Invertase-catalyzed hydrolysis reaction by sucrose under mild ultrasound irradiation was carried out in a 400-cm(3) bioreactor with a polyethylene film bottom, and the effects of ultrasound on the hydrolysis were investigated under a wide range of biochemical and physical exposure conditions. The effects were measured as a function of pH values, sucrose concentrations, and sound intensities. From these experimental results, an enhancement of reaction rate was observed in the low concentration region of sucrose. Ir was also clarified that in the high-concentration region of sucrose, continuous wave ultrasound had some substantial effects for the activity of the enzyme-catalytic reaction.