Lipase-silicone biocomposites: Efficient and versatile immobilized biocatalysts

The last few decades have seen an explosion in the application of enzymes to organic chemistry, as these biological catalysts have continued to demonstrate their unique synthetic capabilities. Despite this, a key prerequisite for establishing enzymes as standard reagents in synthetic chemistry, specifically the availability of generic technologies providing inexpensive, robust, 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, namely, lipases. The procedure is based upon the adsorption of crude and pure Lipases onto poly(hydroxymethylsiloxane), followed by the incorporation of the formed adsorbates into room-temperature vulcanizable silicones, to form biocatalytic composites. This provides hyperactivated catalysts showing activity enhancements of up to 54-fold as compared with the native enzymes, catalytic densities of up to several hundred kilo-units per gram of immobilizate, and high operational activity and stability in aqueous and organic media. The flexibility of silicone polymer chemistry enables the catalytic biocomposites to be prepared with a variety of physicochemistries, and to be fabricated 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-silicone composites are discussed, and the extended performances of selected catalysts are compared with those of the free enzymes and commercial heterogeneous biocatalysts in model synthetic reactions.