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  • Title: Activity modulation and reusability of beta-D-galactosidase confined in sol-gel derived porous silicate glass.
    Author: Crescimbeni MC, Nolan V, Clop PD, Marín GN, Perillo MA.
    Journal: Colloids Surf B Biointerfaces; 2010 Apr 01; 76(2):387-96. PubMed ID: 20042321.
    Abstract:
    In the present work we applied the sol-gel method to obtain glass lentils entrapping beta-D-galactosidase (beta-Gal) (Ebeta-Gal) within a silicate matrix. The effect of pH, temperature, polarity and salt concentration on the activity of Ebeta-Gal was studied. Apparent kinetic parameters for ortho-nitro-phenyl-beta-D-galactopyranoside hydrolysis catalyzed by Ebeta-Gal (V'max, K'M) were lower compared to the soluble enzyme (Sbeta-Gal), reflecting the solute diffusion restriction imposed by the matrix observed in the time curves, a partial protein inactivation upon encapsulation, and an improvement in the affinity of Ebeta-Gal for the substrate as compared with Sbeta-Gal. At pH<4, Ebeta-Gal stability was higher than that of Sbeta-Gal. Ebeta-Gal could be reused after storage at 4 degrees C for up to 90 days, and retained its activity profile within the range of pH=2-10 and saline concentration 0-400 mM. Pre-incubation at 75 degrees C for 30 min fully inactivated Sbeta-Gal while Ebeta-Gal retained approximately 90% of its activity, even in the reused samples. Encapsulation did not introduce additional impairments to the reaction rate measured in heterogeneous dispersions, beyond those derived from their own particle-crowded environment. This reusable Ebeta-Gal was resistant to typical technological conditions applied in milk processing that would lead to the unfolding and inactivation of Sbeta-Gal. The results are discussed from the biophysical viewpoint.
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