Formation of hybrid gels from an aqueous mixture of alginate and alkoxysilanes has been applied to immobilization of whole cells of Pichia pastoris catalyzing oxidation of benzyl alcohol in organic solvent. The amount of benzaldehyde produced after a prolonged reaction period was 1.2 and 1.8 times greater with the hybrid gels of alginate + silicate and alginate + methyl-substituted silicate, respectively, than with the alginate single gel. This was ascribed to a facilitated release rate of aldehyde, which acted as a strong inhibitor against the enzyme alcohol oxidase, from the inside of the cells to organic medium through hydrophobic gel matrix.