Comparison study of organosolv pretreatment on hybrid pennisetum for enzymatic saccharification and lignin isolation

Abstract

Organosolv pretreatment is a promising method for enhancing the enzymatic hydrolysis of lignocellulosic biomass and the production of value-added chemicals. However, information on solvents and their interactions with biomass—specifically, their effects on residues and isolated lignin—is limited, hindering the effective utilization of biomass. Herein, the effects of organosolvs (including γ-valerolactone (GVL), tetrahydrofurfuryl alcohol (THFA), ethanol and acetone) on enzymatic saccharification and lignin isolation of hybrid Pennisetum (HP) under 100 °C for 2 h were investigated. Compared with water, organic solvents can significantly enhance delignification, reducing the crystallinity of cellulose, thereby improving the enzymatic digestibility and lignin recovery. The enzymatic digestibility of substrates reached 87.5% (about 80.8% of the raw HP glucan was recovered) for the THFA pretreatment, which was 38.7% higher than water-treated material and 131.5% higher than untreated raw material. Moreover, Hansen solubility parameters (HSP) was used to evaluate the effects of solvents, which showed a strong correlation between lignin removal and the molecular weight distribution of isolated lignins, suggesting that HSP can aid in finding appropriate organic solvents for pretreatment. Finally, the chemical structures and thermal properties of solid residues and precipitated lignins were analyzed via SEM, XRD, FTIR and thermogravimetric analysis.