Immobilization Of Xylanase Research Articles

Co-administration of xylo-oligosaccharides produced by immobilized Aspergillus terreus xylanase with carbimazole to mitigate its adverse effects on the adrenal gland

Carbimazole has disadvantages on different body organs, especially the thyroid gland and, rarely, the adrenal glands. Most studies have not suggested any solution or medication for ameliorating the noxious effects of drugs on the glands. Our study focused on the production of xylooligosaccharide (XOS), which, when coadministered with carbimazole, relieves the toxic effects of the drug on the adrenal glands. In addition to accelerating the regeneration of adrenal gland cells, XOS significantly decreases the oxidative stress caused by obesity. This XOS produced by Aspergillus terreus xylanase was covalently immobilized using microbial Scleroglucan gel beads, which improved the immobilization yield, efficiency, and operational stability. Over a wide pH range (6–7.5), the covalent immobilization of xylanase on scleroglucan increased xylanase activity compared to that of its free form. Additionally, the reaction temperature was increased to 65 °C. However, the immobilized enzyme demonstrated superior thermal stability, sustaining 80.22% of its original activity at 60 °C for 120 min. Additionally, the full activity of the immobilized enzyme was sustained after 12 consecutive cycles, and the activity reached 78.33% after 18 cycles. After 41 days of storage at 4 °C, the immobilized enzyme was still active at approximately 98%. The immobilized enzyme has the capability to produce xylo-oligosaccharides (XOSs). Subsequently, these XOSs can be coadministered alongside carbimazole to mitigate the adverse effects of the drug on the adrenal glands. In addition to accelerating the regeneration of adrenal gland cells, XOS significantly decreases the oxidative stress caused by obesity.

Immobilization of Xylanase on ZnO nanoparticles obtained by green synthesis from Eupatorium cannabinum L. and its application in enrichment of fruit juices

Juice production is one of the main components of the nutritional food industry. Therefore, improving fruit juice quality and preventing the formation of negative by-products is important for human health. The role of environmentally friendly, safe and economically more affordable green nanocarriers in improving the quality of fruit juice is increasing day by day. For this purpose, zinc oxide nanoparticles (ZnONPs) were prepared from the aqueous extract of the Eupatorium cannabinum L. using the green synthesis method. After immobilization, structural and morphological characterizations of the prepared ZnONPs and xylanase (Xyl)@ZnONPs were carried out, which confirmed that both the synthesis of ZnONPs and the immobilization of Xyl enzyme on ZnONPs were successfully carried out. The biochemical parameters of Xyl@ZnONPs such as optimum pH and temperature, kinetic parameters, thermal stability, reusability, and storage stability were investigated and compared with free Xyl. After immobilization, the optimum pH of free Xyl shifted from 5.0 to an alkaline pH of 8.0, while no change in the optimum temperature (70 °C) was observed for both enzymes. While the activation energy of free Xyl was 5.56 kJ/mol, it was found to be 7.27 kJ/mol for Xyl@ZnONPs. Xyl@ZnONPs outperformed free Xyl due to its long-term storage stability and reusability. Moreover, Xyl@ZnONPs retained 50 % of its activity after 5 reuses and 87 % of its activity after 4 weeks of storage at room temperature. In addition, a decrease in Km value and an increase in Vmax value were observed after immobilization, which means the increased catalytic activity of the Xyl@ZnONPs. As a result of re-using Xyl@ZnONPs in orange juice for 6 cycles, clarification yield of 66.43 % was obtained under optimized conditions. Overall, this study prepared a suitable, environmentally friendly, and robust carrier support for Xyl immobilization and developed a biocatalyst that will provide high performance in the industrial field.

