Bhiri Mariem Siela Raoudha Ghorbel Semia Ellouz Chaabouni 《Applied biochemistry and biotechnology》2012,168(4):851-863
An extracellular, endo-??-1,4-xylanase was purified to homogeneity from the culture filtrate of the filamentous fungus Penicillium occitanis Pol6, grown on oat spelt xylan. The purified enzyme (PoXyn2) showed a single band on SDS?CPAGE with an apparent molecular weight of 30?kDa. The xylanase activity was optimal at pH?3.0 and 65?°C. The specific activity measured for oat spelt xylan was 2,368?U?mg?1. The apparent K m and V max values were 8.33?mg?ml?1 and 58.82???mol?min?1?ml?1, respectively, as measured on oat spelt xylan. Thin-layer chromatography experiments revealed that purified PoXyn2 degrades xylan in an endo-fashion releasing xylobiose as main end product. The genomic DNA and cDNA encoding this protein were cloned and sequenced. This PoXyn2 presents an open reading frame of 962?bp, not interrupted by any introns and encoding for a mature protein of 320 amino acids and 29.88?kDa. 相似文献
3.
Bhiri F Chaabouni SE Limam F Ghrir R Marzouki N 《Applied biochemistry and biotechnology》2008,149(2):169-182
The Pol6 mutant of Penicillium occitanis fungus is of great biotechnological interest since it possesses a high capacity of cellulases and β-glucosidase production
with high cellulose degradation efficiency (Jain et al., Enzyme Microb Technol, 12:691–696, 1990; Hadj-Taieb et al., Appl Microbiol Biotechnol, 37:197–201, 1992; Ellouz Chaabouni et al., Enzyme Microb Technol, 16:538–542, 1994; Ellouz Chaabouni et al., Appl Microbiol Biotechnol, 43:267–269, 1995). In this work, two forms of β-glucosidase (β-glu 1 and β-glu 2) were purified from the culture supernatant
of the Pol6 strain by gel filtration, ion exchange chromatography, and preparative anionic native electrophoresis. These enzymes
were eluted as two distinct species from the diethylamino ethanol Sepharose CL6B and anionic native electrophoresis. However,
both behaved identically on sodium dodecyl sulfate polyacrylamide gel electrophoresis (MW, 98 kDa), shared the same amino
acid composition, carbohydrate content (8%), and kinetic properties. Moreover, they strongly cross-reacted immunologically.
They were active on cellobiose and pNPG with Km values of 1.43 and 0.37 mM, respectively. β-glu 1 and β-glu 2 were competitively inhibited by 1 mM of glucose and 0.03 mM
of δ-gluconolactone. They were also significantly inhibited by Hg2+ and Cu2 at 2 mM. The addition of purified enzymes to the poor β-glucosidase crude extract of Trichoderma reesei increased its hydrolytic efficiency on H3P04 swollen cellulose but had no effect with P. occitanis crude extract. Besides their hydrolytic activities, β-glu 1 and β-glu 2 were endowed with trans-glycosidase activity at high
concentration of glucose. 相似文献
4.
Fatma Chaari Monia Blibech Fatma Bhiri Sameh Maktouf Raoudha Ellouz-Ghorbel Semia Ellouz-Chaabouni 《Applied biochemistry and biotechnology》2012,168(3):616-628
Lichenase from Bacillus licheniformis UEB CF was immobilized on Amberlite IR120 H. The immobilization yield and lichenase activity were 87 and 92.81?% of initial activity, respectively. The immobilized enzyme exhibited a shift in the optimal pH from 5.0 to 3.0, but the activity optimal temperature was not affected. The immobilized enzyme showed a residual activity of 50?% after five uses. It also exhibited high storage stability and retained 50?% of its initial activity after 120?days at 4?°C. The main hydrolysis products yielded from lichenan were trisaccharide and tetrasaccharide. The resulting mixed-linkage beta-oligosaccharides could be used as a special nutriment for lactic bacteria. 相似文献
5.
