Among physical and nutritional parameters optimized by "one variable at a time" approach, four cultural variables ( sucrose, MgSO4 center dot 7H(2)O, inoculum size, and incubation period) significantly affected glucoamylase production. These variables were, therefore, selected for optimization using response surface methodology. The p-values of the coefficients for linear effect of sucrose and inoculum size were less than 0.0001, suggesting them to be the key experimental variables in glucoamylase production. The enzyme production ( 34 U/ml) attained under optimized conditions ( sucrose, 2%; MgSO4 center dot 7H(2)O, 0.13%; yeast extract, 0.1%; inoculum size, 5 x 106 spores per 50 ml production medium; incubation time, 48 h; temperature, 40 C; and pH 7.0) was comparable with the value predicted by polynomial model (34.2 U/ml). An over all 3.1-fold higher enzyme titers were attained due to response surface optimization. The experimental model was validated by carrying out glucoamylase production in shake flasks of increasing capacity (0.25 - 2.0 l) and 22-1 laboratory bioreactors ( stirred tank and airlift), where the enzyme production was sustainable. Furthermore, the fermentation time was reduced from 48 h in shake flasks to 32 h in bioreactors.