Tailored adsorption of enzymes onto mesoporous silicates.

Enzymes often display high regio- and chemoselectivity and therefore are of great interest for industrial processes. However, in these processes, they can show low stability and are not reusable. Immobilisation can optimize stability and activity, providing controlled mass transport of substrate and enabling re-use of the biocatalyst. Immobilisation also allows for continuous processes. Mesoporous silicates provide a means of immobilizing proteins and enzymes in a stable environment while retaining physiological function. Mesoporous silicates possess large surface areas, highly ordered pore structures and a very narrow pore size distribution. Pore sizes range from 3-20nm making them ideal for protein encapsulation. One recurrent problem with physi-sorption onto mesoporous silicates is leaching of the enzyme. Covalent attachment can reduce leaching but can increase rigidity which could lead to a loss in activity. Methods of tailoring the properties of both the mesoporous silicate surface and the protein surface to improve adsorption and catalytic activity have been explored with a view to generate a stable biocatalyst. A biocatalyst has been generated through the tailored adsorption of a tagged enzyme onto a metal functionalized mesoporous silicate. By employing a standard method of protein purification, a His-tagged enzyme has been immobilized onto a nickel functionalized mesoporous silicate. Enzymes that have been studied include subtilisin E, hydroxynitrile lyase and bile salt hydrolase. Denatured Histagged subtilisin E was successfully immobilized onto nickel functionalized SBA 15. His-tagged bile salt hydrolase was successfully immobilized onto the surface of nickel functionalized MCF and SBA 15. Manihot esculenta hydroxynitrile lyase could not be immobilised with a histidine tag as the tag was not exposed for binding.