Optimization of maleic acid pretreatment of oil palm empty fruit bunches (OPEFB) using response surface methodology to produce reducing sugars

Abstract

The application of maleic acid (MA) has led to increase efficiency and selectivity in biomass pretreatment process. This study aimed to determine the optimum condition of MA pretreatment of oil palm empty fruit bunch (OPEFB) using Response Surface Methodology (RSM) with Composite Central Design (CCD) to increase the reducing sugar yield (RSY). The variables in this optimization process were acid concentration (0.16–1.84 %), temperature (153.2–186.8 °C), and pretreatment time (9.55−90 min) with RSY as the response parameter. The results show that the optimum condition of MA pretreatment of OPEFB is at a temperature of 176.57 °C, pretreatment time of 70 min and MA concentration of 1.5 % with RSY of 22.32 %. Pretreatment facilitates the improvement of the OPEFB structure and digestibility in hydrolysis process. After pretreatment, the hemicelluloses content and degree of crystallinity of OPEFB decreased, which enables easier enzyme access to hydrolyze cellulose into glucose. The disruption of surface morphology of pretreated OPEFB also facilitates in increasing of enzymatic hydrolysis performance. Compared to untreated OPEFB, the RSY of pretreated OPEFB with MA and Liquid Hot Water (LHW) is higher by 42.98 %.