Research On The Multi-objective Programming And Bi-level Programming Methods For Steady-state Optimization Of Biochemical Systems

Biotechnology is in a period of rapid development,and the status of biochemical system engineering is becoming more and more important.However,it is difficult to optimize and control the biochemical process because of its nonlinear,time variability and uncertainty.Moreover,in real life,the goal to be considered is not only one but two or more,And the objective conflict with each other,mutual restraint,therefore,how to improve the conversion rate of raw materials and the yield of the target product,and then improve the production level of the entire biochemical industry is the most important part of the biochemical system research.In this thesis,the steady-state optimization of biochemical system is studied.The main contents and results are as follows:1.For the problem of multi-objective optimization of biochemical system,under the framework of S-system,a new method for finding the optimal solution is presented.Firstly,the ordinary differential equation model of the biochemical system is rewritten into the form of the S-system,and the S-system form of the multi-objective optimization problem is obtained;Then the multi-objective nonlinear optimization problem is transformed into a multi-objective linear programming problem;Based on the NBI(Normal Boundary Intersection)method,the multi-objective linear programming problem is transformed into a series of single objective linear optimization problems.Compared with weighted sum and genetic algorithm,the results obtained in this thesis can obtain the Pareto optimal solution with more uniform distribution.2.For the problem of steady-state optimization of biochemical system,under the framework of GMA(Generalized Mass Action)system,a bi-level programming optimization model is proposed,and the objective function of the optimization problem isto maximize the flux;The objective function of the optimization problem is to minimize the metabolic cost of biochemical system;In order to effectively solve the proposed bi-level programming model,Firstly,the objective function of the outer layer and inner layer is expressed as a power function.Then,the double level programming problem is transformed into a relatively simple problem by using logarithmic transformation.Finally,the new dual problem is transformed into a nonlinear optimization problem by using the dual theory of linear programming,and obtain its solution.The computational results show that the results obtained by this method are more practical than the existing methods.