Enzymatic Fibre Modification During Production of Dissolving Wood Pulp for Regenerated Cellulosic Materials

Abstract

The production of regenerated cellulosic fibres, such as viscose, modal and lyocell, is based mainly on the use of dissolving wood pulp as raw material. Enzymatic processes are an excellent alternative to conventional chemical routes in the production of dissolving pulp, in terms of energy efficiency, reagent consumption and pulp yield. The two main characteristics of a dissolving pulp are the cellulose purity and the molecular weight, both of which can be controlled with the aid of enzymes. A purification process for paper-grade kraft pulp has been proposed, based on the use of xylanases in combination with hot and cold caustic extraction, without the conventional pre-hydrolysis step before kraft pulping. This enzyme aided purification allowed the production of a dissolving pulp that met the specifications for the manufacture of viscose, < 3% xylan, > 92% ISO brightness and 70% Fock’s reactivity. Endoglucanases (EGs) can efficiently reduce the average molecular weight of the cellulose while simultaneously increasing the pulp reactivity for viscose production. It is shown in this study that lytic polysaccharide monooxygenases act synergistically with EGs in the modification of bleached dissolving pulp.

Characterization of a Dual Cellulolytic/Xylanolytic AA9 Lytic Polysaccharide Monooxygenase from Thermothelomyces thermophilus and its Utilization Toward Nanocellulose Production in a Multi-Step Bioprocess

“…Nanoscale cellulose samples after treatment with tailored hemicellulose cocktail (sample D, processes 4–6) showed lower stability, with the best colloidal stability to be observed for sample D Celluclast (−20.7 mV). In accordance to previous reports, initial hemicellulose removal seems to affect the properties of the isolated nanocellulose. , Similar ζ-potential values have been reported for samples obtained from different types of plant and tunicate biomass with similar enzyme-mediated processes, where treatment with LPMO leads to an increased colloidal stability. ,,, …”

“…In accordance to previous reports, initial hemicellulose removal seems to affect the properties of the isolated nanocellulose. 64,65 Similar ζ-potential values have been reported for samples obtained from different types of plant and tunicate biomass with similar enzymemediated processes, where treatment with LPMO leads to an increased colloidal stability. 7,13,22,24 The morphology of the isolated cellulose nanostructures, as well as their average diameter and size distribution were evaluated with AFM analysis.…”

“…Enzyme-mediated removal of hemicellulose is generally preferred over chemical treatments, such as acid pre-hydrolysis for kraft pulping, not only due to the low toxicity, neutralization issues, and energy requirements but also because it prevents extensive degradation of the substrate causing yield losses. 6,65 The hemicellulose-free samples were then subjected to hydrolysis by employing a commercial cellulase mixture (samples C Celluclast and D Celluclast ), an endoglucanase EG7 (samples C EG7 and D EG7 ), or two different endoglucanases EG7 and EG5 (samples C EG7-EG5 and D EG7-EG5 ) for the isolation of nanoscale cellulose (Figure S7). The use of endoglucanases, instead of the crude cocktail Celluclast, aimed at controlling the overall saccharification process at the expense of nanocellulose yield and target mainly the degradation of the cellulose amorphous areas.…”

“…Hemicellulose removal has been demonstrated as a crucial step for ensuring high yields and improved quality of nanocellulose, which is also demonstrated in the present study. Enzyme-mediated removal of hemicellulose is generally preferred over chemical treatments, such as acid pre-hydrolysis for kraft pulping, not only due to the low toxicity, neutralization issues, and energy requirements but also because it prevents extensive degradation of the substrate causing yield losses. , …”

Alkalization of Kraft Pulps from Pine and Eucalyptus and Its Effect on Enzymatic Saccharification and Viscosity Control of Cellulose

“…The most susceptible pine sample to both EG treatments was CCE5-treated sample, while the most resistant was the bleached pine sample ( Figure 10 b). Previous studies have shown that CCE treatments can aid the viscosity reduction mediated by EG treatment [ 13 , 63 , 66 , 67 , 68 ].…”