Parameter Identification And Optimization Of Switched System In Uncoupled Fed-batch Fermentation Based On Genetic Regulation

The thesis studies the uncoupled microbial fed-batch fermentation process of glycerol bioconversion to 1,3-propanediol(1,3-PD)with genetic regulation.Based on the definition of biological robustness,the parameter identification problem of switched system in fed-batch fermentation is discussed.In order to increase the output of the terminal target product 1,3-PD,a corresponding optimal control model is established in this thesis.An numerical optimization algorithm is constructed by using the relaxation method to solve this optimal control model,and the conclusion provides data reference for the actual fermentation experiment.The main contents and results of this paper are summarized follows.A novel sixteen-dimensional nonlinear switched system model is established containing four pathways in consideration of comprehensive factors that both the intracellular and extracellular environments,regulation of dha regulator and the possible inhibition ways of intracellular intermediate metabolite 3-hygroxypropionaldehyde(3-HPA)to glycerol dehydratase(GDHt)are involved.Based on the definition of robustness of state variables to parameters,taking the weighted sum of the relative errors between the calculated values on the extracellular state variables and the experimental values coupling with the robustness on the intracellular state variables as the performance index,a parameter identification model for the uncoupled fed-batch fermentation is formulated.An improved parallel Particle Swarm Optimization —Sequential Quadratic Programming algorithm(PPSO–SQP)is described.The identification model is numerically solved by using the above algorithm,and the optimal system parameters and most possible inhibition way of 3-HPA to GDHt are numerically determined.Based on the obtained parameter identification model,in order to increase the concentration of 1,3-PD at the terminal time,taking the feeding rates of glycerol and alkali,the switched times of difference models and the model sequence as the control variables,an optimal control model is proposed with the concentration of 1,3-PD on the terminal time as performance index.By means of relaxation method,the switched control problem is transformed into a relaxation problem.We solve the relaxationproblem using the uniform approximation theory,and the optimal solution obtained by the relaxation method is mapped to the optimal solution of the original problem by using the pulse width modulation operator.Based on this idea,an uniform approximation algorithm is constructed to solve the above model,and a satisfactory feeding strategy and corresponding switching mode sequence are obtained.