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

The goal of this proposed research is to utilize each of stalks juice, the acid hydrolysate of both lignocellulosic components of the juice extracted stalks and grains of 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 minerals 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 was also converted 67% of the starch in the grains into reducing sugars. After 72 h of fermentation, the medium containing starch grains hydrolysate gave the highest ethanol production (23.93 g/l) with yield of 0.50 g alcohol per g sugar and fermentation efficiency of 97.39% comparing with other two mediums having stalks juice and stalks hydrolysate (SH) as carbon sources. Also the yeasts in this medium consumed highest amount of sugars and gave the highest biomass yield followed by that containing stalks hydrolysate. Waste water which was remained after recovering of ethanol and removing the 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.