Efficient pretreatment using dimethyl isosorbide as a biobased solvent for potential complete biomass valorization

03 March 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

An efficient and sustainable pretreatment, such as organosolv pretreatment that produces high-quality lignin and highly digestible carbohydrates, could enable the potential complete utilization of lignocellulosic biomass. Demand for bio-based solvents with a high boiling point, low viscosity, and negligible toxicity is increasing. Herein, we report the use of dimethyl isosorbide (DMI) as a solvent to fractionate lignocellulosic biomass into its main components for the first time. High lignin removal efficiency (91.2%) with good cellulose retention (around 80%) could be achieved during the pretreatment of Eucalyptus by DMI/H2O co-solvents under a mild condition. A near-complete cellulose conversion to its monosaccharide could be realized at a relatively low enzyme loading of 20 FPU g−1 glucan. The addition of water could suppress the condensation of lignin, yielding high-quality lignin with a good fraction of β-O-4 linkages reserved (24.8%) and homogeneous molecular weight (Đ<2) suitable for depolymerization to mono-aromatic chemicals. Besides its highly digestible nature, the high quality of the cellulose-rich residue is also demonstrated from a material perspective. A more efficient fibrillation of obtained pulp to nanocellulose was developed, leading to a promising potential of energy saving compared to the traditional bleaching pathway. Overall, this work developed a mild pretreatment technology as a potential basis for a green and closed-loop biorefinery concept for converting lignocellulosic biomass to multiple products (high-quality lignin, fermentable sugars, or functional materials).

Keywords

Biomass pretreatment
Biobased solvents
Dimethyl isosorbide
Closed-loop biorefinery
Cellulose
Lignin

Supplementary materials

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Title
Efficient pretreatment using dimethyl isosorbide as a biobased solvent for potential complete biomass valorization
Description
Firstly,Dimethyl isosorbide (DMI) has not been studied in biomass field at all. DMI-water co-solvent synergically enables lignin removal at a high efficiency (~92%) and yielding lignin with high-quality (~25% β-O-4 links preserved) under a mild condition (120°C) from hardwood which is a feedstock difficult to delignify. Other solvents reported, for example, tetrahydrofuran (THF) could achieve high lignin removal efficiency (~85%) at higher temperature (160°C) but with low β-O-4 links content in lignin (~13%) while γ-valerolactone (GVL) obtains higher quality lignin (~34% β-O-4 links preserved) but with lignin removal efficiency compromised (~52%). These results show DMI has advantages in delignifying under milder conditions for lignin with better quality at the same time. Secondly, the yielded cellulose rich pulp is quite pure thanks to the efficient removal of hemicellulose, leading to high standard pulp or nanocellulose after a relatively simple fibrillation. This could benefit clean pulping and functional materials production.
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