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1.
Microbial endo-beta-1,4-xylanases (EXs, EC 3.2.1.8) belonging to glycanase families 10 and 11 differ in their action on water-unextractable arabinoxylan (WU-AX). WU-AX was incubated with different levels of a Thermoascus aurantiacus family 10 and a Sporotrichum thermophile family 11 endoxylanases. At 10 g l(-1) arabinoxylan, enzyme concentrations (KE values) needed to obtain half-maximal hydrolysis rates (V(max) values) were 4.4 nM for the xylanase from T. aurantiacus and 7.1 nM for the xylanase from S. thermophile. Determination of Vmax/KE revealed that the family 10 enzyme hydrolysed two times more efficiently WU-AX than the family 11 enzyme. Molecular weights of the products formed were assessed and separation of feruloyl-oligosaccharides was achieved by anion-exchange and size-exclusion chromatography (SEC). The main difference between the feruloylated products by xylanases of family 10 and 11 concerned the length of the products containing feruloyl-arabinosyl substitution. The xylanase from T. aurantiacus liberated from WU-AX a feruloyl arabinoxylodisaccharide (FAX2) as the shortest feruloylated fragment in contrast with the enzyme from S. thermophile, which liberated a feruloyl arabinoxylotrisaccharide (FAX3). These results indicated that different factors govern WU-AX breakdown by the two endoxylanases.  相似文献   

2.
Endoxylanase (EC 3.2.1.8) substrate selectivity, i.e., its relative activity toward water-unextractable arabinoxylan (WU-AX) and water-extractable arabinoxylan (WE-AX) substrates, is important for its functionality in biotechnological processes such as bread-making and gluten starch separation. A screening method for rapidly determining said substrate selectivity was developed. Endoxylanase activity toward WU-AX was estimated by incubation of insoluble chromogenic substrate with a range of enzyme concentrations in microtiter plates, followed by colorimetric measurement of the dye released in the supernatant. A similar approach using soluble substrate and ethanol precipitation of unhydrolysed AX fragments was used to estimate enzyme activity toward WE-AX. A substrate selectivity factor was defined as the ratio of enzyme activity toward insoluble substrate over enzyme activity toward soluble substrate. A Bacillus subtilis and an Aspergillus aculeatus endoxylanase, known to have widely varying relative rates of hydrolysis of WU-AX and WE-AX, varied most in their substrate selectivity, while the endoxylanases of Aspergillus niger, Trichoderma longibrachiatum, and Trichoderma viride displayed intermediate such relative activities.  相似文献   

3.
The major water-soluble arabinoxylan fraction from rye grain, containing 4-linked β- -xylopyranosyl residues of which about 43% were substituted solely at O-3 and 7% at both O-2 and O-3 with terminal - -arabinofuranosyl units, was hydrolysed to different extents using semi-purified xylanase from Trichoderma reesei. Products were fractionated on Biogel P-2 and structurally elucidated by sugar, methylation and high-field 1H-NMR analysis. Moderate hydrolysis released arabinose, xylose, xylobiose, xylotriose and xylotetraose together with xylo-oligosaccharides (DP ≥ 4) in which one or more of the residues were substituted at O-3 with a terminal arabinose unit. The xylose residues substituted with arabinose units at both O-2 and O-3 became enriched in the remaining polymeric fraction. Extensive hydrolysis with the enzyme released arabinose, xylose and xylobiose as major products together with small amounts of two oligosaccharides and a polymeric fraction. One of the oligosaccharides was identified as xylotriose in which the non-reducing end was substituted at O-2 and O-3 with terminal arabinose units and the other as xylotetraose in which one of the interjacent residues was substituted with arabinose units in the same way. The polymeric fraction contained a main chain of 4-linked xylose residues in which 60–70% of the residues were substituted at both O-2 and O-3 with arabinose units.

