Reversible immobilization of glucoamylase onto magnetic chitosan nanocarriers

A simple preparation process for the monodispersed pH-sensitive core-shell magnetic microspheres was carried out consisting of chitosan self-assembled on magnetic iron oxide nanoparticles. Meanwhile, glucoamylase was immobilized as a model enzyme on this carrier of Fe₃O₄/CS microspheres by ionic adsorption. The morphology, inner structure, and high magnetic sensitivity of the resulting magnetic chitosan microspheres were studied, respectively, with a field emission scanning electron microscope (SEM), transmission electron microscope (TEM), FT-IR spectroscopy, thermogravimetric analysis (TGA), and a vibrating sample magnetometer (VSM). Subsequently, the properties of glucoamylase immobilized on the regenerated supports were also investigated by determining storage stability, pH stability, reusability, magnetic response, and regeneration of supports. The results from characterization and determination remarkably indicated that the immobilized glucoamylase obtained presents excellent storage stability, pH stability, reusability, magnetic response, and regeneration of supports. Therefore, this kind of magnetic Fe₃O₄/CS microspheres with perfect monodispersity should be an ideal support for enzyme immobilization.     

Reversible immobilization of glucoamylase onto magnetic carbon nanotubes functionalized with dendrimer

Magnetic carbon nanotubes (MCNTs) with necklace-like nanostructures was prepared via hydrothermal method, and hyperbranched poly(amidoamine) (PAMAM) was grafted on the surface of MCNTs on the basis of the Michael addition of methyl acrylate and the amidation of the resulting ester with a large excess of ethylenediamine (EDA), which could achieve generational growth under such uniform stepwise reactions. The terminal –NH₂ groups from the dendritic PAMAM were reacted with differently functionalized groups to form functionalized MCNTs. Subsequently, enzyme was immobilized on the functionalized MCNTs through adsorption, covalent bond, and metal-ion affinity interactions. The immobilization of glucoamylase, hereby chosen as model enzyme, onto the differently functionalized MCNTs is further demonstrated and assessed based on its activity, thermal stability, as well as reusability. Besides ease in recovery by magnetic separation, the immobilized glucoamylase on functionalized MCNTs offers superior stability and reusability, without compromising the substrate specificity of free glucoamylase. Furthermore, the results indicate that the metal-chelate dendrimer offers an efficient route to immobilize enzymes via metal-ion affinity interactions. The applicability of the regenerated supports in the current study is relevant for the conjugation of other enzymes beyond glucoamylase.     

Reversible immobilization of glucoamylase onto magnetic polystyrene beads with multifunctional groups

A novel and simple process for the surface functionalization of micron-sized monodisperse magnetic polystyrene (PS) microbeads was reported. The polystyrene seed particles were prepared prior to the dispersion polymerization method. Afterwards, series of surface chemical modifications on polystyrene microspheres were conducted, and three end-functional microspheres with carboxyl, imidazolyl and sulphydryl groups were obtained. The functional magnetic polystyrene microspheres were prepared by impregnation and subsequent precipitation of ferric and ferrous ions into the polystyrene particles. Finally, the functional magnetic polystyrene was used for the reversible immobilization of glucoamylase via metal-affinity adsorption. The results indicated that the obtained immobilized glucoamylase presented excellent reusability, applicability, magnetic response and regeneration of supports. The magnetic PS microspheres retained >65% of its initial activity at 65 °C over 6 h; and the lowest residual activity of immobilized glucoamylase prepared by regenerated supports still remained about 50% of the initial activity after the 10th cycles.     

