Lipase-silicone biocomposites: Efficient and versatile immobilized biocatalysts

The last few decades have seen an explosion in the application of enzymes t o organic chemistry, as these biological catalysts have continued to demons trate their unique synthetic capabilities. Despite this, a key prerequisite for establishing enzymes as standard reagents in synthetic chemistry, spec ifically the availability of generic technologies providing inexpensive, ro bust, and reusable heterogeneous biological catalysts, still remains to be fulfilled. Herein, we describe a novel and hi,ghly efficient immobilization methodology for one of the most utilitarian classes of biocatalysts, namel y, lipases. The procedure is based upon the adsorption of crude and pure Li pases onto poly(hydroxymethylsiloxane), followed by the incorporation of th e formed adsorbates into room-temperature vulcanizable silicones, to form b iocatalytic composites. This provides hyperactivated catalysts showing acti vity enhancements of up to 54-fold as compared with the native enzymes, cat alytic densities of up to several hundred kilo-units per gram of immobiliza te, and high operational activity and stability in aqueous and organic medi a. The flexibility of silicone polymer chemistry enables the catalytic bioc omposites to be prepared with a variety of physicochemistries, and to be fa bricated as solid monoliths, sheets of thick films, particulates, and solid foams, thereby allowing the production of tailored catalysts for a variety of applications. The production and properties of a range of lipase-silico ne composites are discussed, and the extended performances of selected cata lysts are compared with those of the free enzymes and commercial heterogene ous biocatalysts in model synthetic reactions.