Evaluation of sugar yeast consumption by measuring electrical medium resistance

The real-time monitoring of alcoholic fermentation (sugar consumption) is very important in industrial processes. Several techniques (i.e., using a biosensor) have been proposed to realize this goal. In this work, we propose a new method to follow sugar yeast consumption. This novel method is based on the changes in the medium resistance (Rm) that are induced by the CO₂ bubbles produced during a fermentative process. We applied a 50-mV and 700-Hz signal to 75 ml of a yeast suspension in a tripolar cell. A gold electrode was used as the working electrode, whereas an Ag/AgCl electrode and a stainless-steel electrode served as the reference and counter electrodes, respectively. We then added glucose to the yeast suspension and obtained a 700% increase in the Rm after 8 minutes. The addition of sucrose instead of glucose as the carbon source resulted in a 1200% increase in the Rm. To confirm that these changes are the result of CO₂ bubbles in the fermentation medium, we designed a tetrapolar cell in which CO₂ gas was insufflated at the bottom of the cell and concluded that the changes were due to CO₂ bubbles produced during the fermentation. Consequently, this new method is a low-cost and rapid technology to follow the sugar consumption in yeast.