Cellulase-friendly dual-functional deep eutectic solvents for enhancing reactivity of dissolving pulp to produce cellulose acetate.

Abstract

High-quality dissolving pulp is essential for cellulose acetate (CA) production. However, the inherent stability of existing dissolving pulp significantly impedes chemical penetration, posing a huge challenge. Here, a novel deep eutectic solvent (DES)-assisted endoglucanase-enriched cellulase (EG) process is developed to enhance the pulp reactivity, facilitating the production of acetate-grade dissolving pulp. DES fulfills the dual functionality, specifically disrupting hydrogen bonds of cellulose to promote fiber swelling and acting as a main component within the buffer to protect the cellulase activity. Zinc acetate-based DES-assisted EG (ZAC-EG) treatment profoundly alters the structural properties of the pulp by reducing the degree of polymerization from 1227 to 958, decreasing the crystallinity and augmenting the crystallite size. Furthermore, the acetylation value significantly increases from 331 to 1148, comfortably surpassing the standards set for acetate-grade dissolving pulp. CA films prepared from ZAC-EG pulp exhibit high light transmittance (98.6 %) and tensile strength (62.2 ± 3.2 MPa), surpassing commercial CA films. This work presents a green and efficient method for the industrial production and utilization of acetate-grade dissolving pulp.