Abstract Modeling the different phases of the bacterial growth curve and the production of α-amylase by Bacillus sp. KR-8104 in a solid-state fermentation process based on variation in dry weight was the aim of this study. The result showed that the growth of bacterial cells and the production of α-amylase on a wheat bran substrate could be expressed by simple models incorporating the mathematical definition of each phase and the variation in dry substrate weight over the incubation time. Experimental data collected from a series of batch fermentations were used to validate the models proposed. In both cases, the model simulation matched well with the experimental observations, which made it possible to conclude that these models can be successfully employed for the development of growth and α-amylase production in solid-state fermentation processes.