Model-based optimization of temperature and feed control strategies for glycerol production by fed-batch culture of osmophilic yeast Candida krusei

Abstract

In this study, the optimization of temperature and feed control strategies for glycerol production by fed-batch culture of osmophilic yeast Candida krusei was investigated to maximize the final yield whilst to control the residual glucose at a low concentration. For the purposes of convenient control performance and easy numerical solution, the entire fermentation process was proposed being divided into multi-subintervals. In each subinterval, temperature was controlled constantly; while glucose and corn steep liquor were fed in pulse form at each start. Both piecewise-constant temperature (PCT) and discrete-pulse feed (DPF) control strategies were optimized by the complex method of Box based on previous macro-kinetic model and verified experimentally in a 600 ml airlift loop reactor. It was found that, by model-based optimization of only DPF control strategies, the final glycerol yield were significantly improved compared with those by previous empirical strategies. The yield could be improved further by optimization of both PCT and DPF control strategies and by selecting the first half of the whole fermentation process as the control emphasis. The optimization approach proposed appeared promising to solve the multivariable control problem in many fermentation processes.