Glucose oxidase immobilized polyethylene-g-acrylic acid membrane for glucose oxidase sensor

A polyethylene-g-acrylic acid (PE-g-AA) graft copolymer was prepared via gamma-ray-irradiation-induced postirradiation procedures, and was used as support material for the immobilization of glucose oxidase. Soluble carbodiimides were used as the coupling agent. Reasonable yields were obtained with CMC but not with EDAC, EEDQ, or WRK. A number of factors were studied. (1) The use of water-soluble carbodiimides as condensing agent was attempted and the optimum condition for coupling glucose oxidase to PE-g-AA was established; (2) the effect of pH and temperature on the reactivity of native and immobilized glucose oxidase was studied. When exposed to temperatures in excess of 60 degrees C, the immobilized glucose oxidase was less sensitive to thermal inactivation than the native enzyme. The optimum pH value for the performance of the enzyme-immobilized membrane was 5. 6. For 200 tests, the response error of glucose sensor was less than 4% and its linear detected range was 0-1000 ppm. The obtained glucose oxidase-immobilized PE-g-AA membranes were kept in pH 5. 6 acetate buffer solution at 4 degrees C. The glucose oxidase activity of the membrane was determined at sevenday intervals. The membranes still have 92% glucose oxidase activity even after eight weeks of storage.     

Glucose oxidase immobilized electrode for potentiometric estimation of glucose

Glucose oxidase has been immobilized onto a thin platinum strip, by co-crosslinking with bovine serum albumin and glutaraldehyde. The retention of redox characteristics of glucose oxidase has been verified by cyclic voltammetry. The activity of the immobilized enzyme reduces to a quarter of its value when the enzyme is in solution but improves when coimmobilized with 1 urea. The potentiometric response builds up and remains stable after 100 s. It is sensitive to the thickness of the immobilizing matrix, pH and temperature. An improvement in the performance of the electrode has been achieved by coimmobilizing 2 urea and metal ions such as Mg²⁺ and Mn²⁺. The presence of Cu has been proved to be detrimental. The electrode has been calibrated in the 0.1–5.0 mM glucose concentration range. It gives a stable response for more than 50 independent assays and can be stored for 60 days without significant loss of function.     

Glucose oxidase biosynthesis using immobilized mycelium of Aspergillus niger

A simple method is described for the immobilization of Aspergillus niger GIV-10 which produces an extracellular glucose oxidase. A. niger conidia were immobilized on sintered glass Raschig rings, pumice stones or polyurethane foam. Mycella growing out from the spores produced extracellular glucose oxidase: the highest production was with the pumice stone carrlers. This technique facilitates the growth of the filamentous cultures in the spongy structure of a support with continuous accumulation of biomass. After 24 to 36 h, a culture liquid with 2.7 to 3.1 U of glucose oxidase/ml was obtained. This procedure also made possible repeated batch enzyme production and as many as 25 subsequent 24-h batches could be fermented by using the same carrier with only a small loss of glucose oxidase activity.The authors are with the Institute of Microbiology, M. Curie-Sklodowska University, Akademicka 19, 20-003 Lublin, Poland.     

Glucose oxidase enzyme immobilized porous silica for improved performance of a glucose biosensor

High activity of glucose oxidase (GOD) enzyme (immobilized in porous silica particles) is desirable for a better glucose biosensor. In this work, effect of pore diameter of two porous hosts on enzyme immobilization, activity and glucose sensing was compared. The hosts were amine functionalized: (i) microporous silica (NH₂-MS) and (ii) mesoporous silica (NH₂-SBA-15). Based on whether the dimension of GOD is either larger or smaller than the pore diameter, GOD was immobilized on either external or internal surface of NH₂-MS and NH₂-SBA-15, with loadings of 512.5 and 634 mg/g, respectively. However, GOD in NH₂-SBA-15 gave a higher normalized absolute activity (NAA), which led to an amperometric sensor with a larger linear range of 0.4–13.0 mM glucose. In comparison, GOD in NH₂-MS had a lower NAA and a smaller linear range of 0.4–3.1 mM. In fact, the present GOD-NH₂-SBA-15 electrode based sensor was better than other MS and SBA-15 based electrodes reported in literature. Thus, achieving only a high GOD loading (as in NH₂-MS) does not necessarily give a good sensor performance. Instead, a host with a relatively larger pore than enzyme, together with optimized electrode composition ensures the sensor to be functional in both hyper- and hypoglycemic range.     

