Fractionation and delignification of empty fruit bunches with low reaction severity for high sugar recovery

•Fractionation and delignification pretreatment has been conducted with EFB.•Operational condition was optimized using CS and compositional changes respectively.•5-Carbon and 6-carbon sugars and lignin could be separated with high selectivity.•Very low level of sugar degradation products could be found in hydrolyzate.•EFB has more amenable property for fractionation and consecutive delignification. Fractionation and delignification of empty fruit bunches (EFB) was conducted in a series of two steps under low reaction severity with the aim of minimizing the neutralization of hydrolyzates. In EFB underwent acid fractionation, the glucan content was increased to 62.4%, at which point 86.9% of the hemicellulosic sugar and 20.5% of the lignin were extracted from the raw EFB. Xylose-rich hydrolyzate, indicating a high selectivity of 17.7 could be separated. Through the consecutive delignification of acid-fractionated EFB using sodium hydroxide, solid residue with a high glucan content (70.4%) and low hemicellulosic sugar content (3.7%) could be obtained, which indicated that 95.9% of the hemicellulosic sugar and 67.5% of the lignin were extracted based on raw EFB. The final pretreated solid residue was converted to glucose through enzyme hydrolysis, which resulted in an enzymatic digestibility of 76.9% was achieved.