Alkaline pretreatment methods followed by acid hydrolysis of Saccharum spontaneum for bioethanol production

Different alkaline pretreatment methods (NaOH, NaOH + 10% urea and aqueous ammonia) were optimized for maximum delignification of Saccharum spontaneum at 30 °C. Maximum delignification were obtained as 47.8%, 51% and 48% from NaOH (7% NaOH, 48 h, and 10% biomass loading), NaOH + urea (7% NaOH + 10% urea, 48 h and 10% biomass loading) and 30% ammonia (40 days and 10% biomass loading) respectively. H2SO4 60% (v/v), 10% biomass loading at 30 °C for 4 h, were optimized conditions to solubilize the cellulose and hemicellulose from solid residue obtained after different optimized alkaline pretreatments. Slurry thus obtained was diluted to obtain final acid concentration of 10% (v/v) for real hydrolysis of cellulose and hemicellulose at 100 °C for 1 h. Among all pretreatment methods applied, the best result 0.58 g (85%) reducing sugars/g of initial biomass after acid hydrolysis was obtained from aqueous ammonia pretreated biomass. Scheffersomyces stipitis CBS6054 was used to ferment the hydrolysate; ethanol yield (Yp/s) and productivity (rp) were found to be 0.35 g/g and 0.22 g/L/h respectively.