The semi-purified enzyme contained xylanase and arabinosidase activities which rapidly degraded un- and mono-substituted xylose residues while the degradation of double-substituted xylose residues was much slower. The results show that the mono- and double-substituted xylose residues were present in different polymers or different regions of the same polymer.  相似文献   


4.
The relative activity of an endoxylanase towards water-unextractable (WU-AX) and water-extractable arabinoxylan (WE-AX) substrates, referred to as endoxylanase substrate selectivity, impacts the enzyme functionality in cereal-based biotechnological processes such as bread-making and gluten starch separation. A set of six endoxylanases representing a range of substrate selectivities as determined by a screening method using chromophoric substrates [Anal. Biochem.2003, 319, 73-77] was used to examine the impact of such selectivity on changes in structural characteristics of wheat WU-AX and WE-AX upon enzymic hydrolysis. While WE-AX degradation by the selected endoxylanases was very comparable with respect to apparent molecular mass (MM) profiles and arabinose to xylose ratio of the hydrolysates formed, WU-AX solubilisation and subsequent degradation of solubilised fragments gave rise to widely varying MM profiles, depending on the substrate selectivity of the enzymes. Enzymes with high selectivity towards WU-AX de facto generated higher MM fragments from WU-AX than enzymes with low selectivity. The arabinose to xylose ratios of solubilised fragments were independent of the degree of solubilisation.  相似文献   

5.
本研究选取众所周知的典型白腐真菌树舌灵芝Ganoderma applanatum、毛栓孔菌Trametes hirsuta和木蹄层孔菌Fomes fomentarius作为研究对象,对其利用木质纤维生物质进行发酵及添加有机营养、无机盐、金属离子、表面活性剂等进行了探索,期间以测定漆酶、滤纸纤维素酶、木聚糖酶活性表征3种...  相似文献   

6.
Xylanolytic enzymes, with both endo-xylanase and arabinoxylan arabinofuranohydrolase (AXH) activities, are attractive for the economically feasible conversion of recalcitrant arabinoxylan. However, their characterization and utilization of these enzymes in biotechnological applications have been limited. Here, we characterize a novel bifunctional enzyme, rAbf43A, cloned from a bacterial consortium that exhibits AXH and endo-xylanase activities. Hydrolytic pattern analyses revealed that the AXH activity belongs to AXHd3 because it attacked only the C(O)-3-linked arabinofuranosyl residues of double-substituted xylopyranosyl units of arabinoxylan and arabinoxylan-derived oligosaccharides, which are usually resistant to hydrolysis. The enzyme rAbf43A also liberated a series of xylo-oligosaccharides (XOSs) from beechwood xylan, xylohexaose and xylopentaose, indicating that rAbf43A exhibited endo-xylanase activity. Homology modelling based on AlphaFold2 and site-directed mutagenesis identified three non-catalytic residues (H161, A270 and L505) located in the substrate-binding pocket essential for its dual-functionality, while the mutation of A117 located in the −1 subsite to the proline residue only affected its endo-xylanase activity. Additionally, rAbf43A showed significant synergistic action with the bifunctional xylanase/feruloyl esterase rXyn10A/Fae1A from the same bacterial consortium on insoluble wheat arabinoxylan and de-starched wheat bran degradation. When rXyn10A/Fae1A was added to the rAbf43A pre-hydrolyzed reactions, the amount of released reducing sugars, xylose and ferulic acid increased by 9.43% and 25.16%, 189.37% and 93.54%, 31.39% and 32.30%, respectively, in comparison with the sum of hydrolysis products released by each enzyme alone. The unique characteristics of rAbf43A position it as a promising candidate not only for designing high-performance enzyme cocktails but also for investigating the structure–function relationship of GH43 multifunctional enzymes.  相似文献   

7.
A Bacillus spp. strain SPS-0, isolated from a hot spring in Portugal, produced an extracellular xylanase upon growth on wheat bran arabinoxylan. The enzyme was purified to homogeneity by ammonium sulfate precipitation, anion exchange, gel filtration, and affinity chromatography. The optimum temperature and pH for activity was 75 degrees C and 6.0. Xylanase was stable up to 70 degrees C for 4 h at pH 6.0 in the presence of xylane. Xylanase was completely inhibited by the Hg(2+) ions. beta-Mercaptoethanol, dithiothreitol, and Mn(2+) stimulated the xylanase activity. The products of birchwood xylan hydrolysis were xylose, xylobiose, xylotriose, and xylotetraose. Kinetic experiments at 60 degrees C and pH 6.0 gave V(max) and K(m)values of 2420 nkat/mg and 0.7 mg/ml.  相似文献   

