The effects of FeCl3 concentration on hydrothermal pretreatment of oil palm fronds to enhance reducing sugar production

Abstract

The effects of FeCl3 concentration on hydrothermal pretreatment of oil palm fronds (OPF) to enhance reducing sugar production have been systematically investigated for the first time. The hydrothermal pretreatment was carried out in autoclave reactor with Teflon at 190 oC for 30 min with various FeCl3 concentrations of 0.075; 0.150; and 0.225 M. The residue from hydrothermal pretreatment (then noted as a substrate) was hydrolyzed by the enzyme (Cellulase Onozuka RS) in water bath shaker at 50 °C for 48 h. The amount of reducing sugar was analyzed by DNS (dinitrosalicylic acid) method using UV-visible spectroscopy. The reduced mass of substrate, change of color, alteration of pH of filtrate, and functional group analysis using Fourier Transform Infrared Spectroscopy (FTIR) results indicated the decomposition of OPF structures. The highest reducing sugar (3.800 g/L) of the substrate was obtained when the concentration of 0.225 M was used, which was higher than the pretreatment without FeCl3 added (2.673 g/L). Overall, our study concludes that the hydrothermal pretreatment assisted by FeCl3 can catalyze the decomposition of OPF structures to give the enzymes accessibility and enhance the reducing sugar production.