Hydrothermal pretreatment of oil palm fronds for increasing enzymatic saccharification
The development of second generation bioethanol from lignocellulosic material is considered crucial in solving the problem between using crops for food demand or energy resources for fuel production. First generation bioethanol is derived mainly from food crops such as starch materials and sugar-based crops; however, they can create some issues such as greenhouse gas emissions and therefore increase the cost of food. Lignocellulosic residues such as wood (softwood and hardwood), straw, and grass are becoming increasingly popular as a renewable energy resources due to their year-long availability.1,2,3 Oil palm frond (OPF) is a suitable raw material as it is an abundant waste material produced by the palm oil industry in Indonesia. South Kalimantan alone generated 6.7 million tons of oil palm lignocellulosic biomass in 2017, which was comprised of 60% OPF.4 However, efficient and effective conversion of lignocellulosic materials into ethanol and other high-added value chemicals remains a challenge.
Pretreatment technology is an important factor in the bioconversion of lignocellulosic material due to its naturally recalcitrant structure. Many methods, chemical, physical, and biological have been investigated for use in the pretreatment of lignocellulosic material.5 The aim of pretreatment is to remove all compositional and structural obstacles such as hemicellulose and lignin, to enhance the rate of enzyme digestibility, and to increase the amount of fermentable sugars. One such pretreatment, hydrothermal pretreatment technology has been found to have some benefits over other technologies with no requirement of chemical agents other than water as the solvent and it is conducted at subcritical temperature. Under these conditions, the hydronium ion from water ionization acts as a catalyst in the reaction. Additionally, there are number of other advantages including the low total cost in production and the method is more environmentally-friendly.
In this study, a systematic investigation of the reaction time and temperature of hydrothermal pretreatment of OPF on chemical properties such as mass loss, pH of filtrate, color changes, and FTIR spectra was conducted. In addition, the effect of pretreatment on the enzymatic digestibility of cellulose was also determined.