Bioethanol Production from Lignocellulosic Materials: Pretreatment, Saccharification and Fermentation

In the lignocellulosic materials (wheat stem, pearl millet stem and sorghum stem), the cellulose content is 35–38%, lignin is 12–25%, hemicelluloses is 25–30% and rest is other components. The sugar concentrate after pretreatment [Dilute sulphuric acid (2%v/v), 121°C, 15 psi for 30 min] of wheat stem (170 mg/g), pearl millet stem (120 mg/g) and sorghum stem (lOOmg/g). Sequential application of overtiming (pH 10.0) and activated charcoal (1.5%, w/v) adsorption was used to remove these toxic compounds from the acid hydrolysate. The acid-pre-treated biomass of wheat stem, pearl millet stem and sorghum stem was further delignified through combined pretreatment of sodium sulphite (5.0% w/v) and sodium chlorite (3.0% w/v), which resulted in about 67 - 75% lignin removal. Enzymatic hydrolysis with combinations of enzymes of delignified cellulosic substrates showed best saccharification after 78 h incubation at 500°C and pH 5.0 in pearl millet (95%). Fermentation of acid and enzymatic hydrolysates with Candida tropicalis and saccharomyces cere-visiae at 30°C and pH 6.0, wheat stem 16.4 g/l, pearl millet 31.4 g/l and 16.3g/l of ethanol concentration with corresponding yields of 0.39, 0.37and 0.41g/g after 78 h, respectively.