Determining the lignin distribution in plant fiber cell walls based on chemical and biological methods

Cellulosic fibers are widely used in biocomposites, paper and paperboard products, and other fiber-based materials. The properties of fiber-based materials are significantly affected by lignin characteristics, especially the lignin distribution in cellulosic fiber cell walls. In this study, chemical (sodium chlorite) and biological (laccase/mediator system) techniques were used to control three fiber models with different lignin contents at about 20%, 10%, 5%, respectively. The lignin distribution in cell walls was determined based on the “enzymatic peeling” method and SEM–EDS analysis. Results showed that the lignin concentrations in fiber cell walls prepared from the combined chemical and biological techniques were lower in the outer region and higher in the inner region than those from the chemical treatment only, which is due to the fact that laccase-induced lignin degradation is only limited to the outer region and not able to get into the inner region. The fiber model with less lignin in the inner region of the cell wall had a better deformation performance (the flexibility of 1.559 × 10⁹ N⁻¹ m⁻²) than that with more lignin in the same region. The relationships of fiber models of different specific lignin distribution with their deformability were established, which could be valuable to extend the wide value-added applications of fiber-based materials.