Production of xylobiose from the autohydrolysis explosion liquor of corncob using Thermotoga maritima xylanase B (XynB) immobilized on nickel-chelated Eupergit C

Transformation of corncob into high-value xylooligosaccharides using glycoside hydrolase families 10 and 11 xylanases from Trichoderma asperellum ND-1

Effective production of xylooligosaccharides (XOS) with lower proportion of xylose entails unique and robust xylanases. In this study, two novel xylanases from Trichoderma asperellum ND-1 belonging to glycoside hydrolase families 10 (XynTR10) and 11 (XynTR11) were over-expressed in Komagataella phaffii X-33 and characterized to be robust enzymes with high halotolerance and ethanol tolerant. Both enzymes displayed strict substrate specificity towards beechwood xylan and wheat arabinoxylan. (Glu153/Glu258) and (Glu161/Glu252) were key catalytic sites for XynTR10 and XynTR11. Notably, XynTR11 could rapidly degrade xylan/XOS into xylobiose without xylose via transglycosylation. Direct degradation of corncob using XynTR10 and XynTR111 displayed that while XynTR10 yielded 77% xylobiose and 25% xylose, XynTR11 yielded much less xylose (11%) and comparable amounts of xylobiose (63%). XynTR10 or XynTR111 has great potential as a catalyst for bioconversion of xylan-containing agricultural waste into high-value products (biofuel or XOS), which is of significant benefit for the economy and environment.

Metal chelate-epoxy bifunctional membranes for selective adsorption and covalent immobilization of a His-tagged protein

The preparation and application of metal chelate-epoxy bifunctional membranes for the selective adsorption and covalent immobilization of His-tagged protein switch RG13 were shown in this study. By controlling the concentration of iminodiacetic acid (IDA) and reaction time during the conjugation of IDA on to the epichlorohydrin-activated regenerated cellulose membrane, 5 metal chelate-epoxy bifunctional membranes, with degrees of IDA conjugation in the range of 20%-81%, were prepared. The bifunctional membrane with an IDA conjugation degree of 30%, designated as BFM₃₀, exhibited a sound adsorption capacity of 0.203 mg/cm² with a relatively high content of epoxy groups for covalent immobilization, were selected. The concomitant selective adsorption and covalent immobilization of the His-tagged RG13 with BFM₃₀ were carried out by 2-h incubation for protein adsorption and subsequent 16-h incubation for covalent immobilization after the removal of undesired proteins with wash buffer, giving an immobilization yield of 63% and a global activity yield 40%. The RG13 immobilized on the metal chelate-epoxy bifunctional membrane exhibited superior operational stability in a repeated batch process, retaining 94% of its initial activity after 20 cycles. The employment of the bifunctional membranes could significant facilitate enzyme immobilization processes by eliminating the need for prior protein purification.

Optimization of β-1,4-Endoxylanase Production by an Aspergillus niger Strain Growing on Wheat Straw and Application in Xylooligosaccharides Production

Plant biomass constitutes the main source of renewable carbon on the planet. Its valorization has traditionally been focused on the use of cellulose, although hemicellulose is the second most abundant group of polysaccharides on Earth. The main enzymes involved in plant biomass degradation are glycosyl hydrolases, and filamentous fungi are good producers of these enzymes. In this study, a new strain of Aspergillus niger was used for hemicellulase production under solid-state fermentation using wheat straw as single-carbon source. Physicochemical parameters for the production of an endoxylanase were optimized by using a One-Factor-at-a-Time (OFAT) approach and response surface methodology (RSM). Maximum xylanase yield after RSM optimization was increased 3-fold, and 1.41- fold purification was achieved after ultrafiltration and ion-exchange chromatography, with about 6.2% yield. The highest activity of the purified xylanase was observed at 50 °C and pH 6. The enzyme displayed high thermal and pH stability, with more than 90% residual activity between pH 3.0–9.0 and between 30–40 °C, after 24 h of incubation, with half-lives of 30 min at 50 and 60 °C. The enzyme was mostly active against wheat arabinoxylan, and its kinetic parameters were analyzed (K_m = 26.06 mg·mL⁻¹ and V_max = 5.647 U·mg⁻¹). Wheat straw xylan hydrolysis with the purified β-1,4 endoxylanase showed that it was able to release xylooligosaccharides, making it suitable for different applications in food technology.