Xylanase immobilization using activated carrier of gellan gum-agar beads: Improved stability and catalytic activity for the production of antioxidant and anti-proliferative xylooligosaccharides

Immobilization of xylanase produced by the fungus, Aspergillus flavus, was achieved utilizing the activated gellan gum-agar as a carrier. The immobilization conditions were optimized based on Box-Behnken design which comprised the addition of agar (1.23%) to gellan-gum (GL) and processing the obtained beads at pH 7.7 with 1.62% polyethyleneimine (PEI) as the optimum conditions. Alteration of the surface morphologies and elemental constituents of the carrier during the synthesis and immobilization process were inspected using energy-dispersive X-ray analysis (EDX) and scan electron microscope (SEM). The yield and efficiency of the immobilization process were 45.85% and 97.41%, respectively. The immobilized enzyme possessed the highest activity at pH 5–8 and temperature up to 70 °C with activation energy lower than half that of the free form. Higher half-lives and Gibbs free energy were achieved for the immobilized enzyme, sustaining the suitability of the used carrier for promoting enzyme stability. Moreover, the negative entropy values for both free enzyme and the immobilized forms estimated the high stability of the enzyme during the thermal deactivation process. The Km value of the immobilized form was lower than that of the free enzyme, reflecting its enhanced affinity toward xylan substrate. Furthermore, the immobilized enzyme retained 99.3 and 85.7% of its initial xylan hydrolyzing activity after 7, and 11 cycles, respectively. Finally, the applicability of the immobilized form in the hydrolysis of xylan and production of antioxidant and breast cancer anti-proliferative xylooligosaccharide mixture was also estimated.

Immobilization of Xylanase onto Starch Nanoparticles: A Reusable and Robust Nanobiocatalyst for Juice Clarification

AbstractNanoparticles (NPs) have attracted interest recently as a promising support for the immobilization of enzymes.Xylanase (Xyl) has been utilized in the food industry for several purposes. To improve its stability and reusability,starch NPs (SNPs)are synthesized and assessed for Xyl immobilization for the first time. . The characterization results reveal that SNPs are successfully synthesized and Xyl@SNPs are effective as the immobilization carrier. The Xyl is immobilized on SNPs under optimized conditions leading to 91% immobilization efficiency. A shift in optimum pH (from 6.0 to 8.0) and temperature (from 70 to 60 °C) of Xyl is observed after immobilization. The Xyl@SNPs possess improve pH stability and thermal stability as well as operational stability. The Xyl@SNPs are easily reutilized and the residual activity is still higher than 62% after seven times. More importantly, the Xyl@SNPs have a lower Km value and enhance affinity for the substrate compared to the free Xyl. Additionally, the clarity of orange juice is increased by 76.0% by using Xyl@SNPs after 2 h incubation at 60 °C, pH 8.0. These positive results show promising support for the Xyl immobilization of SNPs, confirming that this immobilized enzyme‐based strategy is an effective technique for rapid clarification of targeted juices.

Fabrication of immobilized xylanase by a novel 3D electrostatic printing as an excellent catalyst for corn straw degradation

Extrusion-based 3D printing has been widely utilized in enzyme immobilization to obtain the desired shape, even though the result is less fine. Here, we report a novel 3D electrostatic printing (3DEP) technology that combines the technologies of electrospinning and 3D printing to manufacture fiber membranes that are finer and uniform and used them for xylanase immobilization. After optimizing the preparation conditions for the 3DEP immobilization carrier, the finer, uniform fiber membranes were printed by using a ratio of 10:1 polyvinyl alcohol (PVA) and chitosan (Cs) under a constant voltage (5 kV) and feed rate (0.001 mm/s). Additionally, 50% glutaraldehyde (GA) vapor was used for cross-linking Cs in order to improve the water insolubility of the support. The 3DEP immobilized xylanase was then prepared by mixing xylanase and the printed materials. The resulting immobilized xylanase exhibited excellent stability, with over 95% of enzyme activity following storage for 28 days, and 53% xylan conversion was still retained after reuse over 8 batches. Finally, the 3DEP immobilized xylanase featured good catalytic efficiency in degrading corn straw. Collectively, the results of this study show that 3DEP offered a finer carrier manufacturing technology and could improve the catalytic efficiency of the immobilized enzyme.

