(498b) Conversion of E-AFEX(TM) Pretreated Corn Stover to Ethanol by Bcrl Fast SHF Process

Extractive Ammonia Fiber Expansion (E-AFEX^TM) pretreatment convents cellulose I to cellulose III and removes part of the lignin in the biomass. Hence, E-AFEX^TM pretreated biomass typically has a higher enzyme digestibility compared to AFEX^TM. So far, E-AFEX^TM has not been fully studied in terms of fermentability and ethanol production potential. 

Here we present the performance of BCRL fast SHF process (Jin et.al, 2012, Energy Environ. Sci., 2012, 5(5), 7168-7175.) on E-AFEX^TM pretreated corn stover for ethanol production. We are aiming to achieve 2-3 times higher productivity with an enzyme loading as low as 8 mg/g glucan and similar or higher ethanol yield when compared to current technology. BCRL fast SHF process has been studied on regular AFEX^TM pretreated corn stover and showed high ethanol productivity and reduction of more than 1/3 enzyme loading. In the BCRL fast SHF process, the easily hydrolyzed part of biomass is converted to ethanol first in a 24 h enzymatic hydrolysis and 24 h fermentation process. This way the slow rate period of enzymatic hydrolysis is avoided. The liquid hydrolysate after fermentation is subjected to distillation. The residue solids (difficultly hydrolyzed part of biomass (DHPB)) with some enzymes adsorbed are transferred to the next cycle enzymatic hydrolysis for further hydrolysis. By this approach, parts of the enzymes are reused. After five cycles, the accumulated recalcitrant biomass is further hydrolyzed in the last step. With less degradation products and low initial sugar concentration, the hydrolysis of DHPB is easier to be hydrolyzed. For fermentation, we use high inoculation size (OD₆₀₀  =20) and recycle the yeast cells after fermentation. Details about the condition used and process optimization will be discussed during the presentation.