Purification and characterization of xylanases from Aspergillus giganteus

High-Molecular-Weight Xylanase from B. pumilus US570 Strain: Purification, Characterization and Application in Banana and Orange Peels Hydrolysis and Breadmaking

New xylanase (XylUS570) was purified from the Bacillus pumilus US570 strain. It has a molecular mass of about 232 kDa. This is the first report on the highest molecular weight monomeric xylanase produced by bacteria. The optimum pH and temperature recorded for enzyme activity were 7 and 55 °C, respectively with a half-life time of 10 min at 60 °C. At 37 °C, the enzyme retains more than 50% of its activity at a pH ranging from 6 to 9.5 for 24 h. The XylUS570 exhibited a high activity on xylan, but no activity was detected for cellulosic substrates. The Vmax and Km values exhibited by the purified enzyme on beechwood xylan were 37.05 U mL-1 and 4.189 mg mL-1, respectively. The XylUS570 was used in banana and orange peels hydrolysis and showed potential efficiency to liberate reducing sugars. It could be a good candidate for bio-ethanol production from fruit waste. The purified enzyme was used also as an additive in breadmaking. A decrease in water absorption, an increase in dough rising and improvements in volume and specific volume of the bread were recorded.

Purification, Identification, and Characterization of a Glycoside Hydrolase Family 11-Xylanase with High Activity from Aspergillus niger VTCC 017

Xylanases (EC 3.2.1.8) have been considered as a potential green solution for the sustainable development of a wide range of industries including pulp and paper, food and beverages, animal feed, pharmaceuticals, and biofuels because they are the key enzymes that degrade the xylosidic linkages of xylan, the major component of the second most abundant raw material worldwide. Therefore, there is a critical need for the industrialized xylanases which must have high specific activity, be tolerant to organic solvent or detergent and be active during a wide range of conditions, such as high temperature and pH. In this study, an extracellular xylanase was purified from the culture broth of Aspergillus niger VTCC 017 for primary structure determination and properties characterization. The successive steps of purification comprised centrifugation, Sephadex G-100 filtration, and DEAE-Sephadex chromatography. The purified xylanase (specific activity reached 6596.79 UI/mg protein) was a monomer with a molecular weight of 37 kDa estimating from SDS electrophoresis. The results of LC/MS suggested that the purified protein is indeed an endo-1,4-β-D-xylanase. The purified xylanase showed the optimal temperature of 55 °C, and pH 6.5 with a stable xylanolytic activity within the temperature range of 45-50 °C, and within the pH range of 5.0-8.0. Most divalent metal cations including Zn²⁺, Fe²⁺, Mg²⁺, Cu²⁺, Mn²⁺ showed some inhibition of xylanase activity while the monovalent metal cations such as K⁺ and Ag⁺ exhibited slight stimulating effects on the enzyme activity. The introduction of 10-30% different organic solvents (n-butanol, acetone, isopropanol) and several detergents (Triton X-100, Tween 20, and SDS) slightly reduced the enzyme activity. Moreover, the purified xylanase seemed to be tolerant to methanol and ethanol and was even stimulated by Tween 80. Overall, with these distinctive properties, the putative xylanase could be a successful candidate for numerous industrial uses.

Paecilomyces variotii xylanase production, purification and characterization with antioxidant xylo-oligosaccharides production

