Immobilized enzyme

About: Immobilized enzyme is a research topic. Over the lifetime, 15282 publications have been published within this topic receiving 401860 citations.

Co-immobilized Phosphorylated Cofactors and Enzymes as Self-Sufficient Heterogeneous Biocatalysts for Chemical Processes.

Abstract: Enzyme cofactors play a major role in biocatalysis, as many enzymes require them to catalyze highly valuable reactions in organic synthesis. However, the cofactor recycling is often a hurdle to implement enzymes at the industrial level. The fabrication of heterogeneous biocatalysts co-immobilizing phosphorylated cofactors (PLP, FAD+, and NAD+) and enzymes onto the same solid material is reported to perform chemical reactions without exogeneous addition of cofactors in aqueous media. In these self-sufficient heterogeneous biocatalysts, the immobilized enzymes are catalytically active and the immobilized cofactors catalytically available and retained into the solid phase for several reaction cycles. Finally, we have applied a NAD+-dependent heterogeneous biocatalyst to continuous flow asymmetric reduction of prochiral ketones, thus demonstrating the robustness of this approach for large scale biotransformations.

Stabilization and release of enzymes from silk films.

Abstract: A significant challenge remains to protect protein drugs from inactivation during production, storage, and use. In the present study, the stabilization and release of horseradish peroxidase (HRP) in silk films was investigated. Water-insoluble silk films were prepared under mild aqueous conditions, maintaining the activity of the entrapped enzyme. Depending on film processing and post-processing conditions, HRP retained more than 90% of the initial activity at 4 degrees C, room temperature and 37 degrees C over two months. The stability of protein drugs in silk films is attributed to intermolecular interactions between the silk and the enzymes, based on Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The unique structural feature of silk molecules, periodic hydrophobic-hydrophilic domains, enabled strong interactions with proteins. The entrapped protein was present in two states, untrapped active and trapped inactive forms. The ratio between the two forms varied according to processing conditions. Proteolytic degradation and dissolution of the silk films resulted in the release of the bound enzyme which was otherwise not released by diffusion; enzyme recovered full activity upon release. There was a linear relationship between silk degradation/dissolution and the release of entrapped enzyme. Modifying the secondary structure of the silk matrix and the interactions with the non-crystalline domains resulted in control of the film degradation or dissolution rate, and therefore the release rate of the entrapped enzyme. Based on the above results, silk materials are an intriguing carrier for proteins in terms of both retention of activity and controllable release kinetics from the films.

Hydrogen Peroxide Sensor Based on Coimmobilized Methylene Green and Horseradish Peroxidase in the Same Montmorillonite-Modified Bovine Serum Albumin−Glutaraldehyde Matrix on a Glassy Carbon Electrode Surface

Abstract: A new approach to construct a second-generation amperometric biosensor is described. The classical dye methylene green as a probing-needle mediator and horseradish peroxidase as a base enzyme were coimmobilized in the same montmorillonite-modified bovine serum albumin (BSA)−glutaraldehyde matrix to construct a H2O2 sensor. The immobilization matrix was formed from the pretreated sodium montmorillonite colloid in which the enzyme and the cross-linker were dissolved. Immobilization of methylene green from the dye mother solution was attributed to the adsorption function of the montmorillonite, whereas immobilization of horseradish peroxidase was attributed to the cross-linking function of the BSA−glutaraldehyde as usual. Cyclic voltammetry and potentiostatic measurements indicated that methylene green efficiently mediated electrons from the base electrode to the enzyme in the matrix. The sensor responded rapidly to low H2O2 concentration and achieved 95% of the steady-state current in less than 20 s, with a...

Determination of Organophosphorus and Carbamate Pesticides Using a Piezoelectric Biosensor

Abstract: A biosensor based on the quartz crystal microbalance has been developed for the determination of organophosphorus and carbamate pesticides. Detection is based on the inhibitory effects of these compounds on the activity of acetylcholinesterase immobilized on one of the faces of the crystal. Exposure of the immobilized enzyme to a solution of the histological substrate, 3-indolyl acetate, gives rise to the formation of an indigo pigment insoluble product that deposits (precipitates) on the crystal surface. The rate and extent of the enzymatic reaction can be followed in real time by measuring the frequency changes associated with the mass changes at the crystal surface induced by the accumulation of the enzymatic reaction product (indigo pigment). The presence of paroxon (organophosphorus pesticide) or carbaryl (carbamate pesticide) is detected by a diminution of the signal (frequency change) arising from their inhibitory effects. Calibration curves were constructed by plotting the percentage of inhibition...