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Immobilized enzyme
About: Immobilized enzyme is a research topic. Over the lifetime, 15282 publications have been published within this topic receiving 401860 citations.
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TL;DR: In this paper, Aspergillus niger CECT 2088 cultures were immobilized into a polymeric matrix consisting of polyvinyl alcohol (PVA) hydrogel, cryostructured in liquid nitrogen, to obtain biocatalytically active beads.
115 citations
TL;DR: The electrode could thus provide a more spatially biocompatible microenvironment to enhance the amount and biocatalytic activity of the immobilized enzyme and to better mediate the electron transfer.
Abstract: An amperometric glucose biosensor was prepared using polyaniline (PANI) and chitosan-coupled carbon nanotubes (CS-CNTs) as the signal amplifiers and glucose oxidase (GOD) as the glucose detector on a gold electrode (the Au-g-PANI-c-(CS-CNTs)-GOD biosensor). The PANI layer was prepared via oxidative graft polymerization of aniline from the gold electrode surface premodified by self-assembled monolayer of 4-aminothiophenol. CS-CNTs were covalently coupled to the PANI-modified gold substrate using glutaradehyde as a bifunctional linker. GOD was then covalently bonded to the pendant hydroxyl groups of chitosan using 1,4-carbonyldiimidazole as the bifunctional linker. The surface functionalization processes were ascertained by X-ray photoelectron spectroscopy (XPS) analyses. The field emission scanning electron microscopy (FESEM) images of the Au-g-PANI-c-(CS-CNTs) electrode revealed the formation of a three-dimensional surface network structure. The electrode could thus provide a more spatially biocompatible microenvironment to enhance the amount and biocatalytic activity of the immobilized enzyme and to better mediate the electron transfer. The resulting Au-g-PANI-c-(CS-CNTs)-GOD biosensor exhibited a linear response to glucose in the concentration range of 1-20 mM, good sensitivity (21 μA/(mM·cm(2))), good reproducibility, and retention of >80% of the initial response current after 2 months of storage.
115 citations
TL;DR: An increased number of repeated analyses of 750 samples during 230 days for glucose and 400 samples during 40 days of operation for sucrose have been achieved, which will improve the operating cost effectiveness of the biosensor.
115 citations
TL;DR: A fiber‐optic enzyme biosensor for the direct measurement of organophosphate nerve agents was developed and shows long‐term stability when stored in buffer at 4 °C.
Abstract: A fiber-optic enzyme biosensor for the direct measurement of organophosphate nerve agents was developed. The basic element of this biosensor is organophosphorus hydrolase immobilized on a nylon membrane and attached to the common end of a bifurcated optical fiber bundle. The enzyme catalyzes the hydrolysis of organophosphate compounds to form stoichiometric amounts of chromophoric products that absorb light at specific wavelengths. The back-scattered radiation of the specific incident radiation was measured using a photomultiplier detector and correlated to the organophosphate concentration. The effects of buffer pH, temperature, and the units of enzyme immobilized on the steady-state and kinetic response of the biosensor were investigated to optimize the operating conditions for the fiber-optic enzyme biosensor. These conditions were then used to measure parathion, paraoxon, and coumaphos selectively without interference from carbamates and triazines. Concentrations as low as 2 μM can be measured in less than 2 min using the kinetic response. When stored in buffer at 4 °C the biosensor shows long-term stability.
115 citations
TL;DR: The CLEAs catalyzed esterification reactions in cyclohexane, affording higher conversions than with the free enzyme, especially when longer fatty acids and alcohols were used as substrates.
Abstract: Cross-linked enzyme aggregates (CLEA ® s) were prepared from Candida rugosa lipase (CrL) using glutaraldehyde as the cross-linker. The optimum conditions of the immobilization process were determined (precipitant: ethanol, crosslinker concentration: 25 mM, enzyme concentration: 50 mg/ml, crosslinking time: 45 min.). CLEAs were shown to have several advantages compared to the free enzyme. They were more stable at 50 °C and 60 °C and had good reusability; retaining 40% of their initial activity after 15 recycles in aqueous media and remaining constant at that level thereafter, suggesting some initial leaching in water. The CLEAs catalyzed esterification reactions in cyclohexane, affording higher conversions than with the free enzyme, especially when longer fatty acids and alcohols were used as substrates.
115 citations