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The immobilization of Lipase PS from Pseudomonas cepacia by entrapment within a chemically inert hydrophobic sol-gel support was studied. The gel-entrapped lipase was prepared by the hydrolysis of tetramethoxysilane (TMOS) with methyltrimeth-oxysilane (MTMS), isobutyltrimethoxysilane (iso-BTMS), and n-butyltrimethoxysilane. The immobilized lipase was subsequently used in the hydrolysis of soybean oil to determine its activity, recyclability, and thermostability. The biocatalyst so prepared was equal to or better than the free enzyme in its hydrolytic activity. The catalytic activity of the entrapped lipase strongly depended on the type of precursor that was used in its preparation. The lipase entrapped within TMOS/iso-BTMS showed the highest activity. The catalytic activity of the immobilized lipase was more pronounced during the earlier stages of the reaction. Thermostability of the lipase was significantly improved in the immobilized form. The immobilized lipase was stable up to 70°C, whereas for the free enzyme, moderate to severe loss of activity was observed beyond 40°C. The immobilized lipase was consistently more active and stable than the free enzyme. The immobilized lipase also proved to be very stable, as it retained more than 95% of its initial activity after twelve 1-h reactions.