8.
Bacteria of the faba bean (Vicia faba L.)/Orobanche spp. root environment were evaluated for their potential use as biocontrol agents for the parasitic weed. Bacteria were isolated mainly from the rhizosphere of faba bean as well as from diseased Orobanche underground structures and an Orobanche-suppressive soil from three districts of northern Tunisia. Out of 351 bacterial isolates, 337 were tested for pathogenicity in an inverted pyramidal-shape screening programme including a Lactuca sativa L. seedlings bioassay, root-chamber and pot experiments. In pre-selection screening on L. sativa seedlings, 37 isolates (11%) showed a strong growth inhibitory effect, of which 70 and 84% also had a significant suppressive activity on the pre-emergence structures of O. foetida and O. crenata, respectively, in root-chamber experiments. Among five bacterial isolates selected for pot trials, strain Bf7-9 of Pseudomonas fluorescens showed high biocontrol activity against both species of Orobanche and positively influenced faba bean growth. The bacterium reduced shoot emergence of O. crenata and O. foetida by 64 and 76% and their dry weight by 39 and 63%, respectively, compared with non-inoculated controls. Pseudomonas marginalis strain Nc1-2 exhibited also a tendency to reduce incidence of O. crenata and to improve faba bean performance. Results of the present study suggest that application of naturally occurring rhizosphere bacteria offers an additional approach for biocontrol of Orobanche spp. that can supplement current methods of control in an integrated weed management strategy.  相似文献   

9.
A novel, ultra-large xylanolytic complex (xylanosome) from Streptomyces olivaceoviridis E-86 was purified to homogeneity by ammonium sulfate precipitation and Sephacryl S-300 gel filtration chromatography. The purified xylanosome appeared as a single protein band on the non-denaturing (native) polyacrylamide gel electrophoresis (PAGE) gel with a molecular mass of approximately 1200 kDa. The optimal temperature and pH for xylanase activity was 60 °C and pH 6.0, respectively. The xylanase activity was stable within pH 4.1–10.3. It was stable up to 60 °C at pH 6.0. The xylanosome was highly specific towards oat-spelt xylan, and showed low activity towards corncob powder, but exhibited very low activity towards lichenan, CMC and p-nitrophenyl derivatives. Apparent Km values of the xylansosome for birchwood, beechwood, soluble oat-spelt and insoluble oat-spelt xylans were 2.5, 3.6, 1.7 and 4.9 mg ml−1, respectively. The main hydrolysis products of birchwood xylan were xylotriose, xylobiose and xylose. Analysis of the products from wheat arabinoxylan degradation by xylanosome confirmed that the enzyme had endoxylanase and debranching activities, with xylotriose, xylobiose, xylose and arabinose as the main degradation products. These unique properties of the purified xylanosome from Streptomyces olivaceoviridis E-86 make this enzymatic complex attractive for biotechnological applications.  相似文献   

10.
Following fungal inoculation or natural infection, five biphenyl phytoalexins (aucuparin and its 2′ and 4′ oxygenated derivatives) were induced variously in the sapwood of Aronia, Chaenomeles, Eriobotrya, Malus(three spp.) and of Sorbus aucuparia. By contrast, 14 dibenzofuran phytoalexins were induced variously in sapwood of Cotoneaster (7 spp.), Crateagus, Cydonia, Mespilus, Photinia, Pseudocydonia, Pyracantha, Pyrus and two Sorbus spp. (S. chamaemespilum and S. domestica). These were five cotonefurans, three eriobofurans, five pyrufurans and a 2,3,4,7,8-pentaoxygenated dibenzofuran trimethyl ether. No plant has yet been found to produce both types of phytoalexin, although o-hydroxybiphenyls are theoretically precursors of the dibenzofurans. The ability to synthesize either biphenyls or dibenzofurans appears to be genus-specific, except in the case of Sorbus. In 18 of the 38 species tested, these phytoalexins were accompanied by constitutive antifungal phenolics, most of which appeared to be released from bound (glycosidic) forms during the infection process. These were identified variously as hydroquinone, p-hydroxyacetophenone, acetovanillone, 5,7-dihydroxychromone, chrysin, sakuranetin and naringenin. Woody members of the subfamilies Prunoideae and Spiraeoideae failed to yield any phytoalexins on induction, but did contain constitutive antifungal compounds. The limited frequency of the phytoalexin response within the family as a whole is considered in relation to the accumulation of constitutive antifungal agents in these plants.  相似文献   

