Influence of the alkyl-substituted silane precursor on sol–gel encapsulated lipase activity

Lipase from Candida rugosa was encapsulated within a chemically inert sol–gel support prepared by polycondensation of three precursor types (tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMS) and polydimethylsilane (PDMS)) in the presence and absence of polyethylene glycol (PEG) and polyvinyl alcohol (PVA) as additives. Silica and their derivatives were characterised with regard to mean pore diameter, specific surface area, pore size distribution (BET method), weight loss upon heating thermogramivemetric analysis (TGA), chemical composition Fourier transform infrared spectroscopy (FT-IR), and catalytic activities. Immobilisation yields based on the recovered lipase activity vary from 3.02 to 31.98% and the highest efficiency was attained when lipase was encapsulated using TEOS in the presence of the PEG. Further information was obtained by testing the derivatives in esterification reactions and a different reactivity profile was found. Better performance was obtained with derivatives containing lipase encapsulated within gels prepared with MTMS as precursor in the presence of PEG. This lipase preparation exhibits increased esterification activity (155 μmol g−1 min−1), up to of three times greater than that prepared with TEOS (52 μmol g−1 min−1), and almost twice that prepared with MTMS/PDMS (89 μmol g−1 min−1) as precursors.