Sweet Sorghum as Feedstock for Ethanol Production: Enzymatic Hydrolysis of Steam-Pretreated Bagasse
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Sweet sorghum is an attractive feedstock for ethanol production. The juice extracted from the fresh stem is composed of sucrose, glucose, and fructose and can therefore be readily fermented to alcohol. The solid fraction left behind, the so-called bagasse, is a lignocellulosic residue which can also be processed to ethanol. The objective of our work was to test sweet sorghum, the whole crop, as a potential raw material of ethanol production, i.e., both the extracted sugar juice and the residual bagasse were tested. The juice was investigated at different harvesting dates for sugar content. Fermentability of juices extracted from the stem with and without leaves was compared. Sweet sorghum bagasse was steam-pretreated using various pretreatment conditions (temperatures and residence times). Efficiency of pretreatments was characterized by the degree of cellulose hydrolysis of the whole pretreated slurry and the separated fiber fraction. Two settings of the studied conditions (190 °C, 10 min and 200 °C, 5 min) were found to be efficient to reach conversion of 85–90%.
KeywordsSweet sorghum Ethanol fermentation Lignocellulose Steam pretreatment Enzymatic hydrolysis
This work was financially supported by National Research and Development Programs (NKFP OM00152/2005) and the Hungarian National Research Fund (OTKA–K 72710). Guido Zacchi is gratefully acknowledged for the possibility of steam pretreatment. Enzymes were kindly donated by Novozymes A/S (Bagsvaerd, Denmark). Research Institute, Karcag is acknowledged for the sweet sorghum samples.
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