During foreign protein production using a promoter such as SUC2, which is controllable by the glucose concentration in the culture broth, it is important to determine the optimal glucose concentration for maximum protein production. The optimal glucose concentrations for maximal production of glucoamylase in plasmid-harboring recombinant yeast MMY2SUCSTA culture and in chromosome-integrated recombinant yeast MMY2SUCSTA-I culture were 0.13 and 0.09 g litre(-1), respectively. Using glucose feeding to maintain these optimal glucose concentrations, the extracellular glucoamylase productivities of fed-batch culture were increased (12-fold in MMY2SUCSTA and 23-fold in MMY2SUCSTA-I) over simulation results from batch cultures.