Deconstruction of Woody Biomass via Protic and Aprotic Ionic Liquid Pretreatment for Ethanol Production

Abstract

Ionic liquids (ILs) have emerged as important solvents for conversion of lignocellulosic feedstocks to fuels and chemicals due to their ability to enable efficient biomass deconstruction and fractionation. Woody biomass derived from forest and agricultural residues has the potential to be used for production of biofuels and it's removal from forests can help mitigate disastrous wildfires in fire-prone states like California. This study evaluated woody biomass types (pine, almond, walnut, fir) from California as potential biofuel feedstocks. The feedstocks were pretreated with the ILs cholinium lysinate ([Ch][Lys]) and ethanolamine acetate ([EOA][OAc]), followed by enzymatic hydrolysis and fermentation of lignocellulosic sugars to produce ethanol.Under optimal conditions, [EOA][OAc] pretreatment and enzymatic hydrolysis generated glucose and xylose yields in the range of 24-82% and 14-80%, respectively, while glucose and xylose yield for the [Ch][Lys] ranged between 28-83% and 23-80%, respectively. Maximum fermentable sugar was released from almond wood and the lowest amount was from pine and fir.Blends of feedstocks were also explored and a blend with a mass ratio of 2/2/1 (almond:walnut:pine) resulted in maximum glucose and xylose (> 90%) yields using [Ch][Lys].Fermentation of this hydrolysate using a C5-utilizing strain of Saccharomyces cerevisiae resulted in a maximum ethanol concentration of 17.9 g/L for mixture biomass hydrolysate, corresponding to 60.8 % fermentation efficiency. This study represents the first demonstration of the use of these ILs for pretreatment of woody biomass blends that resulted in a high overall conversion efficiency for ethanol production.

High-Efficiency Conversion of Ionic Liquid-Pretreated Woody Biomass to Ethanol at the Pilot Scale

“…Scale-up of one-pot ionic liquid pretreatment and enzymatic saccharification: In previous work, Das et al 19 demonstrate proof of concept for one-pot conversion of woody biomass to ethanol, utilizing a 2:2:1 blend of almond, walnut, and pine wood, coupled to [Ch][Lys] pretreatment. Blending hardwood (almond and walnut) with softwood pine synergistically increased the conversion efficiency of the mixed feedstock.…”

“…17 More recently, in a work described by Das et. al 19 , conversion of [Ch][Lys]pretreated woody biomass was demonstrated at bench scale using a blend of almond, walnut, and pine wood, achieving a maximum sugar yield of >90 % and an ethanol titer of 18 g/L.…”

“…In this study, we build on the proof of concept demonstrated by Das et al 19 by optimizing pretreatment and scale-up of an integrated one-pot process for deconstruction of California woody biomass and for efficient fermentation of the resulting hydrolysate, documenting strategies to overcome biomass recalcitrance and toxicity towards bioconversion. In particular, we focus on achieving efficient woody biomass deconstruction at high solids loading, and on adapting fermentation conditions to overcome hydrolysate toxicity and achieve full conversion of both glucose and xylose in the resulting intensified hydrolysates.…”

Wood Waste from Fruit Trees: Biomolecules and Their Applications in Agri-Food Industry

“…Focusing on polysaccharide content, almond wood waste contains 22.3% glucan (glucose polymer) and 11.1% xylan (xylose polymer), making a total of 33.4% (dried biomass) fermentable sugars. Furthermore, almond pruning residues were also composed of lignin with a value of 20.0% of biomass [ 84 ].…”

Biocatalysis in ionic liquids: state-of-the-union

“…211 Similarly, good results were obtained in woody biomass processing by conducting the integrated pretreatment, saccharification and fermentation in cholinium lysinate, [Ch][Lys]. 212,213 The cholinium cation and the amino acid anion render this IL biocompatible and self-buffering, respectively. 214,215 DESs have also been used in lignocellulose deconstruction 216…”