Comparison of organosolv pretreatment of masson pine with different solvents in promoting delignification and enzymatic hydrolysis efficiency

Abstract

Organosolv pretreatment has been verified to facilitate the enzymatic hydrolysis by efficient delignification. Recently, novel solvents derived from biomass have been applied in lignocellulose pretreatment. However, few studies on the pretreatment of softwood with novel solvents have been reported. In this study, organosolv pretreatments with three green solvents, including γ-valerolacton (GVL), tetrahydrofuran (THF), and 2-methyltetrahydrofuran (2-MTHF), were performed on masson pine, and compared with conventional ethanol (EtOH) pretreatment. The results showed that GVL pretreatment exhibited the best performance for removing lignins from masson pine, achieving a pretty high lignin removal ratio of 87.2 % at 150 °C with 75 mM H2SO4. Correspondingly, the highest glucose yield of 76.8 % was observed in the enzymatic hydrolysis of GVL pretreated masson pine with a relatively low cellulase loading (20 FPU/g glucan). The relations between relative energy difference of the solvent-lignin interactions and both of the lignin removal and enzymatic digestibility of organosolv pretreated substrates were evaluated. Furthermore, the structural features of four organosolv lignins were characterized, including molecular weights, functional groups, inter-unit linkages and aromatic information. The results provide a better understanding of organosolv pretreatment effects on enzymatic digestibility of softwood biomass, and give comprehensive lignin properties for valorization of organosolv lignins from softwood.