Xylanase immobilized on β-cyclodextrin functionalized magnetic nanoparticles: Implications for antioxidant component extraction and fruit juice quality improvement

Amongst various materials employed for modifying magnetic nanoparticles (MNPs), β-cyclodextrins (β-CDs) possess outstanding features for surface engineering of MNPs to improve the enzyme attachment. Herein, β-CD was modified onto MNPs and fabricated as a unique nanocarrier for the immobilization of xylanase. A variety of analytical techniques were applied to characterize the structural, morphological and chemical features of the as-prepared nanobiocatalyst. Notably, the xylanase immobilized onto the synthesized nanocomplex exhibited efficient reactivity and remarkable stability against harsh environmental condition. Besides, the as-prepared nanobiocatalyst could maintain 50 % of its original catalytic activity even after 12 successive reuses. The storage stability results showed that the free and immobilized xylanases lost approximately 65 % and 35 % of their original activity, respectively, after 90 days. The evaluation of kinetic metrics confirmed the remarkable improvement of immobilized xylanase performance. The effect immobilized xylanase on the reduction of apple and pineapple juices turbidity indicated that the turbidity decrease rate of apple juice occurred quickly (about 32 % in 90 min, for free and immobilized xylanases) rather than pineapple juice (about 20 % in 90 min, for both kinds of enzymes). The nanobiocatalyst also exhibited good recycling as approved by retention of 60 % and 70 % of relative activity after eight reuses in clarification of apple and pineapple juices. Additionally, the ability of immobilized xylanase to the extraction of antioxidant components demonstrated that the nanobiocatalyst can extract antioxidant outstandingly much higher than free enzyme. The resultants of this research indicates the great potential of the immobilized xylanase for employing in a wide range of bio-applications.

An eco-friendly process for xylose production from waste of pulp and paper industry with xylanase catalyst

Plentiful waste is generated by pulp and paper industries during different stages of paper production. Current practices being used harm the environment to a large extent and thus, require a sustainable approach to deal with the waste. Thus, present study investigated the effect of xylose production without NaOH and with pre-treated (2% NaOH) waste paper pulp under the effect of temperature; pH and incubation time with the help of xylanase isolated from Bacillus pumilus. A comparative analysis was drawn with three treatments namely enzymatic, xylanase immobilization onto chitosan and microbial treatment. Chitosan being inert, cheap and biocompatible was chosen as carrier and resulted in 94.87% immobilization yield. Optimum parameter for xylose production was found to be temperature 50 °C and pH 6.0. For incubation time, highest xylose production was seen after 12 hrs (enzymatic and chitosan and immobilized) and on 3rd day (microbial). Therefore, treatment of waste paper pulp with xylanase showed significant results for xylose production which later can be used in the production of various value added products such as xylitol.

Bi-enzymatic nanobiocatalyst based on immobilization of xylanase and pectinase onto functionalized magnetic nanoparticles for efficient fruit juice clarification

An efficient enhancement in fruit juice quality achieves by simultaneously hydrolyzing polysaccharides in one pot reaction. Herein, an efficient approach is reported to fabricate a novel nanobiocatalyt for clarification of fruit juices based on covalent co-immobilization of pectinase and xylanase onto functionalized iron oxide nanoparticles. The highest activity recovery of the co-immobilized enzymes was achieved at 0.5 mg/mL of total protein, 8:1 w/w pectinase to xylanase ratio, and 6 h incubation time. Thermal and pH stabilities studies showed improved performance of co-immobilized enzymes compared to free counterparts. The co-immobilized pectinase and xylanase respectively retained more than 74% and 48% of residual activity after six consecutive cycles. Moreover, 53% turbidity reduction in pineapple juice was achieved after 120 min treatment with developed nanobiocatalyst. Besides, more than 64% of the initial activity of enzymes was retained after nine reuses, suggesting that this bi-enzyme nanobiocatalyst has potential application in industrial juice processing.

