State estimation for novel kinetic model oscillatory behavior with a time delay for bioethanol production

This study presents a novel model for bioethanol production with oscillatory behavior, which incorporates a reaction mechanism based on simple power law kinetics. In addition, compared with other models, the concept of "feedback" defined by the metabolism of Zymomonas mobilis was considered. The inhibition of the by-product is introduced in the proposed kinetics, as well as the time delay with respect to biomass that generates a complex behavior for a limit cycle attractor, which is validated experimentally. The proposed model was employed for a bifurcation numerical analysis using dilution rate and delay time. Finally, this demonstrates an innovative method for estimating the states in a nonlinear time-delayed model using an extended Kalman filter (EKF) observer. A laboratory-scale experiment estimated two out of three internal non-measurable nonlinear states on-line was applied. The biomass concentration was selected as the measured bioreactor’s output via an on-line device, where the estimate variables were the substrate and ethanol concentrations. The research contributes to the understanding of systems, provides insights into the communication dynamics within biological systems, and offers a practical solution for estimating the unmeasured state in realistic scenarios.