Résumé : Macroscopic models of bioprocesses are very useful to build engineering tools like simulators, software sensors, controllers,... This kind of models consists of a system of mass balances for the macroscopic species involved in a reaction scheme. Such a reaction scheme can be determined analytically by a systematic procedure to generate and compare all the C-identifiable schemes given a set of components for which concentration measurements are available. This paper presents the application of this procedure to the modelling of a xylanase production within fed-batch bacterial cultures. Moreover, the adaptation of the procedure to estimate simultaneously the cell lysis rate is described.