Paecilomyces variotii xylanase was, produced in stirred tank bioreactor with yield of 760 U/mL and purified using 70% ammonium sulfate precipitation and ultra-filtration causing 3.29-fold purification with 34.47% activity recovery. The enzyme purity was analyzed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirming its monomeric nature as single band at 32 KDa. Zymography showed xylan hydrolysis activity at the same band. The purified enzyme had optimum activity at 60 °C and pH 5.0. The pH stability range was 5-9 and the temperature stability was up 70 °C. Fe²⁺and Fe³⁺ exhibited inhibition of xylanase enzyme while Cu²⁺, Ca²⁺, Mg²⁺ and Mn²⁺ stimulated its activity. Mercaptoethanol stimulated its activity; however, Na₂-EDTA and SDS inhibited its activity. The purified xylanase could hydrolyze beechwood xylan but not carboxymethyl cellulose (CMC), avicel or soluble starch. Paecilomyces variotii xylanase K_m and V_max for beechwood were determined to be 3.33 mg/mL and 5555 U/mg, respectively. The produced xylanase enzyme applied on beech xylan resulted in different types of XOS. The antioxidant activity of xylo-oligosaccharides increased from 15.22 to 70.57% when the extract concentration was increased from 0.1 to 1.5 mg/mL. The enzyme characteristics and kinetic parameters indicated its high efficiency in the hydrolysis of xylan and its potential effectiveness in lignocellulosic hydrolysis and other industrial application. It also suggests the potential of xylanase enzyme for production of XOS from biomass which are useful in food and pharmaceutical industries.

Cloning, Expression, and Characterization of Xylanase G2 from Aspergillus oryzae VTCC-F187 in Aspergillus niger VTCC-F017

The study focuses on engineering of recombinant Aspergillus niger to produce highly active xylanase. The xylanase G2 encoding gene originating from Aspergillus oryzae VTCC-F187 was cloned, amplified, and inserted into the pAN7.1GluA vector with specific primers possessing BamHI. The recombinant plasmid was introduced into Aspergillus niger VTCC-F017 by chemical methods. The recombinant strain was checked by polymerase chain reaction method and Southern blot. Next, the recombinant protein was expressed and purified by His-tag column. The molecular mass of the purified xylanase G2, as determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), was 21 kDa with a specific activity of 1025 IU/mg towards 0.5% (w/v) of birchwood xylan. The optimal temperature and pH were 55°C and pH 6.5, respectively. The enzyme was stable in a temperature ranges 25–40°C and a pH ranges 5–7. The presence of Tween 80 enhanced xylanase activity. Triton X-100, however, had no impact on the function of the enzyme. The xylanase activity was reduced by Tween 20, SDS, and organic solvents. The enzyme was completely inhibited by Hg2+ and partially by Zn2+, Fe2+, and Ag+, while it was slightly stimulated by K+ and EDTA.

Construction and characterization of a chimeric enzyme of swollenin and xylanase to improve soybean straw hydrolysis

A study was carried out to produce a fusion protein (Swo-Xyn) using the Trichoderma reesei swollenin and Lentinula edodes xylanase and to investigate its characteristics and application in degrading soybean straw. In parallel, L. edodes xylanase (Xyn) alone was used as a control protein in application tests. The Swo-Xyn was recombined, expressed and produced by Pichia pastoris and had the maximum activity at 40 °C and pH 3.0 using xylan as substrate. The Swo-Xyn exhibited preferential hydrolysis of Xylan. The Swo-Xyn had slight low Km value (23.90 vs. 25.36 mg/ml) but significantly low Vmax value (162.4 vs. 227.2 μmol/mg·min) and specific activity (18.82 vs. 38.97 U/mg) relative to the Xyn. The Swo-Xyn activity was enhanced by Zn2+ in dose dependent manners with the peak activity at 30 mM of Zn2+. The Swo-Xyn could tolerate 15% of methanol, ethanol, aceton, and DMSO with >60% residual activity. The Swo-Xyn had the greater tolerance to SDS, EDTA, 2-ME than the Xyn and could be activated by DTT, Triton X-100, and Tween 20. Compared with the Xyn, the hydrolysis and sequent cellulose enzymolysis of soybean straw could be better improved by the Swo-Xyn. The Swo-Xyn should be more useful for improving the utilization of soybean straw.