Improving the catalytic activity of thermostable xylanase from Thermotoga maritima via mutagenesis of non-catalytic residues at glycone subsites

Endo-β-1,4-xylanase from Thermotoga maritima, TmxB, is an industrially attractive enzyme due to its extreme thermostability. To improve its application value, four variants were designed on the basis of multiple sequence and three-dimensional structure alignments. Wild-type TmxB (wt-TmxB) and its mutants were produced via a Pichia pastoris expression system. Among four single-site mutants, the tyrosine substitution of a threonine residue (T74Y) at putative -3/-4 subsite led to a 1.3-fold increase in specific activity at 40 °C - 100 °C and pH 5 for 5 min, with beechwood xylan as the substrate. T74Y had an improved catalytic efficiency (k_cat/K_m), being 1.6 times that of wt-TmxB. Variants DY (two amino acid insertions) and N68Q displayed a slight increase (1.2 fold) and dramatic decline (1.7 fold) in catalytic efficiency, respectively. Mutant E67Y was totally inactive under all test conditions. Structural modeling and docking simulation elucidated structural insights into the molecular mechanism of activity changes for these TmxB variants. This study helps in further understanding the roles of the non-catalytic amino acids at the glycone subsites of xylanases from glycoside hydrolase family 10.

An endoxylanase rapidly hydrolyzes xylan into major product xylobiose via transglycosylation of xylose to xylotriose or xylotetraose

Here, we proposed an effective strategy to enhance a novel endoxylanase (Taxy11) activity and elucidated an efficient catalysis mechanism to produce xylooligosaccharides (XOSs). Codon optimization and recruitment of natural propeptide in Pichia pastoris resulted in achievement of Taxy11 activity to 1405.65 ± 51.24 U/mL. Analysis of action mode reveals that Taxy11 requires at least three xylose (xylotriose) residues for hydrolysis to yield xylobiose. Results of site-directed mutagenesis indicate that residues Glu¹¹⁹, Glu²¹⁰, and Asp⁵³ of Taxy11 are key catalytic sites, while Asp²⁰³ plays an auxiliary role. The novel mechanism whereby Taxy11 catalyzes conversion of xylan or XOSs into major product xylobiose involves transglycosylation of xylose to xylotriose or xylotetraose as substrate, to form xylotetraose or xylopentaose intermediate, respectively. Taxy11 displayed highly hydrolytic activity toward corncob xylan, producing 50.44 % of xylobiose within 0.5 h. This work provides a cost-effective and sustainable way to produce value-added biomolecules XOSs (xylobiose-enriched) from agricultural waste.

Biochars from Lignin-rich Residue of Furfural Manufacturing Process for Heavy Metal Ions Remediation

The pentose/furfural industrial manufacturing process uses corn cob residue as a raw material, where such a process yields significant amount of lignin-rich residue (LCR) at the end, which is commonly disposed by burning. In this study, the conversion of LCR to biochars (BCs), and their subsequent applications for heavy metal ion removal, were investigated. The BCs were prepared through hydrothermal carbonization and post-activation, using either ZnCl2 or H3PO4 treatment. The as-prepared activated BCs were characterized using N2 adsorption-desorption isotherms, XRD, FT-IR, SEM and TEM, and their performance in removing heavy metal ions (Pb2+, Cu2+, Cd2+) from aqueous solutions was assessed. The ZnCl2-activated BCs (BC-ZnCl2) exhibit a higher adsorption capacity than the H3PO4-activated BCs (BC-H3PO4), mainly due to the differences in their chemical/physical characteristics. The related adsorption kinetics and isotherms were analyzed.

Purification and characterization of an endo-xylanase from Trichoderma sp., with xylobiose as the main product from xylan hydrolysis

Fungal endo-β-1,4-xylanases (endo-xylanases) can hydrolyze xylan into xylooligosaccharides (XOS), and have potential biotechnological applications for the exploitation of natural renewable polysaccharides. In the current study, we aimed to screen and characterize an efficient fungal endo-xylanase from 100 natural humus-rich soil samples collected in Guizhou Province, China, using extracted sugarcane bagasse xylan (SBX) as the sole carbon source. Initially, 182 fungal isolates producing xylanases were selected, among which Trichoderma sp. strain TP3-36 was identified as showing the highest xylanase activity of 295 U/mL with xylobiose (X2) as the main product when beechwood xylan was used as substrate. Subsequently, a glycoside hydrolase family 11 endo-xylanase, TXyn11A, was purified from strain TP3-36, and its optimal pH and temperature for activity against beechwood xylan were identified to be 5.0 and 55 °C, respectively. TXyn11A was stable across a broad pH range (3.0-10.0), and exhibited strict substrate specificity, including xylan from beechwood, wheat, rye, and sugarcane bagasse, with K_m and V_max values of 5 mg/mL and 1250 μmol/mg min, respectively, toward beechwood xylan. Intriguingly, the main product obtained from hydrolysis of beechwood xylan by TXyn11A was xylobiose, whereas SBX hydrolysis resulted in both X2 and xylotriose. Overall, these characteristics of the endo-xylanase TXyn11A indicate several potential industrial applications.

