Covalent Immobilization of Cellulase Enzyme on Chitosan and Eudragit S-100 Biopolymers for Recovery and Reusability in Denim Fading Application

Abstract

The cellulase enzyme has significant potential for applications in textile chemical processing, offering an environmentally friendly alternative to traditional chemical methods. In conventional enzymatic treatments, the enzymes act as biocatalysts and are typically discarded as effluent after completing their function. However, the single-use nature, high production costs, and limited biological activity of cellulase enzymes hinder their widespread commercial use in the textile industry. This study focuses on the immobilization of a commercial cellulase enzyme onto two distinct reversible soluble–insoluble polymers Chitosan and Eudragit S-100 for the recovery and reusability. Chitosan and Eudragit were chosen as support materials due to their pH-dependent soluble–insoluble properties. These properties allow them to act as homogeneous catalysts in their soluble phase during application (since textile materials are heterogeneous) and enable easy recovery in their insoluble phase for subsequent reuse. The immobilization process was optimized to achieve maximum enzyme activity with ideal enzyme loading percentages. After immobilization on chitosan, the cellulase retained 92% of its initial activity with a loading efficiency of 73.7%, while on Eudragit, it maintained 86.5% activity with a loading efficiency of 75.6%. Fourier-transform infrared spectroscopy (FTIR) was employed to confirm the successful attachment of the cellulase enzyme to the polymers. The immobilized cellulase demonstrated equivalent fading effects compared to the native cellulase in terms of color depth (K/S value) and color metrics (L*, a*, b*), while also reducing physical damage and back-staining—common issues in the traditional denim fading process. Scanning electron microscopy (SEM) and back-staining analyses of the denim samples provided further evidence of these benefits. Moreover, the immobilized cellulase maintained approximately 50% of its activity even after recovery from five denim washing cycles, showcasing the potential for reuse across multiple applications, particularly in textile processing. Thus, cellulase immobilized on chitosan and Eudragit S-100 represents a promising solution for the sustainable use of enzymes in the textile industry.