Immobilization of xylanase enzyme on poly-(HEMA-co-GMA) cryogel

In this study, a polyethyleneimine (PEI) coated poly-(HEMA-co-GMA), hybrid cryogel column (HCC), was designed. HCC was synthesized via polymerization of gel-former factors at minus temperatures. The characterization experiments of the HCC were conducted through SEM, and FTIR experiments. At the end of the experimental periods, there was no significant decrease in the performance of the HCC. Then HCC used as a novel support for xylanase immobilization for the first time. The successful immobilization of xylanase was confirmed by FT-IR, while biochemical properties and stability of the PHG/PI-Xyl were evaluated in terms of optimum pH, optimum temperature, thermostability, storage stability, reusability, and kinetic parameters. The optimum activities for both free and immobilized enzymes were recorded at pH 6.0, while the optimum temperature for free was 55 °C, and for PHG/PI-Xyl was 60 °C. PHG/PI-Xyl displayed remarkable thermal stability for 180 min at 60 °C, with 53.55%, and for free Xyl 32.05% from the initial activity. Meanwhile, it retained up to 49% and 69 % for free and immobilized xylanase of original activities after 4 weeks of storage at room temperature. PHG/PI-Xyl retained about 58% of its original activity after 10 consecutive reuses, while Km for the free Xyl and PHG/PI-Xyl were calculated 4.05 mg/mL and 2.62 mg/mL, whereas Vmax 133.33 U/mL and 188.68 U/mL, respectively. As envisioned, this study suggests a promising way to solve the problems of high price and poor operational stability of the enzyme during biocatalytic.

Covalent immobilization of xylanase and lysing complex into polymer scaffolds with long-term activity retention

Covalent immobilization of xylanase and lysing complex into polymer scaffolds with long-term activity retention

Optimization of the immobilization of xylanase from Thermomyces lanuginosus to produce xylooligosaccharides in a batch type reactor

The xylanase from Thermomyces lanuginosus was immobilized following very different protocols, using 3-aminopropyl (Xyl/CNT-NH2) and carboxylic acid (Xyl/CNT-C) functionalized multi-walled carbon nanotubes or after glutaraldehyde activation of CNT-NH2 (Xyl/CNT-Glu). It was also immobilized on carboxylic acid functionalized multi-walled carbon nanotubes via carbodiimide chemistry (Xyl/CNT-COOH). The free and all the immobilized xylanase derivatives showed maximal catalytic activity at pH 7.5 and at 65 °C. Xyl/CNT-Glu showed 24.0-fold higher thermal stability than the free xylanase at 70 °C. The immobilized xylanase derivatives were used for the production of xylooligosaccarides, the reaction courses and the yields showing a dependence on the immobilization protocol. The highest XOS yield (22.1%) was obtained using Xyl/CNT-Glu after 8 h of reaction at pH 75 and 65 °C.

Efficacious bioconversion of waste walnut shells to xylotetrose and xylopentose by free xylanase (Xy) and MOF immobilized xylanase (Xy-Cu-BTC)

This study uses a cost effective and efficient method for production of higher DP (degree of polymerization) Xylooligosaccharides (XOS) from xylan extracted from the waste walnut shells. Copper based metal organic framework (Cu-BTC MOF) was prepared for immobilization of free xylanase (Xy) enzyme by green synthesis method. Both free and immobilized xylanase (Xy-Cu-BTC) were able to cause the bioconversion of xylan (87.4% yield) into XOS. Predominant production of xylotetrose (X4) and xylopentose (X5) was observed for both the methods. Percentage XOS conversion for free enzyme (Xy) was found to be 4.1% X4 and 60.57% X5 whereas these values increased in case of immobilized system where 11.8% X4 and 64.2% X5 were produced. Xylose production was minute in case of immobilized xylanase 0.88% which makes it a better method for XOS production free from xylose interference. Xy-Cu-BTC MOF can hence be used as an attractive alternative for pure XOS production.

