Based on the optimized technology on 50L scale, B subtilis 754# was used to manufacture guanosine on pilot scale (12M 3) and plant scale (100M 3) to give the production of 29 4g/L and 21 4g/L successively Through scale down the process of plant scale to pilot scale, based on the theory of dynamic metabolic flux, DO was found to be another key factor that limited the scale up process After conquering the DO limitation, the optimized technology was successfully scaled up to plant scale and the production was further increased by 18% to 25 2 g/L