Feasibility of eliminating washing step in bioethanol production using deep eutectic solvent pretreated lignocellulosic substrate

The current scheme of bioethanol production generally involves pretreatment, enzymatic hydrolysis and fermentation. After pretreatment, extensive washing is usually applied prior to enzymatic hydrolysis. This study investigates the potential of eliminating washing step in glucose recovery and ethanol production scheme when DES pretreatment is applied. The feasibility of DES synthesized using choline-chloride with citric acid (ChCl-CA), glycerol (ChCl-Gly), urea (ChCl-Urea) and malonic acid (ChCl-MA) were investigated in pretreating sugarcane bagasse. The pretreatment condition of the best performed DES was then optimized. Subsequently, glucose recovery and bioethanol production using washed and unwashed DES-pretreated bagasse were compared. Results show that ChCl-MA is the most suitable DES to pretreat sugarcane bagasse due to high sugar recovery while having low sugar loss during the process. The pretreatment was best conducted at 130 degrees C, 3.2 h with 4% solid loading. The maximum amount of glucose recovered after 48 h of enzymatic hydrolysis from both washed and unwashed pretreated substrate was insignificantly different. Bioethanol obtained from unwashed pretreated substrate was slightly higher (5.2 g/L) compared to washed substrate (4.9 g/L). This study suggests that the application of recyclable DES in pretreatment, alongside with the potential elimination of washing could improve the current bioethanol production scheme. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the potential of eliminating washing step in glucose recovery and ethanol production scheme when DES pretreatment is applied. The most suitable DES for pretreating sugarcane bagasse was found to be ChCl-MA, which resulted in high sugar recovery and low sugar loss during the process. The maximum amount of glucose recovered after 48 hours of enzymatic hydrolysis from both washed and unwashed pretreated substrate was insignificantly different, but slightly higher bioethanol was obtained from the unwashed pretreated substrate compared to the washed substrate.