Investigating desorption during ethanol elution to improve the quality and antioxidant activity of xylo-oligosaccharides from corn stalk

As the most representative of lignocellulosic materials, corn stalk (CS) will be a great candidate to produce xylo-oligosaccharides (XOS). Owing to the high impurity content of the XOS produced by directly enzymatic hydrolysis of xylan extracted from CS, subsequent refining steps are essential. The present study was aimed to investigate desorption during ethanol elution to improve the quality and antioxidant activity of XOS from CS. The desorption was systematically investigated after optimizing the elution conditions. The results showed that it had an elution watershed when the volume ratio was 2:1. More interestingly, XOS had a obvious priorities of desorption during ethanol gradient elution. The highest purity of XOS was 98.12% from 30% ethanol eluate. Antioxidant activity assay showed that the highest radical scavenging activity of XOS was 89.89% obtained from 70% ethanol eluate at a concentration of 3 mg/mL, which could be used in antioxidant food, feed additives.

Removal of chromophore in enzymatic hydrolysis by acid precipitation to improve the quality of xylo-oligosaccharides from corn stalk

As the most representative functional sugar, the application areas and market demands of xylo-oligosaccharides (XOS) have been expanding year by year. Owing to the complex structure of corn stalk (CS), XOS obtained from CS are accompanied by problems such as low purity and high color value, which degrade the product. To improve the quality of XOS from CS, the enzymatic hydrolysis was precipitated by acid; then, the ethanol elution concentration was systematically investigated after optimizing the adsorption conditions. The results showed that the purity of XOS was increased to 87.28% from 67.31%, and the color value was decreased to 1050 from 4682 when the acid precipitation pH was 2. On the basis of acid precipitation, if the corresponding optimal conditions of XOS adsorption and elution were used, the highest purity of XOS was 97.87% obtained, with the lowest color value, 780, which reached the standard of the commercial XOS.

Engineering a xylanase from Streptomyce rochei L10904 by mutation to improve its catalytic characteristics

Protein engineering was performed by N-terminal region replacement and site-directed mutagenesis in the cord of a xylanase (Srxyn) from Streptomyce rochei L10904 to improve its catalytic characteristics. Three mutants SrxynF, SrxynM and SrxynFM displayed 2.1-fold, 3.2-fold and 5.3-fold higher specific activities than that of Srxyn, respectively. Moreover, all of the mutants showed greater substrate affinity and k_cat/K_m than the native Srxyn. In addition, the enzymes showed improved hydrolysis characteristics, of which the most noteworthy is the enhanced ability of producing xylobiose (X2) and xylotriose (X3) from polymeric substrates. The engineered xylanases have greater potential for applications in oligosaccharide preparation industry.

Characterization and immobilization on nickel-chelated Sepharose of a glutamate decarboxylase A from Lactobacillus brevis BH2 and its application for production of GABA

A gene encoding glutamate decarboxylase A (GadA) from Lactobacillus brevis BH2 was expressed in a His-tagged form in Escherichia coli cells, and recombinant protein exists as a homodimer consisting of identical subunits of 53 kDa. GadA was absolutely dependent on the ammonium sulfate concentration for catalytic activity and secondary structure formation. GadA was immobilized on the metal affinity resin with an immobilization yield of 95.8%. The pH optima of the immobilized enzyme were identical with those of the free enzyme. However, the optimum temperature for immobilized enzyme was 5 °C higher than that for the free enzyme. The immobilized GadA retained its relative activity of 41% after 30 reuses of reaction within 30 days and exhibited a half-life of 19 cycles within 19 days. A packed-bed bioreactor with immobilized GadA showed a maximum yield of 97.8% GABA from 50 mM l-glutamate in a flow-through system under conditions of pH 4.0 and 55 °C.

