The immobilization of the hydrolytic enzyme trypsin onto various mesoporous silicates (MPS) was studied. MPS were prepared using cationic or non-ionic surfactants (average pore diameters were in the range of 28-300 angstrom). All MPS were characterised by X-ray diffraction, scanning electron microscopy and nitrogen porosimetry. Enzyme purity strongly influenced loading. Trypsin adsorbed on NIPS was found to be desorbed more readily by polyethylene glycol than by ammonium sulphate, suggesting that hydrophobic-hydrophilic interactions were important. Immobilized trypsin showed 10-20 times higher activity than the free trypsin and was stable for 4-6 weeks when stored at 4 or 25 degrees C. The trypsin-MPS catalyst was successfully reused for up to 6 cycles (c) 2004 Elsevier B.V. All rights reserved.