Laccase-induced lignin cross-linking and the potential for cellulose-based composite reinforcement

This study investigates the laccase-induced modification of lignin derived from Eucalyptus globulus soda cooking, analyzing its properties and its potential use as a reinforcement material in cellulose-based composites. After assessing the polymerization capacity of different lignin fractions, bulk lignin was incorporated into tissue paper and filter paper to examine its impact on the mechanical and surface properties of the resulting cellulose/lignin composites. In tissue paper (low-grammage), laccase-induced lignin polymerization significantly increased tensile strength from 70 N/m to 122 N/m, along with improvements in elastic modulus and tensile index. In high-grammage filter paper (higher density), lignin modification enhanced the composite's strength and resulted in additional surface changes due to its concentration at the surface. Water contact angle measurements showed a 52 % increase after lignin laccase-mediated modification, indicating reduced wettability. The findings underscore the potential of in-situ laccase-induced lignin modification to enhance both mechanical properties and surface characteristics of cellulose-based composites, offering valuable insights into the polymerization process. • Lignin addition enhanced mechanical properties in both paper structures. • Laccase modification further improved tensile strength, elastic modulus, and tensile index. • Lignin migrated to the surface during drying. • Enzyme treatment increased the water contact angle by 52 %.