Recyclable solid-phase biocatalyst with improved stability by sol-gel entrapment of β-D-galactosidase

beta-D-Galactosidase from Kluyveromyces lactis was for the first time immobilized by entrapment in hybrid organic-inorganic sol-gel materials with microporous structure, obtained from alkoxy silanes and alkyl substituted alkoxy silanes, in different combinations. The immobilization matrix was tailored by fine tuning of several parameters, such as: nature of alkyl group of silane precursors, molar ratio of silane precursors, nature of additives, protein concentration. Unlike other enzymes, beta-D-galactosidase showed the best catalytic activity at low alkyl group content in the sol-gel matrix, at a molar ratio of 7:1 between the tetraalkoxysilane alkyl-trialkoxysilane precursor. The immobilized enzyme demonstrated enhanced storage, pH and thermal stability compared to the soluble enzyme. The composite sol-gel materials were characterized by transmission electron microscopy, scanning electron microscopy, fluorescence confocal microscopy, and porosity measurement. The biocatalyst was successfully reused in five reaction cycles, maintaining more than 60% of the initial activity. (C) 2015 Elsevier B.V. All rights reserved.