MICROAERATION STUDY IN THE ALCOHOLIC FERMENTATION OF SUGARCANE MOLASSES

Aeration has been extensively studied in the alcoholic fermentation processes, since it helps the yeast to tolerate the stress caused by ethanol through the synthesis of sterols and unsaturated fatty acids, involved in maintaining the health of the cell membrane. The objective of this study was to verify the influence of aeration on alcoholic fermentation in fed-batch by Saccharomyces cerevisiae flocculating using sugarcane molasses. Fermentations with the same substrate concentrations and process conditions were performed, analyzing the influence of aeration 0.2 vvm during the whole fermentation. The inoculum consisted of 220 mL of cellular decanter added with 140 mL of molasses solution containing 155 g/L of TRS, totaling 360 mL. During 6 hours the system was fed with molasses base medium with a concentration of 200 g/L of TRS until the reactor reached a volume of 1200 mL, with a flow rate of 0.140 L/h. The temperature was maintained at 32 ± 0.5°C and the pH of the medium was adjusted to 4.5 at the beginning of each fermentation with the addition of HCl 2N. Total fermentation time was 12 h. In both fermentations, the same profile of TRS consumption was observed and in the aerated fermentation the reducing sugar at the end of the fermentation was slightly smaller when compared to the non-aerated fermentation. As for the production of ethanol, there was a decrease in its concentration at all times in the aerated fermentation. At the end of the fermentation, the concentration of ethanol obtained was 35% lower in relation to the concentration of ethanol obtained in the non-aerated fermentation. In the case of fermentations with low concentrations of TRS, aeration favored cell growth, to the detriment of ethanol production, but favored in terms of cell viability.