Active Biocatalysts Based on Pepsin Immobilized in Short Channeled Zr-Ce-SBA-15

Short channeled Zr-Ce-SBA-15 (ZCS) mesoporous materials with hexagonal platelet morphologies were synthesized through a hydrothermal route without addition of mineral acids. Porcine pepsin was immobilized inside ZCS and conventional SBA-15 through physical adsorption. A grafting step with [1-(2-amino-ethyl)-3-aminopropryl] trimethoxysilane (AAPTS) was performed to reduce the pore openings of the host material in order to minimize the enzyme leaching. The hybrid materials were characterized by X-ray diffraction, scanning electron microscope, transmission microscope, N-2 adsorption/desorption and Fourier-transform infrared spectroscope. The results confirmed that pepsin is located inside the channels of the mesoporous materials and the grafting process does not affect the mesoporous structure. The immobilization of pepsin into ZCS and SBA-15 were compared. The results demonstrate that the ZCS materials have higher adsorption rates and adsorption capacities (the maximum adsorption capacity is 257.9 mg/g) compared with SBA-15. The ZCS materials with short channels are superior to conventional SBA-15 facilitating molecular diffusion. The catalytic activity of the hybrid bioinorganic material was tested with hemoglobin. The immobilized pepsin has maintained the necessary degree of freedom to fulfill its catalytic activity.