An ascomycota coculture in batch bioreactor is better than polycultures for cellulase production

Efficient hydrolysis of holocellulose depends on a proper balance between cellulase (endoglucanase, exoglucanase, β-glucosidase) and xylanase activities. The present study aimed to induce the production of cellulases and xylanases using liquid cultures (one, two, three, and four fungal strains on the same bioreactor) of wild strains of Trichoderma harzianum, Aspergillus niger, and Fusarium oxysporum. The strains were identified by amplification and analysis of the ITS rDNA region and the obtained sequences were deposited in Genbank. Enzymes (endoglucanase, exoglucansae, β-glucosidase, and xylanase activities) and the profile of extracellular protein isoforms (SDS-PAGE) produced by different fungal combinations (N = 14) were analyzed by Pearson's correlation matrix and principal component analysis (PCA). According to our results, induction of endoglucanase (19.02%) and β-glucosidase (6.35%) were obtained after 4 days when A. niger and F. oxysporum were cocultured. The combination of A. niger-T. harzianum produced higher endoglucanase in a shorter time than monocultures. On the contrary, when more than two strains were cultured in the same reactor, the relationships of competition were established, trending to diminish the amount of enzymes and the extracellular protein isoforms produced. The xylanase production was sensible to stress produced by mixed cultures, decreasing their activity. This is important when the aim is to produce cellulase-free xylanase. In addition, exoglucanase activity did not change in the combinations tested.

Purification of Endoxylanase from Bacillus pumilus B20 for Production of Prebiotic Xylooligosaccharide Syrup; An In vitro Study

Background: The need for more cost-effective compounds is imperative because the demand for prebiotic compounds is ever on the rise. Objective: The focus of this study is the purification of the endoxylanase from Bacillus pumilus B20 and its application in a cost-effective production of the prebiotic xylooligosaccharide (XOS) syrup having a high concentration of oligosaccharides. Materials and Methods: The extracellular endoxylanase was purified using ammonium sulphate fractionation, DEAE anion exchange, and Sephacryl gel filtration chromatography. The enzymatically produced XOS was used in the preparation of XOS syrup adopting the method of ultrafiltration with 10 and 3 kDa molecular weight cut-off (MWCO) membranes. Culture-dependent technique for the bacterial enumeration using selective probiotic microorganisms in an in vitro analysis was employed to confirm the prebiotic nature of XOS syrup. Results: The molecular mass of the purified xylanase (XylB) was found to be approximately 85 kDa with the optimum pH and temperature of 6.5 and 60 °C, respectively. XylB hydrolyzed the xylan and produced short-chain xylooligosaccharides (XOS). At the end of the two-step ultrafiltration process, the hydrolysate was refi ned to form XOS syrup (44.4%) consisting of XOS with a degree of polymerization (DP) between 2 and 5, and >5. Among all the tested probiotic strains, Lactobacillus brevis exhibited maximum growth in the presence of 0.5% XOS syrup with a specific growth rate of 1.2 h^-1. Conclusion: Through this study, we have identified a method to produce XOS syrup that can be used as an effective prebiotic supplement for the growth of several probiotic strains. Human gut probiotics was used as a model system for in vitro analysis of prebiotic oligosaccharide XOS, but for further confirmation of the prebiotic activity, in vivo feeding studies using animal models are needed to be carried out.

Gene Expression and Molecular Characterization of a Xylanase from Chicken Cecum Metagenome