Dorra Driss Anissa Haddar Raoudha Ghorbel Semia Ellouz Chaabouni 《Applied biochemistry and biotechnology》2014,173(6):1405-1418
Penicillium occitanis xylanase 2 expressed with a His-tag in Pichia pastoris, termed PoXyn2, was immobilized on nickel-chelate Eupergit C by covalent coupling reaction with a high immobilization yield up to 93.49 %. Characterization of the immobilized PoXyn2 was further evaluated. The optimum pH was not affected by immobilization, but the immobilized PoXyn2 exhibited more acidic and large optimum pH range (pH 2.0–4.0) than that of the free PoXyn2 (pH 3.0). The free PoXyn2 had an optimum temperature of 50 °C, whereas that of the immobilized enzyme was shifted to 65 °C. Immobilization increased both pH stability and thermostability when compared with the free enzyme. Time courses of the xylooligosaccharides (XOS) produced from corncob xylan indicated that the immobilized enzyme tends to use shorter xylan chains and to produce more xylobiose and xylotriose initially. At the end of 24-h reaction, XOS mixture contained a total of 21.3 and 34.2 % (w/w) of xylobiose and xylotriose with immobilized xylanase and free xylanase, respectively. The resulting XOS could be used as a special nutrient for lactic bacteria. 相似文献
6.
New Thermostable Amylase from <Emphasis Type="Italic">Bacillus cohnii</Emphasis> US147 with a Broad pH Applicability 总被引:1,自引:0,他引:1
Ghorbel RE Maktouf S Massoud EB Bejar S Chaabouni SE 《Applied biochemistry and biotechnology》2009,157(1):50-60
A new thermophilic bacterial strain identified as Bacillus cohnii US147 was isolated from the southern Tunisian soil. The identification was based on physiological tests and molecular techniques
related to the 16S ribosomal ribonucleic acid. The isolated strain produced amylase, which was purified. This amylase had
an apparent molecular mass of 30 kDa as estimated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Amylase
US147 showed K
m and V
max values of 0.7 mg/ml and 2.2 U/ml, respectively, with starch as the substrate. The enzyme was active in acid and basic pH
and had a maximal activity on starch at pH 9 and 70 °C. The enzyme was stable at pH 9 for 72 h and retained half of its activity
after incubation at 70 °C for 150 min. A partially inhibition (15%, 25%, 23%, 20%, and 22%) was obtained with 1 mM SDS, 1 mM
NaBO3, 1 mM H2O2, 1 mM Zn+2, and 5 mM ethylenediamine tetraacetic acid (EDTA), respectively. The amylase recovered its original activity by the addition
of 10 mM Ca 2+ to the 5 mM EDTA. These properties indicated a possible use of this amylase in starch saccharification, in detergent, and
in other industrial applications. 相似文献
7.
Monia Blibech Raoudha Ellouz Ghorbel Ines Fakhfakh Patricia Ntarima Katheleen Piens Abir Ben Bacha Semia Ellouz Chaabouni 《Applied biochemistry and biotechnology》2010,160(4):1227-1240
The highest β-mannanase activity was produced by Penicillium occitanis Pol6 on flour of carob seed, whereas starch-containing medium gave lower enzymes titles. The low molecular weight enzyme
was purified to homogeneity by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography procedures.
The purified β-mannanase (ManIII) has been identified as a glycoprotein (carbohydrate content 5%) with an apparent molecular
mass of 18 kDa. It was active at 40 °C and pH 4.0. It was stable for 30 min at 70 °C and has a broad pH stability (2.0–12.0).
ManIII showed K
m, V
max, and K
cat values of 17.94 mg/ml, 93.52 U/mg, and 28.13 s−1 with locust bean gum as substrate, respectively. It was inhibited by mannose with a K
I of 0.610−3 mg/ml. ManIII was activated by CuSO4 and CaCl2 (2.5 mM). However, in presence of 2.5 mM Co2+, its activity dropped to 60% of the initial activity. Both N-terminal and internal amino acid sequences of ManIII presented
no homology with mannanases of glycosides hydrolases. During incubation with locust bean gum and Ivory nut mannan, the enzyme
released mainly mannotetraose, mannotriose, and mannobiose. 相似文献
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