Immobilization of xylanase on differently functionalized silica gel supports for orange juice clarification

The immobilization of xylanase from Trichoderma longibrachiatum via ion exchange on 3-propylsulfonic acid (Xyl/Si-SO3) and 3-aminopropyl (Xyl/Si-NH3) functionalized silica gel and covalently on 3-carboxypropyl (Xyl/Si−COOH) and silica gel functionalized with 3-aminopropyl and modified with glutaraldehyde (Xyl/Si-Glu) were performed and the prepared biocatalysts were used for clarification of orange juice. The supports and immobilized biocatalysts were characterized by scanning electron microscopy, and thermal gravimetric analysis. Free and all immobilized xylanase samples showed maximal catalytic activity at pH 6.0. The free xylanase and Xyl/Si-NH3 had a maximal catalytic activity at 50 °C, while Xyl/Si-Glu, Xyl/Si−COOH and Xyl/Si-SO3 exhibited their maximal catalytic activities at 60 °C. The Xyl/Si-Glu showed 4.2-fold higher thermal stability than the free xylanase at 50 °C and pH 6.0. The clarity of orange juice was increased by 74.7, 73.6, 59.3, 60.3, and 78.8 % respectively by using free xylanase, Xyl/Si-Glu, Xyl/Si−COOH, Xyl/Si-SO3 and Xyl/Si-NH3 at 50 °C after 180 min treatment time. The reusability studies showed that Xyl/Si-Glu, Xyl/Si−COOH, Xyl/Si-SO3 and Xyl/Si-NH3 retained 77, 71, 11 and 16 %, respectively, of their initial activities after 10 reuses. These results show that Xyl/Si-Glu and Xyl/Si−COOH are better potential candidates than Xyl/Si-SO3 and Xyl/Si-NH3 in fruit juice clarifying processes.

Zeolite-based nanocomposite as a smart pH-sensitive nanovehicle for release of xylanase as poultry feed supplement

Xylanase improves poultry nutrition by degrading xylan in the cell walls of feed grains and release the entrapped nutrients. However, the application of xylanase as a feed supplement is restricted to its low stability in the environment and gastrointestinal (GI) tract of poultry. To overcome these obstacles, Zeozyme NPs as a smart pH-responsive nanosystem was designed based on xylanase immobilization on zeolitic nanoporous as the major cornerstone that was modified with L-lysine. The immobilized xylanase was followed by encapsulating with a cross-linked CMC-based polymer. Zeozyme NPs was structurally characterized using TEM, SEM, AFM, DLS, TGA and nitrogen adsorption/desorption isotherms at liquid nitrogen temperature. The stability of Zeozyme NPs was evaluated at different temperatures, pH, and in the presence of proteases. Additionally, the release pattern of xylanase was investigated at a digestion model mimicking the GI tract. Xylanase was released selectively at the duodenum and ileum (pH 6–7.1) and remarkably preserved at pH ≤ 6 including proventriculus, gizzard, and crop (pH 1.6–5). The results confirmed that the zeolite equipped with the CMC matrix could enhance the xylanase thermal and pH stability and preserve its activity in the presence of proteases. Moreover, Zeozyme NPs exhibited a smart pH-dependent release of xylanase in an in vitro simulated GI tract.

