Cellulase from Trichoderma reesei (Celluclast 1.5 L, Novozyme) was immobilized by sol-gel encapsulation, using binary or ternary mixtures of tetramethoxysilane (TMOS) with alkyl- or aryl-substituted trimethoxysilanes as precursors. Optimization of immobilization conditions resulted in 92 % recovery of total enzymatic activity in the best immobilized preparate. The immobilized cellulase exhibiting the highest activity, obtained from tetramethoxysilane and methyltrimethoxysilane precursors at 3:1 molar ratio, was investigated in the hydrolysis reaction of microcrystalline cellulose (Avicel PH101). Although the optimal values did not change significantly, both temperature and pH stabilities of the sol-gel entrapped cellulase improved compared to the native enzyme. Immobilization also conferred superior resistance against the inactivation effect of glucose. Reuse of the sol-gel entrapped cellulase showed 40 % retention of the initial activity after five batch hydrolysis cycles, demonstrating the potential of this biocatalyst for large-scale application.

Sol-gel entrapment is an efficient immobilization technique that allows preparation of robust and highly stable biocatalysts. Lipase from Candida antarctica B was immobilized by sol-gel entrapment and by sol-gel entrapment combined with adsorption on Celite 545, using a ternary silane precursor system. After optimization of the immobilization protocol, the best enzyme loading was 17.4 mg/g support for sol-gel entrapped lipase and 10.7 mg/g support for samples obtained by entrapment and adsorption. Sol-gel immobilized enzymes showed excellent values of enantiomeric ratio E and activity when ionic liquid 1-octyl-3-methyl-imidazolium tetrafluoroborate was used as additive. Immobilization increased the stability of the obtained biocatalysts in several organic solvents. Excellent operational stability was obtained for the immobilized lipase, maintaining unaltered catalytic activity and enantioselectivity during 15 reuse cycles. The biocatalysts were characterized using scanning electron microscopy (SEM) and fluorescence microscopy. The improved catalytic efficiency of entrapped lipases recommends their application for large-scale kinetic resolution of optically active secondary alcohols.

Recently, increased attention has been paid to natural sources as raw materials for the development of new added-value products. Flavonoids are a large family of polyphenols which include several classes based on their basic structure: flavanones, flavones, isoflavones, flavonols, flavanols, and anthocyanins. They have a multitude of biological properties, such as anti-inflammatory, antioxidant, antiviral, antimicrobial, anticancer, cardioprotective, and neuroprotective effects. Current trends of research and development on flavonoids relate to identification, extraction, isolation, physico-chemical characterization, and their applications to health benefits. This review presents an up-to-date survey of the most recent developments in the natural flavonoid classes, the biological activity of representative flavonoids, current extraction techniques, and perspectives.

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Lipase from Pseudomonas fluorescens (Amano AK) was immobilized using the sol-gel entrapment technique and sol-gel entrapment combined with adsorption on a solid support (Celite 545). The sol-gel matrices were obtained using as precursors ternary mixtures of tetramethoxysilane and trimethoxysilanes substituted with phenyl or vinyl groups, at different molar ratios, and 1-octyl-3-methyl-immidazolium tetrafluoroborate as additive. The obtained enzymatic preparates were efficient biocatalysts in the acylation reaction of racemic secondary alcohols. Several methods were employed for the characterization of the resulting bioactive materials, in order to correlate the catalytic performance with the morphological and physico-chemical properties of the matrix: Fourier transform infrared spectroscopy (FTIR), BET-analysis of specific surface and porosity, laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and thermogravimetric analysis (TGA). An extensive study attested the excellent temperature stability and reusability of the immobilized lipases, thus indicating their possible utilization in industrial applications.