Integrated Production of Xylitol, Ethanol, and Enzymes from Oil Palm Empty Fruit Bunch through Bioprocessing as an Application of the Biorefinery Concept

Abstract

Oil palm empty fruit bunch (OPEFB), an abundant source of lignocellulosic biomass waste, is rich in hemicellulose and is converted into xylose for xylitol production. The remaining cellulose-rich residue can be efficiently hydrolyzed into glucose, which serves as a substrate for bioethanol and enzymes. This process aligns with an integrated biorefinery model aimed at optimizing the utilization of OPEFB. This study optimizes a two-stage enzymatic hydrolysis fermentation for OPEFB conversion into value-added products. Using a 4% NaOH pretreatment, lignin was degraded while preserving hemicellulose and cellulose. This hydrolysis yielded 12.27 g/L of xylose and 36.86 g/L of glucose. Ethanol production, using varied fermentation media, achieved maximum concentrations of 0.043 g/L for xylitol and 21.35 g/L for ethanol, with substrate-to-product yields of 0.005 g/g and 0.374 g/g, respectively. Furthermore, enzyme production by Aspergillus niger was assessed on multiple parameters, recording a peak cellulase activity of 55.16 ± 20.24 U/mL and enzyme weight of 42.748 kDa. The OPEFB substrate yielded the highest protein content of 0.00942 ± 0.00010 mg/mL. These findings demonstrate the feasibility and efficiency of the two-stage enzymatic hydrolysis strategy in facilitating integrated biorefinery processes for efficient and sustainable OPEFB utilization.