Comparing enzymatic post-treatments by endoglucanase (EG) and lytic polysaccharide monooxygenase (LPMO) on microfibrillated cellulose (MFC) to enhance cellulose film fabrication

Cellulose is the world's most abundant natural polymer and it can be used as a substitute for fossil derived products. The work described here evaluated the use of mono-component enzyme treatment, using endoglucanase (EG) and lytic polysaccharide monooxygenase (LPMO), to improve the properties of micro-fibrillated cellulose (MFC) produced from mechanically refined kraft pulp. Endoglucanase treatment of the pulp significantly reduced the degree of polymerization (DP) of the cellulose by promoting fiber cutting. In contrast, LPMO treatment only slightly reduced the fiber length and pulp viscosity. However, the introduction of carboxylic acid groups by the action of LPMO appeared to enhance the accessible surface area of cellulose. Enzyme-treated MFC showed improved nano-fibrillation with transmittance and water retention values increased after both enzyme treatments. The cellulose films derived from enzyme-treated MFC showed enhanced mechanical properties with the LPMO-treated films showing superior tensile strength (77 MPa) and Young's modulus (3600 MPa). Thermogravimetric analysis (TGA) also indicated improved thermal stability for both enzyme-treated films. LPMO treatments proved more effective, promoting nano-fibrillation while maintaining fiber integrity and enhanced intermolecular interactions.