Preparation and Catalytic Properties of Novel Alginate−Silica−Dehydrogenase Hybrid Biocomposite Beads

In this study, two kinds of novel hybrid biocomposite beads were prepared using alginate as polymer moiety, silica as inorganic moiety, and yeast alcohol dehydrogenase (YADH) as enzyme moiety. Silica was incorporated into the biocomposites through two approaches: in situ hydrolysis and polymerization of tetramethoxysilane in alginate solution, followed by Ca2+ cross-linking (this biocomposite was designated as ALG−SiO2−YADH); physical incorporation of silica gel (SG) into alginate solution, followed by Ca2+ cross-linking (this biocomposite was designated as ALG−SG−YADH). The porous network structure of the biocomposite beads ensured the facile accessibility of enzyme for NADH and formaldehyde. Loading efficiency of YADH in alginate−silica−enzyme hybrid biocomposite beads was higher than that in pure ALG−YADH biocomposite due to the more compact structure and less water loss. The catalytic activity of YADH in alginate−silica−enzyme hybrid biocomposite beads was higher than that in ALG−YADH biocomposite due to less enzyme leakage and improved carrier microenvironment. Furthermore, the storage stability and operational stability of YADH in alginate−silica−enzyme hybrid biocomposite beads were significantly improved due to the increase of the mechanical strength and swelling resistance. Compared to ALG−SG−YADH biocomposite, ALG−SiO2−YADH biocomposite showed much better performance due to the more homogeneous distribution of silica particles in the composite matrix.