Showing papers on "Immobilized enzyme published in 1988"

Immobilized enzyme electrodes

Abstract: Enzyme electrodes are disclosed which are capable of responding amperometrically to the catalytic activity of the enzyme in the presence of its respective substrate and comprising the enzyme immobilized or adsorbed onto the surface of an electrically conductive support member which consists of or comprises a porous layer of resin-bonded carbon or graphite particles, said particles having intimately mixed therewith, or deposited or adsorbed onto the surface of the individual particles prior to bonding to form said layer, a finely divided platinum group metal, thereby to form a porous, substrate layer onto which said enzyme is adsorbed or immobilized and comprising a substantially heterogeneous layer of resin-bonded carbon or graphite particles, with said platinum group metal dispersed substantially uniformly throughout said layer. The preferred substrate materials are resin bonded platinized carbon paper electrodes comprising platinized carbon powder particles having colloidal platinum adsorbed on the surface of the particles and bonded onto a carbon paper substrate using a synthetic resin, preferably polytetrafluoroethylene, as the binder. The preferred enzyme electrodes are glucose oxidase electrodes comprising glucose oxidase adsorbed or immobilized onto the surface of the substrate.

Characteristics of an immobilized lipase for the commercial synthesis of esters

Abstract: The lipase-catalyzed synthesis of ester bonds has been well-documented lately and is of much current commercial interest. Immobilization of a fungal lipase on a unique macroporous support allows not only the ability to operate in non-aqueous media but to catalyze ester synthesis in quantitative yields, employing attractive commercial conditions. Catalyst dose and process configurations will be illustrated. The capability of the catalyst to operate efficiently in reverse under a variety of unnatural, hostile, solvent-containing environments will be discussed. The range of substrates for this immobilized lipase, Lipzome, has been investigated. The enzyme will catalyze ester synthesis with saturated, unsaturated and a variety of branched carboxylic acids. The alcohol specificity for this enzyme also is equally broad. A wide variety of straight-chain, branched and polar alcohols can be substrates. In addition, some examples of alcohol specificity for kinetic isomer resolution will be cited.

Covalent enzyme coupling on cellulose acetate membranes for glucose sensor development.

Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Covalent enzyme coupling on cellulose acetate membranes for glucose sensor development Robert Sternberg, Dilbir S. Bindra, George S. Wilson, Daniel R. Thévenot

Lipase immobilized on a hydrophobic, microporous support for the hydrolysis of fats

Abstract: Enzymatic hydrolysis of triglycerides has been studied as a low energy-consuming alternative to the present steam (Colgate-Emery) process. Cost analysis of the enzymatic process indicates that use of immobilized lipase compares favorably with the present steam process. This paper discusses the search for an adsorbent to use as the support material for the lipase. Hydrophobic microporous powders, membranes and fibers were found to give the best performance, as little of the lipase’s activity was lost upon immobilization. Lipase immobilized on Accurel powder has been studied in various reactor configurations for the hydrolysis of triglycerides. Reactor designs studied include cocurrent and counter-current fixed beds, continuous stirred tank reactors, and the diaphragm reactor. Productivities of the latter two reactor types were 1100 and 1700 kg fatty acid per kg immobilized lipase.

Electrochemical cncentration detector method

Abstract: Electrochemical biosensor systems or apparatus, components thereof, and methods for quantitatively measuring or assaying concentrations of selective substrates or metabolites in aqueous media as a function of electrochemical response to hydrogen peroxide concentration, using immobilized enzyme electrode means selective for the substrate or metabolite being measured.

A new conducting polymer-coated glucose sensor

Abstract: A sensor for glucose formed in a one-step process is described based on a new doped polyindole film coated onto a platinum surface; a polymer-entrapped glucose oxidase electrode can be operated as an amperometric glucose sensor. The new glucose sensor has fast response time (25–40 s) with high storage and operational stability ( > 35 days). Electrochemical rate constants for the new enzyme electrode have been calculated using the expressions derived by Albery et al.(J. Chem. Soc., Faraday Trans. 1, 1986, 82, 1033). It has been found that unsaturated enzyme kinetics are rate-limiting for conducting polymer-coated enzyme electrodes formed in a one-step process.