Recent Advancements of Fungal Xylanase Upstream Production and Downstream Processing

Xylanase is a hydrolytic enzyme produced by fungi and bacteria utilized in various industrial applications such as food, biobleaching, animal feed, and pharmaceuticals. Due to its wide variety of applications, xylanase's large-scale industrial production has gained researchers' interest. Many factors and methods affect fungal xylanase's production in both upstream and downstream processing stages. The upstream production methods used are submerged fermentation (SmF) and solid-state fermentation (SSF), where SmF involves the usage of liquid substrates, while the SSF applies solid substrates to inoculate the microbes. The downstream processing of fungal xylanase includes extraction, purification, and formulation. The extraction methods used to extract fungal xylanase are filtration and solvent extraction. Meanwhile, the purification methods include ultrafiltration, precipitation, chromatography, Aqueous Two-Phase System (ATPS), and Aqueous Two-Phase Affinity Partitioning (ATPAP). The formulation of xylanase product is obtained in either liquid from the extraction-purification results, which can be converted to powder form using technologies such as spray drying to increase storage life. Moreover, immobilization of xylanase with nanoparticles of SiO2 could produce reusable xylanase enzymes. Several future studies have also been suggested. This review aims to explain the upstream and downstream processes of fungal xylanase production as well as the factors that affect those processes.

Site-directed lysine modification of xylanase for oriented immobilization onto silicon dioxide nanoparticles

Enhanced covalent immobilization of xylanase from Chaetomium globosum (XylCg) onto SiO2 nanoparticles was achieved by the modification of surface residues. The mutation of surface residues to lysine by site-directed mutagenesis increased the immobilization efficiency (IE) and immobilization yield (IY). The immobilized mutant XylCg (N172K-H173K-S176K-K133A-K148A) exhibited an IY of 99.5% and IE of 135%, which were 1.8- and 4.3-fold higher than immobilized wildtype (WT). Regarding the catalytic properties, the kcat and kcat/Km values were 1850 s−1 and 2030 mL mg−1 s−1 for the immobilized mutant, and 331 s−1 and 404 mL mg−1 s−1 for the immobilized WT, respectively. Additionally, the immobilized mutant exhibited four times higher thermal stability than the immobilized WT at 60 °C. These results suggest that surface-mutated lysine residues confer good stability and orientation on the support matrix, thus improving the overall performance of xylanase.

Computational modelling approach for the optimization of apple juice clarification using immobilized pectinase and xylanase enzymes

Apple juice is typically marketed as a clear juice, and hence enzymatic treatments are common practices in juice industry. However, enzymatic treatments have been shown to face some challenges when process efficiency, and cost effectiveness are concerned. Therefore, it is necessary to optimize the enzymatic treatment process to maximize efficiency, and reuse enzymes to minimize the overall cost via immobilization. In this context, the present work features the immobilization of pectinase and xylanase from M. hiemalis on genipin-activated alginate beads, with subsequent evaluation of its efficacy in apple juice clarification. A central composite rotatable design (CCRD), coupled with artificial neural network (ANN) for modeling and optimization was used to design the experiments. Deploying a coupling time up to 120 min, and an agitation rate of 213 rpm (pectinase) - 250 rpm (xylanase), a maximum fractional enzyme activity recovered was observed to be about 81–83% for both enzymes. Optimum enzyme loading and genipin concentration were found to be 50 U/ml and 12% (w/v), respectively. The immobilized enzyme preparations were suitable for up to 5 repeated process cycles, losing about 45% (pectinase) - 49% (xylanase) of their initial activity during this time. The maximum clarity of apple juice (%T660, 84%) was achieved at 100 min when pectinase (50 U/ml of juice) and xylanase (20 U/ml of juice) were used in combination at 57 °C. The immobilized enzymes are of industrial relevance in terms of biocompatibility, recoverability, and operational-storage stability.