Glucose biosensor based on glucose oxidase immobilized at gold nanoparticles decorated graphene-carbon nanotubes

Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV–vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of −0.40 V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5 × 10⁻¹⁰ mol cm⁻² and 3.36 s⁻¹, respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10 μM – 2 mM with LOD of 4.1 μM, (2) 2 mM – 5.2 mM with LOD of 0.95 mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible.     

Glucose oxidase and catalase activities ofPenicillium variabile P16 immobilized in polyurethane sponge

Conidia ofPenicillium variabile P16 were immobilized in polyurethane sponge and used in repeated-batch processes in a fluidized-bed reactor. Optimal conditions for production of glucose oxidase and catalase were: inoculum size, 10%; glucose concentration, 80 g L^–1; Ca-carbonate concentration, 15 g L^–1; temperature, 28°C and aeration rate, 4 VV^–1 min^–1. In an extended repeated-batch process, glucose oxidase activity was highest after the fourth batch and catalase activity was highest after the fifth batch. Scanning electron microscopy showed that the fungus grew only in the interior of carrier particles.     

Glucose oxidase synthesis by Aspergillus niger GIV-10 on starch.

The effect of various kinds of starch, as the sole source of organic carbon, on the biosynthesis of glucose oxidase by A. niger GIV-10 was examined. A. niger grown on 6% wheat starch medium provided extracellular and intracellular glucose oxidase with the highest enzymatic activities. A new method of intracellular glucose oxidase extraction (without disruption of mycelium), developed and discussed in this paper, increased 2 to 3.8-times glucose oxidase yield, as compared to that described earlier.     

Glucose oxidase,catalase and gluconic acid production by immobilized mycelium of Penicillum variabile P16

Conidia of Penicillium variabile P16 producing glucose oxidase were immobilized in different carriers and used in repeated-batch processes. Limited free-cell growth and good mechanical stability of the carriers were obtained with Ca-alginale, agar and polyurethane sponge. During prolonged experiments, the polyurethane sponge appeared to be the best carrier in relation to glucose oxidase and catalase activities. The maximum mean volumetric productivity of gluconate was obtained using agar as immobilizing agent.     

Glucose oxidase immobilization on a novel cellulose acetate-polymethylmethacrylate membrane

Glucose oxidase (GOD) was immobilized on cellulose acetate-polymethylmethacrylate (CA-PMMA) membrane. The immobilized GOD showed better performance as compared to the free enzyme in terms of thermal stability retaining 46% of the original activity at 70 degrees C where the original activity corresponded to that obtained at 20 degrees C. FT-IR and SEM were employed to study the membrane morphology and structure after treatment at 70 degrees C. The pH profile of the immobilized and the free enzyme was found to be similar. A 2.4-fold increase in Km value was observed after immobilization whereas Vmax value was lower for the immobilized GOD. Immobilized glucose oxidase showed improved operational stability by maintaining 33% of the initial activity after 35 cycles of repeated use and was found to retain 94% of activity after 1 month storage period. Improved resistance against urea denaturation was achieved and the immobilized glucose oxidase retained 50% of the activity without urea in the presence of 5M urea whereas free enzyme retained only 8% activity.     

Studies on the stability of immobilized xanthine oxidase and urate oxidase.

The stability of immobilized preparations of xanthine oxidase and urate oxidase was studied, and optimized, because of the potential joint use of both enzymes in clinical analysis. Xanthine oxidase was immobilized on cellulose, Sepharose, hornblende, Enzacryl-TIO, and porous glass. Thehalf-lives of these preparations at 30 degree C ranged from 40 min to 5.0 hr. In this respect immobilized enzyme resembled soluble enzyme in dilute solution (0.11 mg/ml), when the half-live was about 3.5 hr. More concentrated enzyme solution (1 mg/ml) had a half-life of 64 hr, and was, therefore, considerably more stable than the untreated immobilized xanthine oxidase preparations. Inclusion of albumen in storage and assay buffer increased the half-life of bound xanthine oxidase. So also did treatment with glutaraldehyde: in the case of xanthine oxidase bound to Enzarcyl-TIO such treatment increased the half-life at 30 degree C from 3 hr to about 100 hr. Immobilized xanthine dehydrogenase was more stable than immobilized xanthine oxidase: the dehydrogenase lost no activity during continuous assay for 5 hr at 30 degree C. The stability of immobilized urate oxidase depended on the quantity of enzyme used and on the time of stirring during immobilization: thus a preparation was made (by stirring urate oxidase (48 mg/g support) with Enzacryl-TIO for 24 hr) which lost no activity during 350 hr at 30 degree C.     

