Pretreatment of Oil Palm Empty Fruit Bunch (OPEFB) at Bench-Scale High Temperature-Pressure Steam Reactor for Enhancement of Enzymatic Saccharification

Abstract

Up scaling of biomass pretreatment from laboratory scale to a bench-scale reactor is one of important steps in the application of the pretreatment for pilot or commercial scale. This study reports the optimization of pretreatment conditions, namely reaction temperature and time, by one factor at a time (OFAT) method for the enhancement of enzymatic saccharification of oil palm empty fruit bunch (OPEFB). OPEFB was pretreated using high temperature-pressure steam reactor with different reaction temperatures (160, 170, 180, 190, 200 °C) and times (10, 20, 30, 40, 50 min). The effectiveness of the pretreatment was determined based on chemical compositions of untreated and pretreated OPEFB and sugar production from enzymatic saccharification of the pretreated OPEFB. Solubilized components in the water that generates the steam were also determined. Pretreatment at 180°C for 20 min provides the highest sugar yields (97.30% of glucose yield per initial cellulose and 88.86% of xylose yield per initial hemicellulose). At the optimum condition 34.9% of lignin and 30.75% of hemicellulose were successfully removed from the OPEFB and resulted in 3.43 delignification selectivity. The relationship between severity factor and by-products generated and the sugars obtained after enzymatic saccharification were discussed. The pretreated OPEFB at the optimum condition was also characterized for its morphological characteristic by scanning electron microscopy (SEM) and crystallinity by X-ray diffractometry (XRD) and then compared it with untreated one. The steam pretreatment caused some fiber disruptions with more defined and opened structures and increased of the crystallinity index (CrI) by 2.9% compared to the untreated OPEFB