A xylanase gene xynA_MG1 with a 1,116-bp open reading frame, encoding an endo-β-1,4-xylanase, was cloned from a chicken cecum metagenome. The translated XynA_MG1 protein consisted of 372 amino acids including a putative signal peptide of 23 amino acids. The calculated molecular mass of the mature XynA_MG1 was 40,013 Da, with a theoretical pI value of 5.76. The amino acid sequence of XynA_MG1 showed 59% identity to endo-β-1,4-xylanase from Prevotella bryantii and Prevotella ruminicola and 58% identity to that from Prevotella copri. XynA_MG1 has two conserved motifs, DVVNE and TEXD, containing two active site glutamates and an invariant asparagine, characteristic of GH10 family xylanase. The xynA_MG1 gene without signal peptide sequence was cloned and fused with thioredoxin protein (Trx.Tag) in pET-32a plasmid and overexpressed in Escherichia coli Tuner™(DE3)pLysS. The purified mature XynA_MG1 was highly salt-tolerant and stable and displayed higher than 96% of its catalytic activity in the reaction containing 1 to 4 M NaCl. It was only slightly affected by common organic solvents added in aqueous solution to up to 5 M. This chicken cecum metagenome-derived xylanase has potential applications in animal feed additives and industrial enzymatic processes requiring exposure to high concentrations of salt and organic solvents.

Biochemical evaluation of xylanases from various filamentous fungi and their application for the deinking of ozone treated newspaper pulp

Filamentous fungi, Aspergillus oryzae MDU-4 was biochemically selected among different species of Aspergillus and Trichoderma, for xylanase production. The enzyme activity and specific activity of partially purified xylanase from A. oryzae MDU-4 was 7452 IU/ml and 13,549 IU/g, respectively. Temperature and pH optima for xylanase were found to be 60°C and 6.0, respectively. The reaction kinetics of xylanase was found to be Km (3.33 mg/ml) and Vmax (18,182 μmol/mg). The implementation of ozone treatment in the deinking of newspaper pulp resulted in high crystallinity index (72.1%) and more fibrillar surface. Furthermore, the xylanase treated pulp showed significant improvement in optical properties such as brightness (57.9% ISO) and effective residual ink concentration (211 ppm). Scanning electron microscopy analysis suggests perforations in xylanase treated pulp samples. Here we report biochemical evaluation of xylanases and a combination of ozone treatment followed by catalytically efficient fungal xylanase selected for the cost competitive deinking of newspaper pulp.

Molecular and kinetic characterization of two extracellular Xylanases isolated from Leucoagaricus gongylophorus

In this work, the xylanolytic profile of Leucoagaricus gongylophorus was studied, and two extracellular enzymes with xylanolytic activity (XyLg1 and XyLg2) were isolated, purified, and characterized. XyLg1 has a molecular mass of about 38 kDa and pI greater than 4.8. For beechwood xylan substrate, XyLg1 showed an optimum temperature of 40 °C, optimum pH between 8.5 and 10.5, and Km = 14.7 ± 7.6 mg mL(-1). Kinetic studies of the XyLg1 using polygalacturonic acid as substrate were developed, and the enzyme showed optimum pH 5.5, optimum temperature between 50 and 60 °C, and Km = 2.2 ± 0.5 mg mL(-1). XyLg2 has molecular weight of about 24 kDa and pI less than 4.8, and thus is an acid protein. Parameters such as optimum temperature (70 °C) and pH (4.0), as well as the kinetic parameters (Km = 7.4 ± 2.0 mg mL(-1)) using beechwood xylan as substrate, were determined for XyLg2. This enzyme has no activity for polygalacturonic acid as substrate. XyLg1 and XyLg2 are the first native xylanases isolated and characterized from L. gongylophorus fungi and, due to their biochemistry and kinetic features, they have potential to be used in biotechnological processes.

Production of fungal amylases using cheap, readily available agriresidues, for potential application in textile industry

