Second generation bioethanol production from Saccharum spontaneum L. ssp. aegyptiacum (Willd.) Hack

Saccharum (Saccharum spontaneum L. ssp. aegyptiacum (Willd.) Hack.), is a rapidly growing, wide ranging 26 high-yield perennial, suitable for second generation bioethanol production. This study evaluated oxalic 27 acid as a pretreatment for bioconversion. Overall sugar yields, sugar degradation products, enzymatic 28 glucan hydrolysis and ethanol production were studied as effects of temperature (150–190 C), reaction 29 time (10–40 min) and oxalic acid concentration 2–8% (w/w). Time and temperature were combined into a 30 single parameter, Severity Factor (SF) [Log (R0)], and related to oxalic acid using a response surface meth- 31 odology. Maximum total sugar yield was attained at a SF of 2.93 and 6.79% (w/w) oxalic acid, while max- 32 imum formation of sugar degradation products was observed at the highest SF (4.05) and 5% (w/w) oxalic 33 acid. These were also the conditions for maximum simultaneous saccharification and fermentation (SSF) 34 of the residual solids. Commercial cellulases and Saccharomyces cerevisiae attained 89.9% glucan conver- 35 sion and 17.8 g/l ethanol. Pichia stipitis CBS 6054 fermented hemicellulosic hydrolysates from less severe 36 conditions to ethanol with a yield of 0.35 (ge/gs). Maximal product yields were 69% of theoretical value 37 and 90% of the SSF conversion efficiency for hydrolysate fermentation and SSF, respectively.