产糖化酶黑曲霉固定化方法比较的研究

采用海藻酸钙凝胶电埋法、以沸石、多孔聚酯等材料为固定化载体的吸附法固定黑曲霉（Aspergillus niger AS3.4309)菌丝细胞,以游离菌丝体作为对照,进行发酵产糖化酶的比较,结果表明：以聚酯泡沫作为固定化载体吸附固定化菌丝细胞产糖化酶活力最高。在产糖化酶的发酵过程中,与游离菌丝体细胞相比,固定化黑曲霉持续产酶时间有一定程度的延长。     

A novel glucoamylase preparation for grain mash saccharification

Summary The capacity to saccharify barley grain mash of Hormoconis resinae glucoamylase P produced by a heterologous host, Trichoderma reesei, was compared with that of Aspergillus niger glucoamylase. The results showed that the glucoamylase P secreted by T. reesei produces more fermentable sugars from mash and thus makes a higher ethanol yield possible in fermentation.     

A novel matrix for the immobilization of acetylcholinesterase

In this study, a new matrix for immobilization of acetylcholinesterase was investigated by using alginate and kappa-carrageenan. The effects of pH, temperature, storage and thermal stability on the free and immobilized acetylcholinesterase activity were examined. Maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) was also investigated for free and immobilized enzymes. For free and immobilized enzymes into Ca-alginate and alginate/kappa-carrageenan polymer blends, optimum pH and temperature was found to be 7 and 30 degrees C, respectively. For free enzyme, maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) values were found to be 6.35 mM and 50 mM min(-1), respectively, the same values for immobilized enzymes were determined as 8.68, 12.7 mM and 39.7, 52.9 mM min(-1), respectively. Storage and thermal stability of acetylcholinesterase was increased by as a result of immobilization.     

Immobilization of glucoamylase on gelatin by transition-metal chelation

The potential applicability of glutaraldehyde-crosslinked-gelatin particles for the immobilization of enzymes by encapsulation has been extended by addition of surface-bound enzyme, leading ultimately to a method for the preparation of dual immobilized enzyme conjugates. Attachment of enzyme to the surface of the capsules was achieved by a transition-metal chelation process in which the incoming enzyme becomes a ligand. Glucoamylase was so immobilized, using titanium-urea, -acrylamide, -citric acid, and -lactose complexes or titanium (IV) chloride as means of introducing the titanium chelating centre. The retentions of enzyme activity for both the surface-bound and pre-encapsulated enzymes were functions of the chelating complex chosen. Differences were observed between the action patterns of the two forms of immobilized enzyme. These action patterns and the production of reversion products are discussed in the light of application of gelatin-immobilized glucoamylase to the production of high-DE glucose syrups.     

A new route for chitosan immobilization onto polyethylene surface

Low-density polyethylene (LDPE) belongs to commodity polymer materials applied in biomedical applications due to its favorable mechanical and chemical properties. The main disadvantage of LDPE in biomedical applications is low resistance to bacterial infections. An antibacterial modification of LDPE appears to be a solution to this problem. In this paper, the chitosan and chitosan/pectin multilayer was immobilized via polyacrylic acid (PAA) brushes grafted on the LDPE surface. The grafting was initiated by a low-temperature plasma treatment of the LDPE surface. Surface and adhesive properties of the samples prepared were investigated by surface analysis techniques. An antibacterial effect was confirmed by inhibition zone measurements of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The chitosan treatment of LDPE led to the highest and most clear inhibition zones (35mm(2) for E. coli and 275mm(2) for S. aureus).     

A novel method for immobilization of invertase from the thermophilic fungus, Thermomyces lanuginosus

An invertase from the thermophilic fungus, Thermomyces lanuginosus was immobilized on phenyl-Sepharose and its properties were studied. Between the soluble and immobilized forms of the invertase, there were not much difference in their optimum pH, K _M and V _max for sucrose. In contrast, the K _M and V _max for raffinose changed significantly. The optimum temperature for the immobilized invertase was lower by 10 C. The immobilized invertase showed remarkable stability at 50 C and was less sensitive to inhibition by metal ions. There was no leaching of the enzyme for at least a month when stored in the refrigerator. The method is novel and specific for the thermophilic invertase as a mesophilic invertase (from yeast) did not bind to phenyl-Sepharose.     

