Decoding biomass recalcitrance: Dispersion of ionic liquid in aqueous solution and efficient extraction of lignans with microwave magnetic field

Abstract

Alkaline ionic liquid aqueous solutions were used to extract biphenyl cyclooctene lignans derivatives, and hydrolyze to the free-state biphenyl cyclooctene lignans simultaneously from Schisandra chinensis by microwave-assisted heating. The hydrogen bonds formatted between ionic liquid and water molecular attacks the amorphous region of cellulose. Selective heating by microwave produce the more polar regions, which results in swelling and fragmentation of raw materials near the hot spots. Therefore, ionic liquid-microwave-assisted extraction method of free-state biphenyl cyclooctene lignans was set up. The solid residue after treatment was characterized by infrared spectroscopy and scanning electron microscopy, which showed that cellulose, hemicellulose, and lignin were removed partially. The water content of ionic liquid solution affected its viscosity and diffusivity, and in turns the extraction efficiency of lignans. The IL solutions with different mole fractions of IL were detected by FTIR and Raman spectroscopy, the result shows that IL solutions with higher water contents (>0.6) won't form clusters. The optimum hydrolysis conditions were 0.2 g of ionic liquid catalyst per 5.0 g of S. chinensis fruits, a microwave irradiation power of 600 W, and heating time of 12 min, which gave a yield of free-state biphenyl cyclooctene lignans of 4.12±0.37 mg g −1. Besides, a hydrolysis mechanism of ester-bond biphenyl cyclooctene lignans and decreasing "biomass recalcitrance effect" by ionic liquid microwave-assisted method was proposed.

Microwave Encounters Ionic Liquid: Synergistic Mechanism, Synthesis and Emerging Applications

“…Afterward, the hydrogen bonds formed between ILs and water molecules attack the amorphous region of cellulose. When MW irradiation is imposed, selective heating of ILs by MWs produces localized overheating domains, in the vicinity of which the swelling and fragmentation of raw materials occurs . Furthermore, MW irradiation is capable of heating intracellular water molecules, leading to cell disruption and therefore acceleration of intracellular compounds transferring from biomass to solvents …”

Oil Palm Empty Fruit Bunch Waste Pretreatment with Benzotriazolium-Based Ionic Liquids for Cellulose Conversion to Glucose: Experiments with Computational Bibliometric Analysis

“…These factors affect the enzymatic hydrolysis of polysaccharides into sugars. Several strategies can be done to make the pretreatment efficient, namely (1) the lignin and hemicellulose cross-linked matrix that attaches to the cellulose fiber needs to be removed or disrupted, (2) hydrogen bonds in crystalline cellulose also need to be disturbed, and (3) surface area and porosity of cellulose need to be increased for further extraction and hydrolysis (Xia et al, 2020). Therefore, the development of pretreatment methods, selection of operating conditions, and design of pretreatment equipment is usually an empirically trial-and-error process (Yiin et al, 2021).…”