SIMPLE ENTRAPMENT OF ALCALASE IN DIFFERENT SILICA XEROGELS USING THE TWO STEPS SOL-GEL METHOD

The present study has focused on the entrapment of Alcalase in different xerogels obtained by using various molar ratios of methyltriethoxysilane, dimethyldietoxisilane and tetraethoxysilane. Silica and their derivatives were characterized with regard to specific surface area (nitrogen adsorbtion), chemical composition (Fourier transform infrared spectroscopy (FT-IR)), weight loss upon heating (thermogravimetric analysis (TGA)) and catalytic activity

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

Influence of synthesis parameters on luminescence emission properties of some sol-gel derived Eu3+ doped willemite phosphors

Europium doped zinc silicate phosphor sample, corresponding to general formula, Zn2-(x+y)EuxLiySi0 4 , (where x = 0.01 or 0.02 and y = 0, 0.01, or 0, 02), have been synthesized by acid, or two steps (acid-base) catalyzed sol-gel processing, in the presence, or absence of Li+ ions, as charge compensator. The obtained xerogel samples was successively annealed, at different steps, up to 1000°C, for 180 minutes time soaking for each temperature. Starting from 700°C temperature, the formation of Si-O-Zn linkage was put in evidence by FT-IR spectra. The appearance of IR signals corresponding to willemite vibration modes has been observed for 900°C calcined samples. At UV excitation beam, the luminescence spectra of Zn2Si0 4 :Eu3+ synthesized phosphors samples show some emission peaks in the red region of spectra, assigned to 5Do—> Fj (j = 0, 1, 2, 3, 4 and 5) spin forbidden f-f transitions of Eu3+ ions, respectively. Specifically they were situated around 575 nm, 590 nm, 615 nm, 624 nm, 650 nm and 700 nm. The most intense emission was observed for the 1000°C calcined sample, with 0.02 moles Eu3+ activator content, prepared with charge compensator

Synthesis and luminescence properties of some Ce3+ doped silica sols

Ce -doped silica sols samples were prepared by acid, or two steps catalyzed sol-gel process, at different concentration of Ce3+ dopant. As silica precursors, tetraetoxysilane, or tetrametoxysilane, or a precursors mixture consisting of tetraetoxysilane and isobuthyltrietoxysilane, were used. By UV excitation, all synthesized samples presented strong luminescence emission with maxima situated at ~ 386 nm. Regarding the emission efficiency, better results were achieved at lower Ce3+ concentrations. Depending on precursors nature, a favorable influence had the use of precursors mixture