Entrapment Of Lipase Research Articles

Entrapment of lipases in hydrophobic magnetite-containing sol-gel materials: magnetic separation of heterogeneous biocatalysts

The simultaneous entrapment of a lipase such as Pseudomonas cepacia or Candida antarctica and nanostructured superparamagnetic magnetite (Fe 3O 4) in hydrophobic sol–gel materials derived from CH 3Si(OCH 3) 3 (MTMOS) or other hydrophobic precursors leads to catalytically active, mechanically stable and magnetically separable heterogeneous biocatalysts. The relative enzyme activity in the test reaction involving the esterification of lauric acid by n-octanol in isooctane is typically 200–300%, with respect to the same reaction using a conventional suspension of the non-immobilized enzyme. Separation of the catalyst by applying a simple magnet poses no problems. In the kinetic resolution of 2-pentylamine, enantioselectivity is essentially complete (ee=97–99%).

Immobilization of lipase with polyion complex and its esterification activity in organic medium.

A novel method to immobilize lipase on inorganic particles or on an inorganic porous plate is proposed. The method consists of entrapment of lipase into polyion complex, followed by fixation of the complex on the inorganic supports. It was simpler and offered much saving in time, comparing with conventional entrapping and covalently binding methods. Both the lipases immobilized on the particles and the plate showed high catalytic activity for esterification in organic medium, and the activity depended on kinds of polyion complex and water contents in the immobilized-lipases. The immobilized-lipases sustained their activity up to a significantly high temperature of 60° C, which suggests that lipase and polyion complex interact to enhance thermal stability of lipase. Activity holding with repeated uses was also studied.

Characterization of hydrophobic sol-gel materials containing entrapped lipases

The entrapment of lipases in hydrophobic sol-gel materials of RSi(OCH3)3 or mixtures of RSi(OCH3)3 and Si(OCH3)4 results in heterogeneous biocatalysts having dramatically enhanced enzyme activities as measured by the esterification of lauric acid by n-octanol in isooctane. These materials have been characterized by solid state NMR studies, revealing the degree of cross-linking. It is shown that this parameter generally does not correlate with relative enzyme activity. Likewise, the specific surface area or the pore size does not seem to be the decisive factor in determining the relative enzyme activities of the lipase-containing hybrid gels and the corresponding SiO2-gels obtained from Si(OCH3)4. Scanning electron microscopic studies (SEM) show that the hybrid gels all have a similar morphology. On the basis of these studies a model is proposed according to which most of the lipase enzyme is entrapped near the surface of the gel particles, where it is readily accessible by substrate molecules.

Sol-gel entrapment of lipase using a mixture of tetramethoxysilane and methyltrimethoxysilane as the alkoxide precursor: Esterification activity in organic media

The sol-gel method, using a mixture of tetramethoxysilane (TMOS) and methyltrimethoxysilane (MTrMOS) as the silicon alkoxide precursor, has been applied to entrapment of lipase catalyzing esterification reactions in organic media. Increasing molar ratio of MTrMOS to TMOS led to formation of opaque and non-shrinkable gels and resulted in an increase in the esterification activity of lipase. The hybrid gel-entrapped lipase based on [MTrMOS]/[TMOS] ratio of 4 exhibited almost equal activity with those of the deposited lipase on different supports at 35°C, and retained ca. ten times higher activity than the deposited counterparts at 65 °C.

Efficient Heterogeneous Biocatalysts by Entrapment of Lipases in Hydrophobic Sol–Gel Materials

Alkyltrimethoxysilanes yield much better host matrices for lipases than tetramethoxysilane (see picture). This is revealed by the esterifications discussed herein catalyzed by lipases that are immobilized in RSi(OMe)3 gels. These heterogeneous biocatalysts are readily reusable and should also be suitable for continuous processes.

Entrapment of lipase in silica glass by the sol-gel method and its esterification activity in organic media

Silica glass-entrapped lipase was prepared by the sol-gel method using tetramethoxysilane, and its esterification activity in n-hexane was examined for isoamylbutyrate formation. The hydrogel preparation containing a large amount of water exhibited enough activity. Although the activity of xerogel-entrapped lipase drastically decreased probably due to shrinkage of the gel matrix, the lyophilized gel retained much higher activity than the air-dried gel.