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Sweet sorghum as a whole-crop feedstock for ethanol production

Barcelos, Carolina A., Maeda, Roberto N., Santa Anna, Lídia Maria M., Pereira, Nei
Biomass and bioenergy 2016 v.94 pp. 46-56
Saccharomyces cerevisiae, Scheffersomyces stipitis, alternative crops, bagasse, enzymatic hydrolysis, ethanol, ethanol production, feedstocks, fermentation, grains, hemicellulose, hydrolysates, hydrolysis, juices, lignin, lignocellulose, nutrients, saccharification, sweet sorghum
The potential of sweet sorghum as an alternative crop for ethanol production was investigated in this study. Initially, the enzymatic hydrolysis of sorghum grains was optimized, and the hydrolysate produced under optimal conditions was used for ethanol production with an industrial strain of Saccharomyces cerevisiae, resulting in an ethanol concentration of 87 g L−1. From the sugary fraction (sweet sorghum juice), 72 g L−1 ethanol was produced. The sweet sorghum bagasse was submitted to acid pretreatment for hemicellulose removal and hydrolysis, and a flocculant strain of Scheffersomyces stipitis was used to evaluate the fermentability of the hemicellulosic hydrolysate. This process yielded an ethanol concentration of 30 g L−1 at 23 h of fermentation. After acid pretreatment, the remaining solid underwent an alkaline extraction for lignin removal. This partially delignified material, known as partially delignified lignin (PDC), was enriched with nutrients in a solid/liquid ratio of 1 g/3.33 mL and subjected to simultaneous saccharification and fermentation (SSF) process, resulting in an ethanol concentration of 85 g L−1 at 21 h of fermentation. Thus, from the conversion of starchy, sugary and lignocellulosic fractions approximately 160 L ethanol.ton−1 sweet sorghum was obtained. This amount corresponds to 13,600 L ethanol.ha−1.