The study aimed at isolation and screening of fungal amylase producer, optimization of solid state fermentation conditions for maximum amylase production by the best amylase producer, and characterization of the crude amylases, so produced. Aspergillus fumigatus NTCC1222 showed the highest amylase activity (164.1 U/mL) in secondary screening under SSF conditions and was selected for further studies. The test strain showed maximum amylase production (341.7 U/mL) and supernatant protein concentration (9.7 mg/mL) for incubation period (6 days), temperature (35 °C), initial pH (6.0), nutrient salt solution as moistening agent, and beef extract as nitrogen source. Pomegranate peel produced maximum amylase activity, but wheat bran (only slightly lesser amylase activity as compared to that of pomegranate peel) was chosen for further studies, keeping in mind the seasonal availability of pomegranate peel. TLC confirmed the amylase produced to be α -type and 60 kDa was the molecular weight of the partially purified amylase. The enzyme showed maximum enzyme activity at pH 6.0, temperature of 55 °C, and incubation time of 60 minutes. UV (616.0 U/mL) and chemical (814.2 U/mL) mutation enhanced amylase activity as compared to wild test strain. The study indicates that Aspergillus fumigatus NTCC1222 can be an important source of amylase and the crude enzyme, hence obtained, can be cost effectively applied in multiple sections of textile wet processing.

Gene cloning, expression and characterization of a novel xylanase from the marine bacterium, Glaciecola mesophila KMM241

Marine xylanases are rather less studied compared to terrestrial xylanases. In this study, a new xylanase gene, xynB, was cloned from the marine bacterium, Glaciecola mesophila KMM241, and expressed in Escherichia coli. xynB encodes a multi-domain xylanase XynB of glycoside hydrolase (GH) family 8. The recombinant XynB comprises an N-terminal domain (NTD) with unknown function and a catalytic domain, which is structurally novel among the characterized xylanases of GH family 8. XynB has the highest identity (38%) to rXyn8 among the characterized xylanases. The recombinant XynB showed maximal activity at pH 6–7 and 35 °C. It is thermolabile and salt-tolerant. XynB is an endo-xylanase that demands at least five sugar moieties for effective cleavage and to hydrolyze xylohexaose and xylopentaose into xylotetraose, xylotriose and xylobiose. NTD was expressed in Escherichia coli to analyze its function. The recombinant NTD exhibited a high binding ability to insoluble xylan and avicel and little binding ability to chitosan and chitin. Since the NTD shows no obvious homology to any known carbohydrate-binding module (CBM) sequence in public databases, XynB may contain a new type of CBM.

Gene cloning, expression and characterization of a new cold-active and salt-tolerant endo-beta-1,4-xylanase from marine Glaciecola mesophila KMM 241

Although a lot of xylanases are studied, only a few xylanases from marine microorganisms have been reported. A new xylanase gene, xynA, was cloned from marine bacterium Glaciecola mesophila KMM 241. Gene xynA contains 1,272 bp and encodes a 423-amino acid xylanase precursor. The recombinant xylanase, XynA, expressed in Escherichia coli BL21 is a monomer with a molecular mass of 43 kDa. Among the characterized xylanases, XynA shares the highest identity (46%) to the xylanase from Flavobacterium sp. strain MSY2. The optimum pH and temperature for XynA is 7.0 and 30 degrees C. XynA retains 23% activity and 27% catalytic efficiency at 4 degrees C. XynA has low thermostability, remaining 20% activity after 60-min incubation at 30 degrees C. Its apparent melting temperature (T (m)) is 44.5 degrees C. These results indicate that XynA is a cold-active xylanase. XynA shows a high level of salt-tolerance, with the highest activity at 0.5 M NaCl and retaining 90% activity in 2.5 M NaCl. It may be the first salt-tolerant xylanase reported. XynA is a strict endo-beta-1,4-xylanase with a demand of at least four sugar moieties for effective cleavage. It efficiently hydrolyzes xylo-oligosaccharides and xylan into xylobiose and xylotriose without producing xylose, suggesting its potential in xylo-oligosaccharides production.

