A mild biomass pretreatment using γ-valerolactone for concentrated sugar production

Abstract

Here we report that γ-valerolactone (GVL), a biomass-derived solvent, can be used to facilitate the mild pretreatment of lignocellulosic biomass. An 80% GVL, 20% water solvent system was used to pretreat hardwood at the mild temperature of 120°C with an acid loading of 75 mM H 2 SO 4 . Up to 80% of original lignin was removed with 96-99% of original cellulose retained in the pretreated substrates. The use of a mild temperature and low acid concentrations caused negligible degradation of sugars. Up to 99% of the original glucan and 96% of the original xylan could be recovered after pretreatment. The pretreated substrate was quantitatively converted to sugars (99% and 100% total glucose and xylose yield) with an enzyme loading of 15 FPU g −1 glucan. These digestibilities were three times higher than those obtained when using other organic solvents such as tetrahydrofuran or ethanol, and 20 times higher than when pure water was used during pretreatment. Over 99.5% of GVL could be recovered by liquid-CO 2 extraction of the pretreated slurries while removing less than 1% of the sugars. This approach produced pretreatment slurries that could easily undergo high-solids (30% w/v) enzymatic hydrolysis without any substrate washing or drying. We obtained glucose and xylose yields of up to 90% and 97%, respectively, and generated sugar streams with sugar concentrations up to 182 g L −1 .The sugar-based biorefinery platform has been increasingly studied for the purpose of sustainably producing chemicals, fuels and materials from lignocellulosic biomass.

Minimal viable sugar yield of biomass pretreatment

“…The first analysis considers six different pretreatment concepts using only beech wood as feedstock: dilute acid (DA), ionic liquid (IL), Kraft, liquid hot water (LHW), a one‐phasic organosolv (OS) and a two‐phasic organosolv (Organocat (OC)) (cf. supplementary material File S1 for selection of references).…”

Bioethanol from Lignocellulosic Biomass

“…Another option that has been revitalized is pretreatment with ionic liquids to fractionate biomass at mild reaction conditions [23, 141,142]. The use of gamma-valerolactone (GVL) was introduced more recently to remove lignin from biomass and promote its deconstruction [143]. Most recently, adding tetrahydrofuran (THF) in solution with water significantly enhanced dilute acid deconstruction of biomass at lower reaction temperatures by simultaneously promoting high sugar recovery from hemicellulose into the liquid, producing highly digestible glucan-rich solids, and extracting lignin by precipitation from solution after removing low boiling tetrahydrofuran (THF) [144].…”

Introduction to High Pressure CO2 and H2O Technologies in Sustainable Biomass Processing

“…Notably, liquid CO 2 was used to extract over 99% of GVL from the reaction media of several biomass conversion processes. 59,60 After its addition, a CO 2 -expanded phase was created with GVL, which was no longer miscible with water. This lead to the production of a GVL phase and a concentrated aqueous phase containing over 90% of the carbohydrates produced from biomass which allowed for an easy recovery of GVL.…”

“…This lead to the production of a GVL phase and a concentrated aqueous phase containing over 90% of the carbohydrates produced from biomass which allowed for an easy recovery of GVL. [59][60][61][62] Another important approach developed for biorefinery processes has been the use of CO 2 explosion to disrupt raw cellulosic substrates. [63][64][65][66][67] The instantaneous release of CO 2 at high pressure promotes the disruption of the cellulosic structure and leads to increases in the accessible surface area of the substrate used for further hydrolysis.…”