A fuzzy logic controller to control nutrient dosage in a fed-batch baker's yeast process
A fuzzy logic controller designed to control glucose feeding in a fed-batch baker's yeast process is presented. Feeding is carried out in portions and the controller determines the time at which glucose should be added and computes the size of the portion to provide the maximum glucose uptake rate. Moreover, the controller detects and prevents the occurrence of overdosage. The experimental results indicate that yield and specific growth rate obtained with the controller approached 55% and 0.13 h−1, respectively.
Fuzzy logic control and soft sensing applications in food and beverage processes
Abstract Biotechnological processes – particularly fermentation processes - play a very important technological an economical role for the production steps in the food and beverage sector. In order to ensure constantly high product quality combined with efficient manufacturing, intelligent control systems and strategies are required. However, biosystems contain living organisms and therefore underlie particular process dynamics such as nonlinear and time-varying behavior. Furthermore, initial process conditions cannot be kept constant and therefore precise process reproducibility hardly can be achieved. On that account these multivariate systems put high requirements to the practical on-line observation, control, monitoring and prediction of significant process key parameters whose acquirement is of crucial importance for a comprehensive understanding and control of the process. During the last decades great efforts have been undertaken to cope with those challenges by means of intelligent soft computing and reveal great opportunities to integrate human expertise and learning procedures for improved process control strategies of biological systems. Particularly fuzzy logic based control systems show high potential to manage the complex production processes and to deal with fragmental process information. This review critically presents the chances as well as the limitations of fuzzy and hybrid expert system approaches in food and beverage process control from a theoretical and application based point of view.
Modelling the dynamic behaviour ofSaccharomyces cerevisiae and its application in control experiments
SummaryA simple structured model describing the response of a baker's yeast culture to a glucose pulse is presented. The model is based on a limited oxidation capacity of yeast leading to a switchover from oxidative to oxido-reductive metabolism. The maximum specific consumption rates of glucose, ethanol and oxygen are modelled by first order transfer functions. These maximum rates have also been estimated experimentally as a function of the dilution rate in a continuous culture. The rates predicted by the model correspond to the measured maximum specific consumption rates. So, the model can describe a continuous culture of baker's yeast very well. The applicability of the model is tested by inserting it in a control loop and comparing the response of the model with the results of a controlled fermentation.The model behaved satisfactorily for the description of the pulse experiment as well as during the simulation of the control experiments. Although the model for balanced growth was rejected in simulating pulse responses, its results were conveniently when inserted in a control loop.