(602c) Situ Detection of Fermentative Activity by Redox Potential Measure and Its Applications During Ethanol Fermentation

Redox potential reflects the complex physiological information in cells that can be detected for optimizing the fermentation processes. However, control redox potential by delicate approaches is not easy due to lack of mathematic relationships between redox potential profiles and fermentation parameters. In this work, three important parameters including temperature, pH and dissolved oxygen are chosen to buildup a dynamic model according to Nerst equation. Fermentative activity defined as the specific consummation rate of substrate is connected with the redox potential profiles slope, but not the redox potential value. Base on this model, a feeding scheme was developed to maintain the glucose concentration at a low level in order to eliminate the substrate inhibition, and an aeration scheme was proposed to prolong the duration with rapid ethanol production under high cell viability. Besides, when utilizing the self-flocculating yeast, redox potential controlled repeated batch fermentation realizes the cells recycle and then higher ethanol productivity is achieved because of very high density yeast cells.