Fig. 1

Overview of the fed-batch principle. a The oxygen transfer capacity k_LaC in a bioreactor limits the volumetric oxygen consumption rate r_O if aerobic conditions need to be maintained. Due to the relationship between the volumetric rates for growth (r_X), substrate consumption (r_S) and oxygen (r_O), r_O can be controlled by a control of the volumetric substrate uptake by a controlled substrate feed (F Feed rate, V reactor volume, Si substrate concentration in the feed solution). As the volumetric rates are the product of the specific rates (q_O, μ, q_S) with the actual biomass X, at a constant feed rate the specific rates decrease at increasing biomass and thus the level of dissolved oxygen is dependent on the feed rate, but largely independent on the cell density. b Principle view of a fed-batch bioreactor with a feed reservoir and the fee pump which controls the fee rate. c A typical simulation plot for a fed-batch cultivation on mineral salt medium with glucose as the only carbon source and a constant feed rate. The graph shows the Feed rate (F), dissolved oxygen tension (DOT), biomass (X), Substrate (S, often glucose) and the specific growth rate (my)