Suitability of Sorghum bicolor L. stalks and grains for bioproduction of ethanol

The goal of this proposed research is to utilize each of the stalk juice, the acid hydrolysate of both lignocellulosic components of the juice extracted stalks and grains of the non food sweet sorghum crop as a carbon source during bioproduction of ethanol using Saccharomyces cerevisiae and simultaneous saccharification fermentation (SSF) process. The obtained results revealed variation in proximate composition of carbohydrate compounds and mineral content between the sweet sorghum crop parts used in this study. The acid hydrolysis of the lignocellulosic components of stalks led to hydrolyze 11.18% of cellulose, 76.91% of hemicelluloses and 24.27% of lignin. It also converted 67% of the starch in the grains into reducing sugars. After 72 h of fermentation, the medium containing starch grain hydrolysate gave the highest ethanol production (23.93 g/l) with a yield of 0.50 g alcohol per g sugar and fermentation efficiency of 97.39% comparing with other two mediums having stalk juice and stalk hydrolysate (SH) as carbon sources. Also the yeasts in this medium consumed the highest amount of sugars and gave the highest biomass yield followed by that containing the stalk hydrolysate. Waste water which remained after the recovery of ethanol and the removal of biomass from the fermentation medium had considerable levels of potassium, sodium, Mg, Ca, Fe, Cu and Mn and can be recommended for use in plant irrigation.