Assessment of Natural Deep Eutectic Solvent Pretreatment on Sugar Production from Lignocellulosic Biomass

Before the conversion of lignocellulosic biomass into fuel such as ethanol, the biomass needs to be pretreated and the yield of ethanol is highly dependent on the pretreatment efficiency. This study investigate the performance of deep eutectic solvent (DES) in pretreating sago waste which is a type of starchy biomass. The suitable type of DES in sago waste pretreatment was selected based on three criteria, which is the structural characteristic, the sugar yield during enzymatic hydrolysis and the amount of sugar loss during pretreatment. In this study, three types of DES namely Choline Chloride-Urea (ChCl-Urea), Choline Chloride-Citric acid (ChCl-CA) and Choline Chloride-Glycerol (ChCl-Glycerol) was investigated. The effect of temperature and duration on DES pretreatment was also investigated. All DES reagents were able to disrupt the structure and increase the porosity of sago waste during pretreatment. ChCl-Urea was selected in this study as it shows apparent structural disruption as examined under Scanning Electron Microscope (SEM). The highest glucose yield of 5.2 mg/mL was derived from enzymatic hydrolysis of ChCl-Urea pretreated sago waste. Moreover, reducing sugar loss during ChCl-Urea pretreatment was low, with only 0.8 mg/mL recorded. The most suitable temperature and duration for ChCl-Urea pretreatment is at 110°C and 3 hr. In a nutshell, the application of DES in pretreatment is feasible and other aspects such as the biodegradability and recyclability of DES is worth investigating to improve the economic feasibility of this pretreatment technique