An ultrafiltration reactor was developed for the continuous saccharification of liquefied corn starch using glucoamylase. At an enzyme concentration of 1 g/L and a substrate concentration of 300 g/L, maltose and maltotriose were still detected in the reactor permeate after 4 hr of operation. At higher enzyme concentrations (6 and 12 g/L), the reactor achieved steady-state operation within 1–3 hr at all substrate concentrations studied. At an enzyme concentration of 12 g/L, residence time did not affect the final conversion of liquefied starch to glucose. The ultrafiltration reactor produced glucose syrups at residence times of 2–3 hr and substrate concentrations up to 30% w/v.