This article evaluates the effectiveness of a segregated model for prediction of growth and differentiation of Bacillus licheniformis in a submerged-culture fermentation system. The segregated model accounts for each of the three morphological forms of the Bacillus life cycle. The sporangium biomass was characterized using an age-population model to reflect the age-dependent progress toward spore formation. Constitutive relationships governing the rates of vegetative cell reproduction, spore germination commitment to sporulation, and substrate consumption are proposed. Based on this model framework the dynamic cell growth and differentiation equations were developed. Batch, steady-state and step-test fermentation data from a laboratory-scale fermentor were incorporated into a maximum likelihood parameter estimation scheme for model identification. Confident estimates of growth and differentiation parameters were obtained for the segregated model using biomass measurements. In addition, the model describes successfully growth and differentiation in batch and steady-state operating modes.