Evaluation of man-tailored cellulose-based carriers in glucoamylase immobilization

Covalent immobilization of glucoamylase on the cellulose-based carrier Granocel was optimized by changing the anchor groups and the methods of activation/immobilization. Binding of the enzyme was via its primary amino groups. It was shown that using carbodiimide and divinyl sulfone for the activation of -COOH and -OH groups on the carrier resulted in the preparations with very low activity. A third method, using pentaethylenehexamine with glutaraldehyde, led to the attachment through a long spacer arm and to the preparations with the highest activity. Further optimization of the carrier's structure consisted of changing pore diameters and amount of functional groups on the carrier surface. The highest activity of bound glucoamylase was obtained by linking the protein via glutaraldehyde on NH(2)-Granocel having high pore size and high number of functional groups. The immobilized enzyme was stable throughout extended storage and possessed higher thermal stability.     

A novel glucose biosensor based on the immobilization of glucose oxidase onto gold nanoparticles-modified Pb nanowires

A novel glucose biosensor was developed, based on the immobilization of glucose oxidase (GOD) with cross-linking in the matrix of bovine serum albumin (BSA) on a Pt electrode, which was modified with gold nanoparticles decorated Pb nanowires (GNPs-Pb NWs). Pb nanowires (Pb NWs) were synthesized by an l-cysteine-assisted self-assembly route, and then gold nanoparticles (GNPs) were attached onto the nanowire surface through –SH–Au specific interaction. The morphological characterization of GNPs-Pb NWs was examined by transmission electron microscopy (TEM). Cyclic voltammetry and chronoamperometry were used to study and to optimize the electrochemical performance of the resulting biosensor. The synergistic effect of Pb NWs and GNPs made the biosensor exhibit excellent electrocatalytic activity and good response performance to glucose. The effects of pH and applied potential on the amperometric response of the biosensor have been systemically studied. In pH 7.0, the biosensor showed the sensitivity of 135.5 μA mM⁻¹ cm⁻², the detection limit of 2 μM (S/N = 3), and the response time <5 s with a linear range of 5–2200 μM. Furthermore, the biosensor exhibits good reproducibility, long-term stability and relative good anti-interference.     

Covalent immobilization of triacylglycerol lipase onto functionalized novel mesoporous silica supports

A novel mesoporous silica material was synthesized via a silicate salt route in the presence of polyvinyl alcohol as the structure-directing agent under acidic conditions. The material was functionalized and employed as the supports (LPS-1 and LPS-2) for immobilizing triacylglycerol lipase from porcine pancreas (PPL). Not only they had a good thermal stability and reusability but also the activity recovery of LPS-1 and LPS-2 reached to 69% and 76%, respectively. The optimal pH and temperature region of the LPS supports immobilized PPL for hydrolysis of olive oil were at 8.0 and 55-60 degrees C. Kinetic parameters such as maximum velocity (V(max)) and the Michaelis constant (K(m)) were determined for the free and the immobilized lipase and LPS-2 immobilized PPL had the highest catalytic efficiency in the three. Meanwhile, the LPS supports exhibited many advantages than small porous materials for immobilizing PPL.     

Keratin and polyamide-coated inorganic matrices as supports for glucoamylase immobilization

Previously solubilized feather keratin and polyamide were used for coating sand, glass beads and silica gel. These new seven supports were employed for comparative studies on pure glucoamylase / EC 3.2.1.3 / immobilization. The immobilization yield of glucoamylase on keratin and polyamide coated supports was comparable with conventional matrices used earlier. The highest activity per 1 g of support was shown by the enzyme bound to polyamide-coated CPG, and the bests operational stability by the enzyme immobilized on polyamide-coated CPG with keratin subsequently deposited on it.     