Effect of temperature cycling on the activity and productivity of immobilized beta-galactosidase in a thermally reversible hydrogel bead reactor.

Abstract: The enzyme β-galactosidase has been immobilized within thermally reversible hydrogel beads that exhibit LCST (lower critical solution temperature) behavior. The hydrogel beads containing the immobilized enzymes swell and expand below the LCST and deswell and shrink above the LCST. This behavior is reversible. The enzyme was physically entrapped in a crosslinked hydrogel of a copolymer of N-isopropylacrylamide (NIPAAm) and acrylamide (AAm), and formed as beads in an inverse suspension polymerization. The beads were placed in a packed bed column reactor which was operated in a continuous, single pass mode, either isothermally at 30 or 35°C, or with temperature cycling between 30 and 35°C. The thermal cycling significantly enhanced overall reactor enzyme activity relative to isothermal operation at either the higher or lower temperature. It is postulated that mass transfer rates within the hydrogel beads are greatly enhanced by the movement of water in and out of the beads during the expansion or collapse of the polymer chain network as temperature is cycled.

Optical sensors. Part 34. Fibre optic glucose biosensor with an oxygen optrode as the transducer

Abstract: A biosensor for the continuous determination of glucose is presented Glucose oxidase was immobilised covalently on a nylon membrane and the consumption of oxygen was measured by following, via fibre optic bundles, the changes in the fluorescence of an oxygen-sensitive dye whose fluorescence is quenched dynamically by molecular oxygen The dye is dissolved in a very thin silicone membrane placed beneath the enzyme layer As a result of the oxidation by the enzyme a certain amount of oxygen is consumed This amount is indicated by the fluorescent dye The measurements were performed in flowing air-saturated solutions containing 01 M pH 70 phosphate buffer The effects of the amount of immobilised enzyme and the thickness of the indicator layer on response times (t90= 1–6 min), analytical ranges (01–20 mM) and relative signal changes (up to 26%) were investigated

Process considerations of continuous fat modification with an immobilized lipase

Abstract: Lipases will catalyze the incorporation of new fatty acids into the triglyceride component of a fat (acidolysis) or can rearrange/redistribute the existing fatty acid radicals in the fat’s triglycerides (transesterification). Both processes can dramatically change the physical characteristics of the fat. Immobilization of the lipase allows for the use of the catalyst in a continuous column operation. Examples illustrating the commercial utility of such immobilized enzymes are presented. Process configurations, scale-up issues and catalyst lifetime/productivity are discussed.

Simultaneous immobilization of glucose oxidase and a mediator in conducting polymer films

Abstract: Simultaneous immobilization of glucose oxidase and ferrocenecarboxylate as an electron relay in polypyrrole films was successfully accomplished to provide a simple biosensor capable of detecting glucose rapidly in a wide concentration range without use of any mediator in solution.

Improvement in stability of an immobilized fungal laccase

Abstract: A laccase of the basidiomyceteTrametes versicolor was immobilized on porous glass beads that were activated with 3-aminopropyltriethoxysilane and glutaraldehyde. The support immobilized 100% of the enzyme, whereupon 90% of the original activity was retained. After immobilization, the enzyme was active in a wider pH and temperature range, and its heat stability and reuse were greatly improved compared to those of the free laccase. The immobilized enzyme was found reusable in treating different substrates, either recycled alone or in a sequential order.