11.
Summary Aspergillus niger, strain 110.42 (CBS), has been selected as a producer of high xylanolytic activities. The time course of xylanase and -xylosidase production as well as the effect of pH and temperature on the activity of these enzymes were studied. HPLC analysis of the enzymatic degradation of arabinoxylan showed a nearly complete conversion to pentose sugars. Aspects of using crude xylanase preparations for enzymatic saccharification of xylans are discussed.  相似文献   

12.
Saccharum officinarum bagasse (common name: sugarcane bagasse) and Pennisetum purpureum (also known as Napier grass) are among the most promising feedstocks for bioethanol production in Argentina and Brazil. In this study, both biomasses were assessed before and after acid pretreatment and following hydrolysis with Nasutitermes aquilinus and Cortaritermes fulviceps termite gut digestome. The chemical composition analysis of the biomasses after diluted acid pretreatment showed that the hemicellulose fraction was partially removed. The (hemi) cellulolytic activities were evaluated in bacterial culture supernatants of termite gut homogenates grown in treated and untreated biomasses. In all cases, we detected significantly higher endoglucanase and xylanase activities using pretreated biomasses compared to untreated biomasses, carboxymethylcellulose and xylan. Several protein bands with (hemi) cellulolytic activity were detected in zymograms and two-dimensional gel electrophoresis. Some proteins of these bands or spots were identified as xylanolytic peptides by mass spectrometry. Finally, the diversity of cultured cellulolytic bacterial endosymbionts associated to both Argentinean native termite species was analyzed. This study describes, for the first time, bacterial endosymbionts and endogenous (hemi) cellulases of two Argentinean native termites as well as their potential application in degradation of lignocellulosic biomass for bioethanol production.  相似文献   

13.
Six xylan-hydrolyzing enzymes have been isolated from the preparations Celloviridin G20x and Xybeten-Xyl, obtained previously based on the strain Trichoderma longibrachiatum (Trichoderma reesei) TW-1. The enzymes isolated were represented by three xylanases (XYLs), XYL I (20 kDa, pi 5.5), XYL II (21 kDa, pI 9.5), XYL III (30 kDa, pI 9.1); endoglucanase I (EG I), an enzyme exhibiting xylanase activity (57 kDa, pI 4.6); and two exodepolymerases, beta-xylosidase (beta-XYL; 80 kDa, pI 4.5) and alpha-L-arabinofuranosidase I (alpha-L-AF I; 55 kDa, pI 7.4). The substrate specificity of the enzymes isolated was determined. XYL II exhibited maximum specific xylanase activity (190 U/mg). The content of the enzymes in the preparation was assessed. Maximum contributions to the total xylanase activities of the preparations Celloviridin G20x and Xy-beten-Xyl were made by EG I and XYL II, respectively. Effects of temperature and pH on the enzyme activities, their stabilities under various conditions, and the kinetics of exhaustive hydrolysis of glucuronoxylan and arabinoxylan were studied. Combinations of endodepolymerases (XYL I, XYL II, XYL III, or EG I) and exodepolymerases (alpha-L-AF I or beta-XYL) produced synergistic effects on arabinoxylan cleavage. The reverse was the case when endodepolymerases, such as XYL I or EG I, were combined with alpha-L-AF I.  相似文献   