Purification and characterization of xylanase from Aspergillus ficuum AF-98

The purification and characterization of xylanase from Aspergillus ficuum AF-98 were investigated in this work. The extracellular xylanase from this fungal was purified 32.6-fold to homogeneity throughout the precipitation with 50-80% (NH(4))(2)SO(4), DEAE-Sephadex A-50 ion exchange chromatography and Sephadex G-100 chromatography. The purified xylanase (specific activity at 288.7 U/ mg protein) was a monomeric protein with a molecular mass of 35.0 kDa as determined by SDS-PAGE. The optimal temperature and pH for the action of the enzyme were at 45 degrees C and 5.0, respectively. The xylanase was activated by Cu(2+) up to 115.8% of activity, and was strongly inhibited by Hg(2+), Pb(2+) up to 52.8% and 89%, respectively. The xylanase exhibited K(m) and V(max) values of 3.267 mg/mL, 18.38 M/min/mg for beechwood xylan and 3.747 mg/mL, 11.1M/min/mg for birchwood xylan, respectively.

Molecular cloning and heterologous expression of a new xylanase gene from Plectosphaerella cucumerina

A gene encoding a new xylanase, named xynZG, was cloned by the genome-walking PCR method from the nematophagous fungus Plectosphaerella cucumerina. The genomic DNA sequence of xynZG contains a 780 bp open reading frame separated by two introns with the sizes of 50 and 46 bp. To our knowledge, this would be the first functional gene cloned from P. cucumerina. The 684 bp cDNA was cloned into vector pHBM905B and transformed into Pichia pastoris GS115 to select xylanase-secreting transformants on RBB-xylan containing plate. The optimal secreting time was 3 days at 25 degrees C and enzymatic activities in the culture supernatants reached the maximum level of 362 U ml(-1). The molecular mass of the enzyme was estimated to be 19 kDa on SDS-PAGE. The optimal pH and temperature of the purified enzyme is 6 and 40 degrees C, respectively. The purified enzyme is stable at room temperature for at least 10 h. The Km and Vmax values for birchwood xylan are 2.06 mg ml(-1) and 0.49 mmol min(-1)mg(-1), respectively. The inhibitory effects of various mental ions were investigated. It is interesting to note that Cu2+ ion, which strongly inhibits most other xylanases studied, reduces enzyme activity by only 40%. Furthermore, enzyme activity is unaffected by EDTA even at a concentration of 5 mM.

Xyn11A, a multidomain multicatalytic enzyme fromPseudobutyrivibrio xylanivorans Mz5T

The rumen bacterium Pseudobutyrivibrio xylanivorans Mz5T has a potent xylanolytic enzyme system. A small native peptide (approximately 30-kDa, designated Xyn11A) from the bacterium was first isolated and characterized by Edman degradation. The gene coding for Xyn11A was identified using PCR amplification with consensus primers. It was then fully sequenced to reveal an open reading frame of 1809 bp. The predicted N-terminal domain exhibited xylanolytic activity and was classed to the family 11 of glycosyl hydrolases; it is followed by a region with homology to a family 6 cellulose binding module. The C-terminal domain codes for a putative NodB-like polysaccharide deacetylase which is predicted to be an acetyl esterase implicated in debranching activity in the xylan backbone. As similar domain organization was also found in several other xylanases from a diverse range of bacteria, a common ancestor of such a xylanase is considered to be present and spread, possibly by horizontal gene transfer, to other microorganisms from different ecological niches.

Isolation and properties of Aspergillus niger IBT-90 xylanase for bakery

Xylanase of low molecular weight (K II) was isolated from the fungus Aspergillus niger IBT-90 cultivated in medium with wheat bran. K II was purified by precipitation with ammonium sulphate (20-80% saturation) and gel filtration on Biogel P-10. This enzyme is most active in hydrolysis of birchwood xylan at 50 degrees C and pH 5.5. Xylanase K II has an ability to degrade 1,4-beta-bonds and to debranch substrates. It degrades not only xylans but also cellulose, an important factor for its application in bakery. Ag+, Fe3+ and NBS are strong inhibitors of the enzyme. DTT and Na+ activate xylanase K II by 24 and 13%, respectively. Enzyme K II used as additive to flour improves dough properties, increases the volume of wheat-rye and whole meal bread, and increases the porosity of crumb and the moisture of the final product, consequently extending the shelf life of bread.