Characterization of glucose oxidase immobilized on collagen

Summary The enzyme glucose oxidase (E.C. 1.1.3.4) was immobilized on collagen — a proteinaceous material found in biological systems as a structural material for a wide variety of cells and membranes. The novel technique of electrocodeposition, which utilizes the principles of electrophoresis, was used to deposit the enzyme-collagen complex on stainless steel helical supports. This technique has been developed in our laboratory. The mechanism of complex formation between collagen and enzyme involves multiple salt linkages, hydrogen bonds and van der Waals interactions.As a first step toward examining its feasible technical use, the kinetic behavior of the collagen-supported glucose oxidase was studied in a batch recycle type reactor and was compared with that for the soluble form. A novel reactor configuration consisting of multiple concentric electrocodeposited helical coils was used. The reactor was found to attain a stable level of activity which was maintained for several months under cyclic testing. The optimum levels of pH and temperature for the immobilized form of the enzyme were the same as those of the soluble enzyme, but the immobilized enzyme was more active than the soluble form at higher temperatures and pH. The values of the Michaelis-Menten parameters indicate that the overall reaction rate of the immobilized enzyme may be partially restricted by bulk and matrix diffusion.     

Various applications of immobilized glucose oxidase and polyphenol oxidase in a conducting polymer matrix

In this study, glucose oxidase and polyphenol oxidase were immobilized in conducting polymer matrices; polypyrrole and poly(N-(4-(3-thienyl methylene)-oxycarbonyl phenyl) maleimide-co-pyrrole) via electrochemical method. Fourier transform infrared and scanning electron microscope were employed to characterize the copolymer of (N-(4-(3-thienyl methylene)-oxycarbonyl phenyl) maleimide) with pyrrole. Kinetic parameters, maximum reaction rate and Michealis-Menten constant, were determined. Effects of temperature and pH were examined for immobilized enzymes. Also, storage and operational stabilities of enzyme electrodes were investigated. Glucose and polyphenol oxidase enzyme electrodes were used for determination of the glucose amount in orange juices and human serum and phenolic amount in red wines, respectively.     

Preparation and properties of immobilized methanol oxidase

Methanol oxidase produced by the yeast Hansenula polymorpha DL-1 was used for the enzymatic oxidation of methanol to formaldehyde. The kinetics of enzyme and protein release during cell desruption were studied at the laboratory scale with a Braun homogenizer and the pilot plant scale with a Manton–Gaulin homogenizer. Conditions were defined for maximum release and retention of high activity in cell-free extracts. Methanol oxidase was immobilized by adsorption on DEAE-cellulose from enzymes in cell-free extracts or from ammonium sulfate purified purified fractions. The kinetics of formaldehyde formation with both soluble and immobilized enzyme was studied in batch and continuous reactors.     

Electroreduction of oxygen by cytochrome C oxidase immobilized in electrode-supported lipid bilayer membranes

Cytochrome c oxidase is the terminal enzyme in mammalian respiration, and one of its main functions is to catalyze the reduction of oxygen under physiological conditions. Direct reduction of oxygen at electrodes requires application of substantial overpotentials. In this work, bovine cytochrome c oxidase has been immobilized in electrode-supported lipid bilayer membranes to investigate the electroreduction of oxygen under flow conditions. The effect that temperature, solution pH, and solution composition have on the reduction of oxygen by this novel enzyme-modified electrode is reported. Results indicate that the electroreduction of oxygen is most pronounced at low pH (6.4) and elevated temperature (38 degrees). At an applied potential of -350 mV vs. Ag/AgCl (1M KCl), a current density of ca. 7 microA/cm2 was obtained. The current responses obtained at these electrodes are stable over a period of ca. 10-14 days (10-15% decrease in response). The cytochrome c oxidase-modified electrodes described here could potentially be used for the direct electroreduction of oxygen to water in a biofuel cell.     

