Ethanol production from sweet sorghum juice using very high gravity technology: Effects of carbon and nitrogen supplementations

Ethanol production from sweet sorghum juice by Saccharomyces cerevisiae NP01 was investigated under very high gravity (VHG) fermentation and various carbon adjuncts and nitrogen sources. When sucrose was used as an adjunct, the sweet sorghum juice containing total sugar of 280 g l−1, 3 g yeast extract l−1 and 5 g peptone l−1 gave the maximum ethanol production efficiency with concentration, productivity and yield of 120.68 ± 0.54 g l−1, 2.01 ± 0.01 g l−1 h−1 and 0.51 ± 0.00 g g−1, respectively. When sugarcane molasses was used as an adjunct, the juice under the same conditions gave the maximum ethanol concentration, productivity and yield with the values of 109.34 ± 0.78 g l−1, 1.52 ± 0.01 g l−1 h−1 and 0.45 ± 0.01 g g−1, respectively. In addition, ammonium sulphate was not suitable for use as a nitrogen supplement in the sweet sorghum juice for ethanol production since it caused the reduction in ethanol concentration and yield for approximately 14% when compared to those of the unsupplemented juices.