Studies on Free and Immobilized Lipases from Mucor miehei

Abstract: An extracellular lipase produced by fermentation with a selected strain ofMucor miehei has been purified partially in two forms: A and B. The forms have a high degree of antigenic identity and have similar pH-activity profiles with tributyroylglycerol as the substrate with optima at pH 7. The differences are A, in contrast to B, requires activation at alkaline pH before analysis; A binds with concanavalin A more completely than B, the net charges are slightly different at pH 8; the isoelectric points are different. Our results indicate that the B lipase is formed by partial deglycosylation of the A lipase and that this influences the activity toward emulsions. The two enzymes have been immobilized by adsorption. These preparations and the soluble forms were highly specific for primary ester of triacylglycerols (TG), usually hydrolyzed TG of 12:0, 14:0, 16:0 and 18:1 more rapidly than those of 4:0, 6:0, 8:0 and 10:0 in mixtures of monoacid TG (4:0 to 18:1), and were not stereospecific for TG. Immobilization altered the specificity of the preparations somewhat in that slightly more 14:0 and 16:0 were released.

[53] Enzyme stabilization by immobilization

Abstract: Publisher Summary This chapter introduces several techniques for biocatalyst immobilization that include inclusion, adsorption, cross-linking, or covalent grafting. One of the key parameters with regard to the feasibility of a biotechnological process is the combination of efficiency and stability of the biocatalyst used. Immobilization very often results in a greatly increased resistance to various denaturation factors: extreme pH and temperature values, high ionic strength, denaturating reagents, and proteases. Another approach to stabilization is to modify the biocatalyst microenvironment by the use of additives, such as salts, polyols, sugars, and various polymers. It has thus been possible to obtain enzyme preparations with a highly increased resistance to denaturation factors, for example, certain protease preparations used in the manufacture of detergents. The chapter discusses the possibilities of biocatalyst stabilization, on the one hand by immobilization and on the other hand by immobilization plus additives, with the help of a few significant examples. Direct comparison of the operational stability—that is, in the presence of a continuous supply of substrate—of an immobilized enzyme with that of a free enzyme is possible in the ultrafiltration reactor.

Luminescence Fiber-Optic Biosensor

Abstract: A novel type of biosensors involving immobilized bioluminescence enzymes and a fiber-optic probe has been developed. The enzymes were immobilized on preactivated Nylon membranes placed in close contact with the tip of a bundle of optical glass fibers. The fiber-optic sensor was immersed in a stirred and thermostated cell protected from ambient light by a PVC jacket. The light emitted by the luminescence reactions was conducted through the fiber bundle to the photomultiplier tube of a luminometer. With immobilized firefly luciferase from Photinus pyralis, light emission could be linearly related to ATP concentration in the range 2.8 × 10−10 − 1.4 × 10−6 M. When co-immobilizing bacterial luciferase and oxidoreductase from Vibrio fischeri, NADH measurements could be performed from 3 × 10−10 M to 3 × 10−6 M. The luminol chemiluminescence reaction catalyzed by immobilized horseradish peroxidase has also been used for hydrogen peroxide determination. The standard curve was linear from 2 × 10−8 M to 2 ×...

Analytical uses of immobilized biological compounds for detection, medical, and industrial uses

Abstract: A. Immobilization Techniques - General.- Enzymes Immobilized on Inorganic Supports.- Immobilization of Bioagents by Radiation.- Structural and Transport Properties of Polymeric Carriers for Bioagents and Immobilization Techniques and Their Applications.- B. Clinical and Pharmaceutical Applications.- Immobilized Enzymes in Therapy.- Uses of Immobilized Biological Compounds in Pharmaceutical Analysis.- Application of Immobilized Enzymes in Diagnostics.- Immobilized Dehydrogenase Enzymes Coupled with a NADH Sensor.- Targeting of Immobilized Drugs.- C. Biosensors.- Enzyme and Microbial Sensor.- Redox Mediators and Their Application in Amperometric Sensors.- Uni-, Bi- and Tri-Enzyme Electrodes for Analysis.- Enzyme Electrochemical Sensors for "In Vivo" Analysis with Artificial Pancreas.- Biosensors in Clinical and Pharmaceutical Analysis.- Graft Copolymers as Supports for the Immobilization of Biological Compounds.- D. Defense Applications.- Use of Protein Coatings on Piezoelectric Crystals for Assay of Gaseous Pollutants.- E. Fet Detectors.- Use of Immobilized Enzymes in FET Detectors.- Micro-Biosensor.- F. Optrodes - Spectroscopy.- The Development of Fibre-Optic Sensors by Immobilization of Fluorescent Probes.- Developing Biosensors.- Immobilized Biological Compounds in Bio- and Chemiluminescence Assays.- Immobilized Biospecific Proteins in Analytical Clinical Chemistry.- G. Immunosensors.- Immunosensors.- Electrochemical Immunosensors.- H. Flow Analysis.- Flow Injection Analysis - Recent Developments and Future Trends.- Extension to Enzymatic Electrodes of a General Procedure for the Construction of Flow-Through ISE's Based on the Use of Conductive Epoxy as Support of the Sensor.- I. Industrial and Analytical Applications.- Biosensor-Based Analyzers From Design to Instrument.- Commercial Aspects of the Use of Immobilized Compounds.- Design Considerations of an Immobilized Enzyme Electrode for Measurement of Glucose in Whole Blood.- Diffusion Limited Enzyme Electrodes.- Enzyme Electrodes for Sugar Substitute Aspartame.- Author Index.

