A review on organosolv pretreatment of softwood with a focus on enzymatic hydrolysis of cellulose

Abstract

A clean and efficient fractionation of biomass into cellulose, hemicellulose and lignin streams is a key step in biofuel and biorefinery industries. Lignin-free cellulose and hemicellulose streams can be enzymatically hydrolysed to sugars for fermentation to different biofuels, high value biochemicals and biopolymers. Towards this objective, organosolv pretreatment is the promising strategy to separate lignin from carbohydrates. Scientific information on the organosolv pretreatment using lignocellulosic biomass in general and various organic wastes is available with a focus on lignin separation and its use. Amongst different lignocellulosic biomass, softwood is a challenging feedstock due to recalcitrance towards enzymatic hydrolysis of cellulose. The aim of this review is to describe technical and research efforts on various organosolv processes developed specifically for softwood as a feedstock and how it influences enzymatic hydrolysis of cellulose. Process severity factor, selection of the solvent and choice of a catalyst in organosolv process are discussed. The differences in conventional pulping versus organosolv pretreatment and physico-chemical changes that occur in organosolv fractionated cellulose, lignin and hemicellulose are explained. Pilot and demonstration scale organosolv treatment plants and the challenges they face going towards commercialisation, as well as a path to the future growth and advancement in softwood organosolv processes, are discussed. Graphical abstract

Engineering All-Round Cellulase for Bioethanol Production

“…The organic solvent inhibitors often influence the enzymatic fermentation, which often occur after organic solvent pretreatment in the 2G ethanol process . Therefore, we further investigated the tolerance of CBHI variants in four additional organic solvent inhibitors (e.g., 1,4-dioxane (Dioxan), dimethyl sulfoxide (DMSO), methanol, and hexane).…”

“…The organic solvent inhibitors often influence the enzymatic fermentation, which often occur after organic solvent pretreatment in the 2G ethanol process. 28 Therefore, we further 4f). And R2 and R4 enhanced 2.5-and 6.9-fold inhibitor tolerance in the presence of 50% (v/v) DMSO, respectively (Figure 4f).…”

Sustainable lignin modifications and processing methods: green chemistry as the way forward

“…The delignification processes are not included in this review given that they are well discussed in literature. 5,[28][29][30][31][32][33] In the field of lignin research, several interesting reviews have been published. However, these reviews mainly focus on one aspect of lignin valorization, i.e., either the fractionation and/or depolymerization of lignin from lignocellulosic biomass, 5,34,35 the synthesis of lignin-derived polymers, 36 or the application of lignin-derived polymers (reinforcement filler, antioxidant, and adsorbents).…”

“…The delignification processes are not included in this review given that they are well discussed in literature. 5,28–33 In the field of lignin research, several interesting reviews have been published. However, these reviews mainly focus on one aspect of lignin valorization, i.e.…”

Valorization of Lignocellulosic Biomass into Biofuels and Value-Added Products for Sustainable Environment: A Comprehensive Review

“…Organosolv pretreatment is one of the promising methods for the effective valorization of lignocellulosic biomass into value-added chemicals that could facilitate the shift towards increased use of renewable biomass substrates. Organosolv pretreatment uses organic solvents (ethanol, methanol, formic acid, acetic acid, phenol, glycerol, or, acetone) or their aqueous solutions to specially extract or remove lignin from lignocellulosic feedstocks [82]. The organosolv pretreatment provides for highly efficient generation of ethanol, lignin and other biochemicals from biomass when compared to other pretreatment techniques.…”