A study on biocatalysts immobilized in nanospace

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The objectives of the research are to prepare stable biocatalyst systems encapsulated in nanoporous, hydrophobic space and to apply them to green-chemical organic synthesis in organic media. As a nanoporous material, we chose highly-ordered mesoporous silica with a pore size of 6-9 nanometer in diameter, which was prepared using Si(OEt)_4, and triblockcopolymer. The internal surface of the mesoporous silica was then modified by silane coupling agents having amino, hydroxyl, and carboxylic functional groups. Lipase enzyme was immobilized in the chemically-modified mesoporous silicas, and applied to esterification between an equimolar amount of carboxylic acid and alcohol under ambient conditions. We compared biocatalysis between lipase encapsulated in the chemically modified mesoporous silicas and commercially available lipase supported on Celite. We found several advantages: 1) Our lipase system showed 20 times as high biocatalysis in esterification as the conventional lipase, 2) the volume of our immobilized lipase is much smaller than that of Celite-supported lipase, 3) the stability of the lipase in mesoporous silica is much superior, and 4) no leaching of lipase from the pores of chemically-modified mesoporous silica was observed.