Enzymatic coloration for enhancing antibacterial features of silk: horseradish peroxidase-catalyzed polymerization of gallic acid with Chitosan

In this study, gallic acid-g-chitosan colored complex were produced using the HRP-catalyzed method. Then, these were used to successfully dye silk fabrics. The dyed silk fabrics were characterized through K/S, color fastness, and antibacterial tests. We studied the polymerization mechanism in detail using FT-IR and ESI-MS technologies, then the dyeing process and optimum reaction conditions were further investigated using the K/S values. Chitosan and gallic acid were polymerized to form a dark yellow polymer, which was successfully colored on silk fabrics. In addition, significant color differences were observed between fabrics dyed without chitosan and fabrics dyed in the presence of chitosan. In particular, the fabric treated with the pre-polymerization dyeing process showed high antibacterial properties, color fastness, and color depth compared to other dyeing processes. We found that the optimum reaction conditions for dyeing silk fabrics are as follows: 3-hour incubation period, 50 ℃ temperature, 3 mM gallic acid; 3 g/L chitosan. While the GA and CS pre-treatment or co-treatment process resulted in lower color fastness, the pre-polymerization approach offered enhanced fastness and overall performance. Based on the findings, the pre-polymerization process is recommended as the most effective method for dyeing silk fabrics with chitosan and natural dyes, optimizing both aesthetic and functional properties.