Enzyme immobilization in MCM-41 molecular sieve

The immobilization of globular enzymes, cytochrome c (bovine heart), papain (papaya latex) and trypsin (bovine pancreas), in the mesoporous molecular sieve MCM-41 was studied. The physical adsorption in the hexagonal 40 Angstrom pure silica phase of MCM-41 showed a clear dependence on enzyme size. The efficiency of papain and trypsin immobilization was pH dependent and favorable at pH values < 7, while immobilization of cytochrome c was most efficient at pH > 7 and less susceptible to pH changes. Peroxidase (horseradish) was not significantly retained by the MCM-41 support. Silanation of the mesopore openings after trypsin adsorption eliminated the leaching of enzyme into solution at high pH. The entrapped trypsin enzyme was active for the hydrolysis of N-alpha-benzoyl-DL-arginine-4-nitroanilide (BAPNA). Results for the inhibition of this reaction by poly-L-lysine of various molecular weights are reported. The stability of trypsin was also enhanced by the physical entrapment in MCM-41.