Simple Technique for Preparing Stable and Recyclable Cross-Linked Enzyme Aggregates with Crude-Pored Microspherical Silica Core

With the aim of providing a highly stable and easy recyclable biocatalyst, we prepared a new biocatalyst formulation based on cross-linked enzyme aggregate (CLEA) technology by the physical adsorption of cross-linked phenylalanine ammonia lyase on a highly porous microspherical silica gel solid support (S-CLEAs). The main factors in the preparation of S-CLEAs were optimized by response surface methodology (RSM). Analysis by scanning electron microscopy (SEM), FT-IR spectroscopy, and confocal laser scanning microscopy (CLSM) indicated that the CLEAs were successfully immobilized on the crude-pored microspherical silica gel. Compared to standard CLEAs, the S-CLEAs can be easily separated from the reaction mixture by natural precipitation without centrifugation and filtration treatments. Although the S-CLEAs revealed an excellent stability of the enzyme against high temperature and denaturants, the volumetric activity of the S-CLEAs decreased because of the presence of silica gel. In a word, the S-CLEA technology in this study might open an attractive route toward effectively improving the catalytic properties of traditional CLEAs.