Abstract
An investigation is performed into the efficiency of the Streptomyces griseus HUT 6037 enzyme immobilized in three different mesoporous silicas, namely mesoporous silica film, mesocellular foam, and rod-like SBA-15. It is shown that for all three supports, the pH value changes the surface charge and charge density and hence determines the maximum loading capacity of the enzyme. The products of the enzyme hydrolytic reaction are analyzed by 1H-NMR. The results show that among the three silica supports, the mesoporous silica film (with a channel length in the range of 60–100 nm) maximizes the accessibility of the immobilized enzyme. The loading capacity of the enzyme is up to 95% at pH 7 and the activity of the immobilized enzyme is maintained for more than 15 days when using a silica film support. The order of the activity of the enzyme immobilized in different mesoporous silica supports is: mesoporous silica film > mesocellular foam > rod-like SBA-15. Furthermore, the immobilized enzyme can be easily separated from the reaction solution via simple filtration or centrifugation methods and re-used for hydrolytic reaction as required.
Highlights
Silica-based materials have been extensively studied in various elds of chemistry and materials science recently, with particular emphasis on their application as antibacterial agents,[1] biosensors,[2] supports, and adsorbents.[3,4] Silica-based materials include, but are not limited to, porous glass,[5] sol–gel silica,[6] and mesoporous materials.[4,5] Among these materials, mesoporous silicas (MSs) have attracted particular attention as a platform for the protection of enzyme molecules due to their large, wellordered and rigid pore structures.[7]
Recent studies on enzyme loading have focused more on SBA-15 materials with pore sizes of ca. 5–15 nm and mesocellular siliceous foams with pore sizes of 15–40 nm.[22]
Transmission electron microscopy (TEM) and SEM images in Fig. 1C and D shows that the mesocellular foam has a hollow vesicle structure with a diameter of 30–60 nm
Summary
Silica-based materials have been extensively studied in various elds of chemistry and materials science recently, with particular emphasis on their application as antibacterial agents,[1] biosensors,[2] supports, and adsorbents.[3,4] Silica-based materials include, but are not limited to, porous glass,[5] sol–gel silica,[6] and mesoporous materials.[4,5] Among these materials, mesoporous silicas (MSs) have attracted particular attention as a platform for the protection of enzyme molecules due to their large, wellordered and rigid pore structures.[7]. The pore sizes of MSs are tunable in the range of 2–50 nm and are comparable to the dimensions of typical enzymes (typically 3–7 nm) As a result, they have attracted great interest as matrix materials for enzyme immobilization.[11,12,13,14,15,16,17,18,19,20,21,22,23] Various studies have shown that MCM-41 materials have a pore size of just 3.0 nm, and are limited to the immobilization of enzymes with small sizes.[15,16,17] despite their high surface areas The economic potential of the mesoporous silica lm is demonstrated by recovering the enzyme from the reaction solution using a simple centrifugation method and reusing the recycled enzyme to perform a further hydrolytic reaction process
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