Fuzzy control systems for the regulation of substrate feeding rate in the fed-batch cultivation of Scutellaria baicalensis G

A structured kinetic model is proposed to describe cell growth, secondary metabolite, and flavone glycosides, synthesis in batch suspension culture of Scutellaria baicalensis G. plant cell. Optimal initial glucose concentration was determined through the investigation of specific growth rate at various glucose concentrations, and then two kinds of substrate feeding strategies are proposed. One is that the glucose concentration of 28 g/L is maintained to promote the cell growth at the first period, and afterward the glucose concentration of 5 g/L is maintained to promote flavone glycosides based on experimental result of batch culture. The other is to find the optimal concentration profile by kinetic model simulation using a genetic algorithm. The fuzzy logic controller was constructed for the control of substrate concentration in fed-batch operation. The fuzzy rule of a simple fuzzy logic controller was composed based on the operator's experience and knowledge. Because of a few drawbacks in a simple fuzzy logic controller, a self-organizing fuzzy logic controller was constructed using a genetic algorithm. Through the reproduction, crossover, and mutation operators, the self-organizing fuzzy logic controller was automatically constructed, and applied to the fed-batch cultivation of Scutellaria baicalensis G. The experimental result of self-organizing fuzzy logic control showed that the control performance and the productivity of flavone glycosides could be enhanced in comparison with the results of simple fuzzy control.