Amylases immobilization by sol–gel entrapment: application for starch hydrolysis

α-amylase from Bacillus subtilis, α-amylase from Aspergillus oryzae, and β-amylase from barley were encapsulated within silica-based matrix by acid-catalyzed sol–gel process. The resulting systems were characterized by Fourier transform infrared spectroscopy (FT-IR) in the attenuated total reflection (ATR) mode, nitrogen adsorption (BET and BJH methods), scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). The products from enzymatic hydrolysis of starch were analyzed by the DNS method (reducing sugars) and high-performance liquid chromatography (HPLC). The biocatalytic activity of the immobilized systems (reducing sugars in the range of 0–30.5 μmol/mL) was compared with that of the free systems (reducing sugars in the range of 11.7–33.7 μmol/mL). The porosity analysis showed that xerogels with a high surface area (above 300 m²/g) were obtained. The morphological analyses carried out by microscopy demonstrated the existence of predominantly granular (relatively spherical particles) structures. HPLC results show large differences in the musts obtained from the free enzymes and the corresponding immobilized systems. The encapsulated systems demonstrated high activity and differentiated form of saccharifying the starch.