A fuzzy expert system for the optimization of glutamic acid production

A fuzzy expert system was developed to allow the effective use of semi-quantitative or imprecise information in the determination of the optimal operating conditions of a fermentation process. The system incorporated fuzzy relations representing both the trends of experimental data and semi-quantitative information obtained from the literature. The inference method used consisted primarily of search and reasoning based on fuzzy set theory. The resulting expert system incorporated a generalized inference engine designed to deal with various types of fermentation processes, it only being necessary to alter the knowledge database in order to adapt the system to process modifications. The construction of the knowledge database from experimental data or semi-quantitative information was designed to be carried out semi-automatically using a graphic computer tool.The expert system was applied to the optimization of glutamic acid production by fermentation. The optimal conditions predicted by the expert system were found experimentally to give maximum production.List of Symbols A, B names of objects - A _i , B _i linguistic level of A and B, respectively - E₁, E₂ ordinary sets - I depth of search for inference - I _M maximum of I - M, X, Y names of sets - R ₁, R ₂ fuzzy relations - P_total g amount of glutamic acid production - Pen⁺ h penicillin addition time - S_vp1 h^–1 specific rate of glutamic acid production in 1st production phase - S_vp2 h^–1 specific rate of glutamic acid production in 2nd production phase - T _growth h growth period - T _lag h lag time - T _plag h lag time of production defined in Fig. 6 - T _p1 h period of 1st production - T _p2 h period of 2nd production - T _total h total production time - X _p g average cell mass of production phase - x, y, z real numbers - max(x, y) or x y maximum of x and y - min(x, y) or x y minimum of x and y