Second generation sol-gel encapsulated lipases:: Robust heterogeneous biocatalysts

The original procedure for the encapsulation of lipases in sol-gel materials produced by the fluoride-catalyzed hydrolysis of mixtures of RSi(OCH3)(3) and Si(OCH3)(4) has been improved considerably. This involves higher enzyme loading, variation of the alkylsilane precursor, and the use of additives such as isopropyl alcohol, 18-crown-6, Tween 80(R), methyl-beta-cyclodextrin and/or KCl. A dramatic increase in enzyme activity is observed. The sol-gel lipase immobilizates are also excellent catalysts in the kinetic resolution of chiral alcohols and amines, recycling without any substantial loss in enantioselectivity and a residual activity of 70% being possible even after 20 reaction cycles.