Immobilization/stabilization of lipase from Candida rugosa.

Abstract: With the aim of fixing the enzyme to the maxtrix by multiple covalent linkages, lipase fromCandida rugosa (formerlycylindracea) has been insolubilized through its amino groups on Sepharose 6B previously activated with 2,3-epoxy-1-propanol. Two main variables that are known to control the number of bonds formed have been tested: the contact time between enzyme and activated support, and the temperature at which the immobilization reaction is carried out. Studies on activity and stability of the different derivatives prepared showed that higher temperatures and longer contact times lead to insolubilized enzymes that are more resistant to inactivation by temperature and the presence of organic solvents. At 50°C and pH 7.2, the insoluble lipase was found to be 140 times more stable than its soluble counterpart.

Enzyme immobilization and bioaffinity separations with perfluorocarbon polymer-based supports

Abstract: A bioaffinity separation method is provided along with a solid affinity support utilized in that method. Additionally, immobilized enzyme systems are provided for use as enzyme electrode systems. The support is based on an inert perfluorocarbon polymer carrier with ligands or binders attached to its surface. The ligand, binder or enzyme is preferably modified by attaching a perfluorocarbon anchor group, and the modified ligand, binder or enzyme is attached to the carrier through the anchor group. Methods for preparing such supports and their use in capturing target molecules from samples and in analytical applications are also provided.

A reference electrode and a measuring apparatus using the same

Abstract: A reference electrode for use in a flow type measuring apparatus incorporating an immobilized enzyme working electrode, wherein a hydrophilic gel layer is provided on a silver chloride containing layer in order to prevent flow-out of silver ions that are likely to adversely affect enzyme activity, so that the silver chloride containing layer goes into contact through the hydrophilic gel layer with an electrolytic solution containing a substance to be measured

Bioreactor Immobilized Enzymes and Cells: Fundamentals and Applications

Abstract: Any books that you read, no matter how you got the sentences that have been read from the books, surely they will give you goodness. But, we will show you one of recommendation of the book that you need to read. This bioreactor immobilized enzymes and cells fundamentals and applications is what we surely mean. We will show you the reasonable reasons why you need to read this book. This book is a kind of precious book written by an experienced author.

Lipase immobilized by adsorption: effect of support hydrophobicity on the reaction rate of ester synthesis in cyclohexane

Abstract: Candida cylindraceae lipase was immobilized by adsorption to various hydrophilic and hydrophobic supports and studied with respect to the esterification rates of a primary and a secondary alcohol, respectively, in organic media. The reaction rates were compared with the rate of esterification with “free lipase”. When the secondary alcohol, (R, S)-1-phenylethanol, was used the highest reaction rates were measured for lipase adsorbed to the hydrophobic supports. When the primary alcohol, heptanol, was used “free lipase” exhibited the highest reaction rate. A kinetic explantation of these results is proposed.