Immobilization of xylanase purified from Bacillus pumilus VLK-1 and its application in enrichment of orange and grape juices

This study was conducted to evaluate the efficacy of purified free and immobilized xylanase in enrichment of fruit juices. Extracellular xylanase produced from Bacillus pumilus VLK-1 was purified to apparent homogeneity by 15.4-fold with 88.3 % recovery in a single step using CM-Sephadex C-50. Purified xylanase showed a single band on SDS-polyacrylamide gel with a molecular mass of 22.0 kDa. The purified enzyme was immobilized on glutaraldehyde-activated aluminum oxide pellets and the immobilization process parameters were optimized statistically through response surface methodology. The bound enzyme displayed an increase in optimum temperature from 60 to 65 ºC and pH from 8.0 to 9.0. The pH and temperature stability of the enzyme was also enhanced after immobilization. It could be reused for 10 consecutive cycles with 58 % residual enzyme activity. The potential of purified xylanase (free and immobilized) in juice enrichment from grape (Vitis amurensis) and orange (Citrus sinensis) pulps has been investigated. The optimization of this process using free xylanase revealed maximum juice yield, clarity and reducing sugar on treatment with 20 IU/g fruit pulp for 30 min at 50 ºC. Treatment of both the fruit pulps with xylanase under optimized conditions resulted in an increase in juice yield, clarity, reducing sugars, titratable acidity, and filterability but a decline in turbidity and viscosity. Immobilized enzyme was more effective in improving juice quality as compared to its soluble counterpart. The results showed B. pumilus VLK-1 xylanase, in both free and immobilized form, as a potential candidate for use in fruit juice enrichment.

Enzymatic hydrolysis of autohydrolyzed wheat straw followed by refining to produce fermentable sugars

Wheat straw was pretreated using an autohydrolysis process with different temperatures (160-200 °C) and times (10-20 min) in order to allow the recovery of hemicellulose in the filtrate and help open up the structure of the biomass for improved accessibility of enzymes during enzymatic hydrolysis. Autohydrolysis at 190 °C for 10 min provided the highest overall sugar (12.2/100g raw wheat straw) in the autohydrolysis filtrate and recovered 62.3% of solid residue. Before enzymatic hydrolysis, the pulps obtained from each pretreatment condition were subjected to a refining post-treatment to improve enzyme accessibility. Enzymatic hydrolysis was performed for all the pretreated solids with and without refining post-treatment at the enzyme loadings of 4 and 10 FPU/g oven dry substrate for 96 h. A total of 30.4 g sugars can be recovered from 100g wheat straw at 180 °C for 20 min with 4 FPU/g enzyme charge.

Production of xylooligosaccharides from corncob xylan by fungal xylanase and their utilization by probiotics

The selective production of xylooligosaccharides (XOS) was carried out using partially purified xylanase from Aspergillus foetidus MTCC 4898. Corncob xylan was extracted using a mild alkali treatment which yielded 178.73±5.8 g of xylan/kg of corncobs. Partially purified β-xylosidase free xylanase was found efficient in releasing xylooligosaccharides from corncob xylan. Maximum yield of xylooligosaccharides was 6.73±0.23 mg/ml after 8 h of reaction time using 20 U of xylanase at 45°C. Purification of XOS was done using activated charcoal column chromatography. The purified XOS preparation contained mainly xylobiose and xylotriose. XOS mixture was found suitable for food industry looking at its high thermal stability at low pH. Prebiotic effect of XOS was evaluated by in vitro fermentation of XOS using known probiotic strains viz. Bifidobacterium adolescentis, Bifidobacterium bifidum, Lactobacillus fermentum, Lactobacillus acidophilus. The results of this study revealed better growth of Bifidobacterium spp. on XOS than Lactobacillus spp.

Biomass to Bioethanol: Initiatives of the Future for Lignin

Lignin, which is one of the most abundant natural materials, represents a vastly underutilized natural polymer. With the emerging necessity to develop alternative sustainable transportation fuels, bioethanol produced from lignocellulosic biomass is considered as a viable option to petroleum-derived fuels. The effective utilization of biomass feedstock necessitates the development of cost-effective pretreatment technologies that are necessary to separate the three main biopolymers (cellulose, hemicellulose, and lignin). One of the key issues concerning the pretreatment process is the full recovery of the feedstock through optimum utilization of all lignocellulosic components, including nonsugar compounds, as marketable products. Thus, availability of high-quality lignin in large quantities should stimulate development in new lignin applications in the fields of fibres, biodegradable polymers, adhesives, and surface treatment (rust converter).

