The kinetics of the biotransformation of D-sorbitol to L-sorbose by Acetobacter suboxydans (NRRL B-72) features both substrate and product inhibition. Model-based reactor operating strategies can eliminate the inhibitions and improve the yield and productivity of the fermentation. Unstructured models are usually unable to acknowledge complex intracellular physiological changes and therefore their application to dynamic growth conditions is limited. By considering RNA as a bottleneck growth limiting compound a structured mathematical model was developed to describe the transient growth of Acetobacter suboxydans. The model parameters were determined by a non-linear regression technique which minimized the deviation between the model prediction and the experimental (extracellular and intracellular) continuous culture data. The model was used to simulate the transient culture behaviour during the step-down in the dilution rates (from 0.1 h(-1) to 0.05 h(-1)) in the continuous culture experiments. The experimental results and the model simulation results showed reasonable agreement.