title: Cybernetic model predictive control of a continuous bioreactor with cell recycle.
abstract: The control of poly-beta-hydroxybutyrate (PHB) productivity in a continuous bioreactor with cell recycle is studied by simulation. A cybernetic model of PHB synthesis in Alcaligenes eutrophus is developed. Model parameters are identified using experimental data, and simulation results are presented. The model is interfaced to a multirate model predictive control (MPC) algorithm. PHB productivity and concentration are controlled by manipulating dilution rate and recycle ratio. Unmeasured time varying disturbances are imposed to study regulatory control performance, including unreachable setpoints. With proper controller tuning, the nonlinear MPC algorithm can track productivity and concentration setpoints despite a change in the sign of PHB productivity gain with respect to dilution rate. It is shown that the nonlinear MPC algorithm is able to track the maximum achievable productivity for unreachable setpoints under significant process/model mismatch. The impact of model uncertainty upon controller performance is explored. The multirate MPC algorithm is tested using three controllers employing models that vary in complexity of regulation. It is shown that controller performance deteriorates as a function of decreasing biological complexity.
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, USA.
authors.forename: Kapil G
authors.initials: KG
authors.lastname: Gadkar
authors.forename: Francis J
authors.initials: FJ
authors.lastname: Doyle
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Crowley
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Varner
mesh_terms: D000465:Algorithms; D019149:Bioreactors / Q000382:microbiology*; D018929:Cell Culture Techniques / Q000379:methods*; D003198:Computer Simulation; D020118:Cupriavidus necator / Q000254:growth & development* / Q000378:metabolism*; D003491:Cybernetics / Q000379:methods*; D004734:Energy Metabolism / Q000502:physiology; D005246:Feedback; D006706:Homeostasis / Q000502:physiology; D006885:Hydroxybutyrates / Q000378:metabolism*; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000502:physiology; D011091:Polyesters / Q000378:metabolism*; D000094122:Polyhydroxybutyrates
chemical_list: D006885:Hydroxybutyrates; D009097:Multienzyme Complexes; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates