This study presents an analysis of a Bifidobacterium longum ATCC 15707 optimization study. Kinetic growth models were fitted to cultivations from a central composite circumscribed (CCC) experiment design for three variables (temperature as well as glucose and yeast extract concentration). The parameters of these kinetic models, mu(max), Ks, Y-XS and m(S), were used as responses of the experiment design. This novel concept of combining optimization and modeling presented slightly different optimal conditions for B. longum growth from the original optimization study. However, the optimum of this study could be based on more scientific arguments. The parameters of the kinetic model represent the physiological effects that the cultivation parameters impose on the organism. A difference was observed in the optimum of the initial glucose concentration, which was originally thought to benefit process efficiency. This re-analysis showed that it is better for all aspects of cell physiology (substrate efficiency and growth rate) to use a lower initial glucose concentration. (C) 2007 Elsevier Ltd. All rights reserved.