Fibers enzyme immobilization

Immobilization by chemical bonding gives strong, irreversible attachments to a solid support. The bonds are normally covalent but they can be electrostatic. Typical supports are functionalized glass and ceramic beads and fibers. Enzymes are sometimes cross-linked to form a gel. Occasionally, enz5anes can be flocculated while retaining catalytic activity. 

O. Miyawaki, K. Nakamura, and T. Yano, Experimental investigation of continuous NAD recycling by conjugated enzymes immobilized in ultrafiltration hollow fiber, J. Chem. Eng. Jpn., 15(3), 224-228 (1982). 

Figure 10. Miniature biofuel cell segment consisting of mediated enzymes immobilized on 7-//m-diameter fibers. Reprinted with permission from ref 106. Copyright 2001 American Chemical Society.

Asymmetric hollow fibers provide an interesting support for enzyme immobilization, in this case the membrane structure allows the retention of the enzyme into the sponge layer of the fibers by crossflow filtration. The amount of biocatalyst loaded, its distribution and activity through the support and its lifetime are very important parameters to properly orientate the development of such systems. The specific effect that the support has upon the enzyme, however, greatly depend upon both the support and the enzyme involved in the immobilization as well as the method of immobilization used. 

Artificial catalysts have also been incorporated into amphiphilic structures (Guler and Stupp, 2007). These catalysts were imidazolyl-functiona-lized peptides, which demonstrate a greater rate of 2,4-dinitrophenyl acetate hydrolysis when immobilized on the peptide amphiphile than the rate observed when the same enzyme is present in solution. Although the density of the enzymes on the fiber surface has not been established, the authors attribute the increase in enzymatic activity to the likely concentration of enzyme along the fiber surface, and this study illustrates one of the advantages of enzyme immobilization. 

Polypeptide fibers are being rapidly developed as wires and structures for applications as diverse as enzyme immobilization, biosensing, and bioma-terials. Larger macroscopic structures are also being developed from protein fibers. As our ability to manipulate these structures grows so too will the range of applications to which these fibers can be applied. 

Acetylcholineesterase and choline oxidase Enzyme immobilized over tetra-thiafulvalene tetracyanoquinodi-methane crystals packed into a cavity at the tip of a carbon-fiber electrode. The immobilization matrix consisted of dialdehyde starch/glutaraldehyde, and the sensor was covered with an outer Nafion membrane. The ampero-metric performance of the sensor was studied with the use of FIA system. An applied potential of +100 mV versus SCE (Pt-wire auxiliary electrode) and a carrier flow rate of 1 mL/min. The Ch and ACh biosensors exhibited linear response upto 100 pM and 50 pM, respectively. Response times were 8.2 s. [97]... 

Li et al. [152] fabricated electrospun PAN fiber mats immobilized with C. rugosa lipase by amidination. Enzyme molecules were covalently bound to the fiber mats and formed small protein aggregates. The immobilized lipase on the electrospun PAN fiber mats showed a good biocatalystic activity for soybean oil... 

Besides these conventional reactors with spherical immobilizates, urease has also been immobilized inside nylon tubing and pipette tips ( enzyme pipette , Sundaram and Jayonne, 1979), on nylon fibers ( enzyme brush , Raghavan et al., 1986), and on the surface of a magnetic stirrer (Guilbault and Starklov, 1975). The urease reaction was in each case carried out at optimal pH after removal of the immobilized enzyme NH3 was assayed electrochemically or photometrically according to Berthelot s method. 

Others Enzyme immobilization Encapsulation of nutraceuticals Chromatography Analytical reagent Synthetic fiber Chitosan-coated paper Manufacturing material for fiber Film and sponges... 

Nanomaterials are a new class of research material that have been tested for enzyme immobilization. Sawicka et al. measured urea concentration by using nanocomposite fibers of urease and polyvinylpyrrolidone (PVP) [146]. Biocomposite nanotibers were prepared by electrospinning a solution in which urease and PVP were dissolved, leading to improvement in response time and sensitivity. 

When symmetric membranes are used or when enzymes are fed to the spongy part of asymmetric membranes, enzyme immobilization results in either a uniform fixation of enzymes throughout the membrane wall, or in the formation of a carrier-enzyme insoluble network in the sponge of the membrane. Mass transfer through this solid phase must therefore be taken into account. A theoretical model neglecting radial convective transport and the dense layer in asymmetric membranes is available in the literature.81 The reacting solution is still assumed to be fed to the core of the hollow fibers. Steady state, laminar flow, and isothermal conditions are assumed. Moreover, the enzymes are assumed to be uniformly distributed and the membrane wall curvature is neglected. Differential dimensionless mass balance equations can be written as follows ... 

Keywords Candida antarctica lipase B Enzyme immobilization Coconut fiber ... 

Adsorption kinetic was investigated, and the influence of contact time between coconut fiber and lipase, at different enzyme concentrations from 0 U/ml (control without enzyme) to 90 U/ml, were evaluated. No hydrolytic activity was detected when the fiber without immobilized enzyme (control) was used as catalyst. Figure 1 pictures the influence of different initial concentrations of lipase in the supernatant ( 0 equal to 30, 60, or 90 U/ml) on the hydrol)ftic activity of immobilized CALB. The experimental data were subjected to statistical analysis (analysis of variance). At the probability level of p<0.05 (data not shown), it was observed that immobilized amount increases as time increased until 2 h (in... 

Reusability of immobilized CALB was tested in subsequent cycles of methyl butyrate hydrolysis. It can be observed in Fig. 7 that CALB-7A retained less than 50% of its initial hydrolytic activity after the third cycle of reaction whereas Novozyme 435 retained almost 70% after the tenth cycle (Fig. 7). Other authors [36] observed that CALB immobilized on activated carbon retained more than 55% of its initial activity after the sixth cycle of methyl butyrate hydrolysis. The worse operational stability of CALB immobilized on coconut fiber, when compared to CALB immobilized on activated carbon and to Novozyme 435, may be due to enzyme desorption during reaction, induced by the hydrophobic substrate, and by the low enzyme load adsorbed. As discussed before, the driven forces of CALB adsorption on coconut fiber are electrostatic interactions that are weaker than hydrophobic interactions, which predominate on Novozyme 435 and CALB adsorbed on activated carbon. Furthermore, both aetivated carbon and the resin used in the preparation of Novozyme 435 are porous support with high superficial area available for enzyme immobilization, allowing obtaining of high enzyme load. Coconut fiber, on the other hand, does not have a porous structure, and it has a low surface area [27], making it difficult to achieve high enzyme loads. 

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