Combination of ultrasonication and deep eutectic solvent in pretreatment of lignocellulosic biomass for enhanced enzymatic saccharification

The synergistic effect of ultrasonication with deep eutectic solvent (DES) on pretreatment of oil palm empty fruit bunch (OPEFB) was investigated. Three different types of DESs, namely choline chloride:lactic acid (ChCl:LA), choline chloride:urea (ChCl:U) and choline chloride:glycerol (ChCl:G) were applied. The performance of the pretreatment was evaluated based on yield of reducing sugars, lignin content, crystallinity index, structural and morphology changes. ChCl:LA pretreated OPEFB attained the highest yield of reducing sugars (36.7%) under the action of ultrasonication for 15 min at sonication power 60% (210 W) and temperature 50 degrees C, followed by ChCl:U (35.8%) and ChCl:G (35.3%). Under these conditions, ChCl:LA pretreated OPEFB showed significant change in structural and morphology, associated with the lowest crystallinity and lignin content. ChCl:LA promoted the pretreatment process in view of its intrinsic properties of low viscosity and low surface tension. The incorporation of ultrasonication in DES pretreatment significantly increased the reducing sugars yield suggested the synergistic effect of ultrasonication with DES pretreatment. These signifies that ultrasound-assisted DES pretreatment could be a promising alternative pretreatment technique for lignocellulosic biomass.

Automated summary

The synergistic effect of ultrasonication with deep eutectic solvent (DES) on pretreatment of oil palm empty fruit bunch (OPEFB) has proven to significantly enhance the process, with Choline chloride:lactic acid (ChCl:LA) leading to the highest yield of reducing sugars and the lowest crystallinity and lignin content, possibly due to its intrinsic properties of low viscosity and low surface tension. The incorporation of ultrasonication in DES pretreatment resulted in a significant increase in reducing sugars yield, highlighting the promising potential of ultrasound-assisted DES pretreatment as an alternative technique for lignocellulosic biomass.