scispace - formally typeset
Search or ask a question
Topic

Immobilized enzyme

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


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the regeneration of the cofactor nicotinamide adenine dinucleotide (NAD) from its reduced form was coupled with the alcoholdehydrogenation reaction which consumes NAD and produces NADU using alcohol dehydrogenase bound to alumina.
Abstract: Electrochemical regeneration of the cofactor nicotinamide adenine dinucleotide (NAD) from its reduced form (NADH) has been coupled with the alcoholdehydrogenation reaction which consumes NAD and produces NADU using alcohol dehydrogenase bound to alumina. Alcohol (reactant) is added directly to the system while aldehyde (product) leaves the system through an ultrafiltration membrane which prevents loss of the cofactor. This system provides a continuous-flow process for carrying out a cofactor-requiring enzymatic reaction with no net loss or consumption of enzyme or cofactor and without the use of reagents for regenerating the cofactor. Although the process shown here is not economically practical, it may be a harbinger of useful and technically feasible chemical reaction systems based on immobilized enzymes requiring cofactors.

92 citations

Journal ArticleDOI
TL;DR: Asymmetric hydrolysis, ester interchange and ester formation were carried out for menthol resolution with Candida cylindracea lipase in this article under emulsified conditions with water soluble enzyme and in organic medium with an insoluble enzyme preparation.

92 citations

Journal ArticleDOI
TL;DR: The purified lipase from Pseudomonas cepacia was immobilized on a commercially available microporous polypropylene support and showed that the immobilized enzyme was fully active as soon as activity was assayed on a soluble substrate rather than an insoluble one.
Abstract: The purified lipase from Pseudomonas cepacia (PS, Amano) was immobilized on a commercially available microporous polypropylene support. The enzyme was rapidly and completely adsorbed on the support. Special attention was devoted to the demonstration of the lack of diffusional limitations, either internal or external, when a soluble substrate (p-nitrophenylacetate, pNPA) was used. The activity yield was high (100%) with pNPA and very low (0.4%) with p-nitrophenylpalmitate (pNPP). These values clearly showed that the immobilized enzyme was fully active as soon as activity was assayed on a soluble substrate rather than an insoluble one. With the latter one, the low activity was due mainly to a slow rate of substrate diffusion inside the porous support. The same diffusional phenomenon could explain the complete change of fatty acid specificity of the immobilized lipase. After immobilization, the lipase was mainly specific for short chain fatty acid esters, whereas the free enzyme was mainly specific for long chain esters. The activity-versus-temperature profiles were not greatly affected by immobilization with maximal reaction rates in the range 45 degrees to 50 degrees C for both enzyme preparations. However, immobilization increased enzyme stability mainly by decreasing the sensitivity to temperature of the inactivation reaction. Half-lives at 80 degrees C were 11 and 4 min for the immobilized and free enzymes, respectively. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 181-189, 1997.

92 citations

Journal ArticleDOI
TL;DR: A comparative protocol is proposed which considers both the active area available for transduction following nanomaterial deposition and the sensitivity of biosensor designs, and shows results which suggest the most possible reason for the performance enhancement was an increased enzyme loading.
Abstract: This work addresses the comparison of different strategies for improving biosensor performance using nanomaterials. Glucose biosensors based on commonly applied enzyme immobilization approaches, including sol‐gel encapsulation approaches and glutaraldehyde cross-linking strategies, were studied in the presence and absence of multi-walled carbon nanotubes (MWNTs). Although direct comparison of design parameters such as linear range and sensitivity is intuitive, this comparison alone is not an accurate indicator of biosensor efficacy, due to the wide range of electrodes and nanomaterials available for use in current biosensor designs. We proposed a comparative protocol which considers both the active area available for transduction following nanomaterial deposition and the sensitivity. Based on the protocol, when no nanomaterials were involved, TEOS/GOx biosensors exhibited the highest efficacy, followed by BSA/GA/GOx and TMOS/GOx biosensors. A novel biosensor containing carboxylated MWNTs modified with glucose oxidase and an overlying TMOS layer demonstrated optimum efficacy in terms of enhanced current density (18.3 ± 0.5 μ Am M −1 cm −2 ), linear range (0.0037‐12 mM), detection limit (3.7 μM), coefficient of variation (2%), response time (less than 8 s), and stability/selectivity/reproducibility. H2O2 response tests demonstrated that the most possible reason for the performance enhancement was an increased enzyme loading. This design is an excellent platform for versatile biosensing applications.

92 citations

Journal ArticleDOI
TL;DR: It was shown that the use of silica gel facilitates reactions at high glycerol concentrations without alteration of reaction rates or conversion yields and it also was demonstrated that highly hydrophilic polyols enhanced blockage of the enzyme.
Abstract: The crucial role of silica gel in lipase-catalyzed esterification reactions using adsorbed high-polar substates was established. It was found that in these kinds of reactions, the presence of silica gel-adsorbed substrates did not alter the kinetic mechanisms of the synthesis of acylglycerides but improved significantly the conversion yields. An explanation for the critical role of silica gel in these kinds of reactions was proposed whereby the silica gel behaves as a “polar substrate reservoir” and plays a protective role for the immobilized enzyme avoiding its blockage. In this way it was shown that the use of silica gel facilitates reactions at high glycerol concentrations without alteration of reaction rates or conversion yields. It also was demonstrated that highly hydrophilic polyols enhanced blockage of the enzyme. The importance of the presence of an organic solvent in the reaction medium was shown to have a critical role in the conversion yields of the reactions tested. Finally, the influence of different supports used for adsorption of the substrates was compared with respect to their efficiency in protecting the enzymatic activity.

92 citations


Network Information
Related Topics (5)
Cellulose
59K papers, 1.4M citations
84% related
Fermentation
68.8K papers, 1.2M citations
83% related
Aqueous solution
189.5K papers, 3.4M citations
83% related
Ionic liquid
57.2K papers, 1.6M citations
83% related
Adsorption
226.4K papers, 5.9M citations
83% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023219
2022417
2021480
2020548
2019553
2018543