Abstract
The ionoSolv pretreatment generates a cellulose pulp by extracting hemicellulose and lignin using low-cost ionic liquids. In this study, cellulose pulp was obtained from Miscanthus × giganteus using the protic ionic liquid triethylammonium hydrogen sulfate [N2220][HSO4] with 20% water as a co-solvent and characterised in detail for its material properties as a function of pretreatment severity. We measured the particle size distribution, porosity and crystallinity of the unbleached pulps and the molar weight distribution of the cellulose contained within. We report that the surface area increased and the size of the pulp particles decreased as ionoSolv processing progressed. While the native cellulose I structure was maintained, the average degree of polymerisation of the cellulose was reduced to a DPn of around 300, showing the cellulose polymers are shortened. We correlate the pulp properties with enzymatic saccharification yields, concluding that enzymatic saccharification of the cellulose after ionoSolv pretreatment is mainly enhanced by removing hemicellulose and lignin. We also observed that overtreatment deteriorated saccharification yield and that this coincides with cellulose fibrils becoming coated with pseudolignin redeposited from the ionic liquid solution, as demonstrated by FT-IR spectroscopy. Pseudolignin deposition increases the apparent lignin content, which is likely to increase chemical demand in bleaching, suggesting that both glucose release and material use benefit from a minimum lignin content. Overall, this study demonstrates that cellulose pulps isolated with ionoSolv processing are not only a promising intermediate for high-yield release of purified glucose for biorefining, but also have attractive properties for materials applications that require cellulose I fibrils.Graphic abstract
Highlights
IntroductionIt is produced by plants, algae and microbes such as fungi and bacteria (Chen 2014)
Cellulose is a polymer made from glucose linked by b(1 ? 4) glycosidic bonds
It can be seen that ionoSolv pretreatment with [N2220][HSO4] removed and dissolved the majority of the lignin and the hemicellulose as reported previously (Brandt-Talbot et al 2017)
Summary
It is produced by plants, algae and microbes such as fungi and bacteria (Chen 2014). It is usually the most abundant component in the cell walls of woody (lignocellulosic) biomass. Native cellulose is bundled into microfibrils, consisting of long ordered crystalline regions that are interrupted by short amorphous regions (Habibi et al 2010). Adjustments to properties such as hydrophilicity/hydrophobicity can be made through chemical modification of its hydroxyl groups. Lowcost and desirable material properties such as high strength, biodegradability and biocompatibility have made isolated cellulose fibres and their derivatives attractive in industries ranging from paper, packaging and hygiene products to textiles, pharmaceuticals and optics (Berg and Lingqvist 2017; Edgar et al 2001; Osong et al 2016; Shatkin et al 2014)
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