Carboxylation of lyocell fabrics using C-1 lytic polysaccharide monooxygenases (DcLPMO9A) for enhanced affinity to cationic dye

Regenerated cellulosic fibers, such as lyocell fibers, are fully biodegradable and of 100% bio-based origin. With properties like high dry tenacity, they are widely used in many high-quality fiber applications. Yet, targeted surface functionalization could improve their processing such as dyeing. Reactive dyes are the dominant class for dyeing cellulosic fibers because they exhibit high affinity and form covalent bonds with cellulose. By contrast, cationic dyes show poor affinity to unmodified cellulose and are therefore not inherently suitable for lyocell unless additional anionic binding sites are introduced. To address this, we have investigated enzymatic surface functionalization of lyocell fabrics to increase negative charges. The C1-acting lytic polysaccharide monooxygenase (LPMO) Dc LPMO9A from Delitschia confertaspora was employed to functionalize lyocell fabrics to increase cationic dye uptake without substantial loss in fabric yield. The C1 oxidation of lyocell fiber was quantified through selective labeling and fluorescence analysis and directly correlated to cationic dye uptake. Remarkably, rhodamine-6G (R6G) dye uptake increased by up to 75% using less than 1% w/w Dc LPMO9A loadings. Further analysis of fiber properties and yield demonstrated that Dc LPMO9A treatment did not compromise fiber quality.