Establishing a feed-forward control strategy of fed-batch fermentation for the kinetic model of yeast growth

• Main Authors: Yehn Yu, 游越
• Other Authors: Yuan-Kuang Guu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/52111503619881440780

碩士 === 國立屏東科技大學 === 食品科學系所 === 100 === The object of this study is to establish a kinetic model for Saccharomyces cerevisia growth in a fed-batch fermentation to achieve a high cell density using feed-forward strategy. The feeding time course was adjusted based on the prediction of yeast growth to keep the concentration of carbon course in the fermentation medium within a certain rang, so that the growth of S. cerevidiae maintained at its log phase. Component and factorial analyses were also conducted to identify a set of carbon and nitrogen sources for this study. Steepest ascent was used to identify an appropriate C/N ratio. The results indicated that sucrose and soytone were the most effective carbon and nitrogen sources, respectively, for biomass production in this case (p <0.05). When the medium contains 2 g/L of sucrose and has a C/N ratio of 15:1, the yield of cell mass based on the sucrose consumption (YX/S) reaches 51.35%. Under these conditions, the growth of yeast can reach the log phase within 0~3 h post-incubation. The YX/S and specific growth rate (μ) during this log phase were 74.29% and 0.26 h-1, respectively. The concentration of carbon source in the fermentation medium was controlled in a range of 1~2 g/L through adjustment of feeding frequency. Unfortunately, the primary result showed that the sugar concentration in the medium accumulated up to 5 g/L after 18.10 h post-incubation due to unknown influence factors. To adjusted the deviation of the predicted outcome, a holding time of 0.5 h lag phase was applied and an extra delay time was also calculated and added based on the increasing sugar concentration for each feeding interval. For more accurate prediction on sugar consumption, fine tune the prediction model according to the track of experimental sugar demand. The result shows that the prediction model was approximately a quadratic equation, and the variation of substrate concentration seemed to be steadily controlled in a range of the prediction model from 0.85 g/L to 1.90 g/L with a stable growth of yeast in the specific growth rate of 0.16 h-1, and harvest 28.33 folds of initial biomass after 18.95 h post-incubation. In conclusion, the design of this feed-forward model is capable of controlling yeast growth effectively, and may provide a potential approach to develop an automatic process for high cell mass production using yeast.