Investigations to optimize the catalytic performance of CPO encapsulated in PEG 200-doped silica matrices

A systematic investigation of the experimental conditions that affect the performance of chloroperoxidase (CPO) when encapsulated in organic/inorganic hybrid materials was carried out, aimed at optimizing the enzymatic catalytic efficiency. Sol–gel process was used to synthesize silica matrices and the incorporation of polyethylene glycols (PEGs) has allowed us to modify the properties of the matrices and the interactions between the silica network and the enzyme. Sol–gel process conditions, i.e. PEG/TMOS (tetramethylorthosilicate) molar ratio, aging and drying time, along with the H2O2 concentration in the reaction mixture were optimized to obtain a more efficient and reusable catalyst. A stable and easily recycled biocatalyst was obtained, even in the presence of high amounts of oxidizing agent. A stability of up to 3 complete cycles of reaction was obtained. CPO also exhibited an excellent thermostability even at 70 ◦C, being residual activity after 2 h of incubation greater than 90%, and it was a very favorable result, especially in view of synthetic applications of CPO. Moreover, it was found that the immobilized catalyst performance can be maintained unchanged over at least a month simply by storing the washed matrices at 4 ◦C. Further optimization of the experimental conditions will lead in the future to a larger-scale synthetic use of CPO.