Moderate pretreatment strategies for improvement of reducing sugar production from oil palm empty fruit bunches

Pretreatment at mild condition is the strategy to minimize energy consumption, to reduce toxic compounds influencing to further process, and to obtain the high reducing sugar yield as fermentation substrate from cellulose and hemicellulose of oil palm empty fruit bunches (OPEFB). The yield still could be increased by optimizing pretreatment condition and varying several process alternatives. In this study, the effect of acetic acid addition and its corresponding concentration (5-15%), pretreatment temperature (115-125 degrees C), time (60-90 minutes), and two-stage pretreatment (0.01-1M NaOH pretreatment followed by autohydrolysis and autohydrolysis followed by 0.1-1% acetic acid pretreatment) were evaluated. The residual solid after pretreatment was then enzymatically hydrolyzed by Cellic CTec2. The result showed that the addition of acetic acid was able to increase the yield of reducing sugar. In addition, the reducing sugar yield could be still increased when the temperature was escalated, but the extended pretreatment time gave the decline of reducing sugar yield. This yield, however, was still lower than this from NaOH pretreatment followed by autohydrolysis. The maximum yield of this pretreatment could be attained by 1 M NaOH concentration at 125 degrees C for 60 minutes with solid loading 10% (0.71 g/g-OPEFB).