Fractionation of EFB was conducted in two consecutive steps using a batch reaction system: hemicellulose
hydrolysis using acetic acid (AA; 3.0–7.0 wt.%) at 170–190 C for 10–20 min in the first stage, and
lignin solubilization using ammonium hydroxide (5–20 wt.%) at 140–220 C for 5–25 min in the second
stage. The two-stage process effectively fractionated empty fruit bunches (EFB) in terms of hemicellulose
hydrolysis (53.6%) and lignin removal (59.5%). After the two-stage treatment, the fractionated solid contained
65.3% glucan. Among three investigated process parameters, reaction temperature and ammonia
concentration had greater impact on the delignification reaction in the second stage than reaction time.
The two-stage fractionation processing improved the enzymatic digestibility to 72.9% with 15 FPU of
cellulase/g of glucan supplemented with 70 pNPG of b-glycosidase (Novozyme 188)/g-glucan, which
was significantly enhanced from the equivalent digestibility of 28.3% for untreated EFB and 45.7% for
AAH-fractionated solid.