Optimisation of Uncatalysed Steam Explosion of Lignocellulosic Biomasses to Obtain Both C6- and C5-Sugars

The conversion of rice husk and elephant grass into sugars was investigated by uncatalysed steam explosion. The effect of temperature and time was evaluated for the pretreatment steps in order to obtain an optimal content of hexoses in the solid fraction and pentoses in the liquid fraction, according to the conditions of the experimental design. Optimal values of the sugars of interest were reached for each of the studied lignocellulosic biomasses and, regardless of the raw material, there was a similarity between the independent variables of the optimized conditions. After enzymatic hydrolysis using 5% (w/v) of solids and 15 FPU g−1 substrate, steam pretreatment at 205 °C for 11.5 min led to 37.38 g glucose/100 g glucose, while the acid hydrolysis of the liquor resulted in 47.53 g xylose/100 g xylose in the untreated rice husk. For elephant grass, a temperature of 207 °C for 9.5 min generated 56.63 g glucose/100 g glucose and 29.20 g xylose/100 g xylose in the untreated elephant grass. The findings of this research introduce a multivariate approach which may be useful in the design of subsequent biochemical processes.