Activity modulation and reusability of beta-Galactosidase confined in sol-gel derived porous silica glasses

CESCIMBENI, M.; NOLAN, V.; CLOP, P.D.; MARIN, G.; PERILLO, M.A.

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Año: 2010 vol. 76 p. 387 - 396

0927-7765

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 activity of Ebeta-Gal at different pHs, temperatures, polarities and salt concentrations was studied. Apparent kinetic parameters for ortho-nitro-phenyl-b-D-galactopyranoside hydrolysis catalyzed by Ebeta-Gal (Vmax, KM) 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 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 4ºC 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 75ºC 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.