Understanding the evolution of cellulose fibers during enzyme treatment

Abstract

Enzyme treatment is a potential strategy for producing cellulose fibrils but its evolution of the mesoscopic and microcosmic structures is not fully understood. In this work, the effect of the properties and microstructures of cellulose bleached hardwood kraft pulp (BHKP) subjected to different enzyme treatment times (0−10 h) on further fibrillation was explored by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results showed that the enzyme treatment did not change the crystal structure of cellulose but destroyed the intermolecular and intramolecular hydrogen bonds, leading to the increase of the crystal index and size. A thorough investigation on the relation between treatment and evolution of inter-/intra-molecular H-bonds in cellulose including content and cleave sequence of H-bonds was conducted by FTIR peak fitting, second derivative analysis and generalized two-dimensional correlation spectroscopy (2DCOS). Compared to intramolecular H-bonds, the intermolecular H-bonds was first broken with a significant decrease in content. In addition, enzyme treatment could promote the peeling of fibrils, and various properties such as yield, water retention value, aspect ratio, and degree of polymerization, etc. were gradually reduced over time relative to the original material, these discoveries provide a theoretical support to a more effective treatment method for the commercial production of cellulose fibrils.