Development of a nonsingular transformation algorithm and its application to on-line optimal control of poly-beta-hydroxybutyric acid production by Alcaligenes eutrophus.

摘要

In this research, a method which transforms singular control problems to nonsingular problems was developed and applied to various systems to calculate optimal control profiles.; For fed-batch fermentation, the substrate concentration was used as the control variable instead of the usual approach of taking the feed rate as the control variable. The computational difficulty associated with singular controls for higher order systems was eliminated. The optimal control profiles for higher order systems were calculated with the transformation algorithm.; The transformation algorithm was also applied to two singular control variable systems and computational difficulty was circumvented using nutrient concentrations as control variables instead of feed rates. The optimal control profiles of two singular control variable systems have been calculated by the nonsingular transformation algorithm.; The PHB (poly-{dollar}beta{dollar}-hydroxybutyric acid) production by Alcaligenes eutrophus was used as an experimental model system. Alcaligenes eutrophus used glucose as a carbon source and ammonium chloride as a nitrogen source. The feed rate control of glucose and ammonium chloride was important to maximize PHB productivity. The transformation algorithm was used to calculate optimal feed rate profiles of glucose and ammonium chloride.; Although a mathematical model was developed, it was not accurate in describing the experimental system. Feedback concentration control, off-line feed rate optimal control, and on-line optimal control were used to compensate for differences between the model and real system. The performance of an on-line optimal control algorithm was compared with other ones. The final PHB concentration was 10.8 g/L with on-line feedback control, 13.9 g/L with off-line optimal control, and 17.1 g/L with on-line optimal control. The performance index was highest when on-line optimal control with the developed transformation algorithm was used.; For the high cell density culture, a fifteen liter fermentor, MICRO I, was used. The nonsingular transformation algorithm was used to calculate optimal control profiles. The cell concentration achieved was as high as 141 g/L and PHB concentration 105 g/L for 40 hours fed-batch operation. The PHB productivity was 2.63 g/(L hr).; The PHB/HV (poly-{dollar}beta{dollar}-hydroxybutrate-co-poly-{dollar}beta{dollar}-hydroxyvalerate) production by using propionic acid as co-substrate was proposed as another experimental system. The glucose, ammonium chloride, and propionic acid feed rates were used as manipulated variables. The mathematical model was developed and kinetic parameters were estimated for the calculation of optimal feed rate profiles. The optimal control profiles were calculated for the difference performance indices using the transformation algorithm.