Conjugation of chitosan oligosaccharide to papain for controllable anti-felting finishing of wool textiles

The application of protease as a biocatalyst for the anti-felting finishing of wool has been widely explored. However, commercial proteases tend to hydrolyze the non-keratinized proteins in the cell membrane complex (CMC) layer while removing wool scales, resulting in excessive hydrolysis and unacceptable fiber damage. Herein, chitosan oligosaccharide (COS) was covalently grafted to papain using carbodiimide/N-hydroxysuccinimide (EDC/NHS) to prepare a less-destructive modified protease of Pap-COS. Subsequently, one-bath anti-felting finishing of wool was carried out using reducing agent and Pap-COS, aiming at achieving low shrinkage and reduced strength loss. The results reveal that Pap-COS achieved a larger particle size than native papain, accompanied by a prolongation of its half-life and a decrease in the thermal inactivation rate, demonstrating improved stability. Under the same incubation conditions, the felting shrinkage of wool fabrics treated with papain and Pap-COS was similar (approximately 5 %). In contrast, native papain caused a 20.82 % decrease in fabric strength, while Pap-COS resulted in a substantially lower decrease (8.10 %), meeting the requirements of commercial woolen products. Furthermore, the dyeing performance and wearability of the Pap-COS-treated wool fabrics were also dramatically improved. The present work provides an alternative for eco-friendly shrink-resistant finishing of woolen textiles in wool industry.