- Automatic feeding with the following direct control of process parameters;
- Mathematical modelling for calculation of optimal feeding rate profiles and respective substrate concentrations and implementation of the optimized open-loop control strategy.
Both approaches, if they are used separately, do not allow to exploit ensure fed-batch process in optimal way. The mathematical models usually are not enough flexible, for example, regarding the properties of components and other not well defined conditions. However, most of commercially available bioreactors have possibilities to control pO2 over cascades and feeding, but these options are used seldom. Not always it is possible to control pO2 over feeding without corrections of the other parameters, and the optimal pO2 level not always assures an optimal growth limiting substrate concentrations.
In order to increase the efficiency of the automatic fed-batch control mode, it was combined with mathematical modelling with the aim to develop improved process control program using flexible process controller.
This study and developments were carried out in different fermentations applying different pO2 cascade control rules. In cascades, the stirrer rotation speed, oxygen enrichment and substrate feeding rate were used as control variables. During the processes, the O2 and CO2 levels in outlet gases were analyzed. The algorithms and approaches were studied in the cultivation processes based on yeast S. cerevisiae CEN.PK and bacteria Escherichia coli BL21 as host organisms by producing of recombinant proteins.