Abstract
Pretreatment of lignocellulosic materials to disrupt their recalcitrant structures is a crucial step on second generation biofuel production. In this study, response surface methodology (RSM) was used to investigate the effects of dilute sulfuric acid hydrolysis conditions on switchgrass (Panicum virgatum L.). A central composite rotatable design (CCRD) was applied to assess the effect of acid concentration (0.16 – 1.84% (w/w)), solid load (4.9 – 30.1% (w/w)) and hydrolysis time (9.6 – 110.5 min), on glucose, xylose and total sugars (glucose, xylose and arabinose) recovery yields and total inhibitors generated (acetic acid, levulinic acid, 5- hydroxymethylfurfural and furfural) after acid hydrolysis. Afterwards, enzymatic hydrolysis of the solid phase was performed as a second treatment step. Experimental data were fitted to a second order polynomial model to find the optimum acid hydrolysis conditions by multiple regression analysis. The results show a strong dependence of total sugars recovery and total fermentation inhibitors on acid concentration, and a weaker dependence on solid load and acid hydrolysis time. The optimized hydrolysis conditions, predicted by the polynomial model, were 1.72% (w/w) of sulfuric acid concentration and 112.0 min of acid hydrolysis time, for a fixed value of 10.0% (w/w) of solid load, with a total sugars yield of 78.8% for acid hydrolysis combined with a subsequent enzymatic hydrolysis step.
