Statistical optimization of thermo-chemical pretreatment of elephant grass for efficient delignification and enzymatic saccharification

Elephant grass (EG) is an opportunistic, invasive weed and is least explored lignocellulosic waste for bioethanol production. This study unleashes the potential of EG for high-yield production of total reducing sugar (TRS) by enzymatic saccharification using commercial cellulase. This was achieved by the optimization of the delignification process of EG by employing response surface methodology, using alkaline hydrogen peroxide (AHP) concentration, temperature and time duration of pretreatment as significant variables with the lignin content and total carbohydrate content (TCC), as the two major responses. The statistical method optimization of pretreatment of 7.5% (w/v) EG biomass gave the optimum conditions, 4.2% (v/v), AHP, 101.8 °C and 147.6 min. The raw EG contained 22.4% (w/w) lignin and 634 mg/g_{raw EG} TCC. EG pretreated under optimized conditions showed significantly low lignin content, 6.5% (w/w), and TCC, 720 mg/g_{pretreated EG}, resulting in 71% delignification. The AHP pretreated EG (AHPpEG) displayed 26.5% higher crystallinity index and more rough disrupted surface morphology than raw EG. The enzyme saccharification of 10% (w/v) AHPpEG by commercial cellulase gave remarkable TRS yield of 670.6 mg/g, attaining 93% saccharification efficiency. These results provide a promising approach toward utilization of EG as a potential resource for achieving substantial TRS for bioethanol-based biorefineries.