On-line control of feeding of medium components to attain high cell density

On line control coupled with an expert system was constructed for the contr ol of a fed-batch culture with the aim of achieving a high fell density. Du ring the cultivation, the expert system could monitor the extents of suffic iencies in the amounts of chemical elements in the medium every 10 min, and suggest a modification to the feeding control policy if the amount of a pa rticular component was inadequate for cell growth. However, we often encoun ter such a kind of cultivations in which some particular carbon source such as glucose and ethanol should be controlled at low concentration in many c ulture processes, because the excess feeding might cause the growth inhibit ion by its own accumulation in the culture broth, or the biproduct accumula tion like as lactate or acetate, unsuitable substances for smoothed growth. In this study, we developed an online control system based on production r ules which managed the glucose feed rate from DO signal. The online control was carried our by the control computer connected with the other computer for expert system, because a relatively long time (several minutes) was nee ded for the inference of the expert system and the influence of the starvat ion of carbon source on the cell growth is not negligible even in several m inutes. The on-line control system with expert system was applied to the pr oduction of cell mass of E, coli W3110 and the final cell concentration rea ched 137 g-dry cell weight/l.