I. Introduction
Monitoring fermentation processes has been address for a long time. First, measurements errors were concerned and data reconciliation techniques from stoechiometric considerations were used [WAN,83]; [VAN,94]). Another approach utilized data miming or data analysis to deeper exploit information that is contained in repeated fed-batch cultures ([STE, 97]; [KAM, 00]; [LEN, 01]; [NOM, 95]). The origin of the deviation between expected behavior and the actual was then difficult to establish.