Relationship between cellulolytic enzyme lignin structural and lignin nanoparticle-polyvinyl alcohol membrane property: Insights from monolignols and molecular dynamics simulations

Lignin is an abundant and sustainable biopolymer that presence great potential in the production of biofuels and biomaterials. In this work, cellulolytic enzyme lignin (CEL) was obtained from eucalyptus, pine, bamboo, and pennisetum in order to investigate the relationship between their structural and utilization in the production of lignin nanoparticle-polyvinyl alcohol (LNP-PVA) composite film. Results showed that CELs obtained from softwood contained the larger amount of G-type lignin, while CELs obtained from hardwood had more S-type lignin. The particle size of the LNPs was in the order of CEL-PI > CEL-PE > CEL-BB > CEL-EP. In addition, the existence of phenolic hydroxyl group in LNP was beneficial to the improvement of the UV shielding performance of LNP-PVA composite film. The higher content of H-type lignin in LNPs was, the better UV shielding performance of LNP-PVA composite film could be observed. The hydrophobicity of the composite films enhanced in the presence of LNPs with the order of BB-PVA > PE-PVA > PI-PVA > EP-PVA. Moreover, the higher amount of S-type lignin in LNPs was, the better mechanical properties of LNP-PVA composite film could be obtained. EP-PVA showed the best elongation with the respect to breakage and tensile strain performances. Molecular dynamic simulation indicated that the interaction between lignin monomers and PVA is mainly van der Waals force, and the position of methoxy group will affect their interaction strength. This study provided a new strategy for high-value utilization of lignocellulose.