The effects of protease-treated liquefied rice on the production of saccharifying enzyme by immobilized fungal mycelia were investigated. The production of saccharifying enzyme by immobilized fungal mycelia was stimulated by the protease-treated liquefied rice. The origin of the effector was identified as a hydrolyzate of glutelin, a major rice protein. Moreover, the effector was purified by gel permeation chromatography and reversed-phase HPLC, The molecular weight of the purified effector was around 400-500 Da and it was composed of a few amino acids. These results indicate that the oligopeptide derived from the glutelin hydrolyzate regulates the production of saccharifying enzyme by immobilized fungal mycelia. Furthermore, this oligopeptide stimulated the production of raw starch-digesting glucoamylase by immobilized fungal mycelia but did not stimulate the production of other proteins.