High-level expression of extracellular secretion of a β-xylosidase gene from Paecilomyces thermophila in Escherichia coli

A novel β-xylosidase gene (designated as PtXyl43) from thermophilic fungus Paecilomycesthermophila was cloned and extracellularly expressed in Escherichia coli. PtXyl43 belonging to glycoside hydrolase (GH) family 43 has an open reading frame of 1017 bp, encoding 338 amino acids without a predicted signal peptide. No introns were found by comparison of the PtXyl43 genomic DNA and cDNA sequences. The recombinant β-xylosidase (PtXyl43) was secreted into the culture medium in E. coli with a yield of 98.0 U mL(-1) in shake-flask cultures. PtXyl43 was purified 1.2-fold to homogeneity with a recovery yield of 61.5% from the cell-free culture supernatant. It appeared as a single protein band on SDS-PAGE with a molecular mass of approx 52.3 kDa. The enzyme exhibited an optimal activity at 55 °C and pH 7.0, respectively. This is the first report on the cloning and expression of a GH family 43 β-xylosidase gene from thermophilic fungi.

Effect of autohydrolysis of Miscanthus x giganteus on lignin structure and organosolv delignification

The influence of the operating conditions of Miscanthus x Giganteus autohydrolysis on the composition of the solid residues and hydrolysates was examined. Milled wood lignin (MWL) extracted after autohydrolysis treatments performed at the same severity but at different temperatures were studied by (13)C and (31)P NMR in order to obtain a more complete picture of the changes in lignin structure occurring during the autohydrolysis. It was proposed that (1) the lignin homolytical fragmentation route should be enhanced with an increase of the temperature of the autohydrolysis treatment and (2) addition of a catalytic amount of 2-naphthol during the autohydrolysis step not only enhanced the dissolution of lignin but also allowed a better recovery of the hemicellulose sugars. A combined process involving an optimized autohydrolysis step (carried out in presence or not of 2-naphthol) and a low severity ethanol organosolv treatment was described for the separation and recovery of lignin, cellulose and hemicelluloses.

The genus Thermotoga: recent developments

The genus Thermotoga comprises extremely thermophilic (Topt > or = 70 degrees C) and hyperthermophilic (Topt > or = 80 degrees C) bacteria, which have been extensively studied for insights into the basis for life at elevated temperatures and for biotechnological opportunities (e.g. biohydrogen production, biocatalysis). Over the past decade, genome sequences have become available for a number of Thermotoga species, leading to functional genomics efforts to understand growth physiology as well as genomics-based identification and characterization of novel high-temperature biocatalysts. Discussed here are recent developments along these lines for this group of microorganisms.

A comparison of the autohydrolysis and ammonia fiber explosion (AFEX) pretreatments on the subsequent enzymatic hydrolysis of coastal Bermuda grass

Two distinct pretreatment technologies, autohydrolysis and AFEX, have been applied to coastal Bermuda grass (CBG) followed by enzymatic hydrolysis in order to compare the effects of pretreatment on the subsequent sugar generation. Furthermore, the influence of structural features from each pretreatment on biomass digestibility was characterized with SEM, ATR-FTIR, and XRD. Enzymatic conversion of pretreated solids from the pretreatments increased with elevated temperature and longer residence times. AFEX pretreatment at 100 degrees C for 30 min produced a sugar yield of 94.8% of theoretical possible with 30 FPU/g enzymatic loading, the maximum achieved with AFEX. It was also shown that with autohydrolysis at 170 degrees C for 60 min that 55.4% sugar yield of the theoretical possible was produced with a 30 FPU/g enzymatic loading, the maximum with autohydrolysis. AFEX pretreatment does not change the chemical composition of CBG but autohydrolysis reduces hemicellulose content in the pretreated solids. Both pretreatments cause re-localization of lignin components. There was no observed correlation between crystallinity and enzyme digestibility of the pretreated solids. AFEX pretreatment developed more enzymatic accessibility to pretreated solids of CBG than did autohydrolysis pretreatment, leading to more sugar generation through the whole process. The total amount of sugars accounted for with autohydrolysis decreases with increasing temperature, consistent with increased byproduct generation via thermal degradation reactions.

