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

[Display omitted] • ChCl-MA has high pretreatment efficiency with low sugar loss. • Temperature has the most significant effect on ChCl-MA pretreatment. • No significant difference in glucose yield from washed and unwashed substrate. • Unwashed DES-pretreated bagasse has higher ethanol yield. • Feasible to eliminate washing step in bioethanol production scheme. 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 °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. [ABSTRACT FROM AUTHOR]