Reducing Sugars Production from Oil Palm Empty Fruit Bunches (OPEFB) by Combined Dilute Acids-Hydrothermal Pretreatment

OPEFB (oil palm empty fruit bunches) is one of the residues of oil-palm industry which can be utilized as bioethanol feedstock due to its high holocellulose content of about 60%. As with other bioethanol production from lignocellulosic biomass, OPEFB must be pretreated before subsequent enzymatic hydrolysis to break down or loosen the linkage of cellulose, hemicellulose, and lignin. Therefore, this study investigated the influence of three different acids (oxalic, maleic, and sulfuric acids), three concentrations (1, 3, 5%), and three heating durations (15, 30, 45 min) in an autoclave (121.1 °C) on the pretreatment of OPEFB and to evaluate sugar production after enzymatic hydrolysis of the pretreated OPEFB. The results show that maleic acid gave the highest reducing sugar yield of 19.78% at a 5% concentration for a 15 min heating duration. On comparison, 16.41 and 15.40% of reducing sugar yields were obtained from oxalic acid (5%, 15 min) and sulfuric acid (1%, 15 min) pretreated OPEFB, respectively. This study shows the promising result of using maleic acid for lignocellulosic pretreatment compared to oxalic and sulfuric acids.