Effect of enzyme lignin oxidation by laccase on the enzymatic-mechanical production process of lignocellulose nanofibrils from mechanical pulp

The use of endoglucanase enzymes as pretreatment of high-yield pulps to produce lignocellulose nanofibrils (LCNFs) has garnered increasing interest at both industrial and scientific levels. However, the lignin present in the lignocellulosic fibers hinders the enzymatic treatment reducing the efficiency of the further fibrillation process. This work postulates that modifying the structure of the residual lignin in the pulp can help to improve LCNF production. Laccase-mediator system (LMS) was evaluated to promote lignin oxidation of pressurized groundwood pulp from Pinus radiata previous to a treatment with endoglucanases and mechanical refining to produce LCNFs. As a result, it was observed that the LMS treatment improved the accessibility of the endoglucanase enzyme in the fibers, increasing their efficiency. Furthermore, it was observed a reduction in residual lignin and an increment in acidic groups in the LMS treated pulps facilitated the mechanical fibrillation process, enabling the production of LCNFs with a high aspect ratio. It was also observed that the pulps treated with a laccase-endoglucanase combination allowed to production of LCNF suspensions with zeta potential values sufficient for the nanofibrils not to form aggregates and to be considered stable (< − 25 mV).