Autohydrolysis pretreatment of coastal Bermuda grass for increased enzyme hydrolysis

Coastal Bermuda grass (GBG) was pretreated using an autohydrolysis process with different temperatures and times, and the pretreated materials were enzymatically hydrolyzed using a mixture of cellulase, xylanase and beta-glucosidase with different enzyme loadings to evaluate sugar yields. Compared with untreated CBG, autohydrolysis pretreatments at all elevated temperatures and residence times tested enhanced enzymatic digestibility of both cellulose and hemicellulose. Increasing the temperature and residence time also helps to solubilize hemicelluloses, with 83.3% of the hemicelluloses solubilized at 170 degrees C for 60 min treatment. However, higher temperatures and longer times resulted in an overall lower sugar recovery when considering monosaccharides in the prehydrolyzate combined with the enzyme hydrolyzate. Autohydrolysis at 150 degrees C for 60 min provided the highest overall sugar yield for the entire process. A total of 43.3 g of sugars, 70% of the theoretical sugar yield, can be generated from 100g CBG, 15.0 g of monosaccharide in the prehydrolyzate and 28.3 g in the enzyme hydrolyzate. The conversion efficiency could be further improved by optimizing enzyme dosages and xylanases:cellulases ratio and pretreatment conditions to minimize sugar degradation.

Xylanase XYL1p from Scytalidium acidophilum: site-directed mutagenesis and acidophilic adaptation

The role of residues Asp60, Tyr35 and Glu141 in the pH-dependent activity of xylanase XYL1p from Scytalidium acidophilum was investigated by site-directed mutagenesis. These amino acids are highly conserved among the acidophilic family 11 xylanases and located near the catalytic site. XYL1p and its single mutants D60N, Y35W and E141A and three combined mutants DN/YW, DN/EA and YW/EA were over-expressed in Pichia pastoris and purified. Xylanase activities at different pH's and temperatures were determined. All mutations increased the pH optimum by 0.5-1.5 pH units. All mutants have lower specific activities except the E141A mutant that exhibited a 50% increase in specific activity at pH 4.0 and had an overall catalytic efficiency higher than the wild-type enzyme. Thermal unfolding experiments show that both the wild-type and E141A mutant proteins have a T(m) maximum at pH 3.5, the E141A mutant being slightly less stable than the wild-type enzyme. These mutations confirm the importance of these amino acids in the pH adaptation. Mutant E141A with its enhanced specific activity at pH 4.0 and improved overall catalytic efficiency is of possible interest for biotechnological applications.

Value addition to corncob: production and characterization of xylooligosaccharides from alkali pretreated lignin-saccharide complex using Aspergillus oryzae MTCC 5154

Comparison of various pretreatments such as mild alkali/acid treatments and pressure cooking of corncob to expose its lignin-saccharide complex has been carried out to enhance enzymatic hydrolysis of xylan to xylooligosaccharides (XOS). Scanning electron micrographs of lignin-saccharide complex of native and pretreated corncob powder showed that the complex was greatly altered during alkali pretreatment. Hydrolysis of alkali pretreated corncob powder using a commercial endoxylanase produced 81+/-1.5% of XOS in the hydrolyzate equivalent to 5.8+/-0.14 mg ml(-1) of XOS. Reaction parameters for the production of XOS from corncob using endoxylanase from Aspergillus oryzae MTCC 5154 were optimized and an XOS yield of 10.2+/-0.14 mg ml(-1) corresponding to 81+/-3.9% with 73.5% xylobiose was obtained. HPLC/RID and ESI/MS analysis of XOS mixture and purified fractions showed that XOS was a mixture of neutral oligosaccharides of DP, 2-7.

Immobilization of Neocallimastix patriciarum xylanase on artificial oil bodies and statistical optimization of enzyme activity

A thermally stable and alkalophilic xylanase, XynCDBFV, from Neocallimastix patriciarum was overexpressed in Escherichia coli as a recombinant protein fused to the N-terminus of oleosin, a unique structural protein of seed oil bodies. As a result of the reconstitution of the artificial oil bodies (AOBs), the immobilization of active xylanase was accomplished. Response surface methodology (RSM) was employed for the optimization of the immobilized xylanase activity. The central composite design (CCD) and regression analysis methods were effective for determination of optimized temperature and pH conditions for the AOB-immobilized XynCDBFV. The optimal condition for the highest immobilized xylanase activity (3.93IU/mg of total protein) was observed at 59 degrees C and pH 6.0. Further, AOB-immobilized XynCDBFV retained 50% of its maximal activity after 120min at 60 degrees C, and it could be easily and simply recovered from the surface of the solution by brief centrifugation, and could be reused eight times while retaining more than 60% of its activity. These results proved it is a simple and effective method for direct immobilization of xylanases.

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.