Enzyme immobilisation using SBA-15 mesoporous molecular sieves with functionalised surfaces

Functionalised hexagonal mesoporous SBA-15-type molecular sieves with pore sizes in the range 51–56 Å have been prepared using non-ionic block copolymers and used for immobilisation of the enzyme trypsin. Thiol, chloride, amine, and carboxylic acid functional groups were attached by siloxypropane tethers to the siliceous surface of SBA-15 via two methods, post-synthesis grafting and in situ synthesis. Phenylsiloxane groups were also incorporated using these two methods. The resulting solids were rendered porous and used to immobilise trypsin, giving variable but in general higher retention of the enzyme molecules than was observed on unfunctionalised, purely siliceous SBA-15. The resulting supported enzyme catalysts were shown to be active and stable catalysts for the hydrolysis of N-α-benzoyl-DL-arginine-4-nitroanilide (BAPNA). The solids prepared by supporting the enzyme on thiol-functionalised SBA-15 prepared by in situ synthesis were found to be the most promising. Trypsin supported on thiol-functionalised SBA-15 was shown to be recyclable.