Utilization of lignocellulosic waste for ethanol production : Enzymatic digestibility and fermentation of pretreated shea tree sawdust

Enzymatic hydrolysis and fermentation methods were evaluated on alkaline peroxide pretreated shea tree sawdust conversion to ethanol. Optimum pretreatment conditions of 120 °C reaction temperature, 30 min reaction time, and 20 mL L^?1 of water hydrogen peroxide concentration (1%(v/v)H₂O₂) solubilized 679 g kg^?1 of hemicellulose and 172 g kg^?1 of lignin. 617 g kg^?1 cellulose was retained in the solid fraction. The maximum yield of reducing sugar with optimized enzyme loadings by two enzyme preparations (cellulase and β-glucosidase) was 165 g kg^?1 of dry biomass. The ethanol yield was 7.35 g L^?1 after 72 h incubation period under the following conditions: 2% cellulose loading, enzyme concentration was 25 FPU (g cellulose)^?1 loading, yeast inoculums was 10% (v/v), 32 oC, and pH 4.8. The pretreatments gave information about the hindrances caused by lignin presence in lignocellulosic materials and that hemicelluloses are better hydrolyzed than lignin, thereby enhancing enzymatic digestibility of the sawdust material.