Meso-molding three-dimensionally ordered macroporous alumina: A new platform to immobilize enzymes with high performance

The meso-molding three-dimensionally ordered macroporous alumina (3DOM/m-Al) was synthesized via a dual-templating approach (polystyrene (PS) colloidal crystals as hard template and triblock copolymer P123 as soft template) with hydrous aluminum isopropoxide as precursor. The obtained 3DOM/m-Al was characterized, and the results showed that 3DOM/m-Al had ordered macropores (ca. 300 nm in diameter) with wormhole-like mesopores, relatively high surface areas (338.1 m(2)/g), large pore volumes (0.4030 cm(3)/g) and tunable pore sizes. The amino functionalized 3DOM/m-Al by aminopropyltriethoxysilane (APTES) was activated by glutaraldehyde and used as support for the immobilization of three different commercial enzymes (Lipase B from Candida antarctica (CALB), penicillin G acylase (PGA) and nitrile hydratase (NHase)). The result of confocal laser scanning microscopy (CLSM) indicated that the enzyme was successfully immobilized onto glutaraldehyde-activated NH2-3DOM/m-Al. The effect of the immobilized conditions on the specific activity of enzymes was investigated. Compared with free enzymes, the immobilized enzymes exhibited enhanced thermal stability. The three immobilized enzymes (CALB@NH2-3DOM/m-Al, PGA@NH2-3DOM/m-Al and NHase@NH2-3DOM/m-Al) were applied for the synthesis of palmitic acid, 6-aminopenicillanic acid (6-APA) and acrylamide, respectively. After recycling 10 times, CALB@NH2-3DOM/m-Al, PGA@NH2-3DOM/m-Al and NHase@NH2-3DOM/m-Al retained approximately 76%, 87% and 52% of their initial activities, respectively, indicating that the immobilized enzymes had good operational stability. Therefore, this work documented herein provides a versatile platform for enzyme immobilization with several inherent advantages.