The intent of this work was to investigate the effects of control of DO and pH on moranoline (1-deoxynojirimycin) production by Streptomyces lavendulae for large-scale moranoline fermentation. The conclusions reached are as follows : (i) It is most important to maintain DO at 20% saturation from the stage of fermentation when the rate of DO consumption is high. (ii) When the DO is maintain between 20 and 85% saturation, it is important to maintain pH at less than 7. When the fermentation was carried out so as to maintain the DO at 20% saturation in a 30 l fermenter, 10.2-10.5 g . l(-1) of moranoline was produced.