A stoichiometric model was developed for the application of medium design in microbial transglutaminase production by Streptoverticillium mobaraense. The model avoids dealing with all the metabolic reactions involved by simply lumping them into a single reaction. With the help of measurement results, an ana lysis of the nutrients’ roles, and biochemical knowledge of the microorganism, all stoichiometric coefficients in the model were calculated. These coefficients were used for medium design. With this designed medium, microbial transglutaminase activity was increased fourfold, compared to that in the basal medium.