Abstract
In the current study, alkaline hydrogen peroxide pretreated oil palm trunk fibers were subjected to ethanol production via simultaneous saccharification and fermentation (SSF). The effect of high substrate loading, enzyme and substrate feeding strategy, and influence of a pre-hydrolysis step in SSF was studied to scale up ethanol production. In the enzyme feeding strategy, the addition of an enzyme at the start of fed-batch SSF significantly (p < 0.05) increased ethanol concentration to 51.05 g/L, ethanol productivity (Q(P) ) to 0.61 g/L·h, and ethanol yield (Y (P/S)) to 0.31 g/g, with a theoretical ethanol yield of 60.65%. Furthermore, the initial velocity of the enzyme (V (0)) in the first 8 h was 2.27 (g/h) with a glucose concentration of 18.17 g/L. On the other hand, the substrate feeding strategy and pre-hydrolysis simultaneous saccharification and fermentation (PSSF) process were studied in a 1 L fermenter. PSSF in fed batch with 10 and 20% (w/v) significantly improved enzyme hydrolysis, circumvent the problems of high viscosity, reduced overall fermentation time, and gave the highest ethanol concentration of 51.66 g/L, ethanol productivity (Q(P) ) of 0.72 g/L·h, ethanol yield (Y (P/S)) of 0.31 g/g, and theoretical ethanol yield of 60.66%. In addition, PSSF with 10 and 20% significantly increased the initial velocity of the enzyme (V (0)) to 4.64 and 4.40 (g/h) and glucose concentration to 37.14 and 35.27 g/L, respectively. This result indicated that ethanol production by PSSF along with substrate feeding could enhance ethanol production efficiently.