Laccase-Mediated Incorporation of Xylans and Lignin-Carbohydrate Complexes into High-Yield Eucalyptus Kraft Fibers

Water-soluble products derived from biomass processing hold significant potential to enhance biorefinery viability due to their versatile applications. However, their use in the modification of paper products remains underexplored. Here, corn stover and sugarcane bagasse provided water-soluble products being incorporated into high-yield eucalyptus kraft pulps. The water-soluble products were extracted from ball-milled or alkaline-sulfite pretreated biomass using a xylanase-assisted procedure. Feruloylated arabinoxylans and lignin-carbohydrate complexes (LCCs) predominated in the extracted mixtures. The water-soluble products were incorporated into the fibers using laccase-mediated reactions. The fibers incorporated up to 15.4 g of water-soluble products/100 g of pulp, depending on the biomass source and pretreatment type. The highest incorporation levels were achieved with the water-soluble products recovered from ball-milled sugarcane bagasse. This fraction underwent significant polymerization of feruloylated arabinoxylans during laccase treatment. Paper sheets prepared from fibers with high levels of xylan and LCCs exhibited decreased water contact angles, indicating their potential suitability for a more wettable brown tissue paper. High-resolution X-ray photoelectron spectroscopy revealed an increase in the content of carboxyl and ester groups, corroborating the incorporation of xylans and LCCs into the fibers. The study presents novel strategies for modifying fiber properties through the use of agricultural byproducts.