Production of ethanol from raw juice and thick juice of sugar beet by continuous ethanol fermentation with flocculating yeast strain KF-7

Abstract

Sugar beet juice can serve as feedstock for ethanol product due to its high content of fermentable sugars and high energy output/input ratio. Batch ethanol fermentation of raw juice and thick juice proved that addition of mineral nutrients could not improve ethanol concentration, but could accelerate the fermentation rate. Fermentation of thick juice with an initial pH of 9.1 did not affect the fermentation process. The continuous ethanol fermentation of raw juice was performed at 35 °C with a dilution rate of 0.3 h−1, resulting in ethanol concentration, ethanol yield and productivity of 70.7 g L−1, 89.8% and 21.2 g L−1 h−1, respectively. A two-stage reactor was used in the continuous ethanol fermentation of thick juice by feeding fresh yeast cells into the second reactor. This process was stable at a total process dilution rate of 0.11 h−1 with an overall sugar concentration of 190 g L−1 in the influent. The ethanol concentration was kept at approximately 80 g L−1, corresponding to ethanol yield of 82.5% and productivity of 8.8 g L−1 h−1.