Gluconic acid production by an mobilized glucose oxidase reactor with electrochemical regeneration of an artificial electron acceptor

Abstract: A reactor, using the enzymatic electrocatalysis scheme, was developed on a laboratory preparative scale for the catalytic oxidation of glucose into gluconic acid. Glucose oxidase was directly immobilized on the surface of a carbon felt electrode and a solution of glucose and benzo-quinone passed through the electrode in order to regenerate the electron acceptor. The reactor was able to produce continuously 1.5 g gluconate/h with a catalytic current of 0.4 A. This gave a high productivity ca. 100 g/h/L reactor. A one-dimensional model was developed which demonstrated the efficiency of coupling between enzymatic and electrochemical reactions due to the proximity of the two reaction sites. For example the catalytic current was practically independent of mass transfer parameters. The operational stability of immobilized glucose oxidase was increased 50 times at least when electroregenerated benzoquinone was used as oxidant instead of oxygen.

Protein-Modified Electrochemically Active Biomaterial Surface

Abstract: : This research was initiated with a novel approach to electrode immobilization of an enzyme, glucose oxidase, by electropolymerization of pyrrole in the presence of the enzyme. The enzyme was entrapped by the polypyrrole film growing on the electrode surface. Since polypyrrole is an electronically conducting organic polymer, the effect of this immobilization was to enfold the enzyme in a conducting electrode. In addition, the products of the enzyme reaction with glucose were produced in the immediate proximity of this conducting material. The electropolymerized enzyme is active and serves as the basis for a glucose electrode system which remained active for several days. The conditions for electro-polimerization and the characteristics of the immobilized enzyme system were reported in the open literature.

Methods of Cell Immobilization

Abstract: Methods of cell immobilization roughly parallel those of enzyme immobilization and can best be classified by the nature of the mode of attachment, that is, as mechanical, chemical or ionic. In mechanical immobilization, the cells are localized by means of physical barriers. In chemical immobilization, covalent bonds are formed among cells or to a solid phase. In ionic immobilization, electrostatic, van der Waal’s or London forces of attraction are present. Cells can also attach themselves to solid supports in the course of natural growth, using a combination of these means. This classification is obviously not clear-cut but does serve the purpose of organizing the diverse methods of immobilization available. In Table 2.1, examples of cell immobilization are classified by mode of attachment.

Preparation and activity of carbonic anhydrase immobilized on porous silica beads and graphite rods.

Abstract: Techniques for the immobilization of bovine carbonic anhydrase (BCA) on porous silica beads and graphite are presented. Surface coverage on porous silica beads was found to be 1.5 x 10(-5) mmol BCA/m(2), and on graphite it was 1.7 x 10(-3) mmol BCA/m(2) nominal surface area. Greater than 97% (silica support) and 85% (graphite support) enzyme activity was maintained upon storage of the immobilized enzyme for 50 days in pH 8 buffer at 4 degrees C. After 500 days storage, the porous silica bead immobilized enzyme exhibited over 70% activity. Operational stability of the enzyme on silica at 23 degrees C and pH 8 was found to be 50% after 30 days. Catalytic activity expressed as an apparent second-order rate constant K'(Enz) for the hydrolysis of p-nitrophenyl acetate (p-NPA) catalyzed by BCA immobilized on silica beads and graphite at pH 8 and 25 degrees C is 2.6 x 10(2) and 5.6 x 10(2) M(-1)s(-1) respectively. The corresponding K(ENZ) value for the free enzyme is 9.1 x 10(2) M(-1)s(-1). Activity of the immobilized enzyme was found to vary with pH in such a manner that the active site pK, on the porous silica bead support is 6.75, and on graphite it is 7.41. Possible reasons for a microenvironmental influence on carbonic anhydrase pK(a), are discussed. Comparison with literature data shows that the enzyme surface coverage on silica beads reported here is superior to previously reported data on silica beads and polyacrylamide gels and is comparable to an organic matrix support. Shifts in BCA-active site pK(a) values with support material, a lack of pH dependent activity studies in the literature, and differing criteria for reporting enzyme activity complicate literature comparisons of activity; however, immobilized BCA reported here generally exhibits comparable or greater activity than previous reports for immobilized BCA.