Development of a novel immobilization method for enzymes from hyperthermophiles

Peptide tags containing tyrosines (Y-tag) were introduced at the C-terminus of a hyperthermophilic enzyme, alkaline phosphatase from Pyrococcus furiosus (PfuAP). Immobilization of the recombinant PfuAPs onto water-in-oil-in-water (W/O/W) type microcapsules was performed by an in situ polymerization method. All the recombinant PfuAPs prepared in this study were quantitatively immobilized onto microcapsules. The PfuAP-immobilized microcapsules showed no significant loss of enzymatic activity until the 5th round of assays. This result implies that the recombinant PfuAPs were covalently immobilized onto microcapsules. Immobilized PfuAP tagged with a Y-tag having the sequence GGYYY exhibited approximately a twofold higher catalytic activity compared with the wild-type PfuAP. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Covalent immobilization of a glucoamylase to bagasse dialdehyde cellulose

Cellulose fibres from bagasse were oxidized by sodium periodate in sulphuric acid media at positions 2 and 3 of the anhydroglucose unit to produce dialdehyde cellulose. The aldehyde groups of the dialdehyde cellulose were able to react with amino groups of a glucoamylase to form covalent bonds and result in a dialdehyde cellulose immobilized enzyme. The optimum pH of this immobilized enzyme and free enzyme were in the range of 3.0–5.0 and 3.5–5.0, respectively. The optimum temperature for both the free and immobilized enzymes was 60–65 °C. The relative remaining activity of the immobilized enzyme was 36% and its stability was very good, since it could be reused for over 30 cycles. Its activity decreased from the first to the seventh reuse cycles, due to the slow detachment of non-covalently bound enzyme. However, activity tended to stabilize after the seventh cycle of reuse, indicating very stable covalent binding between the enzyme and dialdehyde cellulose.     

A novel hydrogen peroxide biosensor based on the immobilization of horseradish peroxidase onto Au-modified titanium dioxide nanotube arrays

In this study, we report on a promising H(2)O(2) biosensor based on the co-immobilization of horseradish peroxidase (HRP) and chitosan onto Au-modified TiO(2) nanotube arrays. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; a gold thin film was then uniformly coated onto the TiO(2) nanotube arrays by an argon plasma technique. The morphology and composition of the fabricated Au-modified TiO(2) nanotube arrays were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry and chronoamperometry were used to study and to optimize the performance of the resulting electrochemical biosensor. The effect of pH, applied electrode potential, the presence of the electron-mediator methylene blue, and the anodic oxidation time of the Ti substrate on the electrochemical biosensor has been systemically studied. Our electrochemical measurements show that the Au-modified TiO(2) nanotube arrays provide excellent matrices for the immobilization of HRP and that the optimized electrochemical biosensor exhibits long linearity, a low detection limit, high stability and very good reproducibility for the detection of H(2)O(2). Under the optimized conditions the linearity of the developed biosensor for the detection of H(2)O(2) is observed from 5 x 10(-6) to 4 x 10(-4) moll(-1) with a detection limit of 2 x 10(-6) moll(-1) (based on the S/N=3).     

A new method for immobilization of acetylcholinesterase

A new method for immobilization of acetylcholinesterase (AChE) to alginate gel beads by activating the carbonyl groups of alginate using carbodiimide coupling agent has been successfully developed. Maximum reaction rate (V _max) and Michaelis–Menten constant (K _m) were determined for the free and binary immobilized enzyme. The effects of pH, temperature, storage stability, reuse number and thermal stability on the free and immobilized AChE were also investigated. For the free and binary immobilized enzyme on the Ca–alginate gel beads, optimum pH values were found to be 7 and 8, respectively. Optimum temperatures for the free and immobilized enzyme were observed to be 30 and 35 °C, respectively. Upon 60 days of storage the preserved activity of free and immobilized enzyme were found as 4 and 68%, respectively. In addition, reuse number, and thermal stability of the free AChE were increased by as a result of binary immobilization.