Xylanase immobilization onto trichlorotriazine-functionalized polyethylene glycol grafted magnetic nanoparticles: A thermostable and robust nanobiocatalyst for fruit juice clarification

The covalent immobilization of xylanase onto the trichlorotriazine-functionalized polyethylene glycol grafted magnetic nanoparticles was exploited to generate a stabilized xylanase with improved catalytic activity and stability. Several tools were deployed to monitor the synthesis and immobilization processes, the loading capacity of nanocarrier, and the structural/chemical characteristics of the nanobiocatalyst. The optimum immobilization yield of xylanase was 260 mg xylanase/g nanocarrier in 20 mM phosphate buffer, pH 6.5 at 25 °C. A forward shift in optimum pH (6.5 to 7.5) and temperature (60 to 70 °C) of xylanase was observed after immobilization and the performance of immobilized enzyme was improved at high temperatures and pHs as affirmed by enhancement of vmax (2.69 to 6.01 U/mL) and decreases of Ea (14.61 to 13.41 kJ/mol). An increase in Km from 25.51 to 40.42 mg/mL was recorded after immobilization. The obtained results indicated augmented thermal stability of the immobilized xylanase. Notably, it showed good reusability as validated by retention of 50% of its initial activity after nine recycles in enrichment of the pineapple juice clarification after 120 min incubation at 50 °C, pH 4.5. The structural analysis revealed some partial changes in the α-helix and β-sheet content of the enzyme after several recycles.

Hydroxyapatite nanoparticles modified with metal ions for xylanase immobilization

Hydroxyapatite (HA) nanoparticles are promising materials for enzyme immobilization, since they provide a high specific surface area for enzyme loading and can also be modified with metal ions (HA-Me2+) to enable interaction with proteins. The adsorption of proteins on HA-Me2+ has been explored for purification purposes, while the use of this material as a support for the immobilization of enzymes remains to be further investigated. Xylanase is an enzyme of considerable industrial interest, being used in the biofuel, pharmaceutical, pulp, and food & beverage sectors, among others. The immobilization of xylanase can enable recovery of the enzyme after biocatalysis, so that it can be reused several times, hence reducing the costs of industrial processes. Here, a systematic study was performed of the immobilization of xylanase on HA nanoparticles modified with metal ions (Cu2+ and Ni2+). A simple, fast, and efficient immobilization protocol was established using statistical experimental design as a tool, generating derivatives by interactions involving complexation of metals of the support with electron donor groups of the enzyme. The affinity towards xylanase was higher for the HA-Cu2+ support, compared to HA and HA-Ni2+. The pH and temperature profiles for the immobilized enzyme activity remained the same as for the soluble enzyme, indicating that the xylanase did not undergo major changes in its conformational state after immobilization. The HA-Cu2+ support was the most effective in reuse assays, retaining up to 80% activity in the second cycle. The results showed that xylanase could be immobilized on HA nanoparticles modified with Cu2+ and Ni2+ metal ions, using a simple and effective method, indicating the promising potential of the system for applications in different industrial processes.

Immobilization of xylanase on modified grafted alginate polyethyleneimine bead based on impact of sodium cation effect

Alginate- polyethyleneimine gel beads modified by using 0.3 M Na+ were used for covalent immobilization of Aspergillus flavus xylanase. SEM images showed distorted structure with addition of Na+ that impaired the egg-box structure formation offered much covalent binding with xylanase. Immobilization onto (Alg+PEI/Na+) showed an enhancement in the operational stability, immobilization efficiency as well as immobilization yield. Covalent immobilization of xylanase onto (Alg+PEI/Na+) enhanced xylanase activity over a wide range of pHs (4–5.5) comparable to its free formula. As well as an increase in reaction temperature up to 60°C. However, immobilized formula of enzyme showed abroad thermal stability that it retained 79.0% of its initial activity at 70°C up to 30 min whereas, free formula completely lost its activity at this temperature. Thermodynamics studies showed an enhancement in thermal stability at high temperature for the immobilized xylanase. i.e. At 70°C the t1/2 and D-value for free formula of enzyme increased from 24 to165 min and from 79.95to 548.23 min, respectively. Moreover, the enzyme stability enhancement for immobilized formula of xylanase was proved with a remarkable increase in enthalpy and free energy. 93% of the immobilized xylanase activity was retained over 6 weeks of storage at -4°C.