Abstract
To improve ethanol production fermentation efficiency from sweet sorghum juice under a very high gravity (VHG, 280 g/L of total sugar) condition by Saccharomyces cerevisiae NP01, dried spent yeast (DSY), yeast extract, and glycine concentrations were optimized using an L9 (34) orthogonal array design. The results showed that the order of influence on the ethanol concentration (PE) was yeast extract > glycine > DSY. The optimal nutrient concentrations for ethanol production were determined as follows: yeast extract, 3; DSY, 4; and glycine, 5 g/L. When a verification experiment under the projected optimal conditions was done, the P, ethanol yield (Yp/s), and ethanol productivity (Qp) values were 120.1 g/L, 0.47, and 2.50 g/L·h, respectively. These values were similar to those of the positive control experiment with yeast extract supplementation at 9 g/L. The yeast viability under the optimal condition was higher than that of the control experiment. To improve sugar utilization and ethanol production, aeration at 2.5 vvm for 4 h was applied under the optimal nutrient supplementation. The P, Yp/s, and Qp values were significantly increased to 134.3 g/L, 0.50, and 2.80 g/L·h, respectively.
Highlights
Bioethanol is an alternative fuel that has been of much interest for most of the past 50 years [1].Ethanol can be blended with gasoline or can be used alone in dedicated engines
S. cerevisiae NP01 was inoculated into yeast extract malt extract (YM) medium and incubated at 30 ◦ C with an agitation rate of 150 rpm for 15 h [21]
Were approximately 25% to 27% higher than with no supplementation. These results indicate that higher than with no supplementation. These results indicate that supplementation with a combination supplementation with a combination yeast extract and dried spent yeast (DSY) and glycine (as an yeast extract and DSY and glycine significantly promoted osmoprotectant) significantly promoted sugar consumption and ethanol production efficiency
Summary
Bioethanol is an alternative fuel that has been of much interest for most of the past 50 years [1]. Ethanol can be blended with gasoline or can be used alone in dedicated engines. It can be used in advanced flexi-fuel hybrid engines [2]. A strong need exists for efficient ethanol production using low-cost raw materials and production processes. Ethanol can be produced from numerous biomass feedstocks. In addition to the main raw materials, i.e., sugarcane, corn grain, tapioca starch, and sugarcane molasses, sweet sorghum (Sorghum bicolor (L.) Moench) juice is a promising alternative feedstock for bioethanol production. Its stalks contain high levels of fermentable sugars
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