Preparation Of Dendritic Composite Carriers And Their Application In The Immobilization Of Enzymes

As a biocatalyst, free enzyme's defect can't meet with the requirement of modern industry. So it's important to develop a new kind of material which can immobilize the free enzyme efficiently. Dendrimers are recognized as a new class of synthetic material,which have been applied in life science and material science because of their unique structure and property.In this work a series of dendritic composite silica carriers was newly prepared, and used firstly for the immobilization of porcine pancreas lipase. The experimental results clearly show that the content of amino groups distributed on the carrier surface, the chain length and the properties of organic groups have important influence on immobilization efficiency of PPL and the relative activity of immobilized lipase. Among all the carriers, 0.5G( composite carrier has the best efficiency to immobilize PPL mainly due to its highest content (1.646 mmol/g) of basic group on the surface. The activity of immobilized lipase is obviously raised with the increase of the organic chain length and the content of amino group (1.5G(0.5G; 2.0G(1.0G). The activity of immobilized lipase improves respectively in 35.4%,13.1% and 52.3 % after the carriers 0.5G,1.5G and 2.5G are modified by hydrolysis, indicating that the distribution of carboxyl group on the surface of carrier favors the immobilization of lipase in comparison with that of the ester group. The lipase immobilized on 0.5G( composite carrier shows the best activity at 40 oC and in the buffer of pH 7.5. The immobilization conditions are optimized, and found that the best stirring time is 30 min, and the optimal ratio of carrier to lipase about 75mg/g carrier.Moreover, 0.5G( and 1.0G composite carriers have also been used for the immobilization of laccase. The laccase immobilized on 0.5G( composite carrier shows the best activity in the buffer of pH 6.5 (free enzyme is 7.4), ion concentration is 25 mmol/L, stirring time is 10h For 1.0G composite carrier, the optimal ion concentration also is 25 mmol/L.All the results demonstrate that the dendritic composite silica carrier is a kind of valuable immobilization carrier. It provides us a useful platform for investigating how the properties of surface groups on the carriers to affect the immobilization efficiency of enzymes.