Characterization of rifamycin oxidase immobilized on nylon fibers

Summary Rifamycin oxidase, an enzyme used in the biotransformation of rifamycin B to S was immobilized on nylon fibers using glutaraldehyde as the cross linking agent. An activity of 18 U/g of nylon fiber with a binding efficiency of 37% was achieved. The immobilized enzyme showed an operational stability of 7 days and was also protected against thermal inactivation. It exhibited a K_m(app.) of 2.0mM.     

Identification of novel chondroitin proteoglycans in Caenorhabditis elegans: embryonic cell division depends on CPG-1 and CPG-2

Vertebrates produce multiple chondroitin sulfate proteoglycans that play important roles in development and tissue mechanics. In the nematode Caenorhabditis elegans, the chondroitin chains lack sulfate but nevertheless play essential roles in embryonic development and vulval morphogenesis. However, assignment of these functions to specific proteoglycans has been limited by the lack of identified core proteins. We used a combination of biochemical purification, Western blotting, and mass spectrometry to identify nine C. elegans chondroitin proteoglycan core proteins, none of which have homologues in vertebrates or other invertebrates such as Drosophila melanogaster or Hydra vulgaris. CPG-1/CEJ-1 and CPG-2 are expressed during embryonic development and bind chitin, suggesting a structural role in the egg. RNA interference (RNAi) depletion of individual CPGs had no effect on embryonic viability, but simultaneous depletion of CPG-1/CEJ-1 and CPG-2 resulted in multinucleated single-cell embryos. This embryonic lethality phenocopies RNAi depletion of the SQV-5 chondroitin synthase, suggesting that chondroitin chains on these two proteoglycans are required for cytokinesis.     

昆虫葡萄糖氧化酶及其功能

葡萄糖氧化酶(glucose oxidase,GOX)广泛分布于动物、植物及微生物体内,特别是真菌中。与真菌的GOX相比,有关昆虫GOX特性和功能的研究很有限,但近期发现其在昆虫与植物相互关系中起着非常重要的作用。通过与真菌GOX比较,文章主要综述GOX的性质、分布以及昆虫中GOX生理功能、作用和演化,并进一步讨论其研究进展。     

Activity and stability comparison of immobilized NADH oxidase on multi-walled carbon nanotubes,carbon nanospheres,and single-walled carbon nanotubes

Nanomaterials have been studied widely as the supporting materials for enzyme immobilization because in theory, they can provide low diffusion resistance and high surface/volume ratio. Common immobilization methods, such as physical adsorption, covalent binding, crosslinking, and encapsulation, often cause problems in enzyme leaching, 3D structure change and strong mass transfer resistance. We have previously demonstrated a site-specific enzyme immobilization method, which is based on the specific interaction between a His-tagged enzyme and functionalized single-walled carbon nanotubes (SWCNTs), that can overcome the foresaid constraints. In this work, we broadened the use of this immobilization approach by applying it on other nanomaterials, including multi-walled carbon nanotubes and carbon nanospheres. Both supporting materials were modified with N_α,N_α-bis(carboxymethyl)-l-lysine hydrate prior to enzyme immobilization. The resulting nanomaterial–enzyme conjugates could maintain 78–87% of the native enzyme activity and showed significantly better stability than the free enzyme. When compared with the SWCNT–enzyme conjugate, we found that the size variance among these supporting nanomaterials may affect factors such as surface curvature, surface coverage and particle mobility, which in turn results in differences in the activity and stability among these immobilized biocatalysts.     

Glucose transporter 10 and arterial tortuosity syndrome: The vitamin C connection

Arterial Tortuosity Syndrome (ATS) is a heritable disease characterized by twisting and lengthening of the major arteries, hypermobility of the joints, and laxity of skin. ATS is caused by mutations in SLC2A10, encoding Glucose Transporter 10 (GLUT10). The current model of ATS holds that loss of GLUT10 at the nuclear periphery induces a glucose-dependent increase in Transforming Growth Factor-β (TGFβ) that stimulates vessel wall cell proliferation. Instead, we propose that GLUT10 transports ascorbate, a cofactor for collagen and elastin hydroxylases, into the secretory pathway. In ATS, loss of GLUT10 results in defective collagen and/or elastin. TGFβ activation represents a secondary response to a defective extracellular matrix.