Adaptive Control of CO2 Production during Milk Fermentation in a Batch Bioreactor

Abstract

The basic characteristic of batch bioreactors is their inability to inflow or outflow the substances during the fermentation process. This follows in the simple construction and maintenance, which is the significant advantage of batch bioreactors. Unfortunately, this characteristic also results in the inability of the current industrial and laboratory batch bioreactors to control fermentation production during the process duration. In some recent studies, it was shown that changing the temperature could influence the execution of the fermentation process. The presented paper shows that this phenomenon could be used to develop the closed-loop control system for the fermentation production control in batch bioreactors. First, based on theoretical work, experiments, and numerical methods, the appropriate structure of the mathematical model was determined and parameters were identified. Next, the closed-loop control system structure for batch bioreactor was proposed, and the linear and adaptive control system based on this structure and the derived and identified model were developed. Both modeling and adaptive control system design are new and represent original contributions. As expected, due to the non-linearity of the controlled plant, the adaptive control represents a more successful approach. The simulation and experimental results were used to confirm the applicability of the proposed solution.

Practical Approaches to the Control of Milk Fermentation with Kefir Grains

“…For the acquisition of the measured signal of the dissolved CO 2 concentration, the hardware SevenMulti from Mettler Toledo together with LabX direct software was implemented. The control system was realized by means of dSpace 1103 device [22]. Block diagrams of the laboratory measurement and control system are shown in Figures 1 and 2.…”

“…where symbols denote: T': positive semi-definite matrix, and T: positive definite matrix. Considering (22) for the calculation of K i (t), it is obvious that the proposed integral term in the presence of disturbances, whenever perfect following is not possible, may reach unnecessarily large values, or may even diverge. In order to improve the convergence of the adaptive system, the following modification of the integral term was proposed [30]:…”

“…The quantity and quality of the product in the batch bioreactor are decisively dependent on the trajectories of the biological quantities in the fermentation process, affecting the kinetics of the bioprocess [1,3,12,22]. In today's used industrial batch bioreactors without a closed-loop control system, the course of the fermentation process depends only on the substances that were placed in the bioreactor before the beginning of the fermentation process and cannot be influenced during the fermentation process.…”

“…The use of the heating system for control of the fermentation process in batch bioreactors was presented in Refs. [18][19][20][21][22], and use of the stirrer system in Refs. [18,23].…”