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Book ChapterDOI

On The Immobilization of Candida antarctica Lipase B onto Surface Modified Porous Silica Gel Particles

TL;DR: In this article, the surface modification of the porous silica gel was conducted both in an aqueous medium using Tris buffer solution at pH 10.6 and in an organic medium using toluene, respectively.
Abstract: Lipase B from Candida antarctica (CALB) was successfully immobilized onto the surface of porous silica gel particles that had been modified using (3-aminopropyl) triethoxysilane (3-APS or γ-APS) and then crosslinked using glutaraldehyde. The surface modification of the porous silica gel was conducted both in an aqueous medium using Tris buffer solution at pH 10.6 and in an organic medium using toluene, respectively. Subsequently, CALB was immobilized onto the silica gel particles in an aqueous medium using Tris buffer solution at room temperature and at a pH of 7.5. In another approach, CALB was entrapped in porous silica using a biologically inspired green method. The catalytic activity and the thermal stability of the immobilized enzyme systems including a commercial product were assessed by a model esterification reaction between 1-octanol and lauric acid carried out in isooctane at 37 °C. The results demonstrate that the immobilized CALB on silica had both a high catalytic activity and also good thermal stability when compared to free CALB.
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Book ChapterDOI
01 Jan 2014
TL;DR: In this paper, the interaction between enzymes and organically modified alkoxysilanes was studied in an attempt to determine the kinetics of hydrolysis and condensation, as well as to determine a general reaction mechanism.
Abstract: Silica is a common material with uses in a diverse range of products. New methods for producing silica are always being developed. In the past 15 years biological and bio-inspired approaches for silica production have gained momentum. One of the challenges in designing new materials is developing new methods for their production and gaining a complete understanding of all of the processing parameters. We have been studying the interaction(s) between enzymes and organically modified alkoxysilanes in an attempt to determine the kinetics of hydrolysis and condensation, as well as to determine a general reaction mechanism. We believe that the nature of the enzyme (i.e. mode of catalysis, active site, and secondary interactions) contributes to the ability of any given enzyme to act as a catalyst for the production of silica-based materials.
References
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Journal ArticleDOI
TL;DR: This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr with little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose.

225,085 citations

Journal ArticleDOI
TL;DR: The structure of Candida antarctica lipase B shows that the enzyme has a Ser-His-Asp catalytic triad in its active site, which accounts for the substrate specificity and high degree of stereospecificity of this lipase.

836 citations

Journal ArticleDOI
TL;DR: It is shown that butyrylcholinesterase entrapped during the precipitation of silica nanospheres retained all of its activity and was substantially more stable than the free enzyme.
Abstract: Robust immobilization techniques that preserve the activity of biomolecules have many potential applications. Silicates, primarily in the form of sol-gel composites or functionalized mesoporous silica, have been used to encapsulate a wide variety of biomolecules but the harsh conditions required for chemical synthesis limit their applicability. Silaffin polypeptides from diatoms catalyze the formation of silica in vitro at neutral pH and ambient temperature and pressure. Here we show that butyrylcholinesterase entrapped during the precipitation of silica nanospheres retained all of its activity. Ninety percent of the soluble enzyme was immobilized, and the immobilized enzyme was substantially more stable than the free enzyme. The mechanical properties of silica nanospheres facilitated application in a flow-through reactor. The use of biosilica for enzyme immobilization combines the excellent support properties of a silica matrix with a benign immobilization method that retains enzyme activity.

582 citations

Journal ArticleDOI
TL;DR: In this article, 3-Aminopropyl triethoxy silane (APTES) was deposited onto silicon oxide surfaces under various conditions of solvent, heat, and time, and then exposed to different curing environments, including air, heat and ethanol.

553 citations

Journal ArticleDOI
TL;DR: A novel method to achieve lipase immobilization by entrapment in chemically inert hydrophobic silica gels which are prepared by hydrolysis of alkyl‐substituted silanes in the presence of the enzyme is presented.
Abstract: The commercial application of lipases as biocatalysts for organic synthesis requires simple but efficient methods to immobilize the enzyme, yielding highly stable and active biocatalysts which are easy to recover. In this study, we present a novel method to achieve lipase immobilization by entrapment in chemically inert hydrophobic silica gels which are prepared by hydrolysis of alkyl-substituted silanes in the presence of the enzyme. A typical immobilization procedure uses: an aqueous solution of lipase; sodium fluoride as a catalyst; and additives like polyvinyl alcohol or proteins and alkoxysilane derivatives like RSi-(OMe)3 with R = alkyl, aryl, or alkoxy as gel precursors. The effect of various immobilization parameters like stoichiometric ratio of water, silane, type and amount of additive, type and amount of catalyst, and type of silane has been carefully studied. The new method is applicable for a wide variety of lipases, yielding immobilized lipases with esterification activities enhanced by a factor of up to 88, compared to the commercial enzyme powders under identical conditions. Studies on the stability of sol-gel immobilized lipases under reaction conditions or storage (dry, in aqueous or organic medium) revealed an excellent retention of enzymatic activity. The possible reasons for the increased enzyme activities are discussed. © 1996 John Wiley & Sons, Inc.

406 citations