Entrapment of glucoamylase by sol-gel technique in PhTES/TEOS hybrid matrixes

Mesoporous silica particles were prepared by the sol-gel method from different alkoxysilane precursors and used as a host matrix for encapsulation of glucoamylase, an enzyme widely used in fermentative industry. The aim was to investigate the physico-chemical properties of the different silica powders and their effect on the enzyme kinetics. The encapsulated enzymes followed Michaelis-Menten kinetics. The Michaelis constant (KM) and the maximum rate of starch hydrolysis reaction (Vmax) were calculated according to the Michaelis-Menten and Lineweaver-Burke plots. The values of the Michaelis constant (KM) of the encapsulated enzymes were higher than those of the free enzyme. The temperature and pH infl uence on the activity of free and immobilized glucoamylase were also compared. The results of this study show that the enzymes immobilized in organic/inorganic hybrid silica matrixes (obtained by the sol-gel method), allowing the entrapped glucoamylase to retain its biological activity, are suitable for many different applications, (medicinal, clinical, analytical)

PRELIMINARY STUDY FOR USING VINYLTRIACETOXYSILANE AS PRECURSOR IN ENZYME IMMOBILIZATION BASED ON SOL-GEL METHOD

During the last years, sol-gel technology has become a well-established method for the preparation of catalytic active monoliths, bulk, particles and thin films. One reason for the increasing research activities in this field is the opportunity to obtain versatile hybrid materials by incorporation of different molecules, like dyes, enzymes, whole cells, chemicals and drugs. The aim of this research was to evaluate the suitability of vinyltriacetoxysilane (VTAS) as precursor in sol-gel enzyme immobilization and the physicochemical characterization of the final products (silica xerogels)

Performance of immobilized bacterial alpha-amylases in methyltriethoxsilane / tetraetoxysilane sol-gel matrices

The large number of studies related to the field of biomolecules encapsulation in sol-gel hosts clearly indicates that this approach can be considered as a powerful alternative to traditional encapsulation procedures involving biopolymer hosts. In this study, α-amylase was immobilized, by using the sol-gel technique, in silica particles obtained from hydrolysis and polycondensation of tetraethoxysilane (TEOS) and a mixture of methyltriethoxysilane (MTES) and tetraethoxysilane. The influence of the pH and temperature of free and immobilized α-amylase were compared. It was shown that the relative activities of immobilized enzymes are higher than those of free enzymes over broader pH and temperature ranges. The Michaelis constant and the maximum rate of starch hydrolysis reaction were calculated by fitting the experimental data to the Michaelis-Menten equation. It was found that KM and Vmax values of the immobilized enzyme were smaller than those of the free enzyme

Bioorganically doped sol-gel materials containing amyloglucosidase activity

Amyloglucosidase (AMG) from Aspergillus niger was encapsulated in various matrices derived from tetraethoxysilane, methyltriethoxysilane, phenyltriethoxysilane and vinyltriacetoxysilane by different methods of immobilization. The immobilized enzyme was prepared by entrapment in two steps, in one-step and entrapment/deposition, respectively. The activities of the immobilized AMG were assayed and compared with that of the native enzyme. The effects of the organosilaneprecursors and their molar ratios, the immobilization method, the inorganic support (white ceramic, red ceramic, purolite, alumina, TiO2, celite, zeolite) and enzyme loading upon the immobilized enzyme activity were tested. The efficiency of the sol-gel biocomposites can be improved through combination of the fundamental immobilization techniques and selection of the precursors

A computational approach to structural properties of glycoside hydrolase family 4 from bacteria

Structural bioinformatics approaches applied to the alpha- and beta-glycosidases from the GH4 enzyme family reveal that, despite low sequence identity, these enzymes possess quite similar global structural characteristics reflecting a common reaction mechanism. Locally, there are a few distinctive structural characteristics of GH4 alpha- and beta-glycosidases, namely, surface cavities with different geometric characteristics and two regions with highly dissimilar structural organizations and distinct physicochemical properties in the alpha- and beta-glucosidases from Thermotoga maritima. We suggest that these structurally dissimilar regions may be involved in specific protein-protein interactions and this hypothesis is sustained by the predicted distinct functional partners of the investigated proteins. Also, we predict that alpha- and beta-glycosidases from the GH4 enzyme family interact with difenoconazole, a fungicide, but there are different features of these interactions especially concerning the identified structurally distinct regions of the investigated proteins

Improved Optical and Morphological Properties of Vinyl-Substituted Hybrid Silica Materials Incorporating a Zn-Metalloporphyrin

This work is focused on a novel class of hybrid materials exhibiting enhanced optical properties and high surface areas that combine the morphology offered by the vinyl substituted silica host, and the excellent absorption and emission properties of 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin-Zn(II) tetrachloride as a water soluble guest molecule. In order to optimize the synthesis procedure and the performance of the immobilized porphyrin, silica precursor mixtures of different compositions were used. To achieve the requirements regarding the hydrophobicity and the porous structure of the gels for the successful incorporation of porphyrin, the content of vinyltriacetoxysilane was systematically changed and thoroughly investigated. Substitution of the silica gels with organic groups is a viable way to provide new properties to the support. An exhaustive characterization of the synthesized silica samples was realised by complementary physicochemical methods, such as infrared spectroscopy (FT-IR), absorption spectroscopy (UV-Vis) and photoluminescence, nuclear magnetic resonance spectroscopy (29Si-MAS-NMR) transmission and scanning electron microscopy (TEM and SEM), nitrogen absorption (BET), contact angle (CA), small angle X ray and neutron scattering (SAXS and SANS). All hybrids showed an increase in emission intensity in the wide region from 575 to 725 nm (Q bands) in comparison with bare porphyrin. By simply tuning the vinyltriacetoxysilane content, the hydrophilic/hydrophobic profile of the hybrid materials was changed, while maintaining a high surface area. Good control of hydrophobicity is important to enhance properties such as dispersion, stability behaviour, and resistance to water, in order to achieve highly dispersible systems in water for biomedical applications