In industrial fed-batch bioreactors, imperfect mixing coupled with the biological consumption of nutrients causes temporal and spatial concentration gradients leading to the formation of zones very rich in substrate close to the feed port and low or even depleted regions further from it. The direct consequence is that cells experience a changing environment during the cultivation process and, thus, respond differently from laboratory cultivation, where a degree of homogeneity is assumed throughout the reactor. A drastic decline in the performance of the bioprocess is often observed in large-scale reactors due to this nonhomogeneity.