14.
不同碳源和氮源对金针菇降解木质纤维素酶活性的影响   总被引:1,自引:0,他引:1  
安琪  吴雪君  吴冰  戴玉成 《菌物学报》2015,34(4):761-771
以3株栽培的金针菇Flammulina velutipes为材料,研究它们在玉米芯和棉子壳以及不同碳源、氮源培养条件下纤维素、半纤维素和木质素降解酶活性的规律。结果表明,不同金针菇菌株的羧甲基纤维素酶、木聚糖酶和漆酶活力显著不同(P<0.001),同时,培养条件对羧甲基纤维素酶、木聚糖酶和漆酶的活力都有显著影响(P<0.001)。在简单碳源存在的条件下,金针菇的羧甲基纤维素酶和木聚糖酶活力远远低于复杂碳源培养基(P<0.05)。全营养培养基上生长的金针菇的羧甲基纤维素酶和木聚糖酶活力低于缺乏碳源和氮源的培养基(P<0.05)。漆酶活力在无简单氮源培养基上低于全培养基(P<0.05)和无葡萄糖培养基(P<0.05),即复杂碳源和氮源培养基上的漆酶活力低于简单碳源和氮源培养基(P<0.05)。  相似文献   

15.
Twelve species of Streptomyces that formerly belonged to the genus Chainia were screened for the production of xylanase and cellulase. One species, Streptomyces roseiscleroticus (Chainia rosea) NRRL B-11019, produced up to 16.2 IU of xylanase per ml in 48 h. A xylanase from S. roseiscleroticus was purified and characterized. The enzyme was a debranching beta-(1-4)-endoxylanase showing high activity on xylan but essentially no activity against acid-swollen (Walseth) cellulose. It had a very low apparent molecular weight of 5,500 by native gel filtration, but its denatured molecular weight was 22,600 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It had an isoelectric point of 9.5. The pH and temperature optima for hydrolysis of arabinoxylan were 6.5 to 7.0 and 60 degrees C, respectively, and more than 75% of the optimum enzyme activity was retained at pH 8.0. The xylanase had a K(m) of 7.9 mg/ml and an apparent V(max) of 305 mumol . min . mg of protein. The hydrolysis rate was linear for xylan concentrations of less than 4 mg/ml, but significant inhibition was observed at xylan concentrations of more than 10 mg/ml. The predominant products of arabinoxylan hydrolysis included arabinose, xylobiose, and xylotriose.  相似文献   

16.
We investigated in this study the effect of modified arabinoxylan from rice bran (MGN-3) and its fractions on D-galactosamine (D-GalN)-induced IL-18 expression and hepatitis in rats. Male Wistar rats were pretreated with MGN-3 or fractions of the MGN-3 hydrolysate, or with saline 1 h before administering D-GalN (400 mg/kg B.W.). The serum transaminase activities, IL-18 mRNA expression level in the liver and IL-18 concentration in the serum were determined 24 h after injecting D-GalN. Both the oral and intraperitoneal administration of MGN-3 (20 mg/kg B.W.) alleviated D-GalN-induced hepatic injury under these experimental conditions. The low-molecular-weight fraction (LMW) of MGN-3 showed the strongest protective effect on D-GalN-induced liver injury, its main sugar component being glucose. Moreover, the D-GalN-induced IL-18 expression was significantly reduced by treating with MGN-3 and LMW. The results suggest that MGN-3 and LMW could provide significant protection against D-GalN liver injury, and that IL-18 might be involved in their protective influence.  相似文献   

17.
In this study, the prebiotic potential of arabinoxylan oligosaccharides (AXOS) was compared with inulin in two simulators of the human intestinal microbial ecosystem. Microbial breakdown of both oligosaccharides and short-chain fatty acid production was colon compartment specific, with ascending and transverse colon being the predominant site of inulin and AXOS degradation, respectively. Lactate levels (+5.5 mM) increased in the ascending colon during AXOS supplementation, while propionate levels (+5.1 mM) increased in the transverse colon. The concomitant decrease in lactate in the transverse colon suggests that propionate was partially formed over the acrylate pathway. Furthermore, AXOS supplementation strongly decreased butyrate in the ascending colon, this in parallel with a decrease in Roseburia spp. and Bacteroides / Prevotella / Porphyromonas (−1.4 and −2.0 log CFU) levels. Inulin treatment had moderate effects on lactate, propionate and butyrate levels. Denaturing gradient gel electrophoresis analysis revealed that inulin changed microbial metabolism by modulating the microbial community composition. In contrast, AXOS primarily affected microbial metabolism by 'switching on' AXOS-degrading enzymes (xylanase, arabinofuranosidase and xylosidase), without significantly affecting microbial community composition. Our results demonstrate that AXOS has a higher potency than inulin to shift part of the sugar fermentation toward the distal colon parts. Furthermore, due to its stronger propionate-stimulating effect, AXOS is a candidate prebiotic capable of lowering cholesterol and beneficially affecting fat metabolism of the host.  相似文献   

18.
车轮虫感染奥尼罗非鱼的白细胞分类百分比变化   总被引:1,自引:0,他引:1  
李利  张其中 《生态科学》2007,26(5):452-455
车轮虫(Trichodina spp.)是奥尼罗非鱼(Oreochromis aureus×Oreochromis niloticus)养殖中最常见的一种原生动物寄生虫。实验测定了感染组和未感染组中奥尼罗非鱼的各类型白细胞的百分比。感染组该鱼血液中的淋巴细胞和嗜中性粒细胞百分比极显著高于未感染组;未感染组该鱼血液中的单核细胞百分比极显著高于感染组。发现嗜中性粒细胞和淋巴细胞可能在抵御车轮虫入侵中起着重要作用;单核细胞在抵御车轮虫起着一定的作用。表明奥尼罗非鱼感染车轮虫后,细胞免疫增强。  相似文献   

19.
Degradation of xylan requires several enzymes. Two chimeric enzymes, xyln-ara and xyln-xylo, were constructed by linking the catalytic portion of a xylanase (xyln) to either an arabinofuranosidase (ara) or a xylosidase (xylo) with a flexible peptide linker. The recombinant parental enzymes and chimeras were produced in E. coli at high levels and purified for characterization of their enzymatic and kinetic properties as well as activities on natural substrates. The chimeras closely resemble the parental enzymes or their mixtures with regard to protein properties. They share similar temperature profiles and have similar catalytic efficiencies as the parental enzymes when assayed using substrates 4-nitrophenyl-alpha-L-arabinofuranoside or 2-nitrophenyl- beta-D-xylopyranoside. The chimeras also show unique enzymatic characteristics. In xylanase activity assays using Remazol Brilliant Blue-xylan, while the parental xylanase has a pH optimum of pH 8, the chimeras showed shifted pH optima as a consequence of significantly increased activity at pH 6 (the optimal pH for ara and xylo). Both chimeras exhibited additive effects of the parental enzymes when assayed at wide ranges of pH and temperatures. The xyln-xylo chimera had the same activities as the xyln/xylo mixture in hydrolyzing the natural substrates oat spelt xylan and wheat arabinoxylan. Compared to the xyln/ara mixture, the xyln-ara chimera released the same amounts of xylose from oat spelt xylan and approximately 30% more from wheat arabinoxylan at pH 6. Our results demonstrate the feasibility and advantages of generating bifunctional enzymes for the improvement of xylan bioconversion.  相似文献   

20.
韩美玲  边禄森  姜宏浩  安琪 《菌物学报》2020,39(8):1538-1550
以糙皮侧耳Pleurotus ostreatus为材料,研究简单碳氮源及木质素纯品诱导条件对其木质纤维素酶活性的影响。结果表明,不同的碳源培养基和氮源培养基对糙皮侧耳漆酶活性、羧甲基纤维素酶活性和木聚糖酶活性均具有极显著的影响(P<0.001),且对糙皮侧耳菌丝生物量也有极显著的影响(P<0.001)。以蔗糖作主要碳源诱导物时,有利于提高糙皮侧耳漆酶活性;以果糖作主要碳源诱导物时,有利于提高糙皮侧耳羧甲基纤维素酶活性和菌丝生物量的积累;以葡萄糖作主要碳源诱导物时,有利于提高糙皮侧耳木聚糖酶活性。以酵母浸粉作主要氮源诱导物时,有利于提高糙皮侧耳漆酶活性和菌丝生物量的积累;以硝酸钾作为主要氮源诱导物时,有利于提高糙皮侧耳羧甲基纤维素酶活性;以硫酸铵作为主要氮源诱导物时,有利于提高糙皮侧耳木聚糖酶活性。碱性木素的存在,有利于提高糙皮侧耳漆酶活性,但不利于菌丝生物量的积累。与此同时,碱性木素的存在对糙皮侧耳羧甲基纤维素酶和木聚